Making the Right Choice for
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.
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?
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.
Each companies requirements can be
best defined if we consider these 2 questions:
- Will you import
geometry from an external CAD system or will you create the geometry in your
- 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
- If you intend to import geometry from an external
source which formats will you be required to accept?
- DXF (data exchange format). This is an output
format available from AutoCAD and many other systems. It is best suited
for 2D data.
- 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.
- 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.
- 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
- 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.
- 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.
- 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.
- 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.
- 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
- 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).
- 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
- UG native part files (.prt). This is the native
Unigraphics file format and allows files to be read directly without
- If you intend to create your own geometry what will be
- 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.
- 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.
- 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.
- 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
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
- Does your machine have a wire threader?
- 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.
- If your machine has a submerged work tank the
system may also be required to drain and fill the work tank during wire
- Will you be programming multiple opening parts?
- 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.
- 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.
- 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?
- 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.
- 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
- Will you run your machine in unattended machining
- 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.
- 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.
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
- 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:
- 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.
- 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:
Part Thickness and Land height.
Wire Offset Amount and Direction.
Taper and Stop use.
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. 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
- 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.
- 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
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