Mechantron Carver

Final Year Project Report

MECHANTRON CARVER

B.S. ELECTRONIC ENGINEERING, BATCH 2008

Internal AdvisorFahad Ahmed SiddiqueAssistant Professor Electronic Engg. SSUET, Karachi

External AdvisorSadia KazmiManagerBU-CIP(SIEMENS)Karachi

Submitted by

FAHAD SAMI KHAN 2008-EE-200SHUEB IQBAL 2008-EE-201USAMA KHAN 2008-EE-202SYED MUHAMMAD MOIZ 2008-EE-226SYED UMAIR ALI 2008-EE-253

DEPARTMENT OF ELECTRONIC ENGINEERING

SIR SYED UNIVERSITY OF ENGINEERING AND TECHNOLOGY, KARACHI

JANUARY 2012

MECHANTRON CARVER

3-AXIS CNC CARVING MACHINE

BY

FAHAD SAMI KHAN 2008-EE-200 SHUEB IQBAL 2008-EE-201USAMA KHAN 2008-EE-202SYED MUHAMMAD MOIZ 2008-EE-226SYED UMAIR ALI 2008-EE-253

Report submitted in partial fulfillment of the requirements

for the degree

of Bachelor of Science

in Electronic Engineering

DEPARTMENT OF ELECTRONIC ENGINEERING

SIR SYED UNIVERSITY OF ENGINEERING AND TECHNOLOGY, KARACHI

JANUARY 2012

ii

ACKNOWLEDGEMENT

With a deep sense and profound gratitude we take this opportunity to convey our sincere

thanks to ALMIGHTY ALLAH for giving us courage and strength to reach this stage of

life.

We also thank our parents who gave us great moral support at every step. We also

convey thanks to all of those who gave us valuable support to complete this challenging

project.

The success of this project depends largely on the encouragement and guidelines of my

teachers and friends. I, therefore take this opportunity to express my gratitude to the

people who have been instrumental in the successful completion of this project.

I would like to show my greatest appreciation to ASST.PROF. FAHAD AHMED

SIDDIQUE I can’t say enough thanks for their tremendous support and help. I feel

motivated and encouraged every times. Without their encouragement and guidance this

project would not have materialized.

We also wish to express our gratitude to all staff in university. And last but not the least

we acknowledge the efforts of our teachers who have been our source of inspiration

throughout the university years and have shared their knowledge and skills with us.

Fahad Sami Khan 2008-EE-200 Shueb Iqbal 2008-EE-201Usama Khan 2008-EE-202Syed Muhammad Moiz 2008-EE-226Syed Umair Ali 2008-EE-253

January 2012

iii

TABLE OF CONTENTS

ACKNOWLEDGMENT.….......…………………………...………………...…....….....ii

TABLE OF CONTENTS.................................................................................................iv

LIST OF TABLES.........................................................................................................viii

LIST OF FIGURES.........................................................................................................ix

ABSTRACT......................................................................................................................xi

CHAPTER ONE: INTRODUCTION

1.1 INTRODUCTION...................................................................................................1

1.2 ABOUT CNC...........................................................................................................2

1.3 APPLICATIONS OF CNC MACHINES................................................................3

1.4 WHY CNC?.............................................................................................................4

1.5 BENEFITS OF CNC................................................................................................4

1.6 WHY WE ARE USING CNC AS FYP...................................................................5

1.7 INTRODUCTION TO THE HARDWARE.............................................................6

1.8 INTRODUCTION TO THE ELECTRONIC PART................................................7

1.9 INTRODUCTION TO THE SOFTWARE..............................................................7

CHAPTER TWO: THEORY AND LITERATURE

2.1 THEORY OF CNC..................................................................................................8

2.2 INTERPRETER/SOFTWARE OF CNC.................................................................8

2.3 PART PROGRAM.................................................................................................10

2.4 PROGRAM STRUCTURE....................................................................................10

2.5 DESCRIPTION OF CODES..................................................................................13

2.6 SUMMARY...........................................................................................................14

iv

CHAPTER THREE: DETAILS OF THE DESIGNS

3.1 BRIEFING..............................................................................................................15

3.1.1 BALL SCREW...............................................................................................15

3.1.2 STEPPER MOTOR.........................................................................................16

3.1.3 GEARS AND CHAINS..................................................................................17

3.2 DESCRIPTION:.....................................................................................................18

3.3 X-AXIS MOVEMENT..........................................................................................19

3.4 Y-AXIS MOVEMENT..........................................................................................21

3.5 Z-AXIS MOVEMENT...........................................................................................23

3.6 CALCULATION OF TORQUE............................................................................25

CHAPTER FOUR: SYSTEM HARDWARE

4.1 INTRODUCTION OF STEPPER MOTORS........................................................26

4.2 WHY WE ARE USING STEPPER MOTORS?....................................................27

4.3 WHEN STEPPER MOTOR IS USED...................................................................27

4.4 TECHNICAL DESCRIPTION..............................................................................28

4.5 STEPPER MOTOR APPLICATIONS..................................................................30

4.6 STEPPER MOTOR SPECIFICATIONS...............................................................30

4.7 STEPPER MOTOR TYPES...................................................................................31

4.7.1 VARIABLE RELUCTANCE(VR).................................................................31

4.7.2 PERMANENT MAGNET (PM).....................................................................31

4.7.3 HYBRID (HB)................................................................................................32

4.8 STEPPER MOTOR DRIVE TYPES....................................................................33

4.8.1 UNIPOLAR STEPPER MOTOR...................................................................33

4.8.2 BIPOLAR STEPPER MOTOR......................................................................34

4.8.3 UNIPOLAR VERSUS BIPOLAR..................................................................36

4.9 STEPPER MOTOR WIRING SCHEMES.............................................................37

4.10 STEPPER MOTOR STEPPING MODES.............................................................39

4.10.1 ONE PHASE DRIVE / SINGLE STEP DRIVE / WAVE DRIVE..................39

v

4.10.2 TWO PHASE DRIVE / HIGH TORQUE DRIVE / FULL DRIVE.................39

4.10.3 TWO PHASE DRIVE / HALF STEP DRIVE / DUAL DRIVE......................40

4.10.4 MICROSTEPPING...........................................................................................41

CHAPTER FIVE: CNC ELECTRONICS

5.1 INTRODUCTION..................................................................................................43

5.2 MOTION CONTROL............................................................................................45

5.3 ELECTRONIC SYSTEM OVERVIEW................................................................45

5.4 DESCRIPTION OF BLOCK DIAGRAM.............................................................46

5.5 SYSTEM FLOW CHART.....................................................................................47

5.6 CONTROL UNIT (CU) OF OUR MACHINE......................................................48

5.6.1 THE POWER SUPPLY UNIT.......................................................................48

5.6.2 THE CIRCUITRY PROTECTION SYSTEM................................................49

5.6.3 THE MOTOR DRIVERS:..............................................................................49

5.7 STEPPER MOTOR DRIVER IMPLEMENTATION...........................................50

5.8 COMPUTER..........................................................................................................57

5.9 STEPPER MOTOR DRIVER................................................................................58

5.10 STEPPER MOTORS..............................................................................................58

5.10.1 FUNCTIONS..................................................................................................59

5.10.2 WAVE SEQUENCE OF STEPPER MOTOR................................................59

5.11 TRIMMER /MINI ROUTER.................................................................................60

CHAPTER SIX: SYSTEM SOFTWARE

6.1 SYSTEM SOFTWARE..........................................................................................62

6.2 CAD SOFTWARE.................................................................................................63

6.3 CAM SOFTWARE................................................................................................64

6.4 CONTROLLING SOFTWARE.............................................................................65

6.4.1 MACH3...........................................................................................................66

vi

CHAPTER SEVEN: RESULT & DISCUSSION

7.1 RESULT:................................................................................................................68

7.2 DISCUSSION:.......................................................................................................70

7.2.1 MECHANICAL ISSUES:...............................................................................70

7.2.2 ELECTRONIC ISSUES:................................................................................71

7.2.3 SOFTWARE ISSUES:....................................................................................71

CHAPTER EIGHT: FUTURE ENHANCMENT & CONCLUSION

8.1 FUTURE ENHANCEMENT:................................................................................72

8.2 CONCLUSION:.....................................................................................................73

REFERENCES................................................................................................................74

APPENDIX 1:.....................................................................................................................i

APPENDIX 2:....................................................................................................................ii

APPENDIX 3:...................................................................................................................iii

APPENDIX 4:...................................................................................................................iv

