Printer Friendly

Blow moulding in the 90's - CIM is coming!

Blow Molding in the 90's CIM Is Coming!

The electronic information revolution is coming to blow molding. Injection molders and extruders have been in the vanguard of that revolution, implementing advanced on-line monitoring systems that provide access throughout the plant to real-time data on process conditions production totals, and quality trends. Right now, some of the biggest names in bottle making are also preparing to invest in such systems. But two medium-sized custom blow molders have beaten them to the punch. Here's their story of how computer-integrated manufacturing (CIM) is paying off in improved quality and productivity, reduced waste, and enhanced worker and customer satisfaction.

Schoeneck Containers:

A Better Handle on Quality

Blow molders in general tend to be a secretive lot, acknowledges Glenn Knapkiewicz, plant manager of Schoeneck Containers, Inc. in New Berlin, Wis. But he's happy to brag about what's going on at his plant, claimed to be the largest single PVC bottle making facility in the U.S.

Schoeneck runs exclusively PVC on 10 four-station vertical wheel machines of its own design. These machines produce food and household chemical containers from 8 oz to 170 oz for customers such as Procter & Gamble, Colgate Palmolive, Kraft Inc., Beatrice, and Ralston-Purina. Some of those machines date back to the firm's founding in 1972, and still have relay controls. In 1988, Schoeneck embarked on an ambitious program of installing up-to-date microcomputer controls on all its machines, supplementing them with a custom-designed plantwide computer network for real-time process, production and quality monitoring.

The basic motivation for the change, as v.p. David K. Schoeneck describes it, was that "we're in a competitive business. Working with our customers, we saw a need to assure them of higher levels of quality--reduced product variance, tighter control."

"It used to be that our customers would just ask for a bottle that didn't leak," says Knapkiewicz. "Now they're more aware of quality. In the last five years, customers have wanted certificates of quality conformance, with X-bar or Cpk values, sent along with their shipments."

A PAPER-AND-PENCIL START

Adds Shcoeneck, "We started out our quality program with paper and pencil, manually drawing up control charts. We were going from a quality inspection-type system to an operator-controlled system, where the machine operator actually controls the quality on his production line. And as the operator took more control and more responsibility, we needed to give him the quality and statistical tools to have better control of what's happening on his line."

About three and a half years ago, all of the company's 200 workers and managers received several weeks of in-plant training in the quality principles of Dr. W. Edwards Deming, the original "guru" of quality consciousness. For over three years now, each machine operator has been taking a sample bottle from each cavity once an hour, weighing it and measuring critical dimensions with a caliper, and then recording the data on the "X-bar and R charts" that are fundamental to any statistical process control (SPC) program. Those bottles are later sent to the q-c lab for drop tests, leak tests, measurements of wall thickness, and clarity evaluation.

"In years past, machine operators didn't monitor quality," notes Knapkiewicz. "A q-c inspector would go around to each line, take samples back to the lab, weigh and measure them maybe 45 to 60 minutes after they were made, and then have to walk back out to the line to warn the machine operator that he's running 10 grams heavy. If you're running 30 bottles a minute 10 grams heavy, it doesn't take long to blow away a lot of plastic. The beauty of what we're doing now is that the operator knows what his X-bar is."

Even before computerization, Knapkiewicz says, this approach had major benefits. Whereas a typical customer spec on a 90-g bottle might accept [+ or -] 5 g, Knapkiewicz asserts that X-bars throughout the plant are typically [+ or -] 0.2 g from the target weight. This has important consequences in material savings. Adds Dave Schoeneck, "We no longer just accept the initial specs from the customer. We take a look at the process and see if we can tighten them. We prefer to run tighter specs than the customer initially came to us with."

But paper-and-pencil quality charting was cumbersome. "Operators could spend 20 to 40 minutes per hour doing manual SPC calculations. While they're doing that they're not working on improving their process or monitoring it closely. And if something goes wrong with the process, they don't have time to keep up with manual charting, so your SPC records slide." Also, the quality data were updated only once an hour. And there were limits to how fine they could tune a process using 1970s controls.

