ROSEMONT, ILL. — Speakers from two European rotational mold makers — one from Italy, the other from Germany — described how to design molds without the big metal supporting framework, known as the spider, at the Rotoplas conference.
“There's a technology on the market to reduce the massive frame on the mold,” said Sergio Zilioli, key account manager for Persico SpA.
Reducing, or even eliminating, the spider makes the molds much lighter. Zilioli also said you can deliver direct heating to the mold, improving the process.
Persico displayed one of its Light Molds at its Rotoplas booth. It is a two-piece, machined mold for a U.S. customer that rotomolds snow sleds. Instead of putting clamps on the flange of the mold, Persico used a minimal frame with clamps, he said.
According to Zilioli, replacing the heavy spider with a light frame reduced the weight of the mold's frame from 88 pounds down to 60 pounds.
Persico uses finite element analysis to simulate the mold and frame. The company is based in Nembro, Italy.
The other speaker, Oliver Wandres of Maus GmbH in Karlsruhe, Germany, talked about how with pneumatically-actuated clamps and automation, one operator can open and close a space-frame mold. Maus also can design a mold with pins that automatically retract, forming a through-hole in a rotomolded part.
Wandres outlined a case study for a customer molding a spin/foam/skin part that was very difficult to demold. In part because slides were mounted on the mold, the mold was too heavy, and two operators had to struggle with crow bars to open the mold and remove the part.
Maus designed a lighter mold that moved the slides to a device outside of the mold. It moves the slides and other devices in and out on an “external manipulating platform,” Wandres said. Now just one person is needed to run the machine. No more crow bars.
“He loves it,” Wandres said.