DATASHEETS

vii

LIST OF TABLES

2.1 Typical addresses and associated functions 11

2.2 Summary of address groups based on CNC system function 13

4.1 Stepper motor types and its characteristics 33

4.2 Comparison b/w Unipolar & Bipolar 36

4.3 Wave Driving sequence 39

4.4 Full Step Driving sequence 40

4.5 Half Step Driving sequence 40

4.6 Comparison of stepper motor drive sequence 41

viii

LIST OF FIGURES

1.1 Old times (Handwork) 2

1.2 CNC PCB Drilling 3

1.3 CNC Lathe Machine 3

1.4 Result of handwork (time consuming) 4

1.5 Precession & Accuracy 5

2.1 Internal Behaviour 8

3.1 Ball bearing moving in a screw 15

3.2 Stepper motor NEMA 24 16

3.3 NEMA 23 dimension 16

3.4 Gears of the different size 17

3.5 Chains used between gears 17

3.6 Axis on the structure 18

3.7 X, Y & Z axis 18

3.8 Position of the ball screws 19

3.9 Illustrating X-axis movement 20


3.11 Illustrating Y-axis movement 22


3.13 Illustrating Z-axis movement 24

4.1 Basic shape of a stepper 28

4.2 Cross-section of a variable reluctance 31

4.3 Principle of a PM or tin-can stepper motor 32

4.4 Cross-section of a hybrid stepper motor 32

4.5 Unipolar stepper motor 34

4.6 Bipolar stepper motor 35

4.7 Wire stepper motor configuration 37

ix

4.8 Motor standard wire color 37

4.9 Excitation sequence of driving modes 42

5.1 Components of CNC 43

5.2 Electronic components of CNC 44

5.3 Electronic System overview 45

5.4 Block diagram 46

5.5 System flow chart 47

5.6 CU of our project 50

5.7 Drive circuitry for motors 52

5.8 Breakout board PCB 55

5.9 Diagram of Limit Switches 56

5.10 Laptop 57

5.11 L6203 & L297 driver 58

5.12 Wave timing output 59

5.13 Sencan router for carving 60

5.14 Router bits for carving 61

6.1 Whole process of system software 62

6.2 sample design made by using CAD software 63

6.3 Logo of AutoCAD 64

6.4 Logo of LAZYCAM 64

6.5 Environment of LAZYCAM 65

6.6 Environment of Mach3 66

7.1 Carved result 1 68




x

MECHANTRON CARVER

ABSTRACT

We are working upon a CNC (computer numerically controlled) machine which basically

carved or engraved the desired objects.

Our project is that we are working on a CNC machine that will carve text and images in 3

axis and the carving will be done on a wooden block .Computer numerically controlled

which means the motors (NEMA23) and the router (SANTEC) that will Carve will be

numerically controlled by the computer via parallel port it means that we will provide

step by step instructions to the motors from computer using Specific softwares. It is

widely used in automated drilling of wood and metals.

Used in lathes: This is a machine for working wood or metal where a piece is worked on

with the aid of a cutting tool. It is used in laser cutting

As it is mentioned earlier that we will be going to carve or engrave the desired objects

upon wooden piece. We are considering many types of software now days because there

are number of softwares available in the market and we will soon select the most

compatible software and produce some vital results. We have diagnosed our mechanical

and circuits only the compatibility with the software is left over. The whole process will

be tested on each and every step when it will compatible with the software.

From all the details that have been mentioned above we can conclude that we will soon

achieve our desired targets as soon as possible. We will be able to produce some carved

results as demanded with the conditions with the extreme support and efforts of our

internal advisor.

xi

CHAPTER # 1

INTRODUCTION

Chapter # 1 Introduction

CHAPTER ONE

INTRODUCTION

1.1 INTRODUCTION

As for introduction we would like to mention that the name of our project is

MECHANTRON CARVER we named it so because it consists of much mechanical as

well as electronic work so we named it after a word which is a combination of

mechanical and electronics.

What does it do? As the name implies it carves and the answer to the question that what

does it carve is that it carves shapes, Alphabets and some sort of images on a wooden

block.

It does so with the help of a CNC mechanism attached with it so now you can have an

idea of our machine that it is basically a CNC machine that will carve certain images and

shapes or alphabets on a wooden block and it will do so with the help of CNC machine

and our CNC machine comprises of 3 stepper motors some threaded rods iron base and a

beam and moreover a Control Unit (CU) which holds all the electronic part of the project

and that Control Unit controls everything that our hardware do.

After knowing how what our machine comprises of we would like to mention or would

like to give an idea of how CNC mechanism works and from where it came and why we

are using CNC for our final year project its applications and its uses and moreover its

advantages over old traditional methods that were used before the invention of CNC.

Sir Syed University of Engineering & Technology Page 1


1.2 ABOUT CNC

In the old days everything was done by human power and manually by humans but then

we started doing many works by machines and then we controlled machines with motors

mounted on them to move them according to us and then we programmed them so follow

specific instructions given by us and these instructions are given in the form of some

codes that machine and hardware can understand so after all this advancement we started

using the machines with help of computers means we made a relation between machines

and another machine that controls the first machine and the 2nd machine is computer the

other is called the hardware and when we started doing that with computer involvement

the major benefit we had is that the accuracy and the precision of the work increased

exponentially and the speed also increased and the only decrement was of human

involvement previously where 10 to 15 men were needed to complete some sort of

carving after CNC only 1 man is able to do more than that work in less time with more

accuracy and precision .

It came to popularity in 1940’s to 1950’s and after that the invention of CAD and CAM

softwares made the work and controlling of CNC easier.


Figure 1.1 old times (Handwork)


Now mentioned below are some applications of CNC machines.

1.3 APPLICATIONS OF CNC MACHINES

They are used in milling machines

They are used in lathe machines

They are used in laser cutting

They also are used in medical field

They are used in wood works

They are used in metal carving

They are used in PCB making

They are used in coloring big objects like cars and things sort of that in that

case robotic arms are made and they are controlled with the computer

somewhat similar to that of CNC.

They are used in fabric cutting.

They are used

in welding and spinning

and gluing.


Figure 1.2 CNC PCB Drilling

Figure 1.3

CNC Lathe machine


In short now in industries wherever heavy motion is required or heavy work needs to be

done CNC are used and by using CNC humans do much benefit to them.

1.4 WHY CNC?

The problem with the old methods was that they required an operator to operate and the

ability of an operator to do quality work for so long is limited

Whereas if we use CNC instead of that we will have numerous of benefits that why

CNC’s are used and preferred over previous methods.

1.5 BENEFITS OF CNC

There are numerous advantages of CNC machines and some major advantages and

benefits are given below:


Figure 1.4: Result of Handwork (time Consuming)


They are extremely efficient means their work is better and safer than human

work all they need is only they should be programmed once and they will keep

doing that as long as we want them to do the specific work.

They are easy to make and they perform greater work normally they are

comprised of stepper motors and their drivers and some threaded rods that serves

as the path of the machine so that the tool can move in desired direction.

They are very accurate and that is why they are used in many fields where

accuracy is required such as PCB making here extreme accuracy is required and

that is why CNC is used and does its work accurately.

1.6 WHY WE ARE USING CNC AS FYP

They are being widely used in many fields related to electronics and metal working wood

working and their importance can be shown that every big industry has them. So our aim

is to master our skill specially in such an area which is mostly required in every company

and not only this CNC machines are the requirements of many wood workers and metal

carvers so making a CNC machine and mastering our skills in making CNC or being an

expert in CNC work and knowing CNC will help us make our way in the future because

this project will help us and not only this but also this is a very sound project in which


Figure 1.5: precision & accuracy


many electronic concepts are being implemented thus fulfilling the requirement of

making a final year project.

Now it’s enough knowledge about the background of the project now let’s come to the

main introduction about the details of the project and hardware and here it goes:

1.7 INTRODUCTION TO THE HARDWARE

Our hardware consists of an iron made structure whose dimensions are 3.5x3

foots.

Other than this is it has a base and the purpose of base is that the thing that need

to carves on will be placed on the base and the base is made very stronger in order

to hold any force applied by the beam and cutting tool and the weight of the

object.

A beam fitted over base so that it can move over it and it will give the motion

along Y axis

A router which fitted over beam and it can move across the beam and thus it will

give the motion along X axis.

And the router will be able to move o upward and downward direction thus

giving the motion along Z axis.

The horizontal motion is called the motion along X axis.

The vertical motion is called and known as the motion along Y axis.

And the motion in upward and downward direction is called and known as the

motion along or in the Z axis direction.



There are a total of 2 motors fitted on beam, one on its end and the other in the

router.

The purpose of the motor on one end of the beam is to move the router in X axis

direction.

The purpose of the other motor on the router is to move the cutting tool in the

Direction of Z axis.

