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Bottle makers integrate on-line process & quality monitoring.

Bottle Makers Integrate On-Line Process & Quality Monitoring

Sometimes it's not the industry giants that innovate first, leaving the pathfinder role to smaller and more entrepreneurial firms. That appears to be the case in blow molding, where two medium-sized custom bottle makers have pioneered in integrating all their machines into a plantwide computer network that makes real-time process, production and quality data instantly available throughout the plant. Most important, these two firms are enabled to associate quality and process data in real time, eliminating guesswork and after-the-fact corrections. The result has been higher quality, reduced waste, and significant improvements in the skills of the workers who manage the process.


CIM implementation started about the same time at Schoeneck Containers, Inc. in New Berlin, Wis., and at Charter Supply Co. in Philmont, N.Y. (see PT, May '90, p. 48 for an earlier report on these plants). Schoeneck molds exclusively PVC food and household-chemical containers, from 8-oz to 1.3-gal sizes, on its 10 proprietary, four-cavity wheels. Charter Supply molds 2-oz to 1-gal PVC and HDPE containers for household chemicals, cosmetics and toiletries on 13 Bekum and Battenfeld Fischer machines. When they initiated their CIM projects, both firms had a mix of machines dating from the early 1970s to the present, and controls from basic relay type to up-to-date microcomputers.

Both also already had implemented shop-floor systems for statistical quality control (SQC), involving hourly sampling and charting of bottle weights and critical dimensions or wall thicknesses. In Schoeneck's case, this was done with paper and pencil by each machine operator. At Charter Supply, q-c inspectors took the bottles to one of two personal-computer stations on the floor and performed the checks with electronic scales and calipers tied into the PC. That PC was also networked with PC terminals in the offices of the q-c manager and of president G.B. "Jake" Jacobsen. Besides its q-c network, Charter also had a production-control network of PC's on the plant floor and in various plant offices to display current cycle times and cycle counts from all machines.

About two years ago, both firms began planning to improve quality through real-time monitoring systems that would provide process "visibility." Installation started in late '88 and early '89, and both plants finished bringing all machines into their monitoring networks this year.


Schoeneck had its system custom designed with the help of a computer systems integrator, Technology Consulting Corp. of Brookfield, Wis., and the application engineering firm of JAC Manufacturing Inc., Palmyra, Wis. All Schoeneck's wheel machines were retrofitted with Barber-Colman MACO 8000 microcomputer controls, and manual SQC recording was replaced with an automated computer network.

Today, each of Schoeneck's wheels has an operator station with two color CRT screens--a MACO 8000 touchscreen monitor, used to set up, control and monitor machine operation, and a graphic SQC display connected to an IBM 7531 computer, the industrial version of a PC-AT, which is housed in the operator console. An electronic scale and caliper now enter bottle measurements automatically into the IBM 7531. Barcode readers at the packing station on each bottle line are also being tied in with the IBM, to automatically record skids of packed bottles for inventory control.

Each IBM 7531 has a hard disk to store an ample amount of quality and production data; it also records process data from the MACO 8000. Supplementing this local data storage, all data fed into the IBM 7531 at each machine are continually uploaded to an IBM PS/2 in the plant office. This PC distributes data on demand to 15 other PC's in the q-c lab and offices of v.p. David K. Schoeneck and plant manager Glenn Knapkiewicz, as well as the plant supervisor, shift foreman, purchasing, shipping and inventory departments, and others. The q-c lab has its own IBM PS/2, which stores shop-floor quality data and supplements it with data from further lab tests. Meanwhile, an IBM AS/400 office mainframe computer pulls data from the plant-office PS/2 in order to perform inventory control, MRP (material requirements planning), scheduling, and production control, and to generate bills of lading for shipments. It also pulls SQC data from the q-c lab database to generate certificates of quality conformance to accompany each shipment. All told, the computer system, software, and new machine controls have cost Schoeneck about $1 million.

Contrasted with this custom solution, Charter Supply implemented a pre-engineered package consisting of off-the-shelf components, but which nonetheless offers ample flexibility for customizing. Charter was the first to implement a blow molding version of the Hunkar Laboratories CIM-1 system, which has already been proven in injection molding (see PT, March '89, p. 71).

