Molder's growth extends CIM's reach.
When Security Plastics Inc. won its first CIM Leaders Award nearly six years ago, its computer network linked a grand total of 18 presses. Back then, a lone minicomputer served as host, sharing production information with machine controllers on the shop floor in Miami Lakes, Fla. Information from this budding computer-integrated manufacturing system was used mainly to support quality-control efforts. Today, Security's CIM system is bigger, smarter, and still focused on quality. Its network now spans more than 122 machines and three manufacturing locations--one each in Florida, Texas, and Puerto Rico. And Security now controls quality with real-time computer simulations that identify off-spec parts before the molds even open.
The company has also extended the system's reach with new software applications that cut the potential for downstream mistakes--in labeling, shipping, customer service, and other essential non-production tasks. One recent job, a faucet valve stem, has chalked up 13 million parts without a single defect in manufacturing or post-molding tasks. "And that level of quality is very typical," says quality manager Patrick Haley.
The CIM evolution at Security has brought changes in human resources, too. For one thing, the company has stepped up educational programs that train its work force to keep abreast of technological improvements. "Instead of building CIM around existing systems and processes, we train our people to use the latest technology," says CIM manager Michael Bentz. And to satisfy its leanings toward self-reliance, Security dedicates a full-time staff of programmers and process engineers to building up the CIM system. Their achievements have earned Security the 1994 CIM Leader's Award.
AN EXPANDED NETWORK
One thing that hasn't changed at Security is its choice of Digital Equipment Corp.'s PDP-11 minicomputer to support real-time, bidirectional communications with the presses (see PT, Dec. '88 p. 66). Information flows not just from host to press but in the other direction as well. Security has added four more PDP-11s as its operations grew.
Three PDP-11s at the Florida plant now supervise 78 presses, while the smaller Puerto Rico and Texas facilities have one PDP-11 each. All five mini-computers are tied into a DEC VAX midrange computer at the Florida headquarters. The VAX stores the massive quantities of processing information and process-capability data for the company's molds.
Security also runs an IBM AS/400 midrange computer to crunch financial data and perform production-control tasks like scheduling and ordering. The presses, meanwhile, are outfitted with a mixture of machine controls--mostly Barber-Colman MACO 8000 and Van Dorn Demag Pathfinder 2500. Finally, a personal computer sits on nearly every desk for tasks ranging from design to label preparation to programming.
Ethernet connections at the plant level and modem hook-ups at the more distant manufacturing sites link the computers into a common network that spans 2500 miles. Executive manufacturing v.p. Enidio Gomez and other managers at the company can sit in their Florida offices and monitor production in Texas or Puerto Rico--in real time. "A single point of control is our goal," Gomez says.
BUILD IT, DON'T BUY IT
Although there are many off-the-shelf CIM solutions available for injection molding, Security chose a different path. Almost all of its software--including an MRP-II program--were written in house by a full-time programming staff of three. "We can develop software on the host side and the machine side," says Bentz, who started out as an electrical engineer designing CNC controllers. "So we get a lot of integration that commercial process-monitoring products just don't have."
For instance, the company's do-it-yourself approach enabled Security to integrate auxiliary equipment with the machine controllers. This way, hot-runner and chiller controls are controlled through customized screens on the machine controllers. The only auxiliaries Security hasn't integrated are robots and a machine-vision system that monitors mold closing. Security's customized MACO 8000 controllers now have 114 screens, 10 for SPC alone.
Quality manager Haley points out another crucial difference between Security's proprietary system and the commercial packages: Security's system requires a few seconds shorter computer-processing time. "Calculations were made post-cycle on the commercial systems we tested, but we predict part quality in real time while the mold is still closed. We know if the part is good or bad before the mold opens."
In addition, Security's custom system allows a large volume of information to flow back to the host level. Security retrieves 98 process parameters from each press in real time--compared with 12 or so on a commercial system, says Bentz.
If a common thread runs through successful CIM setups, it may be a company's willingness to ask for cooperation from its suppliers. Security sure did, and much of its customization work required an unusual level of vendor support.
Security especially credits its machine-control suppliers for providing customization tools--such as source code, software development kits, and even blank firmware. "Van Dorn and Barber-Colman have always given us what we need," says Bentz.
Even with the help of vendors, tailor-made CIM still doesn't come cheap. Security president Norman Cohan estimates that the CIM-related machine upgrades cost about 820,000 per press. That figure only includes modifications to the machine itself, not network hardware and labor costs. Aside from the programmers, the CIM staff includes a process engineer, a maintenance worker, and a quality inspector, as well as Bentz himself. "That's a lot of people, considering the size of the company," say Bentz. 'There has been a lot of management support."
One of the biggest CIM expenses so far has come from increasing each injection machine's control resolution. Process-control resolution for temperature is now is 0.025 [degrees] F rather than the standard 1 [degrees] F. Position is now read to 0.002 in. and pressure in 0.1-psi increments, both about twice as fine as on standard systems.
According to Bentz, the machines and controllers already had that resolution, but only internally. Software changes meant that the resolution could appear as part of the controller displays. "We had to educate our suppliers," says Bentz. At first, they couldn't understand why Security wanted to read temperature in hundredths of a degree. But Bentz explains, "Our variations are so minimal that we would get a straight line without the increased resolution. You can't perform SPC on a straight line. We had to fight to make that internal resolution available on the screen."
Other custom work at Security can be seen in many screens and reports generated by the VAX midrange computer. One such screenshows quoted versus actual cycle times for each job. If the latter exceeds the former, the figures are highlighted so "we know we're losing money on that job," explains Bentz. That information is routed to the estimating department so it can continuously fine-tune its quotes.
