ATLANTA - The challenge was a significant one. Isuzu Motor Co. Ltd. had designed a one-piece instrument panel/dashboard for its new model Rodeo sport utility vehicle and wanted it made with only one injection gate - no warping, and complete in one shot, without finishing.
The car company had tested the design at Shigeru-Kogyo Industries in Ota-City, Japan. But there still were problems with the parts when the molds and tools had to be shipped to Heartland Automotive Inc., of Greencastle, Ind., the North American wing of Shigeru, in advance of the model launch.
Bob Gruener, process engineering specialist with Heart-land, said the firm molds about 18 different parts for Isuzu, Suburu, Nissan and Ford, but the Isuzu part was to be the company's first try at gas-assisted molding.
Gruener said the part and the process took about two years to accomplish-from the beginning of design to the final product.
``The part was designed by Isuzu and Kogyo-Kasei in Ota-City,'' he said. ``But they had been working on it, and the ones they tried were not right, and they were running out of time for the vehicle's introduction. The parts they had done to test were blistered, and had sink-mark problems.''
Gruener said when they first put the material in the Heartland machines equipped with Gain Technologies Inc.'s gas-assist system, Heartland, Gain and Isuzu engineers thought they were starting what might be as much as six months' testing.
``I think that [the Shigeru engineers in Japan] just did not have the same kind of control on the gas delay as we did,'' he said. ``We decided to shorten the delay time from five seconds to two seconds, but when it was punched in on the controller it was entered as 0.2 seconds, and within an hour and a half we had very good parts.''
He said the shorter the gas delay was, the better the quality of the parts in the 89-second total cycle time per part. The part has been in production for six months now.
According to Steve Van-Hoeck, marketing director of
Gain Technologies, based in Sterling Heights, Mich., the structural foam part was a perfect candidate for gas-assisted injection molding.
The enhanced rigidity, strength and molded-in finish achieved cost savings for the carmaker, required less clamping force, and reduced tool and cycle time.
It was so successful that it won the award for the Best Single Part in the Society of the Plastic Industry Inc.'s Structural Plastics Division's annual new-product design competition. The competition, held during the division's Structural Plastics '96 conference April 1-3 in Atlanta, highlighted the latest in structural plastic parts and systems.
The secret, according to VanHoeck, was designed-in fill channels along the top and bottom of the mold, which allowed complete fill with only one gate, and without hot runners.
Although judges in the competition could not be identified by name, one said he was impressed by the part because of the complexity of the design.
``To accomplish this with just one gate and sprue and no sink mark is very impressive,'' the judge, a mold maker, said.
Another judge said he was impressed by the fact that the piece came out of the mold finished, and with no warp.
``What you see is what you get with this part, and with the gas through the sprue from only one spot was very good,'' he said. ``We talked to Heartland and they showed us the earlier pieces with warping.''
``Before the molds got here, though, we had looked at the design and had sort of taught ourselves about gas-assist with the help of Shigeru and Gain,'' Gruener said. ``It is still the only part we are doing with gas-assist, though. We still have our difficult days, but we are very happy with the part.''