Mp-i Unit-III Shaper 24 Aug 2014 a b Amale

UNIT – III SHAPER

A B AMALE, Deptt.of Mechanical , YCCE

Shaping It uses a single point

cutting tool moved

linearly relative to the

workpart

• A simple machining

operation where flat

surfaces are

produced along the

length of the work

piece

• Work piece to be

machined are smaller


SHAPER

Figure :- Components of a shaper

Process of removing metal from surface by the use of a single point

cutting tool held in ram that reciprocates the tool in a linear direction

across the work piece held on the table of the machine A B AMALE, Deptt.of Mechanical , YCCE

Working principle of a SHAPER MACHINE


Working principle of a SHAPER MACHINE

In case of a shaper , the Job is rigidly held in a suitable device like a

vice which is directly clamped on the machine table

The Tool is held in the Tool Head mounted on the ram of the machine .

This ram reciprocates to and fro and in doing so , makes the Tool to cut

the material in the forward stroke.

No cutting of material takes place during the return stroke of the ram .

Hence it is termed as Idle stroke.

The Job is given as indexed feed ( equal amount after each cut ) in a

direction normal to the line of action of the cutting tool.


PARTS OF SHAPER MACHINE


PARTS OF SHAPING MACHINE

Base – It is a heavy and robust cast iron body which supports the

machine where all parts are mounted.

Column - It's a housing for the operating mechanism and principal

support for all other component parts.

.

Ram - The ram is the reciprocating member of the shaper. It slides

on the accurately machined dovetail guide ways on the top of the

columns and is connected to the reciprocating mechanism.

Crossrail - It is a heavy cast iron construction , attached to the

column at its front on the vertical guide ways. It carries two

mechanisms ; one for elevating the table and the other for cross

traverse of the table.

Vice - It is job holding device and is mounted on the table. It holds

and supports the work during operation.


Tool head:

It also provides the vertical and angular feed movement to the tool

and allow tool to lift automatically to provide relief during return stroke.

It is a device in which it holds the tool. It can slide up and down with

the help of feed screw for adjusting the tool for depth of cut without

changing the table height. and can be swing to a desired angle to set

the tool at a desired position for the operation.

PARTS OF SHAPING MACHINE


PARTS OF SHAPING MACHINE Tool head:


The tool post and the tool slide can be angled as seen below. This allows

the shaper to be used for different types of work

• DIA A: The tool

post has been

turned at an angle

so that side of the

material can be

machined

• DIA B: The tool

post is not

angled so that

the tool can be

used to level a

surface.

• DIA C: The top

slide is slowly feed

into the material

so that a ‘rack’ can

be machined for a

rack and pinion

gear system. A B AMALE, Deptt.of Mechanical , YCCE

Shaper : Table / Machine Table Support

Table – It is made of cast iron and has a box type construction . cross

rails are mounted through which it moves up and down on ways on the

column face and cross feed to allow positioning of the work to the tool.

T-slots are provided on its top for securing the work to it.


Size of the shaper is mainly determined by the maximum length of cut or stroke

it can make.

Size and Specification of a Shaper


Forward stroke is the cutting stroke. Return stroke is the non-cutting stroke

Stroke starts slightly before the work piece (a) = approach of the tool

and ends after the work piece (b) = tool over- travel

Total stroke length = l + a+ b


1. According to the type of mechanism used for

giving reciprocating motion to the ram :

1. Crank Type.

2. Geared Type.

3. Hydraulic type.

Classification of Shaper :


2. According to position and travel of ram

a) Vertical type of shaper- The ram holding the tool

reciprocates in a vertical plane. it is also possible to swivel the ram about the vertical in vertical plane on either side of vertical axis .The work table of a vertical shaper can be given an extra rotary movement in addition to the other movements of a standard shaper table.

b) Horizontal type of shaper- Here the ram reciprocates in a horizontal plane.

c) Traveling head type- It is specially designed for machining heavy and large workpiece which cannot be easily held on table. Ram is so designed that in addition to reciprocating movement it also carries cross movement to provide necessary feed.