1.8 INTRODUCTION TO THE ELECTRONIC PART

The electronics of the project comprises of the following things:

Stepper motors

A cutting tool or trimmer

Motor driver

Parallel breakout circuit board

A power supply

These were the main electronics components of the project and the other components like

transistors and IC’s are soldered in the circuits.

And the in depth details of these components are given in the next section of the report

and in the upcoming next section of the report will be having the components details plus

that their theory and specs.



1.9 INTRODUCTION TO THE SOFTWARE

The whole software system is based on the three softwares. One is CAD software for

making the design. 2nd is CAM software which generates the G-Code for the controlling

software & the Controlling software which read the G-Code and give instructions to the

motors for the required motion.


CHAPTER # 2

THEORY AND LITERATURE

Chapter # 2 Theory and Literature

CHAPTER TWO

THEORY AND LITERATURE

2.1 THEORY OF CNC

As the our project is based on CNC machine so in this section where we will be

providing you with the theory and literature of the components first of all we are going to

describe and give u theory about CNC machines

The Numerical Control Kernel (NCK) unit is the key component of a CNC system and

consists of a variety of modules that are sequentially executed in a synchronized

schedule. In this chapter the code interpreter will be addressed. This is responsible for

converting the part program and machine instructions into internal commands for NC. In

order to understand the code interpreter the first thing is to understand the part program

that is the input to the interpreter. After this, the structure and the functions of the code

interpreter will be addressed in detail.

2.2 INTERPRETER/SOFTWARE OF CNC

The code interpreter is a software module, which translates the part program into internal

commands for moving tools and executing auxiliary functions in a CNC system. Figure

2.1 depicts the internal behaviour of the CNC system and shows the functions of the

Man-Machine Control (MMC), Numerical Control Kernel (NCK), and Drives (DRV).

The part program that a programmer generates based on the shape of the part, cutting

conditions, and tools is entered into CNC via the MMC and the NCK subsequently

generates the control commands for the drivers from the part program through various

stages; calculating the movement path by interpreting the part program, generating



velocity profile and displacement for each axis by interpolation, smoothing the

movement by acceleration/deceleration (acc/dec) control, and generating position control

command. Among these stages, the interpreter could be considered as a simple task for

the conversion of G/M codes to the CNC-understandable internal data structures.

However, the design and implementation of the interpreter is a large and comprehensive

task because programming rules or grammar described in a programming manual and an

operating concept shown in an operation manual should be considered when developing

the interpreter. Therefore, the interpreter is the representative indicator

That shows the design concept and the functional aspect of a CNC and is a big part of

CNC as it generally spends more than 50% of the total development time to develop the

interpreter. In this chapter, the format and function of CNC part programs will be briefly

addressed and the architecture, such as the structure of an interpreter, execution

procedure, and memory structure, will be addressed. However, because the detailed

function of the CNC and the part program are slightly different for each CNC maker, the

program manual should be referenced to find out the detailed functions of any particular

CNC.

Figure 2.1: Internal behaviour



2.3 PART PROGRAM

Although the standard exists for generating a CNC part program, sequentially listing the

commands for executing CNC, each CNC maker has, in practice, their own code system

including their own commands. In this section, the common concept will be described

based on the standard code.

2.4 PROGRAM STRUCTURE

A part program contains the commands, called blocks, for machining a part and each

block can be defined using the following commands.

• NC commands such as G, M, S, T, H, D, F code and related address

• Call of sub program and displaying message

• Setting variable and conditional program calls

In a part program, the English alphabet, Arabic numbers, and symbols are used.

A part program consists of a sequence of NC blocks, each block consists of several

words, and a word is composed of an address and number. The program number is a

number for identifying the particular part program on CNC, where more than one

program part is executed, and is written using a particular address and number in the

heading of a part program. In this book, address P is used but O or # is also used by some

specific CNC makers. A block consists of one block number, at least one word, and the

EOB, meaning the End Of Block. The word is the set of characters in a specific order.

The word is the minimum unit for internal processing and commanding the machine

tools toper form a particular behaviour. The word consists of an address and a subsequent

number NC word: address: value Y −20. The address is constructed from one of the

alphabetic characters (A Z) or a combination of alphabetic characters. The subsequent



number provides the data that is required to execute the behaviour related with the

address. Table 2.1 summarizes the

Addresses that have typically been used and the function that is related with the address.

Table 2.1: Typical addresses and associated functions

Among the addresses described in Table 2.1, the G addresses, for preparatory function,

and the M address, for auxiliary function, are largely related to the performance of CNC

system. G addresses denote commands for tool movement by moving the translational

axes or the rotary axes along the specified path. M addressed note commands for

controlling the on/off functions in machine tools. G-codes are classified into two types:

one is a modal code and the other is non-modal code. A modal type code is effective



throughout the following blocks until the modal cancel command is used. On the other

hand, a non-modal-type code is effective within the commanded block and automatically

cancelled by the next block. Modal-type codes are

Classified into several groups, called modal groups, with respect to the similarity of

function. In one block, it is prohibited to use more than one G-code that is included in the

same modal group. The address groups based on the functions of CNC system are

summarized in Table 2.2. As the standard for editing a part program based on these

addresses, ISO6983 has been widely used. However, each CNC maker has their own

G&M code system where maker-specific functions have been added to ISO 6983.

Accordingly, current G&M code systems for generating part programs depend on the

CNC system.

If the CNC system is changed, it is almost impossible to reuse the existing part program.

Therefore, in order to create a part program manually, it is necessary to refer to the

programming manual of the particular CNC maker. According to the level of CNC

system, the number of feasible addresses varies from several tens to several hundreds.

This means that the more feasible addresses a CNC system has, so the more advanced the

equipment category to which the CNC system belongs. Further, according to the machine

type, the applicable addresses are defined in different ways. The G-code list and the

modal group for a milling machine and a turning machine are summarized in Appendix

A. In the following, the interpreter is the module that has the function of interpreting the

various addresses, words, and grammar.



2.5 DESCRIPTION OF CODES

This table contains the information about the various codes we use in CNC systems and

their fuctions.

Table 2.2: summary of address groups based on CNC system function



2.6 SUMMARY

The interpreter plays the role of converting a user-edited part program into the internal

data format for execution. In order to understand the structure and the internal behaviour

of the interpreter, it is necessary to understand the structure of a part program and the

commands used therein.

In a CNC system, various co ordinate systems, such as the machine coordinate system,

work piece coordinate system, and local coordinate system, are supported for the

convenience of editing a part program and setting up the machine. Also, rotation,

mirroring, and scaling of a coordinate system are provided and by using

These functions it is possible to easily edit the part program.

This was the summary of how a CNC system works and it was basically the theory of

CNC systems and in the next upcoming sections we will also be describing to you how

our actual CNC system works and it also works in accordance with this theory. Actually

most of this work is done by our software named as MACH 3 and another LAZYCAM,

and they will be described in next section where we will be giving description of the

software and actual hardware.

So in this section we told you about the theory of CNC and we told how a CNC systems

works whatever is mentioned above are the steps on which any CNC relies to proceed

and now as far as our CNC is concerned the work and the mechanism mentioned above

in our case it’s all been done by MACH 3 which our controlling software so because of

this powerful software developed by ArtSoft all the above mentioned work is controlled

by mach 3 so we don’t have to worry about that we focused ourselves more towards

electronic work rather than on mechanical work or on software.

And in the coming section you will knowing about the detail of the design and much

about how the whole thing is related and is brought to work.


CHAPTER # 3

DETAILS OF THE DESIGN

Chapter # 3 Details of the Design

CHAPTER THREE

DETAILS OF THE DESIGN

3.1 BRIEFING

Our project which is a CNC carving machine is based on 3 axes. To carve something one

need to move in all the 3 dimensions to achieve the desired length, breadth and depth.

The trimmer which carves should be in a proper place to carve at an object.

The size of our project according to X and Y axis is 3.5’ x 3’. To move in such a long

direction certain components are installed which are discussed below:

Ball screws (of the same length of the size of structure)

Stepper motors

Gears

Chains

3.1.1 BALL SCREW

Ball screws are type of threaded rod on which a nut is with ball bearing inside to move

along the thread of the rod. (as shown in the Figure 3.1)

Figure 3.1: ball bearing moving in a ball screw



3.1.2 STEPPER MOTOR

We are using stepper motor of torque (12.1 N-m) enough for our structure to move

freely. It’s a Nema 23 motor (shown in Figure 3.2 & 3.3). We are using stepper motor

because of precision movement.