A CUSTOM SOLUTION

The company's first decision was to put Barber-Colman MACO 800 microcomputer controls on all machines. The second key step was to talk to IBM Corp. about wanting to get into CIM. (This was before Barber-Colman introduced its CIMAC 8000 monitoring system, which fulfills many CIM functions--see PT, Nov. '89, p. 20.) IBM recommended one of its affiliated application specialist firms, Technology Consulting Corp. (TCC) of Brookfield, Wis., to provide systems integration. TCC designed a plantwide information network of IBM industrial computers that would take data from the MACO controllers and from electronic scales, calipers and barcode readers. Another key contributor was the application engineering firm of JAC Manufacturing Inc., Palmyra, Wis., headed by Jim Christiansen, which installed the system and customized the MACO screen displays.

Schoeneck Containers designed its ownoperator stations, each with two color CRT screens. One is the MACO 8000 touchscreen monitor, used to set up, control and monitor the blow molding machines and trimmers. The second color monitor is for an IBM 7531 computer, the industrial version of a PC-AT. The latter takes a "snapshot" of the process data being read by the MACO at specified intervals, and stores the data on a 20-MB hard disk. The IBM 7531 also takes direct input of product quality data from an electronic gauge and caliper at each operator station. It calculates SPC data and displays the control charts on its screen, using MetriStat software from Business Systems Design, Inc. of Oconomowoc, Wis. When barcode readers are installed at the packing station for each line, these also will be tied directly to the IBM.

The Operator console houses the IBM 7531 computer itself, mounted on a sliding track for convenient access, and a MACO 8000 InstaSet module, for "instant" machine setup via EEPROM cartridge. All the other MACO 8000 control modules are mounted remotely on a wall of the molding area.

Every operator-station IBM 7531 is networked to an IBM PS/2 Model 60 file server with 88 MB of hard-disk storage in the plant office. The server is linked to 15 other PC's throughout the plant--in the q-c lab and offices of Dave Schoeneck, the plant manager, plant supervisor, shift foreman, purchasing, shipping and inventory departments, and others. All are able to simultaneously access up-to-the-minute data from any and all lines.

The q-c lab stores the shop-floor data on an IBM PS/2 Model 30 PC, which supplements the time- and date-stamped quality files with additional qualtiy data from the lab's own tests.

All business software functions--inventory control, purchasing, cost estimating, MRP (material requirements planning), scheduling, production control, payroll, order entry, and the like--are performed on an IBM AS/400 office mainframe computer using a TCC software package called WorkForce. It takes only inventory-related data from the shopfloor database--i.e., barcode readings of packed skids of bottles. The AS/400 uses these inventory data to generate bills of lading for shipments, and also pulls SQC data from the q-c lab database for certificates of conformance.

TCC representative Donald W. Schaefer, Jr. notes that Schoeneck's CIM system was designed for 24-hour-a-day reliability. The MACO 8000 and IBM 7531 at each operator station can operate independently of each other if one of them goes down. Likewise, each IBM 7531 stores data duplicating that on the server, in case either database becomes damaged or lost. Data may be deleted from both computers automatically after the server is backed up on tape. If the network goes down, the shopfloor 7531 keeps storing data until the network revives, and then automatically updates the central database.

THE BENEFITS, SO FAR

The first machine was outfitted with the new system in October '88, and five more in '89. The remaining four machines will be added to the CIM network shortly. When completed, Dave Schoeneck estimates that his firm will have spent $1 million on the project.

The first year of experience with the system has confirmed a number of benefits. Some of these are owing to the switch to microprocessor machine controls. Dave Schoeneck points to tighter parison control with the MACO's electronic programmer, which has more programming points (100) and faster response than Schoeneck's older programmers. The trend toward fine-tuning container designs to shave every last gram of excess weight, says Shoeneck, requires the finer degree of control provided by the new equipment. That also offers opportunities for materials savings on existing jobs, he notes.

