cnc and part program2

7/27/2019 CNC and Part Program2

1/46

3. Numerical control (NC)

NC is a form of programmable automation in which themechanical act ions o f a machine are contro l led

by a program con tain ing coded alphanumericdata. The data represent relative pos i t ionsbetweena work-head (cutting tool) and a work-part (objectbeing processed). The program of instructions can

be changed to process a new job. The capability tochange the program, makes NC suitable for low andmedium production.

The application of NC has two categories:

1. Machine tool applications, such as drilling, milling,turning, and other metal working; and

2. Non-machine tool applications, such as assembly,

drafting and inspection.


2/46

3.1 Introduction to NC and CNC

3.1.1 Basic Components of an NC System

An NC system consists of three basic components:

I. The program of inst ruct ionsis step-by-stepcommands that direct the actions of the equipment- part program that refer to positions of a cuttingtool relative to the worktable (fixture) with spindlespeed, feed rate, cutting tool selection, and otherfunctions.


3/46

II. The machine con trol un i t (MCU) consists ofa microcomputerand related controlhardware that stores instructions and

executes it by converting each command intomechanical actions of the equipment, onecommand at a time. The related hardwareincludes

components to interface with the processingequipment and

Feedback control elements. The MCU alsoincludes one or more

Reading devices for entering part programs intomemory.

III. The process ing equipmentaccomplishesthe processing steps to transform the startingworkpiece into a completed part. Its operationis directed by the MCU.


4/46

3.1.2 Computer Numerical Control (CNC)

CNC can be defined as an NC system whoseMCU is based on a dedicated microcomputerrather than on a hard-wired controller, which isresulted from size and cost significant reductionof digital computers and substantial increase intheir computational capabilities.

Features of CNCThe additional features of CNC System include:

sufficient capacity to Store of more than one partprogram

multiple data entry capabilities forVarious formsof program input (punched and magnetic tape,diskette, RS-232 communications, manual datainput)


5/46

Program editing at the machine tool (testing and

correcting a program at the machine site),.

Fixed cycle and programming subroutines: to

store frequently used machining cycles as

macros that can be called by the program

Interpolation: Positioning features for setup: facilitated

alignment task can be using certain features

Cutter length and size compensation: Acceleration and deceleration calculations.


6/46

Communications interface with othercomputers/ computer-driven devices such as:

(1) Downloading part programs from a central data file,

(2) Collecting operational data,(3) Interfacing with peripheral equipment,

Diagnostics: monitors and detect certainaspects of the machine tool malfunctions.

Common CNC diagnostics system are:

Control start-up diagnostics,

Malfunction and failure analysis,

Extended diagnostics for individual components, Tool life monitoring,

Preventive maintenance notices,

Programming diagnostics


7/46

The MCU for CNCconsists of five elements whichare interconnected by means of a system bus.

System bus

Memory

-ROM -Operating sys

-RAM -Part programs

Central processing

unit (CPU)

Inpu t/outp ut inter face

-Operator panel

-Tape reader

Machine tool contro ls

-Position control

-Spindle Speed control

Sequence controls

-Coolant

- Fixture clamping

-Tool changer

Fig. Configuration of CNC machine control unit


8/46

Direct Numerical Con trol (DNC)

DNC involves the control of a number of machine tools by asingle (mainframe/ Central) computer. A program is transmitteddirectly to MCU at a time and on demand;

The system consists of: Central computer (CC), Bulk memory atCC site, Set of controlled machines and Telecommunicationslines linking machines with CC.

In operation, the computer calls the required part program frombulk memory and sent it (one block at a time) to the designatedmachine tool.

The CC also receives feedback from the machines to indicateoperating performance in the shop.

Thus, a central objective of DNC was to achieve two-waycommunication between the machines and the CC.


9/46

Data & Info Down loaded from CC to

M/c & Shop Floor

Data & Info Loaded from M/c & Shop

Floor to CC

NC part programs Piece counts

Machining cycle time for part program Actual machining cycle times

List of tools needed for job Tool life statistics

Data about when program was last

used

M/c up/down time statistics for m/c

utilization and reliability assessment

Machine setup instructions Product quality data

Table: Flow o f Info b /n Central Compu ter (CC) and M/c Too ls in DNC

Distributed Numerical Control

In the new DNC configuration, CC is connected to MCUs,

which are themselves computers. This permits complete part

programs to be sent to the machine tools, rather than oneblock at a time. Redundant computers improve system

reliability compared with the original DNC. The two-way

information communication flow are:


10/46

The two ways to configuring a DNC system are:

I. Switching network, uses a data switching box to make aconnection from the CC to a given CNC machine fordownloading part programs or uploading data. This limits

the number of machines in the DNC system that dependon part program complexity, frequency of servicerequired, and capabilities of the CC.

