Making the Right Choice

Selecting a wire EDM CAD/CAM System

Now that you have made your decision to purchase a specific wire EDM machine there is one more decision to make. What software package will you use for programming? This last decision may seem minor when compared to the months of study that went into the machine purchase decision. However, this decision can greatly affect the productivity of your machine so it should not be taken lightly.

The Dilemma: How can you make an intelligent decision when you don’t have the pertinent information? Everyone claims that their software will program a wire EDM machine and will do everything you need. How can you know if this is true when you yourself are not even sure of everything that you may want to do?

The Solution: Get as much information as possible. Speak to people involved in the industry. Continue reading this document and use it as one your resources when evaluating potential CAD/CAM systems. This article was written by an individual who has been programming NC/CNC equipment since 1976 and has been involved in the CAD/CAM industry since 1986. In the past 17 years he has personally trained hundreds of customers on the use and implementation of CAD/CAM software specifically for wire EDM applications. The following insights will give you a good starting place in your evaluations.

Your Requirements: Each companies requirements can be best defined if we consider these 3 questions:

Will you import geometry from an external CAD system or will you create the geometry in your CAD/CAM system?

How do you intend to utilize your machine?

Which machine tool will you be programming?

Each of these questions is of critical importance in the decision making process. Let’s look at them one at a time.

Geometry

If you intend to import geometry from an external source which formats will you be required to accept?
1. DXF (data exchange format). This is an output format available from AutoCAD and many other systems. It is best suited for 2D data.
2. DWG (AutoCAD native drawing). This is the AutoCAD native file format. If a DWG file is read directly this will eliminate one of the translations required for other formats.
3. IGES (initial graphics exchange specification). This is a format that was originally developed to allow dissimilar CAD systems to share geometrical data. Today it is probably the most popular method of exchanging 3D CAD data. IGES supports NURBS curves & surfaces.
4. X_T and X_B (native Parasolid). These are solids based formats that are available from all solid modelers that utilize the Parasolid kernel. The most popular of these would be Solid Works and Solid Edge.
5. SAT This is a solids based format that is available from all solid modelers that utilized the ACIS kernel. The most popular of these would be AutoCAD Inventor and CADKEY.
6. SLDPRT (native Solid Works). This is the Solid Works native file format. This format eliminates the need for a translator as the model will be read directly in the Solid Works format.
7. PSM and PAR (native Solid Edge). These are the Solid Edge native file formats. No translation is required if the model is read directly from this native file format.
8. VDA (European automotive standard). VDA-FS (Verband Der Automobilindustrie Flachen Schnittstelle) is a standard file format to exchange surface data. It is popular in Europe due to the endorsement of several major European car manufacturers.
9. STP and STEP (Standard for the Exchange of Product model data). The STEP format is most commonly used in AP203 and AP214. AP203 was the original standard adopted in 1995 and AP214 is the latest standard. This format is most commonly used in the North American automotive industry.
10. CATPART (Catia V5 native part). This is the Catia native part file format. No translation is required if this native file format is read. Earlier versions of Catia used different file formats (.model, .exp, .dlv, .dlv3).
11. ProE native files (.prt, .asm). These formats are both ProE native file formats. If either of these formats are read directly it will eliminate the need for an additional translation
12. UG native part files (.prt). This is the native Unigraphics file format and allows files to be read directly without translation.

If you intend to create your own geometry what will be your requirements?
1. Will you need to draw simple 2-dimensional geometry? If so most systems will be able to provide the necessary drawing tools. The more important question is how easily and quickly will you be able to create the geometry. In this application geometry creation will most likely be the most time consuming aspect of preparing a program, so ease-of-use will be an important factor.
2. Will you have the need to create complex 3-dimensional geometry? If so you need to insure that the software has the ability to create and draw in multiple work planes. Geometry creation should support X, Y and Z data. Many systems require 2-D date (XY) to be created and then moved to a different Z height or work plane. If your parts are complex this can lead to additional drawing time and the chance for errors.
3. Will you need the ability to create solid models? If so your system should have some solid modeling capabilities. In most cases you are going to be drawing simple things like fixtures and material blanks. If serious design is your intention then it is probably best to consider a separate design package since most systems that will function well for programming your wire EDM will not provide an extensive set of design tools.
4. Will your parts commonly contain multiple shapes which need to be machined? If so does the software provide a method for automatically creating these shapes from either a wire-frame or solid CAD file.