Glenn Knapkiewicz adds that temperature control is also better with new auto-tuning controls that are less subject to drift and provide faster cooling response. "It also makes a difference in easier start-up of the lines. We just plug in an InstaSet cartridge and push the button. It used to take us three to four hours or more to tune in a complex parison program on starting up a job, and the InstaSet has cut that in half. On an ordinary job, it takes less than an hour from the time the heats are up until we're making packable containers."

Another advantage, says Knapkiewicz, is that the microprocessor controls are actually easier to service and maintain than the old relays, contrary to expectations. "When you had a big cabinet full of relays and contactors and everything else, you needed substantial electrical knowledge to troubleshoot it. Whereas now if there's a failure, a warning light comes on and tells you to just change a module. It has simplified service for our machine operators and made problems easier to recognize through the warning lights."

A NEW WINDOW ON THE PROCESS

The most important benefit, however, has been greater "process visibility" or insight into what's happening in the machine. An example is being able to see a graphic display of each cycle's actual vs. programmed parison profile. Says Knapkiewicz. "Before, we just set the program and let it run. We might know we had a problem, but we couldn't see where it was occurring."

Another example is clearer awareness of weight variations between cavities: "There's always one cavity heavier than the rest--now we can start looking at why. Before, if the bottles were in spec, we left it alone. Now, we can realize what's happening and try to correct it."

What's more, he adds, "We're going to be able to monitor closely and record information that we haven't before. 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."

Plant superintendent Ernie Macke looks forward to quicker evaluations of new machinery r materials. "If we try out a compound that's less expensive or flows better, having a better grip on what's happening in the process will help us get more instantaneous feedback to our supplier."

Machine operators like Marck Kelnofer find the new system better because it draws attention to process problems in an obvious way. "On setup, everything's right there for you on the screen, no guesswork. You can see on the screen where your flaws are. When you're running, there's a million things to do out there, but the screen flashes red to signal the problem--plus, there's an alarm buzzer."

"The next step in our program," says Schoeneck, "is to do something we never could before--correlate process data with the quality of the product coming out. Then we'll really be able to concentrate on long-term improvement of our process, equipment and materials."

The company is not yet performing SPC analysis on process variables--only on molded container quality characteristics. TCC's Schaefer is working on software to tie together SPC data from the MACO with SQC data from the operators' electronic gauges and lab tests. This will help Schoeneck's technical staff to decide what variables are worth monitoring and how often. Statistically designed experiments will help determine which variables have the most influence on product quality.

On an experimental basis, Schoeneck is monitoring 12 zones of barrel temperature, melt temperature and pressure, cooling-water inlet and outlet temperatures, blowing air pressure, clamp hydraulic pressure, and servovalve operation. Schaefer speculates that they may learn it's not necessary to monitor all these variables continuously--so long as they're within desired limits. Perhaps it will prove possible to monitor only excursions (alarm conditions) on some variables, and record actual values only once an hour when quality samples are taken.

A PHILOSOPHY OF 'OWNERSHIP'

Dave Schoeneck sums up one of the key goals of this CIM project: "Our program is based on our people controlling the process. We put in tools to help them feel ownership in what they're doing on the line to control quality and productivity. Before, they didn't have the feedback to make the proper calls on controlling the process."

Some CIM systems tend to concentrate more production and process infromation at a central terminal and provide less information at the operator station (see below). But that conflicts with Shoeneck's concept of "ownership" and operator responsibility for quality. For Knapkiewicz, the biggest benefit from the system is that it cuts down on counterproductive dial-twiddling while letting operators make needed adjustments for changing raw materials or ambient conditions.

Adds Ernie Macke, "Normally, if you weigh a bottle and it's not right, you adjust the machine. Next time you weigh a bottle and it's not right, you adjust the machine some more. But suppose it's caused by the natural variation of the process. If you look at the X-bar chart on the screen and see that it's within the control limits, you leave it alone. So you don't make adjustments that aren't needed, because that tends to throw the process out of control."