DNC

Computer

Data

switchingbox

MCU MT

MCU MT

MCU MT

MCU MT

MCU MT


11/46

ii. LAN. In centralized structure arrangement, thecomputer system is organized as a hierarchy, with thecentral (host) computer coordinating several satellite

computers that are each responsible for a number ofCNC machines. Local area networks in differentsections and departments of a plant ofteninterconnected in plant-wide and corporate-widenetworks Each type has several possible variations.

MCU MTMCU MTMCU MT MCU MT

DNC

Computer

SatelliteComputer

SatelliteComputer


12/46

3.1.3 Application of NC

The operating principle of NC has many applications.The applications divide into two categories: machinetool applications (those usually associated with metalwork industry) and non-machine tool applications(diverse group of operations in other industries).

I. Mach ine Tool App l ications

The most common applications of NC are in machinetool control which was the first application of NC and isstill important.

Machining Operations and NC Machine Tools.

Machiningis a mnfg process in which the geometry ofthe work is produced by removing excess material. Bycontrolling the relative motion between a cutting tooland the workpiece, the desired geometry is created.


13/46

There are four common types of machining operations:

(a) Turning,

(b) Drilling,(c) Milling,

(d) Grinding.


14/46

Each of the four machining operations are carried outat a certain combination of speed, feed, and depth ofcut, collectively called cutting conditions.

The common NC machine tools with their typicalfeatures are:

NC lathe requires two-axis, continuous path control,either to make straight or contour turning.

NC boring millrequires continuous path, two-axiscontrol for creating internal cylinder

NC drill press use point-to-point control of the spindle/drill bit) and two axis (x-y) control of the worktable.

Some NC drill presses have turrets containing six oreight drill bits.

NC milling machine require continuous path control toperform straight cut or contouring operations.

Cylindrical grinderhas continuous path two-axis

control, similar to an NC lathe.


15/46

NC Appl icat ion Character is t ics

characteristics that are most suited to NC application are:

Batch production: NC is appropriate in small/ medium lot

sizes as dedicated automation and Manual productionwould be uneconomical for these quantities.

Repeat orders: Batches of the same parts are produced atrandom or periodic intervals.

Complex part geometry. such as those found on airfoils and

turbine blades, circles and helixes. Much metal needs to be removed from the work part:

complex part geometry to fabricate large structural sectionswith low weights.

Many separate machining operations on the part: features

requiring different cutting tools, such as drilled and/ortapped holes, slots, flats, and so on.

The part is expensive. When the part is expensive, andmistakes in processing would be costly .


16/46

NC for Other Metalworking Processesinclude:

Punch presses for sheet metal hole punching.

Presses for sheet metal bending.

Welding machines. Both spot and continuous arc welding Thermal cutting Machines, oxy-fuel, laser, plasma arc

cutting.

Tube bending machines to control location and angle ofbend such as frames for bicycles.

II. Other NC Applic ations

The principle of NC has a host of other applications, whichare not always referred to "numerical control. Some of NC-type controls are:

Wire wrap machines

Component insertion machines

Drafting machines

Coordinate measuring machine

Tape laying machines for polymer composites

Filament winding machines for polymer composites


17/46

Advantages and Disadvantages o f NC

Advantages of NC

Nonproductive time is reduced

Greater accuracy and repeatability.

Lower scrap rate.

Inspection requirements arereduced.

More complex part geometries arepossible.

Engineering changes can beaccommodated more gracefully,

Simpler fixtures are needed,

Shorter manufacturing lead times. Reduced parts inventory,

Less floor space required.

Operator kill-level requirements arereduced,

Disadvantages o f NC.

Higher investment cost.

Higher maintenanceeffort.

Part programming.

Higher utilization of NC

equipment


18/46

3.2 NC RART PROGRAMMING

NC part programming consists of planning and

documenting the sequence of processingsteps to be performed on an NC machine. Theprogrammer must have knowledge ofmachining or other processing technology aswell as geometry and trigonometry.

