Cnc lecture3

10/24/2016 1 Numerical Control Machines

CNC-MDP471

Design and Production Engineering Department,

Faculty of Engineering,

Ain Shams University.

Lecture 3

DR. AMR SHAABAN

10/24/2016 2

•Turning part program exercise

•CNC machine tool structure

•Introduction

•Mechanical structure

•Machine control unit

•Tool magazines

10/24/2016 Dr.Amr Shaaban-Numerical Control Machines 3

PART PROGRAMMING

Example


PART PROGRAMMING

1 Select the right holder Turning machine

2 Raw material specification

cylinder (φ 43*105) Allowance for D [Turning=0]

Allowance for L : [Facing (1mm)+parting off (3mm)+safety from part holder(15mm)]

3 Decide the operation

sequence 1-Facing/ 2-straight and taper from φ43 to 36/ 3-straight and taper from φ36 to 17/ 4-Turning the arc/ 5-Chamfering/ 6-Grooving/ 7-parting off

4 Tooling Facing tool(T01)/ turning tool(T02)/ Chamfering tool (T03)/ grooving tool

3mm width (T04)/ parting off tool 3mm width (T05) Tool changer coordinate: 200mm from chuck face & 50mm from center

5 Part program Next slide

105mm

ϕ43


PART PROGRAMMING

1 Facing

N0010 G21 G90 G94 G97 Unit definition/ absolute positioning (safety block)

N0020 G00 X100 Z200 T01 M06 Rapid motion to tool changer/ mounting facing tool

N0030 Z104 Facing starting point z

N0040 X45 S500 M03 Facing starting point x/ spindle rotate c.w

N0050 G01 X0 F20 M08 Facing


PART PROGRAMMING

2 Turning from ϕ43 to ϕ 36

N0060 G92 X0 Z0 Temporary m/c zero offset to the part face

N0070 G00 X100 Z96 T02 M06 Rapid motion to tool changer/ mounting turning tool

N0080 X36 Turning starting point x

N0090 Z1 Turning starting point z

N0100 G01 Z-57.5 F40 Turning straight

N0110 X43 Z-61 Turning taper

Note: Depth of cut 3.5mm is

considered large, it should be machined by multi-step, but ignore

for now


PART PROGRAMMING

3 Turning from ϕ36 to ϕ 17

1

2

3

4

Z-30 Z-48

X17

X21

X26

X31

X36

Z-3

4.7

37

Z-3

9.4

74

Z-4

4.2

11

N0120 G00 X45 retract

N0130 Z1 To the start point Z of track1

N0140 X31 To the start point X of track1

N0140 G01 Z-30 F40 straight turning track1

N0150 X36 Z-34.737 Taper turning track1




PART PROGRAMMING

3 Turning from ϕ36 to ϕ 17 (Continue)

1

2

3

4

Z-30 Z-48

X17

X21

X26

X31

X36

Z-3

4.7

37

Z-3

9.4

74

Z-4

4.2

11










PART PROGRAMMING

3 Turning from ϕ36 to ϕ 17 (Continue)

1

2

3

4

Z-30 Z-48

X17

X21

X26

X31

X36

Z-3

4.7

37

Z-3

9.4

74

Z-4

4.2

11





N0300 X36 Z-48 Taper turning track4


Note: The retract after each track may better be adjusted to Z-48 to ease calculating turning points, however, it causes longer retract paths


PART PROGRAMMING

4 Turning arc R3.5

N0360 X100 Z96 T03 M06 Rapid motion to tool changer/ mounting Chamfering tool

N0320 Z-57.5 To the start point of the arc z

N0330 X36 To the start point of the arc x

Z-57.5 Z-61

X36

X43

N0340 G02 X43 Z-61 I3.5 K0 F40 Turning the arc

N0350 G00 X45 Retract


PART PROGRAMMING

5 Chamfering

N0370 Z-0.5 To the start point of the chamfer z

N0380 X19 To the start point of the chamfer x

N0390 G01 X16 F20 Chamfering


N0410 X100 Z96 T04 M06 Rapid motion to tool changer/ mounting Grooving tool


PART PROGRAMMING

6 Grooving to ϕ10

N0420 Z-12.5 To the start point of the undercut z

N0430 X19 To the start point of the undercut x

N0440 G01 X10 F20 Grooving radial


N0470 X100 Z96 T05 M06 Rapid motion to tool changer/ mounting Parting off tool

N0450 Z-17.5 Grooving axial

Note: Depth of cut 3.5mm is

considered large, it should be machined by multi-step, but ignore

for now


PART PROGRAMMING

7 PARTING OFF

N0480 Z-87.5 To the start point of the parting off z

N0490 X45 To the start point of the undercut x

N0500 G01 X0 F20 Parting off

N0510 G00 X50 Z0 retract

N0510 M30 End program


CNC MACHINE TOOL PARTS

CNC MACHINE

TOOL

MCU Guide ways

Actuators & Drives

Mechanical structure

Sensors Tool magazine


CNC MECHANICAL STRUCTURE



VMC Open structure VMC Closed structure



CAD Model

FE Model

Analysis



Note: Overall evaluation of a CNC

machine tool should not ignore

the behavior of the mechanical

structure. But it should also

include the performance of the

control system.


Machine Control Unit

•Read the coded instructions.

•Decode the coded instructions.

•Implement interpolation.

•Feed the motion commands to the amplifier

circuits for driving the axis mechanism.

•Receive the feedback signal.

•Implement auxiliary control functions.


TOOL MAGAZINE

The required turret station is specified on the program; hence the turret indexes

from one tool station to the next desired station in accordance with the input

data.

The accuracy claimed for indexing (at the spindle nose) is 0.005 mm. Indexing

accuracy is achieved by means of a hydrostatic location bolt which also acts as

the plunger of an oil pump; the plunger is surrounded by a film of oil under

pressure which effectively centralizes and eliminates wear.

INDEXING TURRET


TOOL MAGAZINE

Two types of drum magazine are used in CNC machines:

The first is without a tool catcher. In this case as soon as a tool is required and

been programmed , orders are given by the controller to rotate the drum and

move it to spindle nose to receive the used tool and fix the new one.

Second type a special mechanism (tool catcher), is employed to select the

correct tool and transfer it to the machine spindle, where it is automatically

clamped in position..

DRUM TYPE


TOOL MAGAZINE

The cutting tools are stored in the magazine in a regular rectangular pattern.

The position of each tool is known by the rectangular co-ordinates of its

location. To select a tool, the program is compiled to position the spindle

opposite and co-axial with the required tool. The spindle moves forward and

engages with the shank of the tool and the shank is then gripped by a drawbar

or collets. The spindle is retracted to remove the tool from the magazine, and

the slides are actuated to move the tool to its machining position.

BOX TYPE


TOOL MAGAZINE

Tools are exchanged between the chain magazine, and the spindle by means

of an automatic tool transfer unit. An advantage is that machining can

continue uninterrupted, using the tool in one spindle while tool changing is

taking place between the magazine and the spindle in the rear position. The

table may be traversed in X and Y directions under rapid or feed rates without

interfering with the exchange. On completion of a machining cycle with one

tool, the spindles index through 180° and machining can immediately starts

with the new selected tool.

CHAIN TYPE


THE END

Cnc lecture3

Engineering

Transcript of Cnc lecture3