Penn State Erie takes deep dive into technical aspects of molding

Erie, Pa. — Penn State Erie's Innovation and Emerging Technologies Conference had something for the 185-plus attendees, students and industry veterans with about 30 presentations covering topics including resin drying, liquid color, automation, coining, plastic flow, balancing hot runners and multicavity molds to account for viscosity changes, and improving collaboration between engineering and manufacturing.

Doug Espinoza, manager of RJG Inc.'s TZero program, explained how the consulting operation helps link engineering and production to create a tool launch that's right the first time — by spending time and effort before cutting steel. He advised molders to document and validate the processes involved in molding a part.

"Half the battle is knowing what is happening in the mold," he said.

People in manufacturing these days know to avoid setting up silos of work functions, where departments toss projects over the wall. But Espinosa said TZero uses a documented, organized plan to foster communication when designing an injection mold.

Training and education are the keys, and the missing links at many companies, he said, displaying detailed flow charts to track progress and encourage teamwork.

"Get out there, get folks together and do some problem-solving," he said.

TZero helps design experiments to go through a list of hypotheses. "We can be on the plant floor for two weeks, getting people out of problems," Espinoza said.

TZero uses molding simulation, as RJG is licensed to use Sigmasoft, Moldex3D and Autodesk Moldflow Insight. Espinoza reviewed part design and mold design, where he said "cooling is a big factor."

Measuring machine performance is very important and can sometimes give simulation a bad rap, he said. TZero experts prefer to get real data.

"Don't just use the machine spec and its inputs. You have to have actual machine inputs," Espinoza said.

And changes in resin viscosity can impact part quality, which is why he recommends monitoring the history of mold cavity pressure, using's RJG's Decoupled II and Decoupled III processes.

Two speakers discussed hot runner control.

Marcel Fenner, technical manager and president of Priamus System Technologies LLC, said balancing of high-cavitation molds is necessary to prevent uneven filling. Reasons for variations include different positions of the thermocouples and other factors.

"The biggest one is variation in the viscosity of the resin," he said.

Priamus, working with Synventive — its sister company under Barnes Group Inc. — has developed technology that electronically handles hot runner tip temperatures. Fenner said that gives precise part length and part weight in multicavity molds — even in family molds, which are inherently unbalanced.

Shear rate differences created in a hot runner system often are the cause of blow imbalances related to changes in viscosity, said Eric Gerber, an engineer at Sigma Plastic Services Inc. in Schaumburg, Ill. Other factors that affect melt flow rate include flow length, pressure within the mold cavity and temperature in the mold or the hot runner manifold.

Paul Maguire, president and CEO of Riverdale Global in Aston, Pa., said that liquid color gives 100 percent color distribution in the melt. He outlined Riverdale's RGInfinity system that automatically refills the color container when the fluid level is low.

Maguire also described a system where processors can refill their own drums and custom-mix color in-house, which he joked is the "Home Depot method."

Attendees at the Innovation and Emerging Technologies Conference also heard about drying technology from Gene Flockerzi, general manager of North America for Moretto SpA. Flockerzi joined the Italy-based auxiliary equipment last summer after a long career with Conair Group.

Flockerzi said Moretto's Moisture Meter measures the moisture of every pellet, in real time, as it comes out of the drying hopper. The drying process has lots of unknowns, including whether there is the correct airflow in the drying hopper, is there overdrying and is the equipment properly maintained.

"We're trying to give you a window in the world of materials," he said.

Flockerzi said Moretto has two Moisture Meters installed at U.S. customers and has sold 10 systems so far in the United States. Worldwide, the auxiliary equipment maker has installed about 100 Moisture Meters, he said.

The Moisture Meter also gives full documentation, including time and date stamps for every shot. It also has early warning detection. "You're putting a lot of additives in there, and you hope it all cooks right," Flockerzi said. "This makes sure it's cooked right."

Flockerzi said Moretto's OTX drying hopper (original thermal exchanger) has a special bullet-shaped geometry, a patented design that changes how air flows. "We have a very uniform air flow," he said. OTX drying hoppers can handle from a half-pound of material an hour to about 6,000 pounds an hour.

Moretto's U.S. operation in Columbus, Ohio, covers 15,000 square feet. Flockerzi said the company is looking for building about twice that size.

Trevor Pruden, technical and engineering manager at Arburg Inc. in Rocky Hill, Conn., said injection/compression molding — or "coining" — molds parts with low physical stresses that are constant through the entire part. Coining can prevent sink marks and minimize warpage and can be used with a wide variety of materials, such as thermoplastics, powder injection molding and liquid silicone rubber, he said.

That makes coining a good way to make some types of parts, such as LED optical lenses and semi-crystalline polymers, he said.

Dan Spohr, of Wittmann Battenfeld Inc. in Torrington, Conn., said it's a good idea to replace older robots with new ones that can perform movements in parallel with injection press functions. For instance, an old robot may need to make separate judgments to be sure the part is located on the end-of-arm tooling, then remove the part from the molding area, and finally OK'ing the machine to close again, can consume three seconds in those tasks. "A new robot can be less than one second," he said.

"This is where molders make their money. You want that mold-open time to be as short as possible," he said.