At Polymer Conversions Inc.: a controlled environment is critical to quality.

With process monitoring on all 21 of its injection machines, you might think that Polymer Conversions Inc. (PCI), a custom molder in Orchard Park, N.Y., would have more than enough data to meet its quality-control needs. But PCI specializes in precision parts for medical, automotive, and business-equipment markets. Keeping such demanding customers satisfied has led PCI to take its monitoring efforts well beyond the standard stock of molding pressures, temperatures and times.

Using a SourceCIM system from Hunkar Laboratories in Cincinnati, PCI also keeps a close watch on the ambient conditions in its plant, as well as on dryer dewpoints and tower-water temperatures. The company also has ambitious plans to integrate its secondary operations - which include four kinds of welding and assembly equipment - into its evolving CIM network.

Keep it dry and cool

PCI maintains its molding room at a maximum relative humidity of 40%, regardless of the season. "Even if it's 80% R.H. outside, in here it never gets above 40%," says molding manager Dan Corbett. He notes that humidity control eliminates mold sweating that would threaten part quality and shorten the lifespan of the 300 tools in the plant.

The company also finds it helpful to control molding-room temperatures to a constant 68 F year round, eliminating another variable that could adversely affect product quality.

To monitor and control these two environmental conditions, PCI integrated its HVAC system into its SourceCIM network. PCI also continually monitors humidity and temperature in its assembly and finishing room. "We've found that excess humidity can have a negative effect on our pad-printing operation," Corbett notes.

Resin drying is critical

With several large-volume PETG jobs on its shop floor at any given time, PCI also monitors the dewpoint of the air entering its dryers. "The slightest moisture rise can raise hell with the process," says Corbett. He explains that the company aims to keep resin moisture below 0.005%, and that the drying time to meet that goal will vary with the dewpoint of the drying air.

PCI uses the dewpoint readings to aid in diagnosing an ailing process - especially fluctuations in the injection portion of the molding cycle. "If the peak injection pressure changes, for example, the first thing we'll do is check for any changes in dewpoint," says CIM coordinator Tom Rybicki.

By accounting for the influence of dewpoint fluctuations, PCI has also been able to uncover inconsistent material lots. "We've found differences in materials within the same gaylord," Corbett reports.

Water temperature is key

Another auxiliary system PCI monitors is tower-water temperature, an important factor for maintaining appropriate mold temperatures on its most critical parts. "Some of our processes need to run at a mold temperature of 80 F," Corbett says. "If the tower water comes in too hot, it can create a problem for our chillers." He adds that monitoring data on the tower water was the basis for a decision on upcoming capital investment: "Our current tower can only handle one more molding machine, so we'll eventually have to replace it."

PCI has also found quality-control benefits from monitoring actual A- and B-side temperatures of all its molds. Real-time data helped establish that mold temperature can influence critical part properties - a relationship that had remained obscure when there was a 24-hour lag between molding and quality-control testing. Putting control limits on mold temperature helped eliminate costly rejects on one troublesome medical part. "We easily paid for the initial CIM implementation on that part alone," says Corbett.

Welding is next in line

When all its primary machines and the plant environment are wired up, the next step for PCI will be to integrate its assembly operations into the CIM system. According to Corbett, PCI will at first put some simple data-acquisition units on the vibration-welding machinery in order to monitor distances, times, and pressures - all of which affect weld quality.