Figure 3.2: stepper motor NEMA 24

Figure 3.3: NEMA 23 dimensions



3.1.3 GEARS AND CHAINS

Gears are used to provide power to the ball screws to rotate. It is essential to choose right

size of the gear to transfer maximum power the screws. Chains help the power transfer.

They make bond between gears.

Figure 3.4: Gears of different sizes

Figure 3.5: Chains used between gears



3.2 DESCRIPTION:

The aim of the motor is to move the gantry in horizontal direction. The X-axis is, on

which the gantry is upon. Along the gantry is the Y-axis and vertical on the gantry which

moves up and down is the Z-axis. The movement of X-axis is the gantry itself moving.

The Y-axis movement is the horizontal movement of the trimmer. Z-axis is the vertical

movement of the trimmer which is in and out of the depth.

Figure 3.6: Axes on the structure

The nut of the ball screw is attached to the gantry wall so as the screw rotate the nut

makes the gantry to move in horizontal direction in such a way that when the screw move

clockwise the gantry moves forward and when the screw moves counter clockwise the

gantry in reverse direction.

Figure 3.7: X, Y& Z axis



3.3 X-AXIS MOVEMENT

In X-axis movement the ball screw is attached along the both side of the frame with the

nut sited with the wall of gantry so that balanced movement is achieved. A single motor

is attached in centre of the frame. A gear is attached on the motor and another on each

side of the ball screw. Chain is attached on all the gears and the motor so that power of

the motor is transferred to the ball screw.

Figure 3.8: Position of the ball screws


Ball

screw

Ball

screw


As the pulses are given to the stepper motor the motor rotates in steps resulting in the

rotation of ball screw. As the screw rotate the gantry will move forward and backward.

The gantry is supported on bigger wheels which move on tracks at the side wall of the

frame.

Figure 3.9: Illustrating X-axis movement


X-axis tracks that

supports wheels


3.4 Y-AXIS MOVEMENT

In Y-axis movement the ball screw is attached to the gantry with the nut fixed on the

trimmer box so that the box is moved along the gantry for Y axis movement. Another

motor is attached at the side of wall of the gantry beside the screw. Here also the motor

as well as the screw is attached with the gears on which the chain moves. This transfers

the power from motor to the ball screw.



Ball

screw


When the pulses are sent through the drive towards the stepper motor the motor rotates in

steps resulting in the movement of ball screw in clockwise and counter clockwise

direction. As the screw rotate the box on which the trimmer is attached move along the

side of gantry. The box is supported with bigger wheel on inside of the box which moves

along the track on the gantry

Figure 3.11: Illustrating Y-axis movement


Y-axis tracks that

supports wheels


3.5 Z-AXIS MOVEMENT

In Z-axis movement the ball screw is attached on the box of trimmer perpendicular to the

gantry and its nut is fixed with the trimmer. The motor of this screw is also attached to its

side. The same gears and chain setting is also made in this axis so that maximum power

is transferred to the screw.



Ball

screw


On receiving the pulse from drive, motor rotates which results in the same step wise

rotation of the screw in clockwise and counter clockwise direction. The rotation of screw

causes the trimmer to move in upward and downward direction perpendicular to side of

gantry. It results in different depths of carving. The Z-axis is supported by its screw itself

because there is not that much load to be carried to cause damage in screw.

Figure 3.13: Illustrating Z-axis movement

3.6 CALCULATION OF TORQUE

Torque that is required for the motion of the axis τr, that is increase by placing gear

(having more teeth) on the screws as the gear placed on the motor shaft. So the motor

torque τm increased as required for the motion.


Z-axis tracks that

supports wheels


τr = τm * N 3.1

Where,

τr = torque required for the motion

τm = motor torque

N= ratio of the gears teeth.

τr = 12.1 N-m

N = 4

τr = τm * N

τr = 12.1 * 4

τr = 48.4 N-m


CHAPTER # 4

SYSTEM HARDWARE

Chapter # 4 System Hardware

CHAPTER FOUR

SYSTEM HARDWARE

4.1 INTRODUCTION OF STEPPER MOTORS

Stepping motors fill a unique niche in the motor control world. These motors are

commonly used in measurement and control applications. Sample applications include

ink jet printers, CNC machines and volumetric pumps. Several features common to all

stepper motors make them ideally suited for these types of applications.

These features are as follows:

1. Brushless: Stepper motors are brushless. The commutators and brushes of

conventional motors are some of the most failure-prone components, and they create

electrical arcs that are undesirable or dangerous in some environments.

2. Load Independent: stepper motors will turn at a set speed regardless of load as long

as load does not exceed the torque rating for the motor.

3. Open Loop Positioning: Stepper motors move in quantified increments or steps. As

long as the motor runs within its torque specification, the position of the shaft is known

at all times without the need for a feedback mechanism.

4. Holding Torque: stepper motors are able to hold the shaft stationary.

5. Excellent response: to start-up, stopping and reverse.

One of the most significant advantages of stepper motor is its ability to be accurately

controlled in an open loop system. Open loop control means no feedback information

about the position is needed. This type of control eliminates the need for expensive

sensing and feedback devices such as optical encoders. Your position is known simply by

keeping track of the input step pulses.



4.2 WHY WE ARE USING STEPPER MOTORS?

The following point emphasis to use the stepper motor:

1. The rotation angle of the motor is proportional to the input pulse.

2. The motor has full torque at standstill (if the windings are energized).

3. Precise positioning and repeatability of movement since good stepper motors

have an accuracy of 3-5% of a step and this error is non cumulative from one step

to the next

4. Excellent response to starting/ stopping/ reversing.

5. Very reliable since there are no contact brushes in the motor. Therefore the life of

the motor is simply dependant on the life of the bearing.

6. The motors response to digital input pulse provides open-loop control, making the

motor simpler and less costly to the motor.

7. It is possible to achieve very low speed synchronous rotation with a load that is

directly coupled to the shaft

8. A wide range of rotational speeds can be realized as the speed is proportional to

the frequency of the input pulse

4.3 WHEN STEPPER MOTOR IS USED

A stepper motor can be a good choice whenever controlled movement is required, they

can be used to advantage n applications where you need to control rotation angle, speed,

position and synchronism.

Because of the inherent advantage listed previously, stepper motors have found their

place in many different applications. Some of these include printers, plotters, high-end

office equipment, hard disk drives, medical equipment, fax machines, automotive and

many more.



4.4 TECHNICAL DESCRIPTION

Stepper motors are electromechanical equipments converting electrical energy into

rotation movement. Pulses of electricity drive rotor connected shaft. They are connected

to stepper motor drives which have high switching capability. This driver gets pulses

from a digital controller and each pulse drives the shaft of the motor for a determined

angle. This little angle is called step angle and fixed for each motor. The speed direction

of the movement depends on pulse sequence and pulse frequency.

Figure 4.1: Basic shape of a stepper motor

The rotation has not only a direct relation to the number of input pulses, but its speed is

also related to the frequency of the pulse. Stepper motors vary in the amount of rotation

that the shaft turns each time when a winding is energized. The amount of rotation is

called step angle as mentioned before and vary from 0.9° degrees (1.8° degrees is more

common) to 90° degrees Step angle determines the number of step per revolution. A

stepper with a 1.8° degrees step angle must be pulsed 20 times (1.8° x 200 =360°) for the

shaft to turn one complete revolution sensitivity of stepper motors increases with the

number of steps in one revolution like its cost.

Obviously, a smaller step angle increases the accuracy of a motor, but stepper motors

have an upper limit to the number of pulses they can accept per second, heavy-duty

steppers usually have a maximum pulse rate (or step rate) of 200 or 200 steps per second,



so they have an effective high speed of one to three revolutions per second (60 to

180rpm).

Some smaller steppers can accept a thousand or more pulses per second, but they don’t

provide very torque and are not suitable as driving or steering motors. The stepper motor

coils are typically rated for a particular voltage. The coils ac as inductors when voltage is

supplied to them as such they don’t instantly draw their full current and in fact may never

reach full current at high stepping frequencies. The electromagnetic field produces by the

coil is directly related to the amount of current draw. The larger the electromagnetic field

the more torque the motors have the potential of producing. The solution to increasing

the torque is to ensure that the coils reach full current draw during each step.

Stepper motor can be views as electric motors without commutators. Typically, all

windings in the motor are part of the stator, and the rotor is either a permanent magnet or,

In the case of variable reluctance motors, a toothed block of some magnetically soft

material. All of the commutation must be handled externally by the motor controller, and

typically, the motors and the controllers are designed so that the motor may be held in

any fixed position as well as being rotated one way or the other. It should be noted that

stepper motors couldn’t be motivated to run at their top speeds immediately from a dead

stop. Applying too many pulses right off the bat simply causes the moor to freeze up. To

achieve top speeds, the motor must be gradually accelerated.