Besides operator satisfaction, there have been bottom-line benefits from the system. Knapkiewicz estimates that tighter process control has reduced scrap by 5%. He also estimates 5% higher productivity. "Operators have more time to spend working on their process and not charting SPC variables. And Ernie and I can see what's going on in the plant better by scanning the screen displays at a remote terminal than by wandering around to the lines." Having all the information the operator needs at his fingertips means that "he doesn't have to go running away from the line to find a central station, hope nobody else from a different line is looking at it, and go through all the machinations of calling up a display of his line. He just turns around from his machine and takes a look at his current Cpk or operating efficiency, for example, vs. those of the last two shifts before him."

CUSTOMERS LIKE IT, TOO

Director of sales and marketing Joe Gruszka says, "Customers have definitely noticed the increased consistency in our products. In the last year and a half we've had no rejects from customers. They also like our interest in continuous improvement that goes beyond their initial requirements."

"In the PVC bottle business," says Gruszka, "a one-year contract was considered a long-term commitment. Now we have contracts of two years or more from several customers. That's unheard-of!"

Charter Supply: CIM Is a Great Teacher

Enthusiasm is the first word that comes to mind when Edna Hover starts talking about the new CIM system at Charter Supply Co. in Philmont, N.Y. She's the CIM manager, chief watchdog over the plant's 13 extrusion blow molding lines from an enclosed command post on the production floor. "CIM is a great momentum builder," she says. "It's the opportunity of a lifetime to energize your technical staff. They walk in the door in the morning knowing they can control the machines. And they're developing, they're learning, becoming intuitive about the right adjustment to make on the machines from seeing the shape of the process monitoring curves on the screen."

Charter Supply custom molds over 6 million lb/yr of HDPE and PVC bottles from 2 oz to 1 gal for household chemicals, cosmetics and toiletries. In 1989 the company installed a CIM-1 process and production monitoring system from Hunkar Laboratories, Inc., Cincinnati. Versions of this system had been used commercially for injection molding (see PT, April '88, p. 15; March '89, p. 71; Feb. '90, p. 23). Charter served as the beta site for proving out the system in extrusion blow molding.

The most visible part of the system is Hover's "command station," consisting of an IBM industrial microcomputer in a console housing three color CRT screens that monitor process parameters and production status of all the lines. Standing next to the console is a personal computer that displays SPC analyses and control charters based on the process data from the main console. (It performs a lot of statistical number crunching without interrupting the real-time display of shopfloor information.)

The command station collects data from all 13 Bekum and Battenfeld Fischer machines, which date from the early 1970s to the present and have controls ranging from relay taype to Barber-Colman MACO 8000 microcomputer. What all have in common is a Hunkar Data Acquisition Terminal (DAT) that transmits process data, alarm messages, and operator-entered messages to the command station.

TWO QUALITY NETWORKS

One special feature of the system is Hunkar's SPC-PRO "expert" software. Once desired operating conditions are achieved at the start of a new job, the software automatically assigns tolerance bands around 12 key process variables, according to empirically derived assessments of the relative influence of each variable on product quality characteristics. If any of those parameters strays outside the tolerance limits, the command station flags a "bad" cycle.

The system therefore provides a form of 100% quality control, based on monitoring adherence to qualified process limits. This supplements a pre-existing quality and production monitoring network of personal computers throughout the plant, which dates back several years. "We were pretty innovative in that way for a company our size," says Charter's president, G.B. "Jake" Jacobsen. For five or six years, cycle counts and cycle times from all machines have been displayed on a PC production-control monitor on the plant floor, and also on various plant office PC's. And a year before the arrival of CIM-1, Charter initiated a statistical quality control system on the PC network. Once an hour, q-c inspectors collect sample containers from each machine and take them to one of two PC stations on the shop floor. There they call up the job standard on the screen and perform the required checks with an electronic scale and caliper. The readings are automatically entered into the computer, and the inspector can then call up an updated X-bar and R chart of histogram from the on-screen menu. The chart will appear in a different color, depending on the latest reading: green for acceptible, yellow for borderline, and red for out-of-spec. These quality data are accessible on PC's in Jacobsen's office and that of the q-c manager. Charter Supply is now in the process of integrating the SQC data from the gauges and scales with the SPC data on the Hunkar network.