3. According to type of design of the table

Standard Shaper- The table has only two movements (plain) vertical and horizontal.( X&Y )

Universal Type- In universal shaper in addition to the two movements provided on the table of standard shaper ,the table can be swivelled about an axis parallel to the ram ways and the upper portion of the table can be tilted about a second horizontal axis perpendicular to the first axis. ( X,Y & Z )


4. According to the type of cutting stroke

Push type- This is the most general type of shaper

used in common practice. The metal is removed

when the ram moves away from column.

Draw type- The metal is removed when the ram

moves towards the column of the machine.


Common Mechanism : Slider Crank Chain

19

This form of mechanism consists of a crank, a connecting rod and a slider.

A crank and slider mechanism changes rotary to reciprocal motion or vice

versa. In I.C. engine the reciprocating motion of the piston

caused by exploding fuel is converted into rotary motion as the connecting-

rod moves the crankshaft around.

An air compressor uses this principal in reverse - an electric motor turns

the crankshaft and the piston moves up and down to compress the air


Slider-Crank Chain


SHAPER : Driving Mechanisms

•Quick return mechanisms are used in machine tools

such as shapers and power driven saws for the purpose

of giving the reciprocating cutting tool, a slow cutting /

forward stroke and a quick non cutting / return stroke

with a constant angular velocity of the driving crank.

Quick return motion mechanisms

1. Crank and slotted lever quick return motion mechanism

2. Whitworth quick return motion mechanism

3. Hydraulic Mechanism

types of quick return motion mechanisms used in Shaper :


A KINEMATIC DIAGRAM OF A SHAPING MACHINE showing

Crank and slotted lever quick return motion mechanism


Quick return mechanism – working principle

Crank 1 : which rotates about

fixed link 2

Oscillating link 3 :

Slider 4 : reciprocates in

oscillating slotted lever.

Slider has both sliding as

well as rotary motion.

At the bottom of the slotted arm, the peg is fixed.,

along which slotted arm sweeps by certain angle.

By changing the length of crank , ram stroke can

be changed

Bull gear rotates at uniform speed which drive

the crank ,but ram speed is varying A B AMALE, Deptt.of Mechanical , YCCE

Quick return mechanism – working principle

24

The quick-return mechanism uses a crank, which is powered by a motor (prime mover) as an input and a slider as an output.

Angle covered by the crank is more in cutting stroke.

Hence more time for Cutting stroke.

Cutting stroke = 2200 & Return stroke = 1400

Slider block

position

S1 & S2

Crank rotates in

anticlockwise

direction

S1 S2


http://www.dtonline.org/apps/infopage/app.exe?1&6&1&23&1&0

Crank and slotted lever quick return motion mechanism

• The slotted link mechanism allows the ram to return on its idle stroke quicker than it takes to complete a cutting stroke.

• The length of stroke is altered by moving the crankpin location relative to the centre of the slotted wheel.

• The maximum stroke is set by locating the pin at the farthest point from the centre

• The angle through which the bull wheel rotates on the cutting stroke is larger than the angle of the return stroke.

• The ram will therefore move slower on the cutting stroke and faster on the return stroke.


2. Whitworth quick return motion mechanism

In this, link 2 is fixed .

Driving crank ( link 3 ) rotates at uniform

angular speed.

The slider ( link 4 ) attached to the crank

pin at C slides along slotted bar AC ( link 1 )

, which oscillated at pivot joint D

A2 A1

C A B AMALE, Deptt.of Mechanical , YCCE

Shaper : Hydraulic Drive mechanism

partially closed


3. HYDRAULIC SHAPERS

• Hydraulic mechanism can also be effectively used as Quick return

mechanism.

• Oil from the reservoir is drawn through an oil filter by the double

gear hydraulic pump, which driven by an electric motor. Pump delivers

a constant quantity of oil to the control valve at a moderate pressure.

• From the control valve ,the oil is delivered to either side of the piston in

the feed control cylinder situated under the ram. In this, same volume of

Oil is delivered to both sides of the piston.

• Position of the control valve of the valve chamber determines as to which

side of the piston the oil will be delivered.

