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Wedding CAD to CAM for instant prototypes.

At a large, Midwestern manufacturing facility, the engineering effort includes design/development responsibility for numerous transmissions now in production, and a couple more coming soon. Plus, they average many different models within each type, and there are in excess of 300 parts/transmission (although the primary changes within models are in calibration and involve changing only a small percentage of key parts). Production volumes vary from 500 to 4000/day.

In addition to doing all transmission engineering for the corporation, about 40 percent of all transmission manufacturing is done at this facility. At one time, 80 to 90 percent of their prototype parts were being made by outside vendors. Then, the energy crisis that started in 1974 and lasted through 1978 accelerated the rate of change in transmission design. Instead of one experimental program lasting a couple of years, they were creating three or four new programs a year. Because they couldn't handle this new volume, they elected to expand their in-house facilities.

According to the administrative engineer, "When we first looked at going to DNC, we had been time-sharing with MDSI Corp, so we went to them to see if they had DNC capability. This was in 1979, and they did not.

"With just two machining centers and one turning center, we were spending a substantial amount each month on time-sharing bills. We rarely have repeat jobs, and we have a lot of engineering changes during the development period, so we were constantly regenerating tapes. We knew we had two more machining centers on order, and knew our time-sharing bill could easily go to three times our current level of spending per month. So we had to do something."

In 1979, they visited a sister division and found that their engineering tool-room had a DNC system similar to what was needed. "Based on our experience," the administrative engineer reports, "we felt that Controls & Data Systems, a division of White Consolidated Industries Inc, had the best controls and the most systems in the field." Introducing CAD to CAM

"Shortly after we gave Controls & Data Systems the order for the DNC system," he continues, "I happened to run into a Computervision demonstration at a tool show where they were saying, 'We can generate source-level programming, tool paths, etc.' I went back upstairs, got the Controls & Data Systems' salesman, took him down to the Computervision representative and said, 'Okay, if you say you can do this, and you say you can do that, then why don't you two start talking together and figure out a way to link those two systems together.' Sixteen months later, the link was developed. It was the first link of its kind in the country.

"The two systems--graphics in conjunction with DNC--constitute probably one of the most powerful programming tools there is, as far as I'm concerned. Each separately does a fine job, but when you can combine them, then you have a really powerful tool. The problem is that no vendor has had both sides of the equation, and they only communicate and develop useful software when pressured by their customers.

"Software support in any situation is the most critical factor. Hardware is pretty much standard and usually reliable. The key is always the software. Both of our vendors have responded reasonably well on the software, particularly Controls & Data Systems with good support service.

"We have CV systems at other divisions, but also GE Calma, Applicon, and our own corporate graphics group has an IBM-based system with our own developed software for group technology and process planning.

"Obviously, we've saved money on time-sharing costs, but we have also generated a great deal more spindle on-time than we had before because the operator is not sitting around waiting for tapes or tape changes to be resolved. With the interactive editing feature, the operators can edit the programs in the source-level language right at the machine. Thus, the source-level program is always updated."

By August '81, they had the DNC system in place with four machining centers and three turning centers, which is where it stands right now. They are in the process of acquiring another machining center, and envision three or four more NC machines for their prototype area in the future.

"We are doing parts today that were never attempted in-house before," the administrative engineer explains. "With our machining capability, we are doing most of our specials right here. Anything that needs drilling, milling, or turning, we do in-house. Even complex vane shapes can be done on our four-axis machine, hogging a solid blank into an exotic multi-vaned prototype turbine shape. Eventually, of course, the turbine blades will be made independently, but this prototype will show us that the design concept works.

"We also simulate stampings sometimes by machining the shape from solid material. We have the capability to carve almost anything out of simple metal shapes: large castings, valve-bodies, case covers, extensions, cases, etc. We can generate our own gear blanks with NC and put in the teeth on a standard gear cutter.

"More and more, we are using the ability to access the design data base to generate source-level programs. When we had MDSI, we were using Compac II language and had to change over to SPLIT, Control & Data Systems' language, which is becoming more and more of a common language. SPLIT is basically the grandfather of Compac II; therefore the language changeover by our programmers was made quite easily." How it's working

They are now using the graphic system one half to two thirds of each shift to do their programming. They use only the modeling layer of the design, since there is no need for concern about dimensioning or anything else. This is because the model is representative of the dimensions expressed on different layers on the blueprint. They simply use the modeling layer and go through with built-in software commands to program the part machining using the light pen and keyboard.

