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Computer programming pays off.

Computer programming pays off

Precise Tool & Mold, Youngstown, OH, is a small company manufacturing injection molds for the plastics industry, including companies in Canada, the West Coast, and Florida. They are doing well because 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, two Hillyer 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 are compatible, machine to machine.

They purchased their first CNC Hillyer in 1978 and did all the necessary programming manually for the first three years. One programmer couldn't handle the load, so they hired a second trainee. Programming time per tape was anywhere from one hour to two or three 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,' explains Programmer Jody Soltesiz, "the more diversified our work became. We were able to move into new areas that contributed to our growth. But as we got into three-axis contouring in manual programming, it became virtually impossible to keep up. This forced up to seek out a computer-assisted programming system. We investigated several suppliers, and tried one in-house for a year. But it didn't work out.'

That earlier system was obtained under a contract with a one-year trial period. Final purchase was contingent on the system meeting with their full satisfaction. "During this trial period, we experienced several difficulties,' Jody recalls. "One was storage space--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 limit was hardware, software, or both, but the system asked you to split these longer jobs up.

"Obviously, for more money, we could have gotten a system to handle our contouring tapes, but for less total money we're getting that and more from the system we purchased from Datacut Inc, Ardsley, NY. We also got detaching capabilities, the ability to drop one program and move to another while lengthy computations are going on. We couldn't process one program while we wrote another one before, and we also like the flexibility we now have of being able to use multiple terminals.'

Graphics interaction

"We really like the language,' Jody says. "It's easy to understand, simple to learn, easy to write, just everyday shop-floor language. We have interactive graphics on one of our two systems, but I don't use it much. But it is great for a beginner or for 2-D programming. The time it takes to process a simple box shape is approximately half as long as if you were to just type in the 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 problem area of a part. You can see the area as it develops, and the problem and solution become quickly apparent. At any point, you can use interactive graphics selectively to examine a specific area where the program is hung up.

"Ordinarily, without interactive graphics, we would double check what we've done anyway,' Jody notes. "We take 15 min to 20 min to go over the program before making the tape. We can plot 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 been run.'

Foam it first

"We also take other precautions,' he adds. "We cut test blocks out of pieces of hard foam, particularly where there's a lot of three-axis contouring. Then, quite often, after the block is cut, we use this block on our tracer to rough-in the part to within 1/16. Then the part is transferred to our CNC machine for finishing. The tracer can remove metal much faster. This is often the fastest way to 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 take this intermediate step. We would program it, rough it in, and finish it on the same CNC machine.

"Most of the parts we do are not related in shape. I wish we had 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-ft file,' Jody explains. "An average tape is 150 ft and some run up to 450 ft.

"There are three different files. First, the PT file, which is just the ARPT source code for initial processing. Processing this file creates the DM file, which is the cutter-location file. The final post processing changes the DM into DA, which is the file our machine tools understand. The DM file is the largest in terms of computer memory space requirements, and allows us to do all our plotting, viewing, and analyzing of the program. But the DM file is not interactive graphics. Once the tape is made, we destroy the DM file to regain computer space. If it's required later, to produce a graphic, for example, we just create another DM from the original PT file.'

Nothing's too tough

With their EDM capabilities to supplement the precision capabilities of the CNC machining centers, they can now get all the precision they need. There is no longer any need to turn any job down. "The programming language from the earlier system was a little easier 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 of a small user company much better than a big company like the one we dealt with before.

"Service has been great. If you've got a problem, you can call them and usually within an hour, you'll have a reply. If something goes wrong, they can send you a patch over the phone that will tell you how to initiate what has to be repaired, step by step, guiding you through the repair. Other companies didn't want to let us touch 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 from that and start writing programs right away. But having some manual programming experience beforehand is a big help for any programmer. The key 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 review the machine file and it looks all right, yet you won't know how to find the problem.'

Watch out for huckster tricks when you're checking out potential systems, Jody warns. "In those trade-show demonstrations where they are bragging about processing speed, they're not taking off multiples of 0.030 like we would be doing in our shop. That takes a lot of tape. When we ask for the speed we need to keep processing time down, they show you a sample program that takes only 6 min to run, which sounds quick, but they're stepping at 0.250 which requires only one eighth the processing time as a 0.030 step.'

Photo: Jody Soltesiz at the console.

Photo: Some of the plastic products molded from dies made by Precise Tool & Mold.

Photo: Tracing a foam tape-testout block can be a shortcut to roughing out complex shapes without tying up the CNC machines, because the tracer is faster at removing metal.
COPYRIGHT 1984 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1984 Gale, Cengage Learning. All rights reserved.

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Publication:Tooling & Production
Date:Sep 1, 1984
Words:1329
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