'Piggy-back' robot handles two-color parts.

Simply pulling parts off the press barely begins to tap the capabilities of today's injection molding robots. Often the really big savings come from automating labor-intensive secondary operations. That's what happened at Calsonic North America, which recently adopted a multi-task robotic system for its two-component molding operation in Irvine, Calif.

Calsonic's robotic system, which comes from the Conair Group, Pittsburgh, revolves around a Sepro servo robot with a sprue picker mounted on its main beam. This hybrid robot simultaneously handles the sprue-removal chores and takes away the finished parts. The system also includes a variety of custom automation equipment for parts collection and secondary operations.

Calsonic, which makes automotive air conditioners, recently began two-component molding to produce control buttons for the units. The two-shot process typically produces white polycarbonate lettering over-molded with black ABS. Calsonic molds the parts in a two-barrel 120-ton Nissei press with a rotating platen. Four- and six-cavity family tools produce sets of different buttons.

In Japan, where the company molds similar two-color buttons, Calsonic needs two operators to handle parts-removal, degating, and other secondary operations. In Irvine, the labor requirements are next to nil: "We don't have any operator assigned to that line," says Alan McManus, a senior manufacturing engineer for Calsonic.

Automation hurdles

According to McManus, the buttons presented several tough automation challenges. Chief among them was automating a "debridging" operation that removes a sub-runner from the back of each button. In Japan, this step is a costly bench operation.

When Calsonic first planned its automation cell for Irvine, McManus initially considered milling off the bridge. But he soon ruled out this option for reasons of cost and complexity. Instead, Conair built a system that uses four air-driven blades to shave off the bridge without the need for expensive milling equipment.

Calsonic needed other custom automation to handle complex parts orientation and collection tasks. For example, the company uses a turntable station to orient the parts without the aid of the robot's end-of-arm tooling. Conair also had to develop a custom programming interface to handle the sprue picker and the robot.

One busy robot

In the two-color molding cell, the robot has lots to do in a 30-sec cycle.

Step 1: As the mold opens, the hybrid robot swings into action. The sprue picker grabs the white sprue and drops it into a granulator as the moving platen rotates into position for the next shot.

At the same time, the robot also seizes the finished parts with suction cups and grabs the black runner with a gripper. Both parts and runner go into a degating nest, where the end-of-arm-tooling (EOAT) holds onto the parts and runner during degating.

Step 2: The EOAT moves parts from the degating station to a debridging nest. While the robot takes the black runner to a granulator, the debridging nest shuttles parts to a clamp where they are scraped one by one.

Step 3: The nest indexes again to bring the parts within reach of the robot, which picks up all the parts and places them in a "populating nest." This nest rotates to orient the individual parts for picking and placement in the customized tray that holds several sets of parts for later assembly. Here the EOAT uses a single suction cup to pick the parts one by one from the populating nest and place them into trays on a conveyor. Depending on the number of cavities, the trays hold 12 or 24 shots - for a total of 72 or 96 parts per tray, respectively.

Step 4: The conveyer removes the full tray and indexes an empty one into position.