The VAX also generates customized reports for each job every hour, retrieving 75 parameters from the machine controller. These reports are used mostly for lot traceability, though on some complex parts the reports have helped the company diagnose molding problems. Additional screens report unusual parameters such as velocity profiles and mold temperatures gauged by press-mounted infrared sensors.
The need to capture new parameters and achieve high resolution was driven by Security's 10-year-old SPC program and a more recent move to so-called "decoupled" molding. In this technique, the press is allowed to use the necessary injection pressure to generate a preset injection speed under closed-loop control. "Injection velocity is central in decoupled molding," notes Bentz. This technique has all but eliminated the molder's biggest problems--flashing and short shots. "We've taken these big problems out of the picture and now focus on part dimensions," says Bentz. What's more, by engendering a molding process that's consistently under tight control, the SPC and decoupled molding programs have laid the groundwork for Security's most ambitious program yet--a brand-new quality system.
Everyday in Miami Lakes, Security's quality technicians take a few samples from the injection molding presses. In fact, they take very few samples nowadays because sophisticated computer models based on monitoring process variables identify any off-spec parts before they ever leave the presses. "With modeling we're comfortable sampling once a day, not every two hours," says Haley.
This model-based system, which has totally replaced traditional inspection-based SQC methods on some jobs, is the culmination of all Security's CIM and SPC efforts. "If you don't make a bad part, you don't have to inspect," says Bentz, summing up the rationale for the program.
The models employ a mathematical method called "recursive identification," in which an algorithm relates finished dimensions to process conditions. "The computer develops a formula that describes machine, raw material, and mold for each part," explains Bentz.
Currently, the models look at three critical dimensions on each part, predicting from the process parameters how much the finished part will deviate from specs. Models run on the machine controller, which downloads the algorithm from the PDP-11. It takes about one second to determine whether parts are good or bad, leaving plenty of time for the mold to open and for the controller to tell the robot what to do with that shot. "You don't need the host computer when the model is in the machine," notes Bentz. Due to the 1-sec calculation time, the system currently has about a 5-sec cycle time minimum for the model to work, yet that limitation hasn't stopped Security from running 60 of 300 possible jobs under modeling. And that percentage increases every week.
Each part-and-tool combination requires an individualized model, which needs about 100 samples to set up initially but only five to 10 samples to subsequently update or verify. To build a brand-new model, q-c workers follow sample-collection instructions on the machine controller. Though the model does run in the press, the number crunching that actually creates the model takes place at the host level.
According to Bentz, the models even take shrinkage into account. "You get an instant answer that accounts for shrinkage and warpage without waiting for two hours for parts to set up."
As for the bottom-line benefits, Haley reports that jobs running under the model-based system have gone to nearly zero defects, even though the company has doubled output from 20 to 50 million parts annually.
PART OF A SYSTEM
When first devised in 1991 (PT, Dec. '92, p. 94), Security's mathematical-modeling approach had not yet achieved the status of a full-fledged quality system that could replace SQC. "Our intention all along was to replace SQC," says Bentz. "But there are rules that govern any quality system, even when you can accurately predict dimensions. We had to create those rules from scratch." A range of questions had to be answered, from what procedures to use for answering CIM alarms to how to handle rejected parts.
Then there was the question of how to wean customers from SQC. "For some people, sigma [standard deviation] is a new term, and you must embrace the SQC concept before you embrace eliminating it," says Haley. But many of Security's high-tech customers have been supportive. "Motorola pushed heavier than my boss," says Bentz. "They've helped us. Their strict requirements ([+ or -]6 sigma, or 3.4 ppm) made us a better molder."
Surprisingly, the switch away from SQC won't eliminate the quality inspectors. Instead, it has their full support, though it does change their role. "We ask them to use their brains a little bit more and help us solve problems," says Haley. "It pushes problem solving down the chain." Under the original SQC system, inspectors spent most of their time measuring parts and entering data. tinder the mathematical-modeling system, inspectors will be required to do some analysis to solve molding problems. That changing role has forced Security to step up its training efforts. All molding personnel, for instance, must be certified in decoupled molding techniques, a program that includes classroom training and tests at the press.
Why does Security still rely on workers rather than going to a "lights-out" plant? For one thing, CIM still has limitations. The computer may know when fill or cycle times change but not the root cause of a problem. Inspectors can look for root causes. "The quality department thus becomes more of a service organization than a policing organization," says Haley.
Security has used CIM to extend its quest for total defect elimination further and further downstream, thanks to a number of customized software applications. As Haley points out, zero defects not only means the elimination of off-spec products but also encompasses the elimination of any non-production mistakes. Several new computer programs target these errors:
* A pager application now lets supervisors know when there's trouble on the shop floor. Whenever a CIM alarm sounds, the computer dials a beeper worn by supervisors, who then rush to fix the problem. This kind of response mechanism grows even more important as CIM reduces the number of people on the shop floor--and thus the number of people who will hear any alarms. "You don't have to babysit the machines anymore," says. Haley.
* A new labeling program, again written by a Security programmer, has eliminated the manual entry of labeling information. Much of that work revolved around matching the internal labels, which contain information useful on the production floor, with customer-specified bar-code labels that go on the boxes before shipping. The system uses a radio-frequency scanner to log in information that was once entered manually.
* The company has also developed a computer bulletin board and other dial-in services to better distribute information to its customers. Customers can log on for real-time production information. What's more, production and lot-tracing data can be kept for years on Security's midrange computer, saving customers the trouble of maintaining their own archives. If they need access, they can simply dial up the VAX by modem and download whatever records they need. When it comes to record keeping, "leave the driving to us," says Bentz.
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|Title Annotation:||Plastics Technology's Annual CIM Leaders Award; Security Plastics Inc.'s computer-integrated manufacturing system|
|Date:||Nov 1, 1994|
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