c. kalavrytinos - cnc wire erosion simulation of forklift wheel

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2012

CNC wire EDM Simulation for Forklift Wheel

ABSTRACT

Performing a simulation before the actual manufacturing process of a part can help in

reducing the risk of errors during the process that can lead to scraping of the

workpiece or damaging the tool and/or CNC machine. The aim of this report is to

determine the steps required for a complete simulation process and to analyse its

benefits.

In order to achieve this, two initial letters were designed to be manufactured on a

metal plate using a Wire Erosion or Wire Electric Discharge Machining (EDM) CNC

machine. The manufacturing process simulation was carried out in XCAD, a

Computer Aided Manufacturing (CAM) programme and the NC part programme was

produced using a suitable post processor for the Sodick EX20 Wire EDM machine.

The part programme was then verified and edited in the CIMCO Edit programme and

transferred to the CNC machine where the part was manufactured.

The process resulted in a successful achievement of the dimensional tolerances for

the letter C (Expected 4+/- 0.05mm, Achieved 3.95mm) after a mistake in the tool

radius offset for the letter K was rectified. This mistake resulted in a letter width of

4.61mm instead of the expected 4+/- 0.05mm.

Taking all the above into consideration, simulating a manufacturing process and

verifying for errors and collision avoidance as well as measuring and inspecting the

manufactured part are very important steps for ensuring product quality.

Christos Kalavrytinos Page i


CONTENTS

ABSTRACT............................................................................................................................... I

CONTENTS.............................................................................................................................. II

1.0 INTRODUCTION................................................................................................................1

1.1 OBJECTIVES.....................................................................................................................1

2.0 ELECTRIC DISCHARGE MACHINING..............................................................................1

2.1 REVIEW OF EDM..............................................................................................................1

2.2 COMPARISON OF DIE-SINKER AND WIRE-CUT MACHINES.....................................................3

2.3 WIRE-CUT EDM CHARACTERISTICS...................................................................................3

3.0 EQUIPMENT AND SOFTWARE........................................................................................7

3.1 SODICK EX20 EDM MACHINE...........................................................................................7

3.2 CATIA V5 R20..................................................................................................................7

3.3 POWERSHAPE AND POWERMILL.........................................................................................8

3.4 XCAD PRO 4.2................................................................................................................9

3.5 CIMCO EDIT 4.4..............................................................................................................9

4.0 METHODOLOGY.............................................................................................................10

4.1 DESIGN OF FEATURES.....................................................................................................10

4.2 DESIGN TRANSFER FROM CAD TO CAM..........................................................................10

4.3 POST PROCESSING.........................................................................................................12

4.4 NC PART PROGRAMME TRANSFER TO EDM MACHINE.......................................................13

4.5 PREPARATION BEFORE MACHINING..................................................................................14

4.6 MACHINING..................................................................................................................... 15

4.7 MEASURING AND INSPECTION..........................................................................................16

5.0 RESULTS......................................................................................................................... 19

6.0 DISCUSSION.................................................................................................................... 19

6.1 TOLERANCES..................................................................................................................19

6.2 PROCESS VERIFICATION..................................................................................................20

6.0 CONCLUSIONS...............................................................................................................22

REFERENCES:...................................................................................................................... 23

Christos Kalavrytinos Page ii


1.0 Introduction

The aim of this report is to simulate the manufacturing procedure of certain

geometrical features of a forklift truck wheel using a Computer Aided Manufacturing

(CAM) programme. Furthermore, the features are to be manufactured on a Wire

Electric Discharge Machine (Wire EDM) so that a comparison between the predicted

and actual results can be made.

1.1 Objectives

In order to successful complete the report, the following objectives have to be

achieved:

Research of Electric Discharge Machining

Review of equipment and software

Review of model transfer and simulation

Review of manufacturing procedure

Review of measuring procedure

Comparison of results

Conclusions and recommendations

2.0 Electric Discharge Machining

2.1 Review of EDM

Electric Discharge machining or EDM, is one of the many manufacturing procedures

used nowadays. It is the process of machining electrically conductive materials by

using precisely controlled sparks that occur between an electrode and a workpiece in

the presence of a dielectric fluid. The electrode, as seen in Fig. 1, may be considered

the cutting tool.

Die-sinking (also known as ram) type EDM machines require the electrode to be

machined in the exact opposite shape as the one in the workpiece. Wire-cut EMD

machines, use a continuous wire as the electrode. Sparking takes place from the

electrode wire-side surface to the workpiece.

