Flexible cell for low-volume jobs

When Manchester, Conn.-based custom molder ABA-PGT found itself losing low volume insert molding work because of manual labour costs, the company decided to automate. The company, which specializes in the manufacture of plastic gears and critical-to-function precision motion transfer components, developed a “Flex Cell” automation cell concept that was flexible enough to allow for swift changeovers.

Developed by director of R&D Tim Vale, and proprietary to ABA-PGT, the “Flex Cell” concept includes a molding machine, robot, an automation system for putting inserts into the process, and a similar system to handle finished products. Although the system still requires an operator to place the inserts on the pallets, the job only requires 15 to 30 minutes every two hours, significantly reducing the labour content.

ABA-PGT supplied the “Flex Cell” concept to Wittmann, which had already supplied robotic solutions for the company’s high volume applications, along with all required design parameters for the various parts.

“Coming up with the parameters was a challenge because you were making an educated guess on what type of parts you might see in the future, based on what was quoted in the past,” said Vale. “Designing an automation cell around a clearly defined product is not always that easy, but it’s certainly a degree or two easier than trying to design an automation cell around a bunch of parts that don’t exist yet.”

The parts could be big or small, and the inserts could be screw-machined shafts, stamped metal parts or some other intricate machine shape. Additionally, product changeovers would be required every two or three weeks but could be of shorter or longer intervals, and the automation had to be designed for a 110-ton machine with a minimal capital investment.

Working with ABA-PGT’s existing conveyor supplier TEC Engineering, Wittmann supplied a W631 three-axis linear servo robot equipped with a pneumatic wrist flip (c-axis) and a quick release system for the end of arm tools to allow for product changeovers in less than five minutes.

“The Wittmann-designed and -built EOATs were the key to the success of the cell,” noted Vale. “We had to make a lot happen in a very limited amount of space with these EOATs. The constraints were not just between the mold plates but also on the conveyor side of the system where floor space is at a premium.”

The system was delivered pre-loaded with the first EOAT for a two-cavity gear mold with a screw-machined shaft insert. The “Flex Cell” used an existing mold that had previously required hand loading of inserts and hand packing of trays, and resulted in a cost savings of $21,900 after 100,000 pieces.

A typical EOAT for the system costs anywhere from $15,000 to $25,000, depending on the complexity and number of mold cavities, and the total cost of the eight to 10 pallets for the inserts is about $5,000. In other words, the payback for the customers is very fast.

ABA-PGT now simply adds about $2 more per hour to the machine rate to cover the added cost of the automation, using the “Flex Cell” to get jobs it couldn’t get because of manual labour costs. Currently, there are five jobs sharing time on the cell, resulting in about 80 per cent utilization.

Wittmann Canada Inc. (Richmond Hill, Ont.);

www.wittmann-canada.com; 888-466-8266