Part programming uses a variety of proceduresranging from highly manual to highlyautomated methods. The methods are:

1. Manual part programming,

2. Computer-assisted part programming,

3. Part programming using CAD/CAM, and

4. Manual data input.


19/46

3.2.1 Manual Part Programming

In manual part programming, the programmer preparesthe NC code using the low-level machine language

previously described. The part program is a block-by-block listing of the machining instructions for the givenjob, formatted for the particular machine tool, mostsuited for point-to-point machining.

In preparing the NC part program, the part programmer

must initially define the origin of the coordinate axesand then reference the succeeding motion commandsto this axis system. This is accomplished in the firststatement of the part program.

The important definition in the program are are:

1. NC Coding Systems

2. NC Coordinate System

3. Motion Control Systems


20/46

1. NC Coding Sys tem

The program of instructions is communicated to themachine tool using a coding system. This NC coding systemis the low-level machine language that can be understoodby the MCU.Words in an instruction block are intended to convey all ofthe commands and data needed for the machine tool toexecute the move defined in the block. The words in a blockare usually given in the following order:

Sequence number (N-word) Preparatory word (G-word);

Coordinates (X-, Y-, Z-words for linear axes, A-, B-, C-wordsfor rotational axis

Feed rate (F-word)

Spindle speed (S-word) Tool selection (T -word)

Miscellaneous command (M-word); see the table for definitionof M-words)

End-of-block (EOB symbol)


21/46

G-words or preparatory words consist of two

numerical digits with "G" prefix that prepare the

MCU for the instructions and data contained inthe block so that the subsequent data can be

properly interpreted. In some cases, more than

one G-word is needed.

M-words are used to specify miscellaneous orauxiliary functions that are available on the

machine tool such as starting and stopping the

spindle rotation, turning the cutting fluid on or off.


22/46

Common Word Pref ixes Used in Word Add ress Format

Word Prefix Example Function

N N01 Sequence number;

G G21 Preparatory word;X, Y, Z X75.0 Coordinate data for three linear axes

U, W U25.0 Coor. data for incremental moves in turning

A, B, C A90.0 Coor. data (deg) for rotational axes x; y ; and z.

R R100.0 Radius of arc; in circular interpolation. It can also be

used to cutter radius

I, J, K. I32 J67 Coord. values of arc center, in circular interpolation

F G94 F40 Feed rate per minute or per revolution

S S0800 Spindle speed in rpm or %age of max. speed

T T14 Tool selection, in m/cs with auto tool changer.D 005 Tool dia. in contouring moves for offsetting

P P05 R15.0 Used to store cutter radius data in offset register

number.

M M03 Miscellaneous command


23/46

TAB LE - Common G-wo rds (Preparatory Word)

G-word Funct ion

G00 P-t-p movement (rapid) b/n previous point and end point

G01 Linear interpolation movement.G02; G03 Circular interpolation, clockwise counterclockwise respectively.

G04 Dwell for a specified time

G10 Input of cutter offset data, followed by a P-code and an R-code.

G17; G18; G19 Selection of x-y, x-z and y-z plane in milling respectively.

G20 Input values specified in inches

G28 Return to reference point.

G32 Thread cutting in turning.

G41, G42 Cutter offset compensation, left and right of part surface rspvly.

G50 Specify location of origin relative to starting location of tool.

G90; G91 Programming in absolute incremental coordinates respectively.

G94, G95 Specify feed/minute and feed/revolution respectively

G98; G99 Specify feed/minute and feed/revolution respectively in turning.


24/46

Common M-words Used in Word Address Format

M-Word Function

M00; M01 Program stop; and Optional program stop respectively

M02 End of .program. Machine stops

M03; M04 Start spindle in clockwise and counterclockwise direction

respectively .

M05 Spindle stop

M06 Execute tool change, either manually or automatically.

M07; M08; M09 Turn cutting fluid on flood, on mist and off respectively .

M10; M11 Automatic clamping and unclamping of fixture, machine slides,

etc respectively.

M13; M14 Start spindle in clockwise and counterclockwise direction and

turn on cutting fluid respectively.

M17 Spindle and cutting fluid off.

M19 Turn spindle off at oriented position.

M30 End of program. Machine stop.


