PT Blog

Injection molders have probably all encountered customers that demand projects to be executed with impossibly short lead times. But an entirely different sense of urgency has galvanized plastics processors to devote every resource and stretch their capabilities to meet the need for protective masks and testing devices in the global battle against the novel coronavirus. One such molder is Harbec, Inc. in Ontario, N.Y., which relied on both its molding skills and moldmaking expertise to beat the clock in three COVID-19 related projects—and in the process accomplish new feats with 3D-printed tooling.

Harbec is a custom injection molder and moldmaker with additional metalworking business in aluminum aircraft parts and titanium surgical implants. “We started out as a machine shop,” notes company president Bob Bechtold, “and got into molding to give our tooling customers more confidence in our know-how.”

EVCO Plastics is a global custom injection molder with nine plants and 210 machines devoted to a wide range of markets. Its medical business, in particular, is humming with new projects aimed at combatting the coronavirus pandemic. The company has three plants and a Tech Center at its headquarters location in DeForest, Wis. Both people and machines were transferred from some of these to the EVCO Plastics MED (Medical and Electronic Devices) Plant, which has an ISO Class 8/Class 100,000 clean room, where the bulk of these COVID-19 related projects are underway. At the end of May, EVCO had 17 machines molding COVID-19 related parts, and orders were still increasing.

“We’ve been doing DNA test kits, used for criminal investigations and consumer ancestry analyses, for some time,” says EVCO president Dale Evans. “So we repurposed some resources from that to COVID-19 test components.”

There is general agreement among processing specialists that melt-temperature control remains one of the “last frontiers” of injection molding process control. “You can’t control what you can’t measure” is a fundamental axiom, and the real problem here is the lack of an accurate, repeatable, practical, and generally accepted method of measuring the melt temperature inside the barrel or nozzle of an injection machine.

Methods tried in the past include inserting a sensor through the wall of the nozzle. Experts say the sensor reading with this method is overwhelmingly influenced by the steel temperature of the nozzle rather than the melt. Even if the tip of the sensor is exposed directly to the melt, it will measure only the cooler, slower-moving melt closest to the nozzle wall, due to the laminar-flow behavior of plastics. And it has proven impractical to insert the sensor near to the center of the flowing stream, owing to the dynamic forces on the fragile sensor.

I’ll admit, I’m a bit befuddled about the seemingly conflicting accounts I’ve been getting lately about what’s going on in plastics processing. On the one hand, I’m regularly hearing stories and getting press releases about processors ramping up quickly to turn lines that had been running conventional plastics products into very specific personal protection equipment in the fight against the coronavirus pandemic. I’m hearing stories of molders calling their machine builders and even moldmakers to run parts for them due to their own capacity restraints. I’m reading about states like California, New York and others reversing bans on plastic grocery sacks. I’m being told of processors pre-buying resin to meet an expected surge in demand for their products. I’m hearing about processors buying new lines to meet demand. Good stuff, I’m thinking. Plastics processors are really busy.

Then during grocery shopping I’ll make mental notes about what I see and don’t see on the shelves and what it might mean for processors. Bread? Going fast … lots of bags used there. Juice? Dairy products? The shelves are not bare, but not fully stocked either. People are buying these necessities, so it stands to reason there must be demand for lots of bottles, caps, labels. Hand sanitizer? Seems like lots of the “green” products remain, but everything else is moving. Lots of bottles, pumps, gaskets have to be in the pipeline. Toilet paper? Good luck. But it’s being made—lots of it—and the multi-roll packs are all wrapped in plastic. Fresh fruit and veggies going fast; lots of produce bags are likely being churned out. Done shopping, I loop around the store and see five trucks waiting to be unloaded. Lots of pallets. Lots of stretch film. Good stuff, I’m thinking, again. Plastics processors are really busy.

Today’s modern manufacturing processes utilize loss-in-weight (LIW) feeders as the automated dispensing technology for dry bulk solids. The most current feeding technologies have evolved in many aspects through improved control and design features with an emphasis on process robustness and intelligence. It is expected that feeder controls can easily connect to industrial networks and key process data, which has become a critical criterion in evaluating not only feeder performance but also real-time indication of the complete process.

This article will address what a processor should consider when evaluating his current feeding equipment and the feeder’s ability to monitor, trend and react to process variations. The availability of this data and its management in accordance with Industry 4.0 automation can allow the user to adapt to future manufacturing requirements, which can include greater traceability, flexibility, adaptability and overall effectiveness.