On-line, press-side decoration adds new technical dimension to molding

At Sussex Plastics, hot stamping of molded parts is almost as important as the molding process itself. With 65 percent of its business in the cosmetics market, the Sussex, WI-based molder labels a majority of its product. Lately, Sussex's hot stamping needs have become more complicated. "We do a lot of traditional hot stamping," says Mike Fitzpatrick, director of technical services, "but now we're getting into round and rounded stamping."

The Sussex plant has 52 presses, 55 to 725 tons, mostly Van Dorns, molding cosmetic compacts, lids, and containers, as well as some medical and industrial parts (Figure 1). Not long ago, Fitzpatrick needed an automated system beside the press to receive and automatically stamp parts.

What he received was an Acrobot 1000, manufactured by Permanent Label. It is a computer-controlled, servo-driven heat transfer and hot stamping machine. It prints an area up to 360 degrees on non-round parts. Sussex also got a 30R3 roll-on hot stamping and heat transfer machine, also from Permanent Label. It handles all round parts and also prints an area up to 360°. Both machines are robot-fed and run all the time.

"When I buy a piece of equipment, I don't have a lot of gambling room," Fitzpatrick says. The machines, he says, are reliable and produce well-decorated parts, but they also introduce a level of automated sophistication to the molding process with which most molders are unused to dealing. "You have to be prepared to deal with automated equipment," he notes. The servo motors, gear cases, and balls and screws that drive the machines need periodic maintenance and attention from someone skilled with such equipment.

Take, for example, Dave Jones, general manager of the Spectrum Div. of The Plastek Group in Erie, PA. He has 65 presses, 70 to 725 tons, molding jars, caps, and enclosures for the cosmetics and consumer markets. He has eight Acrobots, four of which are interfaced with a press running a 16-cavity mold in 16-second cycles. He tweaked and fine-tuned the molding process and stamping machines so that each Acrobot stamps one cap every four seconds, which means his print cycle matches his machine cycle. He says the technical dimension added by the stamping machines is a challenge, but "I don't think it's something that difficult. Most any molder should be able to pick it up."

The efficiency of automated, on-line decoration also relies greatly on the quality of the parts being stamped. "The machine can't take just anything," says Fitzpatrick. "A .005 to .006 inch wall thickness variation can make the difference between a good part and a bad part." Jones agrees and says, "The hardest thing is taking the inconsistency from cavity to cavity and mold to mold and hot stamping it."

Neil Meador, manager of machinery manufacturing at Permanent Label, says variations of .004 to .006 inch generally produce acceptable parts. Variations of .006 to .008 inch will cause print to be heavy or light. Variations of .008 to .010 inch can result in heavy or light printing or a complete miss in some cases.

Jones notes that the demand by the decorating machines for consistent parts makes his molding process more consistent, and forces his moldmakers to be more careful.

Back at Sussex, Fitzpatrick says he has four Acrobots and two 30R3s running almost constantly. The 30R3 ranges from $30,000 to $75,000. The Acrobot ranges from $85,000 to $120,000. "I think they're a little expensive," he says, "but if you're going to use them, the payback is there." He estimates the average payback for Sussex has been about 18 months. "And I have to say that, without that machine, I wouldn't have the job," he says.