25/46

2. NC coo rdinate sys tem

Programming of NC machine toolsconsists of little more than specifyinga sequence of x- y coordinates. The

origin of coordinate axis system islocated at the corners or center ofsymmetry, then the operatorindicates to the MCU about the originfor subsequent tool moves.

To program the NC equipment, there

are two axis systems Forflat and prismatic workparts -

The axes are three linear axes (x, y,z) and three rotational axes (a, b, c),to specify angular positions andorient workpart or tool

ForRotational parts - areassociated with NC lathes andturning centers. The path of thecutting tool relative to the rotatingworkpiece is defined in thex-zplane.


26/46

3. Mot ion Contro l SystemsSome processes are performed at discretelocations (e.g., drilling, spot welding) andothers are carried out while workhead is

moving (e.g., turning, arc welding). NC Motion control systems are two:

(1) Point-to-point/ positioning systems; Movethe worktable to a programmed locationwithout regard for the path taken and someprocessing action is accomplished at thelocation. Thus, the program consists of aseries of point locations.

(2) Continuous path systems refer tocontinuous simultaneous control of two or

more axes, which controls tool trajectoryrelative to the workpart, thus enabling togenerate angular surfaces, 2-D curves, or3-D contours. It can be straight-cut orcontouring


27/46

EXAMPLE Point- to-Point Dri l l ing

This example presents the NC part program for drilling the three

holes in the sample part. The x-, y-, and z-axes are defined. Theprogram begins with the tool positioned at at x = 0, y = -50, and z=10 (target point).

NC Part Program Code Comment

N001 G21 G90 G92 X0 Y-050.0 Z0.10.0; Define origin of axes.

N002 G00 X070.0 Y030.0; Rapid move to first holelocation.

N003 G01 G95 Z-15.0 F0.05 Sl000 M03; Drill first hole.

N004 G01 Z010.0; Retract drill from hole.

N005 G00 Y060.0; Rapid move to second hole.

Fig. Aluminum Sample partfor NC part programming


28/46

N006 G01 G95 Z-15.0 FO.05; Drill second hole.

N007 G01 Z010.0; Retract drill from hole.

N008 G00X120.0 Y030.0; Rapid move to third hole location.

N009 G0l G95 Z-15.0 F0.05; Drill third hole.

N0l0 G0l Z0l0.0; Retract drill from hole.

N0ll G00 X0 Y-050.0 M05; Rapid move to target point

NO12 M30;

Fig. Sample part aligned relative to (a) x- and y-axes, and (b) z-axis.

Coordinates are given for significant features in (a).


29/46

EXAMPLE -Two -Axis Mil lingThe part is fixtured so that its top surface is 40mm above the surface of themachine tool table. Thus, the origin will be 40 mm above the table surface.Cutter diameter data has been manually entered into offset register 0.5. At thebeginning, the cutter will be positioned at a target point located at x = 0, y = -50,and z = +10.

NC Part Programme Code Comm ent N00I G2l G90 G92 X0 Y-050.0 Z0l0.0; Define origin of axes.

N002 G00 Z-025.0 Sl000 M03; Rapid to cutter depth, turn spindle

N003 G01 G94 G42 Y0 D0S F40; Engage part, start cutter offset.

N004 G0I Xl60.0; Mill lower part edge.

N005 G0I Y060.0; Mill right straight edge.

N006 G 17 G03 X130.0 Y090.0 R030.0; Circular interpolation around arc.

N007 G0I X035.0; Mill upper part edge.

N008 G0I X0 Y0; Mill left part edge.

N009 G40 G00 X-040.0 M05; Rapid exit from part, cancel offset.

N0l0G00 X0 Y-050.0; Rapid move to target point.

N0ll M30; End of program, stop machine.


30/46

3.2.2 Computer-Assisted Part Programming

Manual part programming can be time consuming, tedious,and subject to errors for parts possessing complex

geometries or requiring many machining operations. Computer-assisted part programming uses English-like

statements that are subsequently translated by thecomputer into the low level machine code.

Tasks are divided between the human and the computer.


31/46

The two main tasks of the programmer are:

(1) defining the geometry of the workpart and

(2) specifying the tool path and operation sequence.

Part Prog with Automatically Programmed Tooling (APT)

To program in APT, the part geometry is defined; then tool isdirected. Thus, there are four types of statements in theAPT language:

1. Geometry statements, also called definition statements,define the part geometry elements.

2. Motion commands are used to specify the tool path.3. Post-processor statements control operation, such as

speed and feeds, tolerance and actuate other capabilities ofthe machine tool.

