Rosemont, Ill. — German rotational mold maker Maus GmbH made a mold using steel and machined aluminum sections to rotomold a portable toilet. Company officials showed the hybrid design at the Rotoplas trade show.
Molds got a lot of attention in presentations during Rotoplas, held Sept. 26-28 in Rosemont. The Association of Rotational Molders sponsors the event.
Regardless of the mold technology, Maus designs every rotational mold with computer-aided design, said Oliver Wandres, managing director of Maus in Karlsruhe, Germany. That includes every part of the mold, down to bolts, so customers can be sure they get the exact mold they want, he said.
Maus last year invested $1.4 million for a five-axis CNC milling machine, which Wandres said is very robust for turning out the milled molds quickly. Maus also makes steel molds, cast aluminum molds and fabricated molds, picking the best process for the technical demands and economics of a rotomolded part, he said.
He gave a case study for the portable toilet. The customer had used older steel molds, and the top and bottom of the toilet have several through holes and other components.
"When it came out of the cooling stage, [operators] really had to use a lot of force to slam out the pins for the through holes," Wandres said.
Maus made a steel mold for the side sections, but decided to make CNC machined aluminum molds for the large roof and the bottom floor, complete with pneumatic cylinders for easy opening and closing of the clamps. In traditional rotomolding, operators unbolt the mold on every shot to remove parts and load resin.
Wandres had a video showing the clamps opening and closing quickly.
"We need to improve the work environment," he said, noting the difficulty of finding people who want factory jobs involving hard physical labor.
Pneumatic clamps offer another benefit. They are retracted when the part is in the cooling station, not by operators in the part-removal stage.
"It's always a repeatable production," Wandres said. "Demolding is a piece of cake, where before the operators were swearing all the time."
In the United States, Maus partners with Norstar Aluminum Molds Inc., based in Cedarburg, Wis.
Another Rotoplas speaker, consultant Martin Spencer, said the key to designing a good rotomolded part is collaboration between all parties, including the customer, designer, mold maker, molder and resin supplier.
"All this team has got to work together. They have to have an open mind and see it through to success," he said.
Spencer, who is managing director of UniqueRoto in Nottingham, England, gave some case studies to prove his point. He also is chairman of the Affiliation of Rotational Moulding Associates, which links rotomolding trade associations from around the world.
A Portuguese molder was tasked with making a self-propelled, remote-controlled floating buoy that ocean rescue teams can operate from a boat. The resulting product is the U-Safe from Noras Performance.
"It can be used in situations where the boat can't get close, where it's wavy or rocky or there's big water," Spencer said.
The company made several prototypes. The part needed to have soft areas, so the U-Safe would not hurt the person being rescued, and rigid areas to house the motors. Designers realized they needed new technology, so they went to Persico SpA, the Italian maker of rotational molds and machinery.
Persico designed an electrically heated mold. Spencer said Persico worked with all parties — even the ocean rescue people who dreamed up the idea.