• The intensity of hydraulic pressure differs on both sides due to difference in

the effective area of piston . With the result, Ram travels at a faster rate in

the return stroke than in the forward stroke.

• The length of the stroke is adjusted by adjusting the distance between the two

stops.


SHAPER : Cutting Speed , Machining Time , MRR


Planer Machine


PLANING MACHINE PARTS The principle parts of the planer ( Standard or Double Housing Planer ) are:

Bed

Table

Column

Cross rail

Tool head


Standard or Double Housing Planer


It is the most common type of planer. It consists of mainly

a massive bed on which the worktable reciprocates, and

two vertical columns or housing, one on each side of the

bed. Each column carries a tool head that can be slide

up and down on the column. A cross rail fitted between

the two columns may carry one or two tool heads that can

slide horizontally on the cross rail. All the tool heads

can be clamped in position, and can be used collectively

or individually depending on the requirements.

Standard or Double Housing Planer


BED The bed of a planer is large in size and heavy in weight.

It supports the column and all other moving parts of the machine

It is made slightly longer than twice the length of the table so that the full stroke

length of the table maybe moved on it.

TABLE

The table supports the work and reciprocates along

the ways of the bed

Table is made from good quality cast iron

The top face of the table is accurately finished in

order to locate the work correctly.

T-slots are provided on the entire length of the table

so that the work and work holding devices may be

bolted upon it. A B AMALE, Deptt.of Mechanical , YCCE

COLUMN These are rigid box-like vertical structures placed on

each side of the bed and are fastened to the

sides of the bed.

They are heavily ribbed to trace up severe forces due to

cutting.

At their front , they are very accurately machined to

form vertical ways along which the cross rail slides up

and down for accommodating different heights of work.

CROSSRAIL It is a rigid box-like casting connecting the two columns.

It may be raised or lowered on the face of the housing and can be clamped at a

desired position by manual or electrical clamping devices.

It should remain absolutely parallel to the top surface of the table.

It is necessary to generate a flat horizontal surface on a work piece because the

tool follows the part on the cross rail during cross feed.


TOOLHEAD Tool heads are mounted on the cross rail by a saddle.

The saddle may be made to move transversely on the cross

rail to give cross feed.

The swivel base is pivoted on the saddle and is graduated on

each side to 60 degrees.


Classification of Planer

Planers are generally divided into 5 types:

Double Housing Planer

Open Side Planer

Edge Type Planer

Divide Table Planer

Pit Type Planer


Open Slide Planer

Open side planer consists of only one vertical column or housing on

which the cross rail is mounted. The column and the cross rail carry

single and double tool heads respectively. This type of machine

permits machining of wider work pieces.


Open Slide Planer

Special care is always needed in designing this machine as it is

subjected to severe twisting forces during the operation on account

of absence of one housing and the cantilever type cross rail.


• Edge Type Planer

This type of machine is used for machining the

edges of heavy work pieces.

Compare with the conventional planer, Bed and the

table of the edge planer are a fixed unit and work is

mounted on a table.

Toolhead is mounted on a movable carriage which

can travel longitudinally along the bed.

Cutting can take place during both directions of

carriage travel.


• Divide Type Planer

It is also called tandem planer and consists of two worktables, which

may be reciprocated together or separately. It is quite well known that, mounting

and setting of work pieces on the worktable consumes more time thereby

restricting the machine for continuous mass production applications. In such

cases, divided table planer can be used, where in, one worktable can be used

for setting up a new work piece, while the second worktable carrying work piece

is being machined. The two tables can be joined together to hold large work

pieces.

• Pit Type Planer

It is used for machining heavy and tall work pieces. The job is

mounted on the floor inside a Pit. Sometimes no clamping is needed when the

work is extremely heavy.

The machine is provided with two short vertical housings which carry a cross rail.

The whole unit travels along the horizontal ways to and fro and thus the tool

moves past the work for machining the surface of the work piece.


Driving / Quick Return mechanism

for driving the table of a Planer

1.Belt drive

2.Direct Reversible Motor Drive

3.Hydraulic Drive.


1.Belt drive

• Crossed belt used for slow forward (cutting stroke) motion of the table.