Actuation of one of the windings in a stepper motor advances the shaft. Continue to

apply the current to the winding and the motor won’t turn any more. In fact, the shaft will

be locked, as if brakes are applied. As a result of this interesting locking effect, you never

need to add a braking circuit to a stepper motor, because it has its own brakes built in. the

amount of breaking power of a stepper motor is expressed as holding torque.



4.5 STEPPER MOTOR APPLICATIONS

Stepper motors generally used in a variety of applications where precise position control

is desirable and the cost or complexity of a feedback control system is unwarranted

Here are few applications where stepper motors are often found:

Printers

CNC Machines

3D printer/prototyping machines

Laser cutters

Pick and place machines

Linear actuators

Hard disks

4.6 STEPPER MOTOR SPECIFICATIONS

NEMA 17, 23, and 34 frame sizes

3000 rpm max speed

1.8 deg step angle

Up to 1710 oz-in. (12.1 N · m) holding torque

200 counts/revolution resolution

NEMA 23 and 34 motor compatibility

Low profile 1 in. (25.4 mm) height design and easy mounting

Industrial construction



4.7 STEPPER MOTOR TYPES

4.7.1 VARIABLE RELUCTANCE(VR)

This type of stepper motor has been around for a long time. It is probably the easiest to

understand from a structural point of view. Figure 1 shows a cross section of a typical

V.R. stepper motor. This type of motor consists of a soft iron multi-toothed rotor and a

wound stator. When the stator windings are energized with DC current the poles become

magnetized. Rotation occurs when the rotor teeth are attracted to the energized stator

poles.

Figure 4.2: Cross-section of a variable reluctance (VR) motor.

4.7.2 PERMANENT MAGNET (PM)

Often referred to as a “tin can” or “canstock” motor the permanent magnet step motor is

a low cost and low resolution type motor with typical step angles of 7.5° to 15°. (48 – 24

steps/revolution) PM motors as the name implies have permanent magnets added to the

motor structure. The rotor no longer has teeth as with the VR motor. Instead the rotor is

magnetized with alternating north and south poles situated in a straight line parallel to the

rotor shaft. These magnetized rotor poles provide an increased magnetic flux intensity

and because of this the PM motor exhibits improved torque characteristics when

compared with the VR type.



Figure 4.3: Principle of a PM or tin-can stepper motor.

4.7.3 HYBRID (HB)

The hybrid stepper motor usually is more expensive than the PM stepper motor, but

provides better performance with respect to step resolution, torque and speed. Typical

step angles for the HB stepper motor range from 3.6° to 0.9° (100 – 400 steps per

revolution). The hybrid stepper motor combines the best features of both the PM and VR

type stepper motors. The rotor is multi-toothed like the VR motor and contains an axially

magnetized concentric magnet around its shaft. The teeth on the rotor provide an even

better path which helps guide the magnetic flux to preferred locations in the air gap. This

Further increases the detent, holding and dynamic torque characteristics of the motor

when compared with both the VR and PM types. Figure 1 shows a cross section of a

typical HB stepper motor.

The two most commonly used types of stepper motors are the permanent magnet and the

hybrid types. Generally speaking, the hybrid motor may be the better choice along with

reducing cost, for it offers better performance with respect to step resolution, torque and

speed.

Figure 4.4: Cross-section of a hybrid stepper motor.



Table 4.1: stepper motor types and its characteristics

Motor type characteristics PM VR Hybrid

Efficiency High Low High

Rotor Inertia High Low Low

Speed High High Low

Torque Fair Low High

Power O/P High Low Low

Damping Good Poor Poor

Typical Step Angle 1.8,15,30 7.5, 15, 30 0.18,0.45

4.8 STEPPER MOTOR DRIVE TYPES

4.8.1 UNIPOLAR STEPPER MOTOR

A unipolar stepper motor has one winding with centre tap per phase. Each section of

windings is switched on for each direction of magnetic field. Since in this arrangement a

magnetic pole can be reversed without switching the direction of current, the

commutation circuit can be made very simple (e.g. a single transistor) for each winding.

Typically, given a phase, the centre tap of each winding is made common: giving three

leads per phase and six leads for a typical two phase motor. Often, these two phase

commons are internally joined, so the motor has only five leads.

A microcontroller or stepper motor controller can be used to activate the drive transistors

in the right order, and this ease of operation makes unipolar motors popular with

hobbyists; they are probably the cheapest way to get precise angular movements.


http://en.wikipedia.org/wiki/Microcontroller


Figure 4.5: Unipolar stepper motor

(For the experimenter, the windings can be identified by touching the terminal wires

together in PM motors. If the terminals of a coil are connected, the shaft becomes harder

to turn. One way to distinguish the centre tap (common wire) from a coil-end wire is by

measuring the resistance. Resistance between common wire and coil-end wire is always

half of what it is between coil-end and coil-end wires. This is because there is twice the

length of coil between the ends and only half from centre (common wire) to the end.) A

quick way to determine if the stepper motor is working is to short circuit every two pairs

and try turning the shaft, whenever a higher than normal resistance is felt, it indicates that

the circuit to the particular winding is closed and that the phase is working.

4.8.2 BIPOLAR STEPPER MOTOR

Bipolar motors have a single winding per phase. The current in a winding needs to be

reversed in order to reverse a magnetic pole, so the driving circuit must be more

complicated; typically with an H-bridge arrangement (however there are several off the

shelf driver chips available to make this a simple affair). There are two leads per phase,

none are common.

Static friction effects using an H-bridge have been observed with certain drive topologies

because windings are better utilized, they are more powerful than a unipolar motor of the

same weight. This is due to the physical space occupied by the windings. A unipolar

motor has twice the amount of wire in the same space, but only half used at any point in


http://en.wikipedia.org/wiki/H-bridge


time, hence is 50% efficient (or approximately 70% of the torque output available).

Though bipolar is more complicated to drive, the abundance of driver chips means this is

much less difficult to achieve.

An 8-lead stepper is wound like a unipolar stepper, but the leads are not joined to

common internally to the motor. This kind of motor can be wired in several

configurations:

Unipolar.

Bipolar with series windings. This gives higher inductance but lower current per

winding.

Bipolar with parallel windings. This requires higher current but can perform

better as the winding inductance is reduced.

Bipolar with a single winding per phase. This method will run the motor on only

half the available windings, which will reduce the available low speed torque but

require less current.

Figure 4.6: Bipolar stepper motor



4.8.3 UNIPOLAR VERSUS BIPOLAR

Permanent magnet and hybrid stepping motors are available with either unipolar or

bipolar or bifilar windings. The choice between using unipolar or bipolar drive system

rests on issues of drive simplicity and power to weight ratio.

Bipolar motors have approximately 30% more torque than an equivalent unipolar motor

of the same volume. The reason for this is that only one half of a winding is energized at

any given time in a unipolar motor. A bipolar motor utilizes the whole of a winding when

energized. The higher torque generated by a bipolar motor does not come without a price.

Bipolar motors require more complex control circuitry than unipolar motors. This will

have an impact on the cost of an application.

If in doubt, a unipolar motor or bifilar motor are good choices. These motors can be

configured as a unipolar or bipolar motor and the application tested with the motors

operating in either mode.

Table 4.2: Comparison b/w Unipolar & Bipolar

Unipolar Bipolar

Unidirectional current flow Bidirectional current flow

Half winding energized at a time Whole winding energized at a time

Less torque as compare to bipolar More torque as compare to unipolar

Low cost High cost

Simple drive system Complex drive system

Usually five or six wires Usually four wires



You can identify weather the stepper motor is Unipolar or Bipolar by the following:

1- Symbol

2- No. of Wire

3- No. of Coil

4.9 STEPPER MOTOR WIRING SCHEMES

Most stepper motors have 6 wires; however there are motors with 4, 5, or 8 wires also.

Each of the four coils is made up of one length of wire with two ends. One end is called

live and the other end is called common. In a five wire stepper motor all four commons

are joined together, in a six wire stepper motor two pairs of common wires are joined

together, and in an eight wire stepper motor none of the four common wires are joined

together.

Figure 4.7: wire stepper motor configuration

Figure 4.8: Motor standard wire color



If you don’t have a schematic diagram for your stepper motor- for example if it was

salvaged from an old printer – it is very easy to work out on motor which wire is which!

You can identify the stepper motor wiring sequence by using the following

1- Standard color

2- Resistance measurement

Systematically use a multimeter to measure the resistance between different pairs of

wires. All four coils will have near identical resistance if they did not the motor

would not function properly. Therefore if the pair of wires is a common, why is this?

