computer aided manufacturing lab

7/28/2019 Computer Aided Manufacturing Lab

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Computer Aided Manufacturing
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Introduction

Raw materials Manufacturing Process Finished part
http://www.leechind.com/images/cylindricalGrinding1b.jpg


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Manufacturing Processes

Turning Drilling Milling Shaping

EDM Laser machining Ultrasonic machining
http://upload.wikimedia.org/wikipedia/commons/9/92/Ultrasonic_machining_schematic.jpg


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How does the table move along X- Y- and Z- axes ?

Machine tools

Lathe Milling machine


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Precise components

Controlling tool movements using numerical data
http://www.mwsmotorsports.com/products/product_info.php?products_id=56&osCsid=d3db07aff76ea68cb162c512546e53a5http://www.google.co.in/imgres?imgurl=http://www.objectivedesign.co.nz/Content/Images/User/Cache/cnc-600.jpg&imgrefurl=http://www.objectivedesign.co.nz/prototyping/cnc-machining&usg=__ievtvC_yLjF3YQwFKFWcUJ3aw3Q=&h=378&w=600&sz=35&hl=en&start=234&um=1&itbs=1&tbnid=WcwsV5BzY-GHCM:&tbnh=85&tbnw=135&prev=/images%3Fq%3DCNC%26start%3D220%26um%3D1%26hl%3Den%26sa%3DN%26ndsp%3D20%26tbs%3Disch:1


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Numerical control

NC has been defined by the Electronic Industries Association (EIA)

as a system in which actions are controlled by the direct insertion ofnumerical data at some points. The system must automatically

interpret at least some portion of this data

Program of

instruction

Control unit

Machine tool


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Components of a CNC machine

In general there are three basic components of an operational NC

1. Programme of instruction.

2. A machine control unit.

3. Machine tool.

Numerical control (NC) - machine can be controlled electronically

Computer Numerically Controlled (CNC) - machine actually has

its own microprocessor and memory

Direct Numerical Control (DNC) - wired to a central computer


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Need for CNC

To manufacture complex curved geometries in 2D or 3D

using controlled cutter motions

Machining components with repeatable accuracy

Unmanned machining operations

Computer Numerical Control (CNC) - A numerical control system in

which the data handling, control sequences, and response to input is

determined by an on-board computer system at the machine tool.
http://www.google.co.in/imgres?imgurl=http://irzoom.com/tiny_mce/plugins/imagemanager/files/whole_site_gallery/Diamond_turning_close.jpg&imgrefurl=http://irzoom.com/home/Ready_to_Buy&usg=__6PehTpaOwYiaAZi6_fERXibJ-8Q=&h=780&w=1166&sz=116&hl=en&start=32&itbs=1&tbnid=1XN0Jsk9LnRHHM:&tbnh=100&tbnw=150&prev=/images%3Fq%3Dturning%26start%3D20%26hl%3Den%26sa%3DN%26gbv%3D2%26ndsp%3D20%26tbs%3Disch:1http://www.google.co.in/imgres?imgurl=http://irzoom.com/tiny_mce/plugins/imagemanager/files/whole_site_gallery/Diamond_turning_close.jpg&imgrefurl=http://irzoom.com/home/Ready_to_Buy&usg=__6PehTpaOwYiaAZi6_fERXibJ-8Q=&h=780&w=1166&sz=116&hl=en&start=32&itbs=1&tbnid=1XN0Jsk9LnRHHM:&tbnh=100&tbnw=150&prev=/images%3Fq%3Dturning%26start%3D20%26hl%3Den%26sa%3DN%26gbv%3D2%26ndsp%3D20%26tbs%3Disch:1http://www.google.co.in/imgres?imgurl=http://irzoom.com/tiny_mce/plugins/imagemanager/files/whole_site_gallery/Diamond_turning_close.jpg&imgrefurl=http://irzoom.com/home/Ready_to_Buy&usg=__6PehTpaOwYiaAZi6_fERXibJ-8Q=&h=780&w=1166&sz=116&hl=en&start=32&itbs=1&tbnid=1XN0Jsk9LnRHHM:&tbnh=100&tbnw=150&prev=/images%3Fq%3Dturning%26start%3D20%26hl%3Den%26sa%3DN%26gbv%3D2%26ndsp%3D20%26tbs%3Disch:1


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Machining center

A machining center can be defined as a machine toolcapable of:

Multiple operation and processes in a single set-uputilizing multiple axis

Typically has an automatic mechanism to changetools
http://img.diytrade.com/cdimg/603157/4330376/0/1190267517/High_Speed_CNC_Milling_Machine.jpg


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Components Of CNC Machine Tool

control

cabinet

Controller

Servodrive

Machine tablePosition

transducer

Leadscrew

Gear

boxTachometer

Motor

Converting the rotational motion of the motors to a linear motion.