4. Auxiliary statements, used to name the part program insert

comments in the program and accomplish similar functions.These statements are constructed of APT vocabularywords, symbols, and numbers, all arranged usingappropriate punctuation. APT vocabulary words consist ofsix or fewer characters. The characters are alphabet with avery few numerical digits. APT vocabulary contains major

words and minor words.


32/46

Defining th e Part Geometr:work piece is composed ofbasic geometric elements and mathematically definedsurfaces. Nearly any component that can be conceivedby a designer can be described by points, straight lines,

planes, circles, cylinders, and others. the task is toidentify and enumerate the geometric elements of thepart in terms of its dimensions and locations relative toother elements.

The general form of an APT geometry statement is:

SYMBOL = GEOMETRYTYPE/descr ipti ve data

example; P1 = POINT /20.0,40.0,60.0

The statement consists of three sections:

1. The symbolused to identify the geometry element.

2. The APT major wordthat identifies the type of geometryelement.

3. The descriptive data that define the element precisely,

completely and uniquely (dimensional and position).


33/46

Points. easily done by designating itsx-, y, and z-coordinatesand intersection:

P1 = POINT /20.0,40.0,60.0

P2 = POINT/INTOF, L1, L2

Lines. A line defined in APT is considered to be of infinitelength in both directions. Also, APT treats a line as a verticalplane that is perpendicular to the x-y plane.

L3 = LINE/P3, P4

L4 = LINE/P5, PARLEL , L3

Planes. A plane can be defined by specifying three non-collinear points through which the plane passes. It can also bedefined as being parallel to previously defined plane.

PL I = PLANE/P1, P2, P3,

PL2 = PLANE/P2, PARLEL, PL1

Circles. In APT, a circle is considered to be a cylindricalsurface that is perpendicular to the x-y plane and extends toinfinity in the z-direction.

C1 = CIRCLE/CENTER, P1, RADIUS, 25.0

C2 = CIRCLE/P4, P5, P6


34/46

Four important APT rules:

1. Coordinate data must be specified in the order x, then y, then z.

2. Any symbols used as descriptive data must have been previouslydefined;

3. A symbol can be used to define only one geometry element.4. Only one symbol can be used to define any given element.

Specifying too l path and operat ions sequence. The tool pathconsists of a sequence of connected line and arc segments, usingpreviously defined geometry elements to guide the cutter.

Mot ion Commands. All APT motion statements follow a commonformat, The format is:

MOTION COMMAND/descrip tive data

e.g GOTO/P1

What move the tool should make (GOTO) and tell the tool where togo (P1).

At the beginning of the sequence of motion statements, the toolmust be given a starting point (target point).

FROM (initial point) /PTARG; FROM/-20.0, -20.0,0

For point-to-point motions, there are only two commands: GOTO (toa particular point location) and GODLTA (incremental move).

GOTO/P2, GOTO/25.0, 40.0, 0

C


35/46

Contouring motion commands are more complicatedthan PTP commands. The tool is controlled by threesurfaces:

Drive surface guides the side of the cutter.

Part surface bottom nose of the tool is guided on. Check surface stops the forward motion of the tool.

Actual or previously defined surface may be selected

There are fourAPT modifier words in the descriptive data (TO, ON,PAST, and TANTO)


36/46

There are fourAPT modifier words in the descriptive data(TO, ON, PAST, and TANTO)


37/46

After the tool reaches thecheck surface the next moveinvolve a right or left turn orother.

There are six motion words,

1. GOLFT - left turn relative tothe last move.

2. GORGT - a right turn relativeto the last move.

3. GOFWD - move forwardrelative to the last move.

4. GOBACK - reverse direction

relative to the last move.5. GOUP - move upward

relative to the last move.

6. GODOWN - move downrelative to the last move.


38/46

Example

FROM/PTARG

GO/TO, PL1, TO, PL2, TO PL3

GORGT/PL3, PAST, PL4 GO/TO, L1, TO, PL2, TO L3

GORGT/L3, PAST, L4

Postpro cessor and Au xi l iary Statements. control the

operation of the machine tool and play a supporting role ingenerating the tool path. Such statements are used todefine cutter size, specify speeds and feeds, turn coolantflow on and off, and control other features of the particularmachine tool.

POSTPROCESSOR COMMAND/desc rip tive dataexamples :

UNITS/MM or INCHES; INTOL/0.02 ; OUTTOL/0.02 ;CTTER/20.0 ; SPINDL/1000, CLW ; FEDRAT/40, RPM;RAPID; COOLNT, FLOOD; LOADTL/DI; DELAY/3D


39/46

Auxi l iary statementsare used to identify the partprogram, specify processor, insert remarks and so on.

PARTNO SAMPLE PART NUMBER ONE

MACHIN/ specify the post-processor, whichspecifies the machine tool.

CLPRNT; "cutter location prints,"

REMARK to insert explanatory comments.

FINI indicates the end of an APT program.


40/46

Compu ter Tasks in Compu ter-As sisted PartProgramming:consists of:

input translation,

arithmetic and cutter offset computations, editing, and

post-processing.

The input t ranslat ion modu leconverts the codedinstructions into computer-usable form, preparatory to

further processing: Syntax check

Assigning a sequence number to each APT statementin the program;

Converting geometry elements into a suitable form forcomputer processing; and

Generating an intermediate file called PROFIL that isutilized in subsequent arithmetic calculations.


41/46

The ar i thmet ic modu leconsists of a set of subroutinesto perform the mathematical computations required todefine the part surface and generate the tool path. Thecomputations are performed on the PROFIL file. The

output of this module is CLFILE "cutter location file.", toolpath data.

In edit ing, the CLFILE is edited, and a CLDATA isgenerated which provides readable data on cutterlocations and machine tool operating commands.

Another APT instruction processed is TRACUT,"transform cutter locations" Which allows a tool pathsequence to be transformed from one coordinate systemto another. The output is a part program that can bepost-processed for the given machine tool.

In post-processing, cutter location data and machiningcommands in the CLDATA file are converted into low-level code that can be interpreted by the NC controller.The output is a part program consisting of G-codes, x-,y-, and z- coordinates, S, F, M, and others in wordaddress format.


42/46

Tool Path Generation Using CAD/CAM


43/46

Tool Path Generation Using CAD/CAM.

The first step is to select the cutting tool from tool libraries.The programmer decides on appropriate tool for theoperation and specify it for the tool path. This permits tool

offset calculations. The basic approach in generating the tool path involves the

use of the interactive graphics system to enter the motioncommands one-by-one, similar to computer-assisted partprogramming. Individual statements in APT are entered,

and the CAD/CAM system provides an immediate graphicdisplay of the action resulting from the command, therebyvalidating the statement.

When the complete part program has been prepared, theCAD/CAM system can provide animated simulation of theprogram for validation purposes.

A more advanced approach is to use automatic softwaremodules available on the CAD/CAM system. Thesemodules are subroutines in the NC programming packagesthat can be called and the required parameters given toexecute the machining cycle.


44/46

Common NC Modules for Automatic Programming are:

Profile milling

Pocket milling

Lettering (engraving, mill)

Contour turningFacing (turning)

Threading (Turning)

M l D t I t / ti l i


45/46

Manual Data Inpu t/conversational programming

Manual and computer-assisted part programming requirea relatively high degree of formal documentation and

procedure. CAD/CAM part programming automates asubstantial portion of the procedure, but a significantcommitment in equipment, software, and training isrequired.

A potential method of simplifying the procedure is to

have the machine operator perform the partprogramming task at the machine tool. This is calledmanual data inpu t(MDI).

MDI is perceived as away for the small machine shop tointroduce NC without a need to acquire special NC part

programming equipment and to hire a part programmer.MDI permits to make a minimal initial investment tobegin the transition to modern CNC technology.


46/46

Communication between the machine operator-programmer and the MDI system is accomplished usinga display monitor and alphanumeric keyboard. Entering

the programming commands into the controller istypically done using a menu-driven procedure in whichthe operator responds to prompts and questions posedby the NC system.

A computer graphics capability such as tool path and

animation of the tool path sequence is included tovisualize the machining operations and verify theprogram.

The skills needed are reading engineering drawing befamiliar with the machining process. Efficient use of thesystem requires that programming for the next part beaccomplished while the current part is being machined.Most MDI systems permit these two functions to beperformed simultaneously to reduce changeover timebetween jobs.

cnc and part program2

Documents