Cupholders, conveyors, and cooperation

Auburn Hills, MI-To passengers in Chrysler's 2001 RS minivan it's just a cup holder, but to a Michigan-based team of manufacturing engineers and executives, it's the result of intense cooperation, design flexibility, and applying the principles of Design for Manufacturing.

Made of ABS plastic, its spring-backed side shield allows it to expand or contract to accommodate 32 sizes of drink containers-everything from a child's juice box to a "Big Gulp." The assembly can even pivot to remain level when the seats are moved, preventing spills.

The cup holder is produced here by Fischer Automotive, a division of Germany's fischerwerke GmbH. Fischer envisioned a cost-effective, automated production system that could be easily expanded if demand increased. To help create it they turned to JR Automation Technologies (Holland, MI).

"It is increasingly common for companies to come to us nowadays with a component and say 'I need to put this together, at such and such a volume, what are your recommendations?' " says Brian Jones, vice president of JR Automation Technologies. As one such customer, Fischer asked for suggestions to improve manufacturability while maintaining functionality.

They also used simultaneous engineering to find the perfect fit between form and production. "We were designing the assembly line at the same time we were designing the part," notes Jeff Nelson, director of manufacturing for Fischer Automotive. "That gave us the chance to ensure that while we were designing the part we were also designing-in ease of manufacturing and assembly."

A key part of this process was Bosch Automation (Buchanan, MI). Fischer had determined that the cost-effective response to its cup holder production needs was an assembly system that was largely automated but which could also accommodate some manual operations. So they looked at the Bosch TS 4 conveyor, a compact, non-synchronous system which could run different sections of the system at different cycle times.

The TS 4 is an "over/under" system in which workpiece-laden pallets travel along an upper track to the various processing stations while empty pallets return to the system's starting point along a lower track directly beneath the upper one.

After just 30 weeks of planning, the system that emerged in the summer of 2000 looked like this: nine assembly stations with three station operators and two workers to unload finished parts-only five people in all-in a compact production line that occupies just 210 square feet. The assembly stations are fed by four injection molding presses, with four others in place and ready to be employed if demand increases. The cup holder required assembly of five parts (four plastic parts and a spring). There are two cup holders in each minivan, and typical production has been 2,500 to 3,000 cup holders per day.

This manufacturing setup was strengthened even more by Fischer's design flexibility and willingness to make minor design changes to benefit production.

For starters, there is the case of the spring that allows the cup holder to accommodate different container sizes. "The spring has two legs on it and originally both legs were designed coming off of the coil at a straight 90 degree angle," says Nelson. "It is inserted into the cup holder assembly by a Fanuc six-axis robot but we found that automatic insertion was not 100% successful. We conferred with JR Automation and did some experimenting, and we ended up changing the angularity of those legs slightly-we're talking about a very small change here, less than five degrees. We also made some minor adjustments to the design of the adjacent plastic parts and to the molds that produced them, providing a lead-in, essentially a chamfer, that the spring legs could hook under. These small changes made automatic insertion a very successful process."

Other changes included the torsion spring in the pivot assembly, and the addition of a crush rib or bump which helps to hold two parts together as they travel on the pallet.

The Bosch system, too, was modified to better fit the system's needs. Along with a slight change in the conveyor's height to improve the efficiency of manual operations, the system's pallets were equipped with molded plastic nests that fit the contour of the plastic parts they were transporting, says Mark Duykens, support specialist for Bosch Automation.

As effective as the Bosch system is, the success of the cup holder line rests not on the strengths of a single company but on the ability of three companies, aided by simultaneous engineering and Design for Manufacturing concepts, to meld their strengths together in pursuit of a common goal.

For more information about TS4 conveyor from Bosch Automation: Enter 535