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Lead screws

Leadscrew

Pitch

Nut

Pitch (p): the distance between adjacent screw threads

Number of teeth per inch (n): n = 1 / p

BLU: Basic Length Unit (machine resolution) BLU = p / n


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Position measurement


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Control Loops

Open loop - No position feedback.

Use stepping motor.

motor

table

pulses


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Coordinate systems

Right hand rule

Z axis align with the spindle - +Z moves away from

the workpiece or the spindle. X axis - Lathe: perpendicular to the spindle.

Horizontal machine: parallel to the table.

Vertical machine: +X points to the right.

x

y

z

x

y

z


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Motion control


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Motion control


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Basic Elements of NC Program

a. Preparatory functions: which unit, which interpolator,

absolute or incremental programming, which circular

interpolation plane, cutter compensation, etc.

b. Coordinates: three translational, and three rotational axes.

c. Machining parameters: feed, and speed.

d. Tool control: tool diameter, next tool number, tool change.

e. Cycle functions: drill cycle, ream cycle, bore cycle, mill cycle,clearance plane.

f. Coolant control: coolant on/off, flood, mist.

g. Miscellaneous control: spindle on/off, tape rewind, spindle

rotation direction, pallet change, clamps control, etc.

h. Interpolators: linear, circular interpolation


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Part Program

Part program: A computer program to specify

- Which tool should be loaded on the machine spindle;

- What are the cutting conditions (speed, feed, coolant ON/OFF etc)

- The start point and end point of a motion segment

- how to move the tool with respect to the machine.


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NC WORDS- F and S Codes

F Code. feed speed.

inch/min (ipm), or ipr.

F code must be given before either G01, G02, or G03 can be used.

Example:

N0100 G02 X7.000 Y2.000 I5.000 J2.000 F6.00

S Code. cutting speed code.

Programmed in rpm.

S code does not turn on the spindle, spindle is turned on by a Mcode.

N0010 S1000


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NC WORDS- T and R Codes

T Code. tool number.

Actual tool change does notoccur until a tool change M

code is specified.

R Code. cycle parameter.

The cycle may be programmed in one

block, such as (cycle programming isvendor specific.):

N0010 G81 X1.000 Y2.000 Z0.000 R 1.300

R plane

Z point

Initial height1

2

3

4

5

(1,2,2)

0.3"

1"

0.7"


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NC WORDS M Codes

M Code. miscellaneous word.

m0

m0

m0

m0

m0

Program stop

Optional stop

End of progr

Spindle CW

Spindle CCW

Tool change

Flood coolant

Mist coolant

Coolant off

End of tape

m06

m07

m08

m09

m30


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Offsets

Fixture G10, G54, G54.1

Diameter

Tool Length compensation

Part-Edge compensation

Cutter Compensation Next Slides


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Tool Radius Compensation

Cutter Compensation

Shifting tool path so that the actual finished cut iseither moved to the left or right of the programmed

path.

Normally, shifted exactly by tool radius

Tool Entry and Exit Issues


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Tool Radius Compensation

Start of Compensation.

G41 (or G42) and G01 in the same block ramp takes place at block N0010.

N0010 G01 G42 X0.500 Y1.700

N0020 G01 X1.500

G41 (or G42) and G01 in separate blocks the compensation is effective fromthe start.

N0010 G41N0020 G01 X0.500 Y1.700

N0030 G01 X1.500

(a) G41 (b) G42

G41

G42

G41

G42

(0.5, 1.7)

(1.5, 1.7)


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Tool Radius CompensationInside Corner.

Cutter path is inside a corner, stops at the inside cutting point

N0010 G41

N0020 G01 X1.500 Y2.000

N0030 G01 X0.000 Y1.600

Use of M96 and M97.

Cutting tool that is larger than the height of the step, M97 must be used

N0010 G41

N0020 G01 X1.000 Y1.000

N0030 G01 Y0.800 M97

N0040 G01 X2.000

G42

G41M96

G41M97

(1.5, 2.0)

(0, 1.6)


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Advantages

Increased Program storage capability at

the machine tool

Program editing at the machine tool Control systems upgrades possible

Option -resident CAM system at machine

tool Tool path verification

computer aided manufacturing lab

Documents