CIM ENFORCES DISCIPLINE

The first phase of the CIM-1 network was installed at the beginning of 1989. Full-scale monitoring of all machines is just now being completed. Edna Hover moved from the q-c department to become CIM manager. She says, "I check the machine data every day to see if we maintained the control limits and we didn't lose the process that makes a good bottle. First thing I do is look at the alarm file for the previous day, then production reports, downtime for each machine and reasons, rejects per line per shift, mold and machine hours run." She also prints out setup sheets, and watchdogs job schedules. "My primary job," she says, "is to make sure we respond in a timely way to problems as they occur, or even before."

She's not alone in using the command station. The plant manager, technicians, line mechanics, q-c personnel, and Jake Jacobsen all stop by periodically to examine the screens. At present, the only other terminal linked to the command station is at a sister company, Plastics Container Corp. Inc. in Champaign, Ill. Occasionally this remote link is used for long-distance consultation on process analysis.

Jacobsen estimates that the CIM-1 system has cost a total of $175,000. After just a year's experience, he feels it is already paying off. "We get more productivity, less downtime, and markedly improved cycle-time efficiency. We have seen an upward trend in cycle efficiency for all machines, but the biggest improvement was in the oldest machines. So we have moved the goal posts a bit and tightened the standards for cycle time." Jacobsen estimates that overall productivity is up at least 10%, that overall rejects have been cut in half, and rejects related to CIM-monitored variables reduced to nearly nothing. "For a while after we got CIM," he recalls, "most of the runs were surprising us. We were running more efficiently and getting done sooner than expected."

"Most of our runs are very short," Jacobsen adds, "so we questioned whether CIM could be of any value to us. But it has proved valuable in getting setups done faster and accurately enough so that when the bottles come out of the machine they can go into the box." This has had one important consequence: "We found that 80% plant capacity utilization was unobtainable before. Now we think we can run comfortably at 90%."

Hover offers part of the explanation: "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? Now we have a very narrow window defined by the CIM system, which generates the setup sheet. I tell them, if we can hit those numbers, we've got it knocked. Because we did it this way last week and had a clean run. It adds a whole lot of credibility to those setup values. The setup men know the target means something--it's no longer an arbitrary number set by someone else who had a different feeling about blow molding. Now they'll go looking to get a hundredth of a second closer to target. They have contests to see who gets closest to my setup numbers."

Hover and Jacobsen say most machines run within [+ or -]2.5[degrees] F of setpoint and [+ or -]0.04 sec on a 7-sec cycle time. Even the oldest machine runs within [+ or -]0.65 sec on an 11-sec cycle, they say.

Even though Charter has used the InstaSet feature of the MACO controls on some of the newer machines to recapture earlier setups, Jacobsen notes that repeatable machine settings are not the main goal--now, his people focus on reproducing certain process conditions, whatever the settings required to produce that result.

A key benefit of CIM is in eliminating gratuitous dial-twiddling. Says Hover, "Before, when cycle time was the key setup target, the technicians could fool with other parameters for days after job startup, and drive everyone nuts with their constant adjustments. The next time we set up that job, no one remembered what the optimum settings were anyway." It's part of Hover's job to keep an eye out for changes to setpoints, which produce an instant alarm message on her screen.

"CIM is a big step in the rationalization of our business," says Jacobsen. "It enforces the discipline to keep within proper operating range. So we don't have people making miscellaneous adjustments to the machines. Before CIM we had three different shifts--you could time the machine adjustments to the whistle on the clock. Now, with CIM, the plant runs like it's one shift."

