How to create nothing – faster

A plastic injection molding application story from Exlar

exlar-tritex-11-actuartorWhether for vacuum cleaners, hearing aids, or blood filters, engineers who design the tool systems for injection molded plastic parts face challenges familiar to everyone: “How fast; how accurate; how long; and (like always) how much?”

Challenge:
In many cases, the right answer to each of these questions has been made possible by re-evaluating the role that hydraulics have traditionally played in that arena. For generations, hydraulic cylinders were the motion control devices of choice for moldmakers. But today, when it comes to creating the precise,rapid motions that typically happen in these molds, electro-mechanical actuators with integrated motors (like the Exlar GSX Series) are getting more attention. According to Jeff Nichols,President of ASIC Corporation, a systems integrator headquartered in West Chester, OH, “In many respects, moldmaking is about creating voids. It’s easy to put resin where you want it — the trick is making sure nothing goes where something else needs to be later.”

Application:
It’s a boy-girl thing. Molds are generally male/female assemblies where the male (or core) forms the finished part’s concave surface. It creates the all-important “nothing”. On a laptop shell, that void houses the electronics;on a plastic plate the voids create separate places for baked beans and potato salad. Cycle time is where money gets made. Volumetrics, gate design, temperature controls … mold makers use a host of tools to fill a mold quickly. But after that’s done, the mold still has to be cycled. How fast the core can be moved in and out impacts production. Traditional hydraulic cylinders are fast. But ASIC reports that in some applications, a GSX actuator can enhance cycle rates by letting related operations get started sooner. This is possible because this kind of actuator constantly feeds the core’s actual position and motion status back to the controller. Longer tool life is an added benefit. “Every time we can replace a hydraulic cylinder with an Exlar electromechanical actuator, we can virtually guarantee a longer tool life.” Nichols continued, “That actuator lets us get the core inserted faster without just slamming the mold together violently. Less stress means longer life.” Retasking the same actuator on different projects is easy. Especially in retrofit situations, ASIC always addresses reuse in their cost analysis. According to Nichols there are caseswhere an actuator spec’d for one mold has more power than needed because it could be reused on another assembly that did require that additional power. “These actuators are really simple to retask. You just plug a laptop into the drive, feed it a new motion profile, and it’s ready to go.”said Nichols. So, how difficult is it to retrofit hydraulic cylinders with electromechanical actuators? The Exlar actuators that ASIC uses are truly “plug ‘n play”. A hydraulic cylinder’s two hoses are replaced with a pair of electrical connections. The mounting flanges are all industry standard. And because the GSX has an internal motor, both have the same form factor. Thus, for comparable stroke lengths, the GSX units fit in the same space.

Benefit:
Cleaner, Quieter and Less Expensive to Run

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Tri-Phase Automation is a distributor of Exlar in Wisconsin.
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