Early adopters in LSR molding share pros, cons

Placentia, Calif. — George Kipe has been in the liquid silicone rubber game since its infancy.

He attended seminars put on by General Electric Co. in the 1970s when the conglomerate's silicone unit was introducing its first LSRs to the industry. And Kipe jumped on board quickly, learning all he could about the new technology. He owned a mold shop as well a firm dedicated to the liquid injection molding of LSRs.

After long-ago divesting the parts making business to his then-partner, he concentrated on Kipe Molds Inc., the Placentia-based maker of molds, cold-runner technology and other accessory tooling run by him and his son, Brint. And after all these years, both Kipes — George serves as president and Brint as general manager — have seen lots of people and companies succeed and fail in the world of LSR.

One thing they've learned is that the plastics people are better at some aspects of the LIM process and the rubber people are better at others. But often, it's someone with good mechanical abilities who has no background ties to either plastics or rubber, who can best figure out the process and make good parts consistently.

George Kipe said he's found the plastics people understand the equipment and the machinery and know how to manipulate it. But typically they hold to the strategy that a mold's a mold, whether it makes a plastic part or a liquid silicone part. The mold, however, is only half of the equation to making good parts, he said. The other half has to do with the process, the silicone, how it's mixed in the machine, how it's dispensed, and the shot control and pressures.

"You can have a really nicely made mold that functions well, and it will produce bad parts because the other things aren't working correctly," George Kipe said.

Brint Kipe said he's found that those working with plastics for a long time sometimes struggle with LSR because the material has the properties of an elastomer.

"They always end up commenting that silicone is the exact opposite of what they've learned for the plastic side of things," he said.

As for those coming from the world of rubber, he said, they tend to be more aware of the machinery, the pressure and other parts of the process, but at the same time may not always agree on what the definition of a "good part" is.

"If it has a lot of flash all over the thing, they trim it off, and that's a good part," he said.

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Brint Kipe said there's no denying there are people with both rubber and plastics backgrounds who are successful with LSR, but there's also a school of thought where an individual with a hybrid-type background might be better than either.

"It seems like a good mechanic with some electronic experience has the least amount of trouble with it," he said.

A lot of that, he believes, is because of the intricacy of the many differing components that go into the manufacturing of an LSR part. Many operations will have a maintenance person, a setup person and a processing person. "Each will just work on their own area, but really it takes all three areas to be in good working order to be successful," Brint Kipe said.

A major key is the maintenance of the whole system, he said, for instance, the pump may be causing a problem. "If you have a processing guy making a bad part, and all he may be doing is tweaking the process," he said. But in reality if the pump is worn out, not clean or set improperly, there's going to be a problem. "Without that total ​ package knowledge, that processing guy is going to have a real hard time figuring it out."

So that's why he says sometimes it's best to have a person working with an LSR system that doesn't have a tie to either rubber or plastics. "A guy with no knowledge at all may take a step back and go all the way back to the pump and find the pump isn't working correctly, or the screw and barrel weren't cleaned up," Brint Kipe said. "And he takes it apart and figures it out without any pre-existing idea of what's causing the problem. … It seems like if you get a good, smart person with mechanical ability that they're successful almost every time."

In the early days of LSR, many companies dabbled a bit in the field, maybe purchasing a LIM machine or two, either because a customer needed a specific part or they wanted to diversify a bit. That tactic may have worked with some, but George Kipe sees a different landscape these days.

He said that companies today — both with rubber and plastic backgrounds — are more likely to form either a division or separate company to focus solely on LSR operations.

"They put together a group of people who are really good at it and develop it from that standpoint," he said. "We've seen some pretty successful [firms] like that."

George Kipe said having a separate LSR business unit is especially important when involved in a new project. Sometimes the customers think it can be wrapped up in a couple days, but when dealing with LSR, that's not always the case. Some end users such as medical companies may understand this, but most customers don't.

Having a team to look at the part from the beginning can help determine whether to expect problems and keep the customers informed.

"In my world here, it's a stressful business because you're always trying to satisfy a customer's wants and needs," George Kipe said. "And at the same time, you're stuck with the reality that some jobs go well and others have problems. And you're trying to diagnose exactly where the problem is coming from and how to solve it."