Computer programming pays off Essay

Computer programming pays off Precise Tool & Mold, Youngstown, OH, is a small companymanufacturing injection molds for the plastics industry, includingcompanies in Canada, the West Coast, and Florida.

They are doing wellbecause they have mastered the most difficult part of moldmaking–making complex NC tapes quickly and efficiently. They can produce dies up to 48 66, using three NC machines, twoHillyer 600s (66 X 44 Y 18 Z) and a Hillyer 700 (50 X 30 Y 18 Z).All have General Automation controls so that all programs arecompatible, machine to machine.

They purchased their first CNC Hillyer in 1978 and did all thenecessary programming manually for the first three years. Oneprogrammer couldn’t handle the load, so they hired a secondtrainee. Programming time per tape was anywhere from one hour to two orthree weeks to write. When they added their second machine in ’81,they added another programmer, but ran into trouble. Programming bottleneck “The more experienced we got on these machines,’ explainsProgrammer Jody Soltesiz, “the more diversified our work became.

We were able to move into new areas that contributed to our growth. Butas we got into three-axis contouring in manual programming, it becamevirtually impossible to keep up. This forced up to seek out acomputer-assisted programming system.

We investigated severalsuppliers, and tried one in-house for a year. But it didn’t workout.’ That earlier system was obtained under a contract with a one-yeartrial period. Final purchase was contingent on the system meeting withtheir full satisfaction. “During this trial period, we experiencedseveral difficulties,’ Jody recalls. “One was storagespace–our parts were just too complex to fit on their hardware. “We do a lot of 3-D contouring now.

With the prior system,the tape could only be so long, 300 ft to 400 ft. With the new system,tapes can run well over 2000 ft. I don’t know whether the limitwas hardware, software, or both, but the system asked you to split theselonger jobs up. “Obviously, for more money, we could have gotten a system tohandle our contouring tapes, but for less total money we’re gettingthat and more from the system we purchased from Datacut Inc, Ardsley,NY. We also got detaching capabilities, the ability to drop one programand move to another while lengthy computations are going on.

Wecouldn’t process one program while we wrote another one before, andwe also like the flexibility we now have of being able to use multipleterminals.’ Graphics interaction “We really like the language,’ Jody says.”It’s easy to understand, simple to learn, easy to write, justeveryday shop-floor language. We have interactive graphics on one ofour two systems, but I don’t use it much. But it is great for abeginner or for 2-D programming. The time it takes to process a simplebox shape is approximately half as long as if you were to just type inthe coordinates and create a program.

It’s a different process.You’re creating a file and viewing it at the same time. “But graphics is ideal for trouble-shooting a specific problemarea of a part. You can see the area as it develops, and the problemand solution become quickly apparent. At any point, you can useinteractive graphics selectively to examine a specific area where theprogram is hung up.

“Ordinarily, without interactive graphics, we would doublecheck what we’ve done anyway,’ Jody notes. “We take 15min to 20 min to go over the program before making the tape. We canplot it on the hard-copy plotter or view it on the screen if we choose,for trouble-shooting, either before or after the tape’s beenrun.’ Foam it first “We also take other precautions,’ he adds. “We cuttest blocks out of pieces of hard foam, particularly where there’sa lot of three-axis contouring. Then, quite often, after the block iscut, we use this block on our tracer to rough-in the part to within1/16. Then the part is transferred to our CNC machine for finishing.

The tracer can remove metal much faster. This is often the fastest wayto arrive at the final shape when the part is complex or has deep cuts.When the part is a simple box 1 deep, for example, we wouldn’t takethis intermediate step. We would program it, rough it in, and finish iton the same CNC machine.

“Most of the parts we do are not related in shape. I wish wehad the chance to do more families of parts. We do do some repetitious contours or related shapes for the door industry.’ Processing files “It can take up to three hours to process a complex 2000-ftfile,’ Jody explains.

“An average tape is 150 ft and some runup to 450 ft. “There are three different files. First, the PT file, whichis just the ARPT source code for initial processing. Processing thisfile creates the DM file, which is the cutter-location file. The finalpost processing changes the DM into DA, which is the file our machinetools understand. The DM file is the largest in terms of computermemory space requirements, and allows us to do all our plotting,viewing, and analyzing of the program.

But the DM file is notinteractive graphics. Once the tape is made, we destroy the DM file toregain computer space. If it’s required later, to produce agraphic, for example, we just create another DM from the original PTfile.’ Nothing’s too tough With their EDM capabilities to supplement the precisioncapabilities of the CNC machining centers, they can now get all theprecision they need. There is no longer any need to turn any job down.”The programming language from the earlier system was a littleeasier to learn,’ Jody admits, “but any user language is fine,once you get used to it.

What you want is results. “Datacut is a small company that can relate to the problems ofa small user company much better than a big company like the one wedealt with before. “Service has been great. If you’ve got a problem, youcan call them and usually within an hour, you’ll have a reply. Ifsomething goes wrong, they can send you a patch over the phone that willtell you how to initiate what has to be repaired, step by step, guidingyou through the repair. Other companies didn’t want to let ustouch anything.

They wanted to send a guy down here to do the repair,and then hit us with a big bill. “Their training was also excellent. You can come back fromthat and start writing programs right away. But having some manualprogramming experience beforehand is a big help for any programmer. Thekey is to be able to relate ARPT language to machine code. Otherwise,when you’re viewing a program with a problem in it, you can reviewthe machine file and it looks all right, yet you won’t know how tofind the problem.’ Watch out for huckster tricks when you’re checking outpotential systems, Jody warns. “In those trade-show demonstrationswhere they are bragging about processing speed, they’re not takingoff multiples of 0.

030 like we would be doing in our shop. That takes alot of tape. When we ask for the speed we need to keep processing timedown, they show you a sample program that takes only 6 min to run, whichsounds quick, but they’re stepping at 0.250 which requires only oneeighth the processing time as a 0.030 step.’ Photo: Jody Soltesiz at the console. Photo: Some of the plastic products molded from dies made byPrecise Tool & Mold.

Photo: Tracing a foam tape-testout block can be a shortcut toroughing out complex shapes without tying up the CNC machines, becausethe tracer is faster at removing metal.

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