• Open belt used for quick return (non cutting stroke) motion of the table.

• Rack and pinion arrangement used for conversion of rotary motion into

reciprocation movement of the table • Belt shifter are provided on machine between fast pulley and loose pulley

• Counter shaft connected to motor situated over the housing and driving

shaft connected to pinion under the table

• Each driven pulley consists of pair of fast and loose pulleys.

D1N1 = D2N2

Driving pulleys

Driven pulleys A B AMALE, Deptt.of Mechanical , YCCE




2. Direct Reversible Motor Drive

Modern planer uses this system of table driving

D.C reversible motor is directly coupled to the main driving

shaft which drives the table through speed reduction gears .

The reversal of the table travel at the end of each stroke is

affected by trip dogs, which change the direction of current

through a change in the field of generator and hence the

direction of rotation of the DC motor.

Wide range of cutting speeds is possible.

The return speed of the table can be made much faster and

hence a lot of saving in machining is possible.


3. Hydraulic Mechanism

Hydraulic drive for the planer table is same as Shaper


Slotting Machine


SLOTTER

Slotter is used for cutting grooves, keyways and slots of

various shapes, for making regular and irregular surfaces

both internal and external, for cutting internal or external

gears.

• Basically slotting machine is a vertical axis

shaper

• Ram reciprocates vertically and the tool

cuts work during the downward stroke only.

• It has a vertical ram and a hand or power

operated rotary table

• The stroke of ram is smaller in slotting machines

than in shapers


Slotter Machine ( Production Slotter )


SLOTTING MACHINE PARTS

• Base: Rigidly built to take up all the cutting forces and entire load of the machine.

• Column: It is a vertical member which is a cast integral with the base and houses driving mechanisms of the ram and feeding mechanisms.

• Saddle: It is mounted upon the guide ways and may be moved toward or away from the column either by power or manual control to supply longitudinal feed to the work.


• Cross-slide: It is mounted upon the guideways of the

saddle and may be moved parallel to the face of the

column.

• Rotary Table: Circular table mounted on the top of the

cross-slide. On the top of the table T-slots are provided to

clamp the work with the use of fixtures.

• Ram and Tool head Assembly: Ram moves (reciprocates )in

a vertical direction between the vertical guide ways provided in

front of the column. At its bottom, it carries the Tool Post in

which the Tool is held. The cutting action takes place during

the downward movement of the ram

SLOTTING MACHINE PARTS


TYPES OF SLOTTING MACHINES

1. Puncher Slotter: It is a heavy, rigid machines

designed for removal of large amount of metal from

large forging and castings. The pinion is driven by a

variable speed reversible electric motor similar to that

of a planer.

2. Production Slotter : This is the common category of

slotter used for general production work. The drive of

the ram is provided by means of slotted disc

mechanism.

3. Precision / Tool Room Slotter : they are of precision

type and are used for very accurate machining. Tilting

type of frame is attached to this machine to enable

machining at different angles. The drive of the ram is

provided by means of slotted link mechanism.


A photographic view of a slotter A slotting machine in action

Production Slotter


Drive Mechanism of a Ram in Slotter Machine

1. Slotted disc mechanism

2. Slotted link and gear mechanism

3. Hydraulic mechanism.


Slotted Disc Drive


Slotted Disc Drive It consists of meshing of pinion ( small )and gear( larger ) . Pinion shaft is

connected to the motor shaft. It in turn, drives the pinion which drives the gear.

The gear being on the same shaft of the slotted disc, drives the slotted disc.

The disc carries the T-slots through which passes the crank pin . Other end of

the crank connected to the connecting rod and connecting rod is attached to

one end of the ram.

The crank and connecting rod mechanism converts circular motion of the disc into

vertical reciprocating motion of the ram.

The length of the stoke can be varied by shifting the crank pin towards or away

from the centre of the slotted disc. The starting and finishing position of the ram

stroke can be adjusted by means of hand lever for stroke adjustment.

The Flywheel , provided at the rear side , acts as a shock absorber at the end of

the stroke.


