Making the Right Choice for Charmilles

Selecting a wire EDM CAD/CAM System

 

Now that you have made your decision to purchase a Charmilles 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 donít 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 2 questions:

 

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

 

  1. How do you intend to utilize your machine?

 

 

 

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

 


 

Geometry

  1. 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.

 

  1. 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 provided 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. If your company intends to make use of solid models then it will be important to understand how the solid will be converted into the geometry that you will need to make your tool paths. Does the software have the ability to create shapes directly from the solid our do you need an intermediate step. Can the software pick up details such as land heights, taper amounts and direction directly from the solid? Can the software automatically create slices of a solid model? If you need to program 4-axis work can the software automatically establish synchronization points from the solid model? All of the answers to these questions will determine how easily you can use solid models to program you parts.

 

Machining Capabilities

  1. 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.
  2. 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?
  3. 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? Sync 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 points 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. It is also important to consider how easily additional sync points can be added. If the sync points are part of the tool path then you may have to go be a redefine the tool path to add more sync points. Typically it will be better if the sync points are part of the geometry rather than the tool path as this will make adding points much easier.
    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.
  4. 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 the 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.

 

Control Type

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. Charmilles machines are currently sold with both the Charmilles Robofil and Charmilles Millennium controls. In the past they were also sold with the Charmilles Fanuc control 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.

 

  1. Charmilles Robofil controls. This control is still offered on some high-end 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.

    1. 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. The ability to integrate CT-Expert into your offline programming software is an important factor as this insures that the number of cuts, offsets and TEC file names will match exactly with the TEC files used at the machine

 

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. If the programming software only outputs a single .ISO file and does not have CT-Expert integrated this will limit you to using a single TEC file. This is an important fact to consider because in many applications you may be cutting a part in which it is desirable to use multiple TEC files since all of the contours may not require the same number of cuts or be cutting through the same thickness of material. 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, clearance and Taper and Twist Modes. For production machining jobs the automated pickup functions can also be programmed in the .CMD file.

 

  1. 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, clearance, automatic corner rounding, taper modes and automated pickup functions. This control can also be programmed offline with a system that generate only a single .ISO file but once again this will likely limit the ability to use multiple TEC files in a single program.

 

  1. Charmilles Fanuc controls. This control was supplied on certain Charmilles machines produced in the late 90ís and early 2000ís. These machines ended with an F designation. If you need to program one of these machines they have the same requirements as the Charmilles Millennium control.

 

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 Charmilles 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.