Because two live wires have two coils between them whereas a common and a live

have just one coil between them

When you have identified the common wires, be sure to label them.

Shortcut for finding proper wiring sequence:

Connect the center tap(s) to the power source (or current-limiting resistor) connect

the remaining 4 wires in any pattern. If it does not work, you only need try these 2

swaps…

1 2 4 8 - (arbitrary first wiring order)

1 2 8 4 - (switch end pair)

1 8 2 4 - (switch middle pair)

You are finished when the motor turns smoothly in either direction. If the motor turns in

the opposite direction from desired, reverse the wires so that ABCD would become

DCBA.



4.10 STEPPER MOTOR STEPPING MODES

Stepper motor drivers often have different modes of operation. These different modes

determine in what sequence the coils are energized to make the motor shaft move

appropriately. There are four types of these stepping modes. However, only three of the

excitation modes are common in most stepper drivers.

4.10.1 ONE PHASE DRIVE / SINGLE STEP DRIVE / WAVE DRIVE

The simplest mode turns one coil ON at a time. 48 pulses are needed to complete one

revolution. Each pulse moves rotor by 7.5 degrees. The following sequence has to be

repeated 12 times for motor to complete one revolution.

Table 4.3 Wave Driving sequence

Pulse Coil a1 Coil b1 Coil a2 Coil b2

1 ON

2 ON

3 ON

4 ON

4.10.2 TWO PHASE DRIVE / HIGH TORQUE DRIVE / FULL DRIVE

High power / precision mode turns ON two coils on at a time. 48 pulses are needed to

complete one revolution. Each pulse moves rotor by 7.5 degrees. The following sequence

has to be repeated 12 times for motor to complete one revolution.



Table 4.4 Full Step Driving sequence


1 ON ON

2 ON ON

3 ON ON

4 ON ON

4.10.3 TWO PHASE DRIVE / HALF STEP DRIVE / DUAL DRIVE

Stepping is doubled and motor needs 96 pulses to complete one revolution. Each pulse

moves rotor by approximately 3.75 degrees. Notice the mix of single stepping mode

(lighter green) and high torque mode (darker green).

Table 4.5 Half Step Driving sequence


1 ON

2 ON ON

3 ON

4 ON ON

5 ON

6 ON ON

7 ON

8 ON ON



4.10.4 MICROSTEPPING

The micro-stepping mode is the most complex of all the stepping modes. That is why

some stepper drivers only offer full and half step modes. Micro-stepping is when the

current applied to each winding is proportional to a mathematical function, providing a

fraction of a full step. The most common divisions are 1/4th, 1/8th, 1/10th, etc. However,

there are some drivers that provide up to 1/256th of a full step. Micro-stepping provides

greater resolution and smoother motor operation. This is very advantageous as it reduces

The need for mechanical gearing when trying to achieve high resolution. However,

micro-stepping can affect the repeatability of the motor. It is important to take into

consideration the step modes and how best to utilize them when designing the CNC

router drive system. It is also very important when choosing a stepper motor driver.

Some drivers will micro-step more smoothly than others.

Table 4.6 Comparison of stepper motor drive sequence

Name Sequence Polarity Description

Wave drive,

One-Phase

0001

0010

0100

1000

---+

--+-

-+--

+---

Consumes the least power. Only one phase is energized

at a time. Assume positional accuracy regardless.

Assures positional accuracy regardless of any winding

imbalance in the motor.

Hi-Torque,

Two-Phase

0011

0110

1100

1001

--++

-++-

++--

+--+

This sequence energizes two adjacent phases, which

offers an improved torque-speed product and greater

holding torque.

Half-Step 0001 ---+ Effectively doubles the stepping resolution of the


http://www.cncroutersource.com/cnc-drive.html


0011

0010

0110

0100

1100

1000

1001

--++

--+-

-++-

-+--

++--

+---

+--+

motor, but the torque is not uniform for each step.

(Since switching occurs between Wave Drive and Hi-

Torque with each step, torque alternates each

step).This sequence reduces motor resonance which

can sometimes cause a motor to stall at a particular

resonant frequency. Note that this sequence is 8 steps

The above table describes 3 useful stepping sequences and their relative merits. The

polarity of terminals is indicated with +/-. After the last step in each sequence the

sequence repeats. Stepping backwards through the sequence reverses the direction of the

motor.

Figure 4.9 Excitation sequence for driving modes


CHAPTER # 5

CNC ELECTRONICS

Chapter # 5 CNC Electronics

CHAPTER FIVE

CNC ELECTRONICS

5.1 INTRODUCTION

CNC electronics are a vital part of any CNC machine aside from the motors and CNC

controllers; there are many electronic components as that assist in the machine operation.

Figure: 5.1: Components of the CNC

There are many electronic aspects of a CNC router that are vital to its function. Things

such as limit and proximity switches, motor wiring, correct cable sizing and selection etc.

These features are, in my opinion, vital to building a reliable machine. Yet many people

neglect these feature because of lack of “know how” or budget. Many of these “add-ons”

cost only pennies to install and could save either your machine or the piece you are

working on. For the most part, adding these components is by no means difficult.

There are also some CNC electronic features that are not often required. Such as manual

pulse generators, home and e-stop buttons, touch-off tool sensors etc. These things may

or may not be essential to the machine, depending on the user, but do increase user



There are the following objects that are included in the overall system of the CNC

machine. They are:

Wirings Power supplies

Limit switches Breakout board

Buttons & Switches Connectors

Figure: 5.2 Electronic components of the CNC

5.2 MOTION CONTROL

Motion control can be applied in many categories such as robotics, CNC operated

machine tools and kinematics where motion control in kinematics are usually simpler. It



can be mainly use now days with packaging, textile, assembly instructions, printing and

semiconductor production. The hardware of a motion control system usually consists of

derive system, motors, controller box, computer. CNC machines used programmable

commands to make input motion to the machine easier rather than using cranks or other

conventional machine tools almost all CNC machine tools can have programmable

motion types whether it would be rapid. The amount of motion the feedback rate in the

axis to move.

Motion control is the simplest function of any CNC machine. It is precise consistent and

automatic system of control. CNC equipment need two or more modes of direction to

which they are called axes .there are two common modes that are linear are rotary.

5.3 ELECTRONIC SYSTEM OVERVIEW

Figure: 5.3: Electronic system overview



5.4 DESCRIPTION OF BLOCK DIAGRAM

The block diagram of the system consist of laptop which sends signals to break out board

and these signals are given to motor drives and motors move to our desired positions.

Finally the trimmer is used to carve the things on wooden pieces.

Figure: 5.4: Block Diagram


Laptop

Breakout board

Motor

Driver

Motor

Driver

Motor

Driver

Motor

Motor

Motor

Power Supply

Parallel Port cable

Trimmer


5.5 SYSTEM FLOW CHART

Figure: 5.5: System flow chart



5.6 CONTROL UNIT (CU) OF OUR MACHINE

The Control Unit (CU) is the brain of a CNC system. A CU completes the all important

link between a computer system and the mechanical components of a CNC machine. The

controller's primary task is to receive conditioned signals from a computer or indexer and

interpret those signals into mechanical motion through motor output. There are several

components that make up a controller and each component works in unison to produce

the desired motor movement. The word “CU or controller” is a generic term that may

refer to one of several devices, but usually refers to the complete machine control system.

This system may include the protection circuitry, stepper or servo motor drivers, power

source, limit switch interfaces, power controls, and other peripherals. Owners, operators,

designers, and builders of CNC devices should understand the tasks performed by these

components and how they affect machine performance. There are three primary CNC

controller components that make up a CNC controller, the power supply unit, the

circuitry protection system, and the motor driver.

5.6.1 THE POWER SUPPLY UNIT

The same conditions are true for CNC devices. They require a low-voltage

communication line, through which the computer tells the machine what to do, and a

power source that provides the power for moving, cutting, and other such operations. A

power converter, usually referred to as the “power supply unit (PSU),” is often used to

change the form of the supplied power from alternating current (AC) from the power

grid, to direct current (DC) that is more easily used by the machine’s drive motors. The

power supply handles large voltages and currents that could be harmful to the NC

circuitry. Therefore, the power source, motor drivers, and motors are often separated



from the computer with a circuitry protection system that isolates surges in electrical

power. The power supply that we are using has max ratings of:

13.38 volts (offload)

29 amp

5.6.2 THE CIRCUITRY PROTECTION SYSTEM

The circuitry protection system contains a breakout board to isolate signals from the

computer, distribute the signals to the desired drivers, and also allows easy hook up of

peripherals such as limit switches that feed information back to the computer. Fuses are

also part of the circuitry protection system. Fuses could save the equipment in case of

electrical spikes, shorts, or faulty wiring.

