Making a good work cell better

Cashmere Molding needed to improve an existing production cell to meet a customer’s demand for increased capacity and low price on a part for a powered facial cleaning device…and got what it wanted with some technology upgrades.

The Woodinville, Wash.-based injection molding company was molding the handle enclosure on client Clarisonic’s Pro-Handle device, including an overmolded elastomer grip and an indicator lens in the form of a light pipe that had to be inserted into the cavity before molding. When Cashmere started the project, it created two sets of molds, running substrates on a 150-ton Engel press, placing the parts in a box, and walking them to a second machine where a worker would manually insert them for overmolding. For the front part of the handle, two lights were inserted in its front, as well as three small brass pins that hold the brush in, a total of four hand-loaded inserts. A family mold, the tool also produced one handle’s back portion, which also had a light. “Production of the part wasn’t perfect – it was hampered by operator error in the hand loading of inserts – but it was good enough for a certain volume of production,” said Mike Gadwell, Cashmere’s director of engineering. “But as the Pro-Handle device caught on and volumes grew, the cost was high and the production started to seem slow.”

Knowing they had to do better, Cashmere worked with automation equipment supplier >SAS< Automation LLC to redesign the cell, investing in new tooling and custom end-of-arm-tooling (EOAT) automation to switch production from two presses and two two-cavity family molds – one of which required five hand-loaded inserts – to one two-shot injection molding machine running a four-cavity family tool that would have inserts placed robotically and produce finished parts.

>SAS< was charged with the goal of creating a customized EOAT that could insert two of the light pipes and work within a two-cavity transfer mold that requires the EOAT to pick two inserts at once. The mold itself had only 0.0015-inch clearance on either side to fit the inserts; Cashmere and >SAS< hit on the idea of including numerous locating features within the tool, with three in each cavity, to help locate the end effector within the cavity. >SAS< also supplied a shuttle table with a built-in sensor that tells the robot if the light piper are in a position to be picked up by the EOAT. If so, the robot, a Wittmann W723 three-axis servo unit, picks up two light pipes, drops them into the press, goes to the ‘A’ side, installs them in the side of the tool, then goes over to the end effector on the ‘B’ side of the tool to pick four parts. The result is two complete products and two substrates ready for overmolding. And as for the three brass pins, the redesigned cell handles those as a post-molding press-in insert.

How well has the cell worked? Cashmere has now carried over the concept for other parts, building three more two-shot tools that use the exact same system. “It was a win-win situation for Clarisonic; they’re saving money and getting very reliable production,” Gadwell said.