Suncast Corp. built its business on injection molding of hose reels, storage products and garden sheds, but two years ago, the company in Batavia, Ill., got into blow molding — in a big way.
Suncast bought extrusion blow molding accumulator-head machines featuring a technology that Bonn, Germany-based Kautex Maschinenbau GmbH originally developed for blow molded gas tanks, using a split parison stretched out into two large sheets.
It's a new way to blow mold large flat panels. The traditional method — turning a parison shaped like a big round balloon and into a flat panel — is a major challenge.
Kautex's solution: Start with a flat parison. In that shape, the plastic does not freeze off while in contact with the mold and thin the outside edges.
“Suncast decided to step out of their comfort zone, with a supplier,” said Chuck Flammer, vice president of sales for North America at Kautex Machines Inc., based in North Branch, N.J. “We took a company that was an injection molder and turned them into a blow molder.”
The first Suncast part using the blow molding technology was a garden-deck box with a simulated woven pattern molded in. The company also blow molds components for sheds.
Suncast and Kautex announced the news in April at NPE2012. But Flammer gave more details and historical perspective on the so-called “flying knives” technology in a presentation Oct. 9 at the Society of Plastics Engineers' Blow Molding Conference in Pittsburgh.
Kautex Maschinenbau is, by far, the biggest maker of systems to blow mold automotive fuel tanks. Flammer said 85 percent of the plastic fuel tanks worldwide are blow molded on Kautex machinery.
That position was threatened in the early 2000s when thermoformed fuel tanks made inroads. Flammer said twin-sheet thermoforming had an advantage over blow molding by making it easier to put components inside the tank, rather than having to attach them from the outside. Stricter regulations limiting vapor emissions helped drive the change.
“So what we had to do was … take that idea of putting stuff inside the tank without losing the six-layer parison,” Flammer said. “We take it and we actually split it into two sheets of six-layer plastic.”
The patented “flying knives” process never took off in automotive fuel tanks, Flammer said. But Suncast has a good application in household and garden products.
A decade ago, Kautex engineers developed a way to spread the continuous round parison into two halves, allowing access to the inside of a fuel tank. Flammer played a video showing the process. The big parison hangs down, then two spreader pins stretch the parison into a long, flat shape. A mechanism also grips the parison.
Flammer got chuckles when he said: “In German we call this the Holy Scheisse moment — for us to use blow molding and basically have it act as a thermoformer.”
Knives cut the spreader pins out of the parison, which then goes into a mold.
Flammer said Suncast had outsourced its blow molding. On some sheds, it injection molded two halves and welded them together. But officials wanted to bring blow molding in-house.
“These [products] should be blow molded,” Flammer said, “They're large, large parts that have to have some structural rigidity. And doing it in blow molding, already having that double-wall structure will give you that.”
Spread-parison technology cuts cycle time 65 percent over regular extrusion blow molding, Flammer said. Kautex closely controls the parison, providing equal wall thickness across the part and minimizing warpage, he said.
Kautex and Suncast have declined to say how many Kautex machines Suncast purchased.
But industry sources have said the investment was for six to eight machines — a major order for the accumulator-head blow molding market, which had been depressed for years.