A low-voltage communication signal passes from the computer through the breakout

board unchanged to the motor drivers. This isolated your computer from the CNC

controller circuit but allows the signals to carry through to your motor drivers.

5.6.3 THE MOTOR DRIVERS:

The motor drivers receive the communication signal and then coordinate pulses of the

desired current and voltage to elicit the movement in the drive motors. The motor drivers

may communicate position information one way to the motor (open loop system), or send

and receive position information (closed loop system), depending on the user’s choice of

drive system. More on these systems may be found in the drivers sections.



Figure 5.6: CU of our project

The CU performs all the necessary information that are sent by the laptop and it performs

the movement of the motors and reach to our desired position and at last the trimmer cuts

the designs on wooden pieces. Some carve results have been shown at the end of the

report.

5.7 STEPPER MOTOR DRIVER IMPLEMENTATION

The signals:

The signal lines coming from the computer operate on 5V DC supplied by the computer

communication port, and is a square wave form called a Transistor-to-Transistor Logic

(TTL) signal. This signal is essentially a series of small pulses from 0V to +5V that

represent 0’s and 1’s in a binary computer language. This signal is a form of a Pulse-

Width Modulated (PWM) signal where the length of the pulse is varied to indicate



information. The width of the pulse determines the binary code sent; either a “0” or a “1”

as communicated by the computer and interpreted by the motor driver. More on the

signals may be found in the signals page.

The signal from the computer to the breakout board is the same as that from the breakout

board to the motor driver. Remember, the breakout board provides circuit protection and

signal distribution. Therefore, the signal coming out of the breakout board is also a 5V

TTL signal of the same form. However, as discussed previously, the signal after the

driver has been conditioned as needed to provide the large “move” voltage and current

needed to drive the machine

Summary Of Components:

The computer generates the signal which passes through the breakout board. The motor

drivers and limits switches hook up to the breakout board. The power supply unit

provides the correct voltage and current required by the motor drivers and the motors.

The motor drivers receive the position signals from the breakout board and supply the

correct power to the motors to make them rotate to the correct positions.



Stepper driver board with L297 L6203:

This is a Bipolar stepper driver 4A - 42V for 1 Axis

Figure 5.7: drive circuit for motors

Working of Stepper driver board with L297 L6203:

This Step motor controller uses the L297 and L6203N driver combination; it can be used

as stand alone or controlled by microcontroller. It is designed to accept step pulses at up

to 25,000 per second. An on-board step pulse generator can be used if desired (40-650

pps range). Single supply operation is standard .All eight inputs are pulled up to +5V by



RP1 (4.7K) and are buffered by 74HC244. The output driver is capable of driving up to

2Amp into each phase of a two-phase bipolar step motor. The motor winding current is

limited by means of a 35KHZ-chopper scheme. The potentiometer (R6) is for varying the

winding currents. The nature of the chopping scheme eliminates the need for external

current limiting resistors on the motor windings; this simplifies connections and

increases efficiency.

A useful of this design is the “idle” current reduction mode. The amount of reduction is

fixed at approximately 50% from whatever the running current is set at. Similarly, the

motor current can be commanded to shut entirely off.

The internal +5V voltages required for operation are derived from the stepper motor

supply. The motor supply voltages should be at least 9V, but must never exceed 32V.

The motors currents and voltage must be adjusted the help of potentiometers to maintain

a certain speed and torque to achieve our desired movements.L6203 is efficiently used

for power driving we have used it for high current because we are using high current

motors just have a precise movement of our structure. If we want to move to higher

currents we have to use the other Mosfets to drive them smoothly.



Communication with PC:

Breakout boards are common electrical components that take a bundled cable and “break

out” each conductor to a terminal that can easily accept a hook-up wire for distribution to

another device. They are a common item in electronic projects and enable easy, clean

installation of electronic devices.

The breakout board is positioned between your computer or indexer and the motor

drivers and serves two purposes in the CNC control system: circuit protection and signal

distribution.

Inside the controller box, we see a direction signal and a step signal being distributed

from the breakout cirrus board to each driver. A common ground line is distributed in the

same fashion. A power source also distributes power to each driver.

Most breakout devices are passive devices that do not offer circuit protection, such as

that shown at the top of this article. For CNC applications, it is highly recommended that

you use an active breakout device with some type of circuitry protection. The most

effective solution involves the use of opto-isolators that use pulses of light to transmit

information across an air gap. Others will have fuses that prevent excessive current

passing through your computer.

Some breakout devices allow you to distribute the power from the power source to the

motor drivers. Others simply distribute the signals and require direct hook-up from the

power source to the drives, bypassing the actual board. Some boards require external

power, and if your power source. Be sure to read the manufacturer’s specifications

carefully and plan accordingly



Breakout board:

Figure 5.8 breakout board PCB

Limit switches:

A mechanical limit switch interlocks a mechanical motion or position with an electrical

circuit. A good starting point for limit-switch selection is contact arrangement. The most

common limit switch is the single-pole contact block with one NO and one NC set of

contacts; however, limit switches are available with up to four poles.

Limit switches also are available with time-delayed contact transfer. This type is useful

in detecting jams that cause the limit switch to remain actuated beyond a predetermined

time interval.



Other limit switch contact arrangements include neutral-position and two-step. Limit

switches feature a neutral-position or center-off type transfers one set of contacts with

movement of the lever in one direction. Lever movement in the opposite direction

transfers the other set of contacts. Limit switches with a two-step arrangement, a small

movement of the lever transfers one set of contacts, and further lever movement in the

same direction transfers the other set of contacts.

Maintained-contact limit switches require a second definite reset motion. These limit

switches are primarily used with reciprocating actuators, or where position memory or

manual reset is required. Spring-return limit switches automatically reset when actuating

force is removed.

Figure 5.9: diagram of limit switches

In the simplest case, a switch has two conductive pieces, often metal, called contacts,

connected to an external circuit, that touch to complete (make) the circuit, and separate to

open (break) the circuit. The contact material is chosen for its resistance to corrosion,

because most metals form insulating oxides that would prevent the switch from working.


http://en.wikipedia.org/wiki/Oxide

http://en.wikipedia.org/wiki/Electrical_insulation

http://en.wikipedia.org/wiki/Corrosion

http://en.wikipedia.org/wiki/Electric_circuit

http://en.wikipedia.org/wiki/Metal


5.8 COMPUTER

We purchase a laptop for our work its specifications are:

Pentium 4 (Compaq)

2.4 GHz

1 gb ram

Parallel port

Lan and video card

Fully installed with the required softwares

Figure 5.10: laptop



5.9 STEPPER MOTOR DRIVER

The stepper motor driver is made with the combination of l297, l298 & l6203.The l297 is

a logic driver while l6203 is a power driver to drive our motors.

Figure 5.11: l6203 & L297 driver

5.10 STEPPER MOTORS

Motor type : Bi- phase pm(permanent magnet) motor

Drive system: bipolar/unipolar

Step angle: 1.8 degrees

Rotation: 200 pulses



5.10.1 FUNCTIONS

Smooth drive function

Automatic current down

Automatic current off

Switch function

5.10.2 WAVE SEQUENCE OF STEPPER MOTOR

Figure 5.12: wave Timing output



5.11 TRIMMER /MINI ROUTER

A router is a tool used to route out (hollow out) an area in the face of a relatively hard

work piece, typically of wood or plastic. The main application of routers is in

woodworking, especially cabinetry.

Like most everything else involving CNC routers, there are a variety of spindle types out

there. Some made for wood, some made for metal, etc. As usual there are many factors

involved when choosing a spindle for either your pre-build machine, or your homemade

CNC machine. We are using a Sencan router that is:

Figure 5.13: sencan router for carving

It is extremely useful for small wood works.


http://en.wikipedia.org/wiki/Cabinet_making

http://en.wikipedia.org/wiki/Woodworking

http://en.wikipedia.org/wiki/Tool


Features:

• Sencan 560602

• No load speed is 30000r/min.

• Rated input power is 500W

• Collet chuck diameter is 6mm

Contents:

• This is our electrical trimmer or cutting tool

• Details are given above.

• This will carve wood and this will be held on the router.

• It will carve with the help of drilling bits different bits are of different uses.

Figure 5.14: router bits for carving

The above bits are used for different shapes carving upon a wooden block. We have used

three different set of bits to have different kinds of designs. Moreover we can have some

other bits for other designing purpose.