The CAD capabilities of your software package should be an important part of the overall evaluation. If you intend to import CAD file provide to you by outside (customers) sources then it would be best to be able to import a large number of different formats. Ideally you would not have to pay extra for these translators but in most cases you can expect to pay for Catia, ProE, Unigraphics and STEP as software companies must pay a licensing fee to utilize these formats. If your company will only deal with internal CAD files then it will only be necessary to verify that the specific translator you require is fully functional with the latest generation of CAD software. It is also a plus if the software is certified by the different CAD vendors. This typically means that the software supports the latest version of the file formats and that the CAD vendor has checked the translation for accuracy.

Machining Capabilities

Does your machine have a wire threader?
1. If your machine has a wire threader you system will need to output the necessary M codes to cut and thread the wire. This can be done automatically or some systems may require you to manually call a command to cut or thread the wire. If the system does not perform this function automatically then this will be one additional area for possible errors in programming.
2. If your machine has a submerged work tank the system may also be required to drain and fill the work tank during wire threading.
Does your machine require a non-standard programming format?
1. If the control system on your machine requires a non-standard programming format then you need to confirm that the programming software is capable of generating the necessary codes and files. Machine controls that require special program formats may offer additional functions that are not available on more standardized controls so this is not necessarily undesirable it simply means that the programming software will be more critical.
Will you be programming multiple opening parts?
1. If your programs will have multiple shapes to be cut it will be necessary to program wire cut, positioning and wire thread commands. The automatic creation of these positioning moves will reduce the number of steps required to program this type of part as well as the chance for errors.
2. If your parts have multiple shapes to be cut does the programming software provide a method of machining multiple shapes without having to individually pick each shape? If you commonly machine a large number of shapes this can eliminate the time consuming task of selecting each shape.
3. If multiple shapes are to be machined does the software offer a method of sorting the order of the machining to create the shortest path?
Do you need to program 4-axis parts?
1. If you have the requirement to create 4-axis program how easy is it to create the synchronization points? Synch points are necessary when the 2 different shapes have different numbers of segments and thus require points of synchronization to be selected along the individual shapes. These point should be able to be selected anywhere along the shapes not only at the end of segments. Many times it may be necessary to add synch points after the initial program has been created. If these points can only exist at the end of a segment then it may be necessary to go back and modify the geometry to add additional segments.
2. Will your 4-axis programs require shapes with non-planar shapes? Many systems only support planar shapes. If your geometry is non-planar then this will require an additional step to create a surface and then slice the surface to create these planar shapes.
Will you run your machine in unattended machining mode?
1. If your machine is equipped with a wire threader and you intend to run the machine while it is unattended then your programming software should support the automation of this type of programming. The most common type of unattended machining is when all of the openings in a part are roughed without dropping a slug. After the roughing the machine will wait for the operator and then each of the slugs is dropped and then the trim cuts can happen fully unattended. If your programming software supports this type of machining it will save the many steps required to generate this type of program manually.
2. If you intend to run your machine unattended at times then you should also inquire about how easy it is to change from one machining technique to another (standard glue-stop to unattended). Will the software automatically sequence the multiple cuts to create the shortest possible tool path? Both of these functions are crucial if you intend to program using this feature since scheduling may change and force a program to be run while an operator is present. Secondly you do not want the machine making longer movements than necessary since each of these positioning moves will be made at least 3 times since the program will contain a rough, cutoff and trim for each opening.

Machine Type (manufacturer)

Each wire EDM manufacturer has different controls and features which makes it very important that the programming software that you select will be able to support the special functions of your machine and also generate the correct NC code to cut the parts. The following list is intended to give you the basics required by each manufacturer. When investigating CAD/CAM software you should address these requirements with each prospective company. This will also give you an easy way to judge how familiar they are with wire EDM.

Agie 100/123 controls. These controls are no longer produced by Agie and will only be found on machines produced prior to 2001. This control uses a very unique programming format. The following is a list of some of the requirements:
1. The NC code can only be output in metric.
2. The NC code can only be output in incremental.
3. The NC code does not accept decimal points.
4. The NC code requires both positive (+) and negative (-) signs to be output.
5. The entry move (lead-in) and first contouring move are actually reversed in order in the NC code
6. If the machines offsetting is to be used all moves must be tangent and entry and exit moves must be perpendicular.
7. 4-axis programs do not use U and V values like most controls but rather Q and R which are angles relative to the directional vector. This is the only control on the market that uses this technique.
AgieVision controls. This is the newest Agie control from Agie and has been available on machines produced after 1996. This control offers many advanced capabilities. The AgieVision control uses 3 different file types.
1. The .ISO file is a standard NC code file which is the contouring data in a standard G-code format. A separate .ISO file is required for each shape to be cut. If you are using no-core machining then 2 separate .ISO files are required for each shape, one for the roughing path and one for the finish profile.
2. The .SBL file is the script file and is used by the AgieVision control to setup all of the necessary parameters for each .ISO file. These parameters include:

i. Wire Start Hole

ii. Exit Point (lead-out)

iii. Taper amount

iv. Part thickness and Land height

v. Collar Type

vi. Separation Cut amount

vii. Part Material and Stock Size

viii. Wire Type and Diameter

ix. Quality Target (tolerance, surface finish, corner accuracy)