This system did not involve retrofitting controls on each blow molder. Instead, a small Data Acquisition Terminal (DAT) on each machine reads process inputs from sensors or the machine controls, and relays these data to an IBM industrial microcomputer inside a central "command console" with three color CRT's, which is housed in an enclosed office on the production floor. There, CIM manager Edna Hover keeps an eye on processing conditions and production status of all machines, prints out setup sheets from stored "recipe" files, and uses a separate PC linked to the command console to generate statistical process control (SPC) charts on machine performance. The overall system has cost $175,000. Charter Supply plans to add to it, with DATs on its bottle printing and heat-transfer decorating machines to bring them into the CIM network.


While both firms can now compare quality and process data in real time, the correlation is not automatic. As the next phase of their CIM projects, the two firms are working to link their process and quality monitoring systems for integrated SPC/SQC analysis. Schoeneck is not yet performing SPC analysis on the data recorded from the MACO 8000s, but is monitoring numerous variables on an experimental basis to determine which are really important to watch, and how often. Meanwhile, Technology Consulting is developing software to correlate such SPC data with its current SQC data from operators' gauges and lab tests.

Hunkar Laboratories is also working on a software interface between Charter Supply's CIM-1 SPC capabilities and the pre-existing SQC network of PCs. In the meantime, however, Charter has the benefit of Hunkar's SPC-PRO "expert" software. Based on empirical studies of real-world production data, the software automatically weights various process parameters according to their influence on product quality, and sets a "window" of upper and lower SPC limits on each parameter according to those weighting factors. The system automatically flags any excursion outside those SPC limits as a "bad" cycle. Jacobsen says the system has been quite reliable in identifying potentially off-spec bottles from SPC data.


Both firms say CIM has provided a "window" into the process, greatly increasing the understanding and skills of technicians and machine operators. Dave Schoeneck calls this giving the operator "ownership" of the process by giving them adequate information "to make the proper calls in controlling the process."

And both firms agree that CIM eliminates counterproductive dial twiddling, which helps stabilize product quality. At Charter Supply, Edna Hover gets an alarm signal on her command console if anyone tries to change the predetermined optimum machine settings. And she sees new respect for the importance of reproducing operating conditions exactly on every run. "Before, we had a target number to meet on setup, but the attitude was that `close enough' was okay. What difference does a tenth of a second make? The setup men now know that the target means something, and they'll work to get a hundredth of a second closer to target. They have contests to see who gets closest to my setup numbers."

Schoeneck's Knapkiewicz estimates that tighter process control with the MACO 8000s has reduced scrap 5%. He also estimates 5% higher productivity with the new SQC system, because "operators have more time to spend working on their process and not charting SQC variables. And I can see what's going on in the plant better by scanning each machine's performance from a remote terminal than by wandering around to the lines." He expects further benefits once SPC analysis is in place. "We're going to be able to monitor and record information that we haven't before," he says. "We may be able to `see' screw wear, for example, through its effects on process variables. We'll be able to identify a trend before it happens."

Charter Supply has already seen that happen. Says Hover, "You get to understand your machines just like they were people. For example, screw rpm for each machine has a signature on the SPC chart. If it deviates from the original fingerprint, you ask why and start looking for the answer. In the last three months, that helped us save two extruder motors from burning out. Also, for the first time, we have a handle on what it looks like if there is a problem with a servovalve on a parison programmer. Now we have tangible evidence to use in maintaining our equipment."

Real-time display of process trends, she adds, means that "we catch things as they're starting to drift. If we see that our cycle-time variation is normally [+ or -] 0.04 sec and it goes to [+ or -] 0.07 sec, we may not be making a bad bottle, but we're losing that fine edge of performance and we want to get at finding and fixing that problem now."

As a result, Jacobsen estimates that overall rejects have been cut in half, and rejects related to CIM-monitored variables have been reduced to almost nothing. Thanks to fewer rejects, faster on-spec startups, and less unscheduled downtime, he says, overall productivity is up at least 10%, "and we now think we can run comfortably at 90% plant capacity utilization, whereas 80% utilization was an unobtainable goal before."

PHOTO : At Schoeneck Containers, each machine operator has access to real-time process information on the MACO 8000 screen at left, and to real-time SQC charts on the BM 7531 screen at right. Electronic scale and caliper enter bottle quality data.

PHOTO : Edna Hover, Charter Supply's CIM manager, watchdogs process and production information from all machines on her central console. PC at right produces SPC charts of process conditions that affects quality.
COPYRIGHT 1990 Gardner Publications, Inc.
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Copyright 1990, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:1990 CIM Leaders; computer-integrated manufacturing; Schoeneck Containers Inc. and Charter Supply Company Inc.
Author:Naitove, Matthew H.
Publication:Plastics Technology
Date:Nov 1, 1990
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