EDM differs from most chip-making machining operations in that the electrode does

not make physical contact with the workpiece for material removal and therefore

EDM has no tool force.

Christos Kalavrytinos Page 1


The electrode must always be spaced away from the workpiece by the distance

required for sparking, known as the sparking gap. Should the electrode contact the

workpiece, sparking will cease and no material will be removed.

Figure 1, Basic components of EDM (Jameson, 2001)

another basic fundamental of the process is that only one spark occurs at any

instant. Sparking occurs in a frequency range of 2000 to 500,000 sparks per second.

EDM is a thermal process; material is removed by heat. Heat is introduced by the

flow o electricity between the electrode and workpiece in the form of a spark. Material

at the closest points between the electrode and workpiece, where the spark

originates and terminates, are heated to the point where the material vaporises.

The area heated by each spark is very small so the dielectric fluid quickly cools the

vaporised material and the electrode and workpiece surfaces. However, it is possible

for metallurgical changes to occur from the spark heating the workpiece surface.

A dielectric material is required to maintain the sparking gap between the electrode

and workpiece. This dielectric material is normally a fluid. Die-sinker EDM machines

normally use deionised water.

The main characteristic of a dielectric fluid is that it is an electrical insulator until

enough electrical voltage is applied to cause it to change into an electrical conductor.

The main functions of the fluid in EDM are: controlling the sparking-gap spacing



between the electrode and workpiece, cooling heated material to form the EDM chip;

and removing EDM chips from the sparking area.

(Jameson, 2001)

2.2 Comparison of Die-sinker and Wire-cut machines

Both die-sinker and wire-cut EDM machines use sparks to remove electrically

conductive material. But while both types are electrical discharge machines, there

are differences in their use and operation. Some of these differences are listed

below.

Dielectric fluid:

Die-sinker EDM machines use hydrocarbon oil and submerse the workpiece

and spark in the fluid; and

Wire-cut EDM machines normally use deionised water and contain only the

sparking area in the fluid.

Applications:

Die-sinker EDM machines are normally used for producing three-dimensional

shapes;

these shapes utilise either cavity-type machining or through-hole machining

wire-cut EDM machines are always used for trough-hole machining, since the

electrode wire must pass through the workpiece being machined.

Sparking:

Die-sinker machines produce sparks that occur between the electrode and

the workpiece.

Wire-cut machines produce sparks that occur between the electrode-side

surface and the workpiece.

(Jameson, 2001)

2.3 Wire-cut EDM characteristics

The wire-cut EDM machine, usually, has a movable X-Y positioning table for the

workpiece, with the electrode wire held in a stationary position. The machine's moves

are controlled by servomotors, commanded by computer numerical control (CNC).

There must always be an opening for the passage of the electrode wire. Electrode

wire is only used once, since the material removed from the wire surface during the

sparking process weakens it. (Jameson, 2001)



The majority of Wire-cut EDM machines also have a U and V axis at the head of the

machine to allow for cutting at various angles, thus producing tapered edges.

Figure 2, illustrates the machine's major assemblies required for operation.

Figure 2, Wire-cut machine major assemblies (Johnson, 2001)

The Wire-cut EDM machine can be used for contour cutting of flat or curved

surfaces. The depth of the cutting plates is adjustable to 300mm. The tool (the wire)

is usually made of copper, brass or tungsten and of outside diameter of 0.25mm.

Processes like EDM, which involve machining in a fluid like de-ionised water do not

normally emit harmful substances into the atmosphere and are a preferred selection

from an environmental viewpoint compared, for example, to laser-beam machining or

other thermal metal cutting techniques.

(Boboulos, 2010)

Cutting path:

According to Johnson, wire-cut EDM can have a cutting path or kerf as small as

0.12 mm using Ø 0.1 mm wire, though the average cutting kerf that achieves the best

economic cost and machining time is 0.335 mm using Ø 0.25 brass wire. The reason

that the cutting width is greater than the width of the wire is because sparking occurs



from the sides of the wire to the work piece, causing erosion. This "overcut" is

necessary, for many applications it is adequately predictable and therefore can be

compensated for. The kerf and spark overcut can be seen in Fig. 3.