LEARNING FROM CIM

The most fundamental benefit that Charter Supply has gained from CIM is greater understanding of its process. By observing the graphic displays of process conditions, says Hover, "You get to understand your machines just like they were people. For example, screw rpm has a signature on the chart. Line 5 looks like this. If it deviates from the original fingerprint, you ask why and start looking for the answer. In the last three months we saved two extruder motors from burning out."

Jacobsen confirms this: "In one case it was at night. Edna called and said the rpm's didn't look right. So we decided to shut down the machine. The next morning the tech guys got a look at it and said if we had let it run another hour we would have burned out the motor. We saved $5000 or more."

"So now we know what a motor brush failure looks like," Hover continues. "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."

In fact, one of the first consequences of installing the CIM system was that it pointed a big finger at pre-existing maintenance problems that had to be fixed before Charter could begin to work on process improvements. Jacobsen estimates they spent $25,000-30,000 on those fix-ups.

"And 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 fixing that problem now, rather than dumping it onto a later shift."

Jacobsen says CIM has brought a major transformation of management philosophy. "Before the arrival of CIM, we looked mainly at cycle time as the key to our daily profit margin. We had a narrow-minded approach. But today we're going from a cycle-only mentality to process rationalization. Today, our first question is, how do we make the best part? Second, how do we make the best part in the shortest time?"

In addition to cycle time, the CIM system is monitoring mold-closed time, blowing time, average and peak melt pressures, screw rpm, oil temperature, and blowing air pressure. These are shown on one screen for each machine, with upper and lower limits and last-cycle value for each parameter. SPC charts can be generated for any variable with a few keystrokes.

Says Jacobsen, "With these graphs we get right into the bowels of the machine. Before we stood outside it and just watched cycle time. We have learned more about our process since we've had CIM than in the previous 11 years I've been here. There used to be a lot of black magic, but now we're beginning to rationalize what we're doing. I don't mean to claim that we know everything. But we have a very good classroom now."

Plant utilities--air pressure and cooling water--are also monitored by DAT's on each machine. Hover recalls, "Three times in the last six months, CIM predicted that the air supply would quit, and it did. We were able to bring on a backup compressor before we had to shut down any of our lines." Jacobsen looks forward to putting DAT's on the screen printing and heat-transfer decorating lines, to bring them into the CIM system as well.

PERSONAL REWARDS FOR STAFF

"It's important not to use CIM in a negative way," warns Hover. "We use it to show people how much better they're performing than before. Not big brother watching you." Jacobsen concurs: "CIM is not a report card to chew somebody's butt with."

In fact, Hover sees a lot less defensiveness among the technical staff. "They're usually the last ones to get credit for keeping the lines running day in and day out. It was common to blame problems on 'that lousy setup crew.' Now all setups are documented. I can show that we had so many hours of good production after setup with no problems until somebody made an adjustment on the machine.

"CIM protects the off-shift technicians--they don't have to hope that someone tells them what went wrong before they got there, because they can see the history on the screen. I was in q-c, and I know it's always the guys on the third shift that get the blame.

"Now, our people feel like they matter. Tangible evidence of a job well done can make all the difference in the world in their pride of accomplishment. You take one of your less experienced technicians, who usually needs a lot of guidance from other people . . . I see them blossom. These are the guys who are now analyzing situations on their own based on the information they get from CIM."
COPYRIGHT 1990 Gardner Publications, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1990, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:computer-integrated manufacturing
Author:Naitove, Matthew H.
Publication:Plastics Technology
Date:May 1, 1990
Words:4856
Previous Article:New equipment for lower-cost RIM.
Next Article:Opportunities take shape in recycling.
Topics:


Related Articles
User-programmable process monitoring now in a low-cost package.
CIM made simpler.
Bottle makers integrate on-line process & quality monitoring.
What it takes to be a 'world-class' injection molder.
CIM & CAD/CAM.
AutoFact '91: news in CAD/CAM, CIM & rapid prototyping.
CIM brings it to you 'live.' (computer-integrated manufacturing; blow molders monitoring)(includes related article)
Blow molder plunges into CIM.
Welcome to the New Detroit of the south.
CIM data banishes rejects.

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters