Reduce Machining Time by 60% with Pro/TOOLMAKER by Jerry Fireman
Producing electrodes for electrical discharge machining (EDM), or spark erosion, is challenging because the toughness of the material and the need for a fine finish typically requires many machining passes. The machine often wastes time cutting air over areas that were already cut to size on previous passes.
 
Modern Moulds and Tools Limited knows all about this problem. The company is a leading producer of tooling for injection and blow molding, die-casting, and thermo-forming. It uses EDM to produce the cavities for most these tools. Up to 50 electrodes are sometimes required to produce a single mold cavity.
 
Previously, the company programmed the vertical machining centers used to produce these electrodes at the machine control using machining macros. The controller was not user-friendly so it took a considerable amount of time to train operators to program the machines.
 
Air cutting reduces productivity. But the biggest problem with this approach was that there was no way to determine where metal was left after each pass. So programmers had to move the tool over the entire part contour for each roughing, semi-finishing, and finishing cut.
 
Operators were also limited to two dimensions in setting the boundaries for the surfaces requiring machining. As a result, the boundaries often exceeded the area that needed to be cut by a considerable margin. The machine spent so much time cutting air that it took 15 hours to machine a typical electrode.
 
“A lot of time was wasted during the machining operations,” says John Horspool, works director for Modern Moulds. “Machining electrodes is critical to our success so we looked for a way to do it more efficiently. We discovered that Pro/TOOLMAKER provides far more productive methods to rough out electrodes and other parts.”
 
Pro/TOOLMAKER’s graphical user interface makes it much easier for operators to produce their own CNC programs. “It only takes one day to train a new operator to create their own programs,” Horspool says. “The graphical user interface is very intuitive to anyone that is familiar with metalcutting operations. Our training focuses on the specialized toolpaths and machining strategies that are provided by the software package.”
 
More accurate surface boundaries. The first step in producing a CNC program is importing the solid model geometry of the electrode. Importing the solid model eliminates the need to manually define the electrode surfaces and also ensures that the surfaces are trimmed to their exact size. This saves machining time by avoiding cutting air on the outer boundaries of the surfaces.
 
Modern Moulds operators next identify the surfaces to be machined and begin matching them up with machining operations. Pro/TOOLMAKER makes this process more productive by providing a wide range of high speed machining strategies that can be used to optimize nearly any type of cut—exit and connections for roughing, rest-roughing, finishing and rest milling, including pencil trace.
 
Modern Moulds produces electrodes, core and cavity detail for mould tools by machining them with a series of progressively smaller end mill and indexable cutters. Normally, depending on the size of the part being machined, the first roughing pass would be programmed using a 25 mm diameter by 5 mm corner radius, and the second with a 15 by 3.5. The last two passes are made with 12 by 1 and 6 by 1 coated solid carbide torodial cutters (high speed machining).
 
Rest-machining function reduces air cutting. The rest-machining function automatically determines what metal remains to be cut after each machining operation. Then when it generates the next pass it rapidly traverses directly to the areas that need to be machined and skips over all the others. This feature substantially reduces air cutting.
 
Using Pro/TOOLMAKER Modern Moulds has developed a library of machining operations, each of which includes the cutting tool, machining speeds, feed rates, ramping, coolant and air. These operations have been developed by the company’s most experienced operators to optimize the machining operations. The machining library helps spread best practices throughout the company and ensures that every machining operation is performed at the ideal operating conditions. The company typically uses machine speeds of 1600 rpm and feed rates of 8 meters per minute.
 
Realistic simulation avoids crashes. After defining all of the operations required producing the electrode, Pro/TOOLMAKER generates a realistic simulation of the complete machining operation. The simulation makes use of pre-existing models of the machine, tooling and fixturing as part of the program so that possible clashes can be eliminated before the program is run on the machine. The simulation also helps operators identify areas for further productivity improvements.
 
Finally, when the operator is happy with the program, he or she uses Pro/TOOLMAKER to generate ready-to-run G-code. Rest-machining, surface trimming, the machining library and other features of Pro/TOOLMAKER make the code so much more efficient that the typical electrode can now be machined in only six hours, 60 percent less time than was required in the past.

 
Modern Moulds and Tools Ltd., based on Lancing, West Sussex, produces tooling for a wide range of molding, casting and forming operations.
 

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