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Big molding gains from small-scale CIM.

With 20 injection presses, Bamar Plastics Inc. of South Bend, Ind., doesn't have the biggest CIM installation around. But this small custom molder of tight-tolerance electrical and automotive parts has reaped huge benefits from the process and production monitoring system it installed two years ago.

Bamar molds parts for automotive and consumer electronics. With typical tolerances around [+ or -]0.1 mm, the opportunity to improve quality initially drove Bamar to hook up its 20 Boy Machines presses of 22 to 80 tons to a CIM system from Syscon-PlantStar also of South Bend. Quality did improve - as did other important benchmarks: Press utilization increased from the mid-80s to over 90%. Downtime fell, as did cycle times. And the plant's staffing requirements routinely drop into "lights-out" territory.


The company's CIM system consists of an IBM RS/6000 host computer connected by an Ethernet network to eight PCs on the shop floor and throughout the company. At the presses, Bamar installed Syscon's MCIM touchscreen data-collection units. Rather than one MCIM per press, Bamar uses one box per four presses, in part to keep installation cost down. Also, automation means there aren't enough people on the shop floor to require a man/machine interface at every machine. "We don't have an operator at every press, so there's no need for an MCIM at every press," says Jim McVay, quality-assurance manager.

Aside from its hard-wired MCIM units, Bamar asked Syscon for a portable MCIM unit that technicians can plug into any press when performing diagnostic or set-up work. "It lets you look at the process in real-time without running back and forth to the closest MCIM," says production manager Dave Johnson.


When its CIM system came on line two years ago, Bamar first used it to set control limits on all its key process parameters. According to McVay, Bamar's quality standards demand that it hold cycle times to within [+ or -]0.2 sec, peak injection pressure to better than [+ or -]15 psi, and ram position to [+ or -]0.5 mm. All these parameters, as well as barrel temperatures, are hooked up to visual alarms, which quickly show any straying processes. "The system gives us a wealth of information," says McVay. "Before, it was seat-of-the-pants molding."

Bamar has enough confidence in that information and in its control limits that the company routinely runs "lights-out" on many weekends and holidays. "We let the system watch the presses and review the process logs later," says McVay. Even on weekday shifts, Bamar runs with as few as two process technicians and two quality inspectors for its entire plant.

Real-time process data has also given Bamar a way to quickly troubleshoot its molding processes. For example, in multi-cavity tools, stuck parts or plugged gates could easily go unnoticed for several shots before the process-monitoring system was put in place. Now, monitoring shot size tips off technicians in a single shot. The monitoring has also given Bamar a way to identify worn machine components, McVay adds.

Cycle times on Bamar's 150 jobs have also improved because any increase in cycle length triggers an alarm and the cause is immediately tracked down. "The system lets us detect variance in the subcycles," says McVay. That feature helps identify which part of the cycle - such as injection or screw recovery - is contributing to prolonged molding cycles.


For production monitoring, Bamar's CIM system also tracks all ongoing jobs and alerts technicians to impending job completions - first on the MCIM and later with a strobe light. Job changeovers are sped by the system's ability to store and download set-up parameters, says production manager James Ebel.

Bamar also makes use of the system's scheduling capabilities. "It tells you when schedule changes threaten subsequent jobs," says Ebel.

Finally, the system generates comprehensive shift production reports. These reports include information on each job's reject rates, utilization rate, cycle time, and time to completion. Having this much information each day would have been impossible before the production-monitoring system was put in place, notes McVay. "Once we were blind; now we can see," he says.
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Title Annotation:custom injection molding
Comment:Big molding gains from small-scale CIM.(custom injection molding)
Publication:Plastics Technology
Geographic Code:1USA
Date:Dec 1, 1997
Previous Article:CIM data banishes rejects.
Next Article:PE & PP prices softer in '98, PS firmer.

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