Figure 3, Kerf and spark overcut.(Johnson, 2001)

Advantages and Disadvantages of Wire-cut EDM:

Some of the Pros of Wire-cut EDM are:

Ability to machine very hard materials

Can machine delicate workpieces due to low tool force

Mechanical properties of workpiece are rarely altered

High dimensional tolerances can be achieved

Small internal radii and filets are only limited by wire kerf

Multiple workpieces can be stacked to increase production rate

Good surface finish depending on number of passes

Dielectric fluid flow improves the removal of metal chips and enhances

cooling characteristics of the tool and workpiece (Boboulos, 2010)

Drawbacks include:

Unsuitability for machining non-conductive materials as it requires special

setup (Kucukturk, Cogun, 2010)

Requirement of a hole for the wire to be threaded through the workpiece

Relatively slow rate of material removal

High power consumption



Longer servicing time due to the presence of a work table and a bath tank

(Boboulos, 2010)

Process provides poor visibility over the machined part (Boboulos, 2010)

3.0 Equipment and Software

3.1 Sodick EX20 EDM machine

This is the CNC machine that was used to manufacture the two initial letters C and K

on the aluminium plate. A similar machine can be seen in Fig. 4.



Figure 4, Sodick EX20 EDM machine

3.2 Catia V5 R20

This CAD programme was used to design the two initials (C and K) on the forklift

truck wheel. Since no actual wheel existed, a simplified model was designed with a

80x80mm restriction surface on a 100x100mm plate to simulate the available area on

the wheel. Then a drawing was produced to extract the 2D elements. Figures 5 and 6

illustrate the 3D model and drawing. The drawing can be found in the Appendix.

Figure 5, 3D model



Figure 6, 2D drawing

3.3 Powershape and Powermill

Delcam's Powershape and Powermill were both used in order to trace the 2D

drawing's active workplane and define a new one to be used in the simulation

programme, as shown in Fig. 7. They both had the same effect, so either of them can

be used for this operation.

Figure 7,Defining workplanes in Powermill

3.4 XCAD Pro 4.2

XCAD is another CAD/CAM programme which was used to simulate the

manufacturing process and to produce the NC part programme. The imported 2D

model is shown in Fig. 8.



Figure 8, XCAD Pro simulation

3.5 CIMCO Edit 4.4

CIMCO Edit, illustrated in Fig. 9, is a CAM software package that was used to view,

edit and simulate the NC part programme.

Figure 9, CIMCO Edit showing the C letter part programme

4.0 Methodology

4.1 Design of features

The features (initials C and K) that were supposed to be manufactured on a forklift

truck wheel, were instead designed to be cut on an aluminium plate due to the lack of



an actual wheel. This simplification, although helpful, influences the actual

manufacturing procedure and, therefore, some issues must be noted.

First of all, if the actual wheel was machined, there would be some height clearance

that would have to be taken into consideration. Moreover, the set up of the machine

would be different due to other means of clamping.

The two letters were designed on Catia V5 so that a 2D sketch containing only the

toolpath needed could be saved as a .dxf and .ig2 file.

A slight angle was given to the initials to improve appearance since they would be

machined on a disk and the width of the letters was chosen to be 4mm with 1mm

internal radii. The dimensional tolerance was stated as 0.05mm or 50 microns.

Measurements for the position of the two holes needed for the wire threading were

also taken. The holes were positioned at convenient locations designated by the

tutor.

4.2 Design transfer from CAD to CAM

Since the main aim of this assignment is to simulate and machine two initial letters on

a workpiece, the 2D features have to be transferred to a CAM programme.

Specifically, this programme is XCAD which is mainly used for Wire EDM

simulations.

Catia to Powermill:

In order to transfer the 2D features, a drawing is first produced in Catia and then

saved both as a .dxf and .ig2 file. Both file formats were tested on Powermill and

Powershape. It was found out that the .dxf and .ig2 files retains its origin/ workplane

which is the bottom left corner of the drawing file. A new workplane is then created at

the bottom left edge of the 100x100mm block as shown in Fig. 6. This is the origin

that will be used during simulation and machining. The position in respect to the

original workplane were X 170mm, Y108.5mm.

This step is followed as it is easier to change the origin in Powermill or Powershape

than in XCAD. The file is then saved as a .dxf format.

Powermill to XCAD:

A new project is then created in XCAD and the units are changed to Mechanical.

Then the .dxf file is imported. When the features C and K appear the setup of the



simulation can begin. The electrode specifications are set to a diameter of 0.25mm

and material brass is selected. A new multipass is created and the features of the

letter K are selected first using the window feature, without selecting the hole. The

start of move parameter is set to the centre of the hole (X 50mm, Y 40mm) and the

start entity is set as the outer slope of the upper angled line of the letter K.

In order to achieve good dimensional tolerance and surface finish, the electrode must

move at a constant speed and avoid being stationary as this might cause more

material to be removed at a specific point. The lead-in and lead-out parameters help

in avoiding this issue by creating a more smooth approach angle to a feature. The

lead-in and lead-out paths for the letter C can be seen in Fig. 10.

A line break is also introduced so that the lead-in path can be applied at a good start

position.

Figure 10, Lead-in and lead-out paths

Now the toolpath can be simulated to check for errors. Then the post processor for

the Sodick control (Sodick2.cfg) is used to produce the part programme.

4.3 Post processing

In the early days of post-processing, a post-processor, illustrated in Fig. 11, was

considered an interface tool between computer-aided manufacturing (CAM) systems

and numerically controlled (NC) machines - a mere translator, reading the

manufacturing instructions issued from a CAM system and writing an appropriate

rendition for a target NC machine. Today however, post-processing has evolved to

include a dynamic range of code optimization tools which are responsible for

outputting the most efficient and productive machine tool code possible.


Start of move

Line break


NC post-processing is responsible for joining two very different technologies, and it

often serves to compensate for weaknesses on either end. Therein lies the crux of

the issue: a post-processor can enhance technology, or it can inhibit it, depending

upon its application.

The NC machine requires input customized for the controller being used and

arguably to a lesser extent, the operator running the machine. Most important, the

NC machine must be driven in a manner that satisfies shop floor criteria, which are

primarily based on safety, efficiency and tradition. Between these two lies the post-

processor. The post-processor is software responsible for translating neutral

instructions from the CAM system into the specific instructions required by the NC

machine.

(www.icam.com)

Figure 11, Post processor schematic (www.icam.com)

In many cases, post processors produce NC programmes with mistakes and

omissions which can be edited either in a programme such as CIMCO Edit or in the

actual controller of the machine after the NC programme has been downloaded.

Figure 12 shows the part programmes generated for the letters C and K respectively

by the Sodick post processor.



Figure 12, NC part programmes for C and K respectively

4.4 NC part programme transfer to EDM machine

After the NC part programme for the letter K was viewed in CIMCO Edit, it was

downloaded to the Sodick EDM. The first line was edited in the controller's screen to

G42 H158 C200 where G42 is the tool radius compensation that adds an offset H to

the right for the wire radius (0.125mm) plus the spark gap (total of 0.158mm).

In order to get the correct result, G41 had to be used instead of G42. This error was

due to the machine operator's judgement and was later rectified for the letter C.

Figure 13 illustrates the machine operator during the NC programme editing on the

machine controller and the machine graphics depicting the toolpath.



Figure 13, NC programme editing and toolpath for K

4.5 Preparation before machining

Before the machining operation, the two holes, one for each initial, had to be drilled.

Since the width of the letters was 4mm, holes with a diameter smaller than that

should have been drilled. However, due to the time pressure, a mistake was made

and a 4.8mm drill was used. Moreover, the dimensions not measured correctly and a

hole was drilled at the wrong place by mistake. The process of drilling the holes at

the correct positions, which were marker earlier, can be seen in Fig. 14a. Figure 14b

illustrates the workpiece that is clamped in place and the technician who is threading

the wire electrode through one of the holes.

The next step was to find the centre of the hole, an operation that was carried out

automatically by the EDM machine. The workpiece moved until it came in contact

with the wire and the correct coordinates for this point were entered. The splash

guard was lowered so that machining could commence.



Figure 14a, Drilling the holes Figure 14b, Threading the wire

4.6 Machining

The letter K was the first to be machined. The workpiece moved from the start of

move point towards the start entity with a shallow angle of approach as set in the

lead-in parameter with a counter-clockwise motion. The total machining time was

approximately 24 minutes, with the total machined length at 185.164mm at an

average feed rate of 7.36mm/min. The electrode was cutting at a voltage of 50 Volts

at 2.1 Amps. It was observer that whenever the electrode was nearing a corner (i.e.

the 1mm radii corners) the cutting speed was slightly reduced to increase

dimensional and geometrical accuracy.

During the machining process, when the wire reached the hole the inside of the letter

K was split and the debris fell and caused a short circuit, thus, stopping the

machining. A screenshot of the machine control prompting the warning is illustrated

in Fig. 15a. Figure 15b shows the finished letter that had to be removed by hand

since a short circuit occurred again.

Then the letter C was machined following the exact procedure as in letter K, with the

difference being the change in the G41 code. This time no short circuits occurred and

the total machining time was approximately 20 minutes with a total machined length

of 149.41mm at an average feed rate of 7.320mm/min.

Both letters and the hole drilled by mistake can be seen in Fig. 16 with their

dimensions measured using a Vernier calliper.



Figure 15a, Electrode contact warning Figure 15b, Finished letter

Figure 16, Finished features with dimensions

4.7 Measuring and inspection

Using dimensional and geometrical tolerances when designing a part is very

important when the material and manufacturing process is concerned.

It is important for the workshop personnel that carry out the measuring and

inspections to have the complete CAD files and drawings of a part to allow them to

compare the results with the requirements set by the designer.

According to the ASME (American Society of Mechanical Engineers) Y14.5-

200 standard, the purpose of geometric dimensioning and tolerancing (GD&T) is to

describe the engineering intent of parts and assemblies. This is not a completely


3.95 mm

4.61 mm


correct explanation of the purpose of GD&T or dimensioning and tolerancing in

general.

The purpose of GD&T is more accurately defined as describing the geometric

requirements for part and assembly geometry. Proper application of GD&T will

ensure that the allowable part and assembly geometry defined on the drawing leads

to parts that have the desired form and fit (within limits) and function as intended.

(ASME, 2009)

In order to measure what tolerances where achieved, a Vernier Calliper was used

providing an accuracy of 0.01mm. or 10 microns. However, another method of

measuring and inspecting is also available with the use of a Coordinate Measuring

Machine or CMM. The typical CM machine can be either manually or automatically

controlled. As an example, BCU owns a Mitutoyo FN905 CMM, shown in Fig. 17,

which can be accurate to 0.005mm or 5 microns. The most important component of a

CM machine is the touch probe on the end of the turret. The Sodick EX20 Wire EDM

machine be accurate to 1-2 microns. It is usual for CM machines to be up to ten

times more accurate than the CNC machine used to manufacture a part. In this case,

the tolerances set during design were 0.05mm or 50 microns. Using a Vernier

Calliper were enough to achieve readings of 3.95mm for the letter C and 4.61mm for

the letter K.

Figure 17, Mitutoyo FN905 CMM

However, if the case was different with higher requirements for dimensional accuracy

or required more precise measuring of the internal radii, a modern CM machine with

a more accurate probe. New touch trigger probes are available nowadays that can

measure dimensional and geometric tolerances very quickly.



Probes are elaborate switches designed to trigger on contact with a highly repeatable

triggering characteristic when an 'event' occurs - contact with the surface of an

object.

(www.renishaw.com)

Touch trigger probes, illustrated in Fig. 18, can also be used in CNC machines with

tool magazines, therefore eliminating the need of taking the workpiece of the CNC

machine and transferring it to a CM machine to be measured. Moreover, measuring

and inspecting during the machining process of a complex part, such as a jet engine

impeller, can help predict any errors before the part is finished.

Time spent manually setting work piece positions and inspecting finished product is

better invested in machining. Probing systems eliminate costly machine down-time

and the scrapping of components associated with manual setting and inspection.

The use of a probe system can result in the following benefits according to

Renishaw:

Increase automation and reduce human intervention:

automate manual setting and measurement processes

reduce direct labour costs

redeploy staff into proactive engineering roles

Reduce rework, concessions and scrap:

improved conformance and consistency

lower unit costs

shorter lead times

Enhance your capability and take on more work:

offer your customers state-of-the-art capabilities

take on more complex work

meet customer demands for traceability



Figure 18, Touch trigger probes (Renishaw.com)

5.0 Results

The dimensions set by the original design were a width of 4mm with a 0.05mm

tolerance. The result was a width of 3.95mm for the letter C and 4.61mm for the letter

K as shown in Table 1.

Feature Design Dimension Machined Dimension Difference

Letter C 4 +/- 0.05mm 3.95mm 0.05mm (OK)

Letter K 4 +/- 0.05mm 4.61mm 0.56mm

Table 1, Design and machined dimensions

6.0 Discussion

6.1 Tolerances

Analysing the results of the design dimensions and the actual machined dimensions,

it is clear that the letter C is just within the pre specified tolerances. However, when

the letter K was measured, it was found to be 0.56mm wider than the tolerances

allowed. This error can be attributed to the misuse of the cutter tool compensation G



code. The tool offset used was set at a radius of 0.158mm or diameter of 0.316 which

if used in the wrong way (i.e. to the left instead of the right) can produce different

results. In this case, and since the wire is cutting at the inside of the letters, the effect

of this error is multiplied and can explain the 0.66mm difference from the letter C

dimension. Other reasons that reduce the accuracy of the machining process are the

selection of the kerf or spark gap as well as the actual accuracy of the servomotors of

the X and Y axes of CNC machine.

When the tool radius offset issue was rectified in the NC part programme of the letter

C, the dimensional tolerances were achieved.

6.2 Process verification

The main CAM programme used for this simulation was XCAD. This provided a

sufficient simulation for machining the features on a metal plate. However, the

features had to be machined on a more complex part, it might have been good

practice to verify the simulation to ensure no collisions occur that can damage the

EDM machine or the workpiece. Vericut is a programme that can perform the NC

programme verification.

VERICUT software is used to simulate CNC machining in order to detect errors,

potential collisions, or areas of inefficiency. VERICUT enables NC programmers to

correct errors before the program is ever loaded on the CNC machine, thereby

eliminating manual prove-outs. VERICUT also optimises NC program cutting speeds

for more efficient machining.

(http://www.cgtech.com/usa/)

Simulation and verification has become a standard feature of CAM applications. CAM

Original Equipment Manufacturers (OEMs) incorporate core clash detection

functionality that takes into account all parts in the machine environment.

The demand for simulation and verification of programs created on conversational

controllers derives from the increasing complexity of machines. By having such a

system simulation integrated with the controller, operators on the shop floor are

reassured that their programming/editing is error-free before running the machine.

(http://www.machineworks.com)

Real-time collision detection:



MachineWorks has been integrated into more sophisticated CNC controllers allowing

the ultimate in safety and control: a built-in intelligence system that will not allow the

machine to crash. The toolpath is monitored live. The software will "look ahead" of

the toolpath and if it detects an imminent crash it will stop the machine and give a

warning.

(http://www.machineworks.com)

All these systems and programmes can be used to increase production and

efficiency of the manufacturing process by reducing the risk of errors during the

process that could result in scraping of the part or ever damaging the tools or CNC

machine.

Figure 19 illustrates the pieces that were cut from the metal plate showing the

mistake made by using the 4.8mm drill tool that was larger than the width of the

letter.

Figure 19, Pieces cut from the metal plate.



6.0 Conclusions

This report shows that setting tolerance values for a design is very important and can

influence the selection of the material and manufacturing process of a part.

The transfer of a design from CAD to CAM is an operation that must be carefully

carried out to ensure the proper setup of origins and material stock are selected.

In this case, an extra CAM programme, Powermill, had to be used in order to set the

correct origin of the part since it proved to be easier than performing the same action

in XCAD.

Since XCAD is an old software package, the interface and graphical user interface

took time to get used to. Moreover, the simulation of the process is simple and there

were no features for collision avoidance.

Furthermore, verification of the NC part programme produced by the machine post

processor is recommended since post processors can sometimes create NC

programmes with errors.

In addition, the correct setting of the CNC machine and editing of the NC part

programme to compensate for parameters such as tool radius, length, etc. is

important. An mistake in the tool radius offset caused an issue in the machining of

the letter K and resulted in a larger than expected diameter.

Moreover, careful measuring and inspection in comparison with the original CAD files

and drawing can point out any mistakes made during the design or manufacturing

process.

Nowadays, CAD to CAM transfers of designs is becoming easier and more user

friendly. CAM programme simulations are improving and allow for features such as

collision detection to improve the manufacturing process.



References:

Books:

ASME (2009). Dimensioning and Tolerancing. New York: ASME.

Boboulos, M. (2010). Manufacturing Processes and Materials: Exercises. Ventus

Publishing ApS. 14-15.

Jameson, Elman C. (2001). Electrical discharge machining. Dearborn, Mich: Society

of Manufacturing Engineers.

Journals:

Kucukturk, G. & Cogun, C. (2010). A new method for machining electrically

nonconductive workpieces using electric discharge machining technique. Machining

Science and Technology: An International Journal, 14(2), 189-207.

Websites:

http://www.advantageedm.com/examples.asp, Accessed on 14/01/12

http://www.cgtech.com/usa/, Accessed on 14/01/12

http://www.icam.com/html/products/whatis/what_is_post.php, Accessed on 14/01/12

http://www.machineworks.com/solutions.htm, Accessed on 14/01/12


c. kalavrytinos - cnc wire erosion simulation of forklift wheel

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