"SPLIT source-level programming involves specifying your cutter moves, part parameters, etc," the administrative engineer adds, "and it's all done via computer, rather than specifying geometry by hand and defining where the tool is going to go. The modeling layer is a picture of the part in electronic terms, and there are no dimensions. All we need do is digitize the area we want to machine, and the computer automatically generates the program to do that. No dimensions are ever used.

"One beauty of this graphic system is that you don't have to have the drawing completed to begin programming. By working very closely with the designer, as soon as he finishes a section of the drawing and releases that section to us, we can program it and start cutting chips. As another section is finished, he calls us up and releases that section. By doing this all the way through for one particular valve body recently, three hours after he finished the design, we cut the last chip on the part! You can't get much faster than that! We certainly never had that capability available before.

"Because of high production volumes, almost everything in manufacturing is dedicated equipment and transfer-line technology. There is some talk for getting into FMS technology for service parts or very small runs. I have personally been preaching FMS for two years, and some people are finally starting to take notice of the fact that there probably is some potential for FMS in automotive applications.

"My biggest concern is the fact that you spend millions of dollars for dedicated equipment that might be used for four or five years, and then is no good anymore when you stop making that part. But with FMS, you just change your programming and fixtures, and you're ready to make new parts.

"Still, I must admit that you would have a tough time making more than 500 parts/day with FMS, particularly large castings. There was a time when an FMS made sense just for our prototype engineering requirements, but we don't have the volumes now that we did then." Programming people

With the advent of the graphics system and its tie-in with the DNC, they are still operating with the same two programmers that they had when they were operating only three machines. They now have seven and they are planning to go to 12 machines eventually, so they are training more operators as programmers to give them some backup.

"Without a good programmer or operator," the administrative engineer feels, "you're in big trouble! More and more, the universities are training people not only in CAD, but also in CAM. These programs are great, but if you don't have somebody with actual machining experience, that programmer is not going to do you much good.

"At this level of DNC, the need for programmers is not going to accelerate too rapidly. As long as transmissions stay hydraulic, the configurations or parts will not change much. Even a switch to other controls and servos at some time in the future would not grossly affect our functions here. We would just be machining different parts, and our present capability would serve us very well in making quick changeovers.

"We also have a toolroom facility upstairs that has twice the plant area of this DNC facility. It has all the standard toolroom equipment: grinders, engine lathes, jib borers, gear-generating machines, etc. This will always be needed for quick fixes, minor changes that don't require a machining center. We may someday put in a 36" chucker upstairs and tie it into our DNC system downstairs to gain a little productivity. That way, two employees on the chucker could probably do the work of five operators with engine lathes." On to 32

The administrative engineer has seen demonstrations of how much faster 32-bit computers are than 16-bit, and was quite impressed. "A study was made of 50 or 60 common designer commands," he relates. "They took 1889 sec for a 16-bit machine to execute and only 739 sec on a 32-bit machine. This was not a vendor-loaded list, but was fairly comprehensive of the kind of work we do. This could mean the difference between a designer waiting 10 sec for the system to respond and losing his chain of thought, versus 3 or 4 sec and working much more efficiently.

"As far as cost goes, the payback for a 32-bit system for us would be about one year; that is, the payback period for the additional cost of converting from our existing 16-bit system. The payback in going to our 16-bit system originally was about 19 months. Part of this potentially shorter payback period is the experience we already have converting to the 16-bit system.

"It is our experience that you don't really recover the greatest savings in the design area. The big savings are in the areas that use the common data base; like DNC, tool design, gaging, etc. Hardware/software costs for going to a 32-bit system would be about 70 percent of what we paid for our 16-bit. I feel that our conversion to 32-bit is inevitable; we simply can't afford to pass it up.

"Overall, I'm just superhappy. We've been able to generate savings in excess of $3.5 million/year!"

If you would like to have more information from Controls & Data Systems, division of White Consolidated Industries Inc, Belvidere, IL, on their contribution to this system, circle E31.
COPYRIGHT 1984 Nelson Publishing
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Copyright 1984 Gale, Cengage Learning. All rights reserved.

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Author:Sprow, Eugene E.
Publication:Tooling & Production
Date:Apr 1, 1984
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