CHAPTER # 6

SYSTEM SOFTWARE

Chapter # 5 System Software

CHAPTER SIX

SYSTEM SOFTWARE

6.1 SYSTEM SOFTWARE

After all the work and construction in the hardware section some sort of software are

must to be used for interfacing the machine or hardware with the computer so for that

purpose we went through many softwares.

The whole software system is based on three softwares, the CAD software, CAM

software and controlling software. Our system will work such like this that whatever

shape design comes in our mind, it will be drawn/ designed in the CAD software. Then

this drawing to be imported to the CAM software, or we can use any image file too. Then

G-code generated through the CAM software will be imported to our controlling

software. The overall software process is shown in figure below:

Figure 6.1: whole process of system software


CAD CAM Mach3


6.2 CAD SOFTWARE

Computer Aided Design is the use of technology for the process of design. It provides the

user with input-tools for the purpose of streamlining design processes. We will make any

shape or design according to our requirement on the Auto CAD.

CAD environments often involve more than just shapes. As in the manual drafting of

technical and engineering drawings, the output of CAD must convey information, such as

materials, processes, dimensions, and tolerances, according to application-specific

conventions.

CAD may be used to design curves and figures in two-dimensional (2D) space; or

curves, surfaces, and solids in three-dimensional (3D) objects.

CAD softwares are not only used in CNC drawings but this combination of CAD CAM

and CNC is making a lot of advancement in many fields.

Figure: 6.2: sample design made by using CAD software


http://en.wikipedia.org/wiki/3D_computer_graphics

http://en.wikipedia.org/wiki/2D_computer_graphics

http://en.wikipedia.org/wiki/Engineering_tolerance

http://en.wikipedia.org/wiki/Dimension

http://en.wikipedia.org/wiki/Material

http://en.wikipedia.org/wiki/Engineering_drawing

http://en.wikipedia.org/wiki/Technical_drawing

http://en.wiktionary.org/wiki/drafting


Uses of CAD software

Cad is used to design cars and their engines , mobile phones ,

homes and by architectures , buildings and mega structures are

somewhere also designed by using CAD softwares almost

everything that is first imagined is then made on computer using

CAD softwares and then it goes into manufacturing.

6.3 CAM SOFTWARE

Computer Aided Manufacturing is the use of computer software to

control machine tools and related machinery in the manufacturing

of work pieces. CAM may also refer to the use of a computer to

assist in all operations of a manufacturing plant, including

planning, management, transportation and storage.

Here we use CAM software to convert our design into the graphical code (G-Code). This

is then imported to our controlling software. The software we going to use as our cam

software is LAZYCAM.

Its purpose is to import standard dxf, cmx, and other file types to allow those that do not

use CAM programs to more easily generate G-code to be run under Mach3.

We can import CAD designs having spesific formats or can import image files ( bitmap ,

jpeg ) .


Figure 6.4: logo of LazyCam

Figure 6.3: logo of AutoCAD

http://en.wikipedia.org/wiki/Manufacturing

http://en.wikipedia.org/wiki/Machine_tool

http://en.wikipedia.org/wiki/Computer_software


CAM software breaks the design into the chains, entities so that G-Code is then

generated according to the parameters.

Then the G-code generated from CAM is posted to the Mach3 which we are using as

controlling software.

6.4 CONTROLLING SOFTWARE

After a piece of work we have chosen our controlling software. We have considered

number of softwares and Mach3 developed by ARTSOFT was supposed to be the most

suitable among all the details of Mach3 are given below:


Figure 6.5: Environment of LAZYCAM


6.4.1 MACH3

Mach 3 will be used for carving and controlling. Mach 3 was developed by ArtSoft in

2001 and it is known to be as the best pc based CNC software on the internet claimed by

tens of thousands of its users.

The Mach series of software was originally developed for the home hobbyist, but has

quickly turned into one of the most versatile control packages for industrial use as well.

Figure 6.6: Environment of Mach3



FEATURES OF MACH3

Converts a standard PC to a fully featured, 6-axis CNC controller

Allows direct import of DXF, BMP, JPG, and HPGL files through LazyCam

Visual G-code display

Generates G-code via LazyCam or Wizards

Fully customizable interface

Customizable M-Codes and Macros using VBscript

USES OF MACH3

It is used in many applications for example:

• It is used in lathes

• it is also used for milling purposes

• It is also used in laser works

• It is well used in plasma works.

• It is also used in gear cutting.


CHAPTER # 7

RESULT AND DISCUSSION

Chapter # 7 Result And Discussion

7.1 RESULT:


Figure 7.1: Carved Result 1



7.2 DISCUSSION:

As we all know that we are not perfect and specially at our level i.e. student level we

usually make so much blunders so we did the same as we were in learning process. We

faced so many difficulties during different phases of our project and they are discussed

below:

7.2.1 MECHANICAL ISSUES:

As our mechanical is the most attractive thing in our project so I would like to mention

the issues that we had faced during making of our mechanical.

The first issue aroused that how we should fix our gears and how we will couple

it with the motors for our desired movement we took an idea from the chain

spocket of bike that how a small motor can lift such a heavy weight .So we

adopted the same idea.

Next the issue aroused how to choose the motors that can lift the weight of about

160 kg of iron, and then we selected NEMA 23 motors that are specially used for

CNC.

Then the issue was how to calculate the torque and how should synchronise it

with our structure so we can move it smoothly for this we used hit and trial

method.

The next issue was that how we should couple the motors with the motors we

tried so many things and at last we concluded to use chain mechanism.



7.2.2 ELECTRONIC ISSUES:

The main issue was that how to drive the motors either we should use proper

drives or we should make by our own but at the end with the motivation of our

internal advisor we made it by our own.

The next issue was that how parallel port will give signals to our motors because

parallel port does not give enough voltage level to the driver so we used external

supply.

The next issue was that how to provide air flow to the drives because ICs were

dissipating lots of heat.

7.2.3 SOFTWARE ISSUES:

The most important issue was that we are using the demo version of software so

we are not able to use all its features.

We had some difficulty in managing the settings of the software because it’s a

professional software but our internal advisor really motivated us


CHAPTER # 8

FUTURE ENHANCEMENT & CONCLUSION

Chapter # 8 Future Enhancement & Conclusion

8.1 FUTURE ENHANCEMENT:

In future you can switch to:

Camera to take any data image as input

PLC (Programmable Logic Controller)

Increase object hardness (up to metal)

HMI (Human Machine Interface)

Machine Downtime Monitoring

Multiple Production System

Pneumatic Mechanical

Auto Tool change

Micro stepping

Laser Cutting

Error Display

Increase Axis


Chapter # 8 Future Enhancement & Conclusion

8.2 CONCLUSION:

We have finally achieved our desired results which we want to have at the end of

year.

Now we are looking forward to get our full mechanical structure more precise

and more accurate.

We have achieved our conditions of the project as well.

We have learnt a lot during this project we came to know what CNC (computer

numerically controlled) machine is.

We have seen its implementation in industries and its vital uses in industries

We got an idea about image processing during it.

We got an idea how parallel port can control the motors

We have distinguished how machines are more handy than human hands.

At last I would like to say this project has changed our level of knowledge and it

has increased so much by doing everything by our own.


References

REFERENCES

[1] Working of CNC, CNC Machine blog, , http://www. cncmachines .com

[2] Structure Idea, About CNC, http://www. cnc masters.com/

[3] About CNC ,Ivan Irons, http://www.ivanirons.com

[4] Mechanical structure, design, http://www.cncdudez.co.uk

[5] Software Demo, Artsoft co., http://www.artsoft.com

[6] Stepper motor Specification, Nema 23, http://www.stepperworld.com

[7] Controlling software guide, Artsoft,

http://www.machsupport.com/documentation.php

[8] About Electronic Circuit, CNC information,

http://www.cncinformation.com

[9] About motor coils, Probotics, http://www.probotics.org

[10] About Drive circuitry, cuteminds, http://www.cuteminds.com


http://www.cuteminds.com/

http://www.probotics.org/

http://www.cncinformation.com/

http://www.machsupport.com/documentation.php

http://www.stepperworld.com/

http://www.artsoft.com/

http://www.cncdudez.co.uk/

http://www.ivanirons.com/

http://www.cncmasters.com/

http://www.cncmachines.com/

APPENDICES

APPENDICES

APPENDIX 1:

Work Distribution

i

APPENDICES

APPENDIX 2:

ii

APPENDICES

APPENDIX 3:

Cost Analysis

Total cost of Mechantron carver is approximate Rs 109,999/-. It is quiet cost efficient as

well. The cost is distributed throughout the project in following way

iii

APPENDICES

APPENDIX 4:

Mechanical Structure of Mechantron

iv

DATASHEETS

Mechantron Carver

Documents

Transcript of Mechantron Carver