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Specialists share insight on molding at Western Plastics Trade Fair

By: Roger Renstrom

August 22, 2013

ANAHEIM, CALIF. — Industry specialists Brian Kennedy, Robert Frey and Suhas Kulkarni shared insights on mold buying, troubleshooting and scientific molding at the Aug. 15 Western Plastics Trade Fair in Anaheim.

Kennedy described how he judges a mold making shop starting with the lobby. He is the principal with consultancy AmBi Group of Claremont, Calif.

"Is everything clean? Is it crowded but not cluttered? Is it uncluttered?"

If the lobby fails his test, Kennedy turns around and leaves.

Kennedy noted regional pricing differences for the U.S. mold making industry: "West is most expensive, East is next most expensive and Midwest is cheapest."

He said China is "less expensive but what was missed" in the bid process. China's worst failing: "water system functions."

Frey suggests a way to problem solve: "Think like a molecule as plastic moves through the machine ... . Put your hands in your pockets and use you head-top computer" before making changes to a process. Frey is lead technical development engineer in Riverside, Calif., for PolyOne Distribution Co.

Frey went through characteristics of the most common molding problems — short shots, flash, burn marks and splay — and encouraged talking with material handlers and machine operators about the issue.

Regarding the use of reground plastics, Frey said: "If it's good material, 20-25 percent is OK. If not good quality, 1 percent is too much."

Using statistical graphs and charts, Kulkami identified viscosity curve, cavity balance, pressure drop, process window, gate seal and cooking time as scientific molding steps "to develop robust process and achieve consistency." Kulkarni is technical consultant with Fimmtech Inc. of Vista, Calif.

As a next step, Kulkami is developing a technical paper with more statistical documentation for presentation at the Society of Plastics Engineers' Antec 2014 conference April 28-30 in Las Vegas.

Kulkarni and two others are establishing a plastics processing innovation and training center with its first class occurring on Sept. 9 and plans to offer material and processing studies and pursue molding-related projects.

"The room is ready" at Timothy Curnutt's Distinctive Plastics Inc. molding facility in Vista, Kulkarni said. "We will get a dedicated machine by the end of the year. Meanwhile, we will use one of Tim's machines."

The SPE southern California section again organized the trade fair presentations, table-top exhibits, dinner and raffle.