The .SBR file is a list file containing the names of all the .ISO files used for the specified program

For a programming system to be effective for this control you need to be able to create all 3 file types. If a system only generates the .ISO files then it will be necessary to perform the remaining functions covered by the script file at the machine controller. Another item to consider is how often the post processor is updated for this machine, since one of the advantages of the AgieVision control is that it can be updated in the field. This allows users of machines with older controllers to be updated to the latest functionality. As Agie adds new capabilities to this control the programming software must be updated to reflect these improvements.

Charmilles Robofil controls. This control is still offered on some Charmilles machines and was the most common control on most Charmilles machines produced prior to 2002. This control also uses 3 different file types. These file types are as follows:
1. The .ISO file is the main NC code file. The program can be written using a single .ISO file with all cuts written in a single file or separate .ISO files can be written for each shape.
2. The .CMD (command) file contains the setup information. This file will vary in complexity depending on whether single or multiple .ISO files are being used. This file contains parameters for the following:

i. Part Thickness and Land height.

ii. Wire Offset Amount and Direction.

iii. Taper and Stop use.

iv. Technology File information.

The .TEC (technology) file contains the cutting and offset information. This file is created at the machine using the CT-Expert software and can also be created offline if the programming software is integrated with the CT-Expert software.

This control can be programmed offline with a system that only outputs the .ISO file but it will then be necessary to generate the .CMD (command) file at the control. The Charmilles control has a number of special functions which should be supported by the programming software. These functions include: Wire Protection Strategy, Corner Control and Twist Mode. For production machining jobs the automated pickup functions can be programmed in the .CMD file.

Charmilles Millennium controls. This is the control supplied on most Charmilles machines produced since 2002. This control uses a more traditional main and sub program method and it also utilizes a .TEC file. It also has the CT-Expert software for creating technology files which can be integrated with offline programming software. This control also supports the Wire Protection Strategy, Corner Control and automated pickup functions.
Mitsubishi controls. Mitsubishi has produced a large number of machine models over a considerable period of time. As the machines have progressed the capabilities have increased. It is important to clarify if a post processor for a specific machine is available and if that post processor has a cutting condition database containing the E-paks, feed rates and offsets provided by Mitsubishi. Mitsubishi machines typically require that a lower power setting be used during the entry move with the full power setting being activated once the cut has been started. The programming system should be capable of outputting 2 sets of E-paks for the initial roughing cut. It would also be helpful if a specified distance for the insertion of the second E-pak could break the contour automatically. Another requirement for certain Mitsubishi machines is the output of a dwell (G04) command after the lead out move when cutting outside shapes. This is necessary due to the wire lag created during a roughing cut under certain conditions. A wire break can occur if this dwell is not programmed. Machines equipped for submerged machining need tank drain and fill commands output when automatic wire threading is to be used. All of these commands could be manually inserted if necessary but it would be best if the software could output them automatically when needed.
Sodick controls. Sodick has also produced a wide variety of machines with different controls. It should be verified that a post processor is available for a specific control. On older Sodick controls it is necessary for the wire offset to be applied and canceled in two stages. This avoids the offset being applied to the entry and exit moves, which will leave a small scallop on the part. Different Sodick controls have different techniques for programming the actual values for the “H” offset registers, so it is necessary to have different post processors capable of outputting this information in either format.

In Conclusion: The wire EDM industry is different than the chip-making industry in the fact that each manufacturer uses a unique control. This means that there needs to be machine specific functionality included in a programming system to effectively take advantage of the features offered by the individual machine manufacturers. This level of specialization will only be possible from software companies who are willing to make a serious commitment to their wire EDM modules. With wire EDM representing a very small percentage of the overall CAM marketplace most software companies will not devote much R & D to a product with such a small potential market. Search out a company who is committed to the wire EDM market and has the years of experience required to provide you with a comprehensive solution to your programming system needs. Another important factor that can only come with years of experience is customer support. You want someone knowledgeable in wire EDM programming to be there to provide support when you have a question.

The CAD/CAM software you purchase will definitely affect the productivity of your wire EDM equipment. This purchase should be given the consideration it deserves. Use the information provided here, talk with people at the wire EDM manufacturer and speak with other people in the business. Do whatever it takes to make sure that you have the necessary information to make an informed decision.