Work Holding Devices in Shaper, Slotter and Planer Machines


INTRODUCTION TO

NC CNC MACHINE


Numerical Control (NC) :

Programmable automation in which the mechanical actions of a ‘machine

tool’ are controlled by a program ( Part Program ) containing coded

alphanumeric data that represents relative positions between a cutting

tool and a work part

Machine

Control Unit

Power

Program

Instructions

Transformati

on

Process

numerical control (NC) • have to read the program each

time a part is run

• they have no means of editing

existing programs)


NC SYSTEM ELEMENTS

Read by tape reader


CNC system and functions of CNC unit

CNC system: is a special computer system that is equipped

with certain interface circuits and servo drivers，and can do part

or all the works can NC system do by running the software

stored in its memories．

CNCs have expandable memories that can store

large numbers of programs，plus subroutines

and correction data．

extensive memory capacity : sophisticated graphic

displays

and dynamic simulation

Can store and allow editing of programs.


CNC SYSTEM ELEMENTS

A typical CNC system consists of the following six elements

• 1. Part program

• 2. Program input device

• 3. Machine control unit

• 4. Drive system

• 5. Machine tool

• 6. Feedback system


1. PART PROGRAM • A part program is a series of coded instructions required to produce a

part. It controls the movement of the machine tool and the on/off control of auxiliary functions such as spindle rotation and coolant. The coded instructions are composed of letters, numbers and symbols and are arranged in a format of functional blocks as in the following example

N10 G01 X5.0 Y2.5 F15.0 | | | | | | | | | Feed rate (15 in/min) | | | Y-coordinate (2.5") | | X-coordinate (5.0") | Linear interpolation mode Sequence number

• The program input device is the mechanism for part programs to be entered into the CNC control. The most commonly used program input devices are keyboards,

2. PROGRAM INPUT DEVICE


3. MACHINE CONTROL UNIT

The machine control unit (MCU) is the heart of a CNC system. It is used

to perform the following functions:

• Read coded instructions

• Decode coded instructions

• Implement interpolations (linear, circular, and helical) to generate axis motion commands

• Feed axis motion commands to the amplifier circuits for driving the axis mechanisms

• Receive the feedback signals of position and speed for each drive axis

• Implement auxiliary control functions such as coolant or spindle on/off, and tool change


• A drive system consists of amplifier circuits, stepping motors or servomotors and ball lead-screws. The MCU feeds control signals (position and speed) of each axis to the amplifier circuits. The control signals are augmented to actuate stepping motors which in turn rotate the ball lead-screws to position the machine table.

4. DRIVE SYSTEM

• CNC controls are used to control various types of machine tools.

Regardless of which type of machine tool is controlled, it always has

a slide table and a spindle to control of position and speed. The

machine table is controlled in the X and Y axes, while the spindle

runs along the Z axis.

5. MACHINE TOOL

6. FEEDBACK SYSTEM • The feedback system is also referred to as the measuring system.

It uses position and speed transducers to continuously monitor the position at which the cutting tool is located at any particular time. The MCU uses the difference between reference signals and feedback signals to generate the control signals for correcting position and speed errors.


TYPES of CNC CONTROL SYSTEMS

DAC = digital-to-analog converter.

• Open-loop control

• Closed-loop control


OPEN - LOOP CNC CONTROL SYSTEM

• In open-loop control system stepper motors are used

• Step motors are driven by electric pulses

• Every pulse rotates the motor spindle through a certain amount

• By counting the pulses, the amount of motion can be controlled

• No feedback signal for error correction

• Lower positioning accuracy


CLOSED - LOOP CNC CONTROL SYSTEMS

69

• In closed-loop control systems DC or AC motors are used

• Position transducers are used to generate position feedback signals for error correction

• Better accuracy can be achieved

• More expensive

• Suitable for large size machine tools


Advantages of CNC

- Easier to program;

- Easy storage of existing programs;

- Easy to change a program

- Avoids human errors

- NC machines are safer to operate

- Complex geometry is produced as cheaply as simple

ones

- Usually generates closer tolerances than manual

machines


Mp-i Unit-III Shaper 24 Aug 2014 a b Amale

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