However, producing powder metal parts has its own set of unique challenges. For starters, powdered metal begins as (of course) powder. This powder, with the consistency of confectioners sugar, is squeezed into shape by a compacting press and is passed through a sintering furnace to harden. The key is transporting the part from the press and through the furnace as quickly as possible. Before the part is hardened in the furnace, it is very fragile and susceptible to damage. Such was the case at GKN's Salem, Indiana, plant.
At the Salem plant, GKN manufactures a series of five different parts that go into the transmission clutch plates of 3/4 ton and 1 ton pickups made by the big three motor companies. Prior to using Shuttleworth equipment, pallets of parts were moved manually through a manufacturing cell that included a compacting press, scale, positioning station, robotic drill, furnace and in-process bin..
Doug Dixon, Manufacturing Engineering Manager for GKN lamented over the problems with this old system. "Moving these parts through by hand was very costly, both in terms of labor and product quality," he said. "Each part weighs about three to four pounds. This doesn't sound like much, but by the end of a shift operators were fatigued and would often bump and chip parts and pallets. We knew there had to be a better way." GKN had previously installed one Shuttleworth conveyor system within the Salem plant. "It was natural to discuss this second project with them," said Dixon.
Kim Hildebrand, Regional Sales Manager for Shuttleworth, oversaw the project. "Shuttleworth had installed one system in GKN - a smaller, low-pressure accumulating system that took parts from a heat treating machine and automatically loaded and unloaded the draw furnace. Parts at the end of the system were manually removed. With the second project, the goal was to totally automate the line."
Shuttleworth's exclusive Slip-Torque, roller-based conveyor system was the perfect solution for the job. Shuttleworth's Slip-Torque conveyor uses individually powered roller shafts covered with segmented, loose-fit rollers. Unlike belt conveyors, the rollers beneath the product slip when products accumulate, reducing product damage in handling brittle powder metal parts and ceramic pallets. This is of the utmost importance.
The first step in the system moves product from the compacting press to a scale where the parts are weighed for accuracy. Shuttleworth engineers designed a unique device to raise from beneath the conveyor surface that lifts and weighs the product. Parts that pass the weight test return to the conveyor surface and are transported down line to the positioning station for the robotic pick up. Parts not passing the weight test are pushed off line by another Shuttleworth device.
Once positioned, parts are selected and drilled by the Motoman robot and placed on the pallet. GKN and Shuttleworth engineers fully integrated the conveyor system with the Motoman robot to accomplish the task without operator intervention.
The full ceramic pallets move, three-wide, to the load end of the furnace. After the furnace, pallets progress on the Shuttleworth conveyor to a second Motoman robot positioning station. The second robot picks up the parts from the pallets and places them in a bin. The complete cell runs approximately 200 feet. The gentle nature of the low-pressure accumulating conveyor allows parts and pallets to remain free of damage throughout the entire process. The empty pallets recirculate on the Shuttleworth closed circuit system.
"Loading and unloading the furnace was a challenge faced on this project," said Hildebrand. "The conveyors at the loading and unloading ends of the furnace approach at 90 degree angles. A traditional push mechanism would wear the rollers due to the abrasive characteristics of the ceramic pallets."
Shuttleworth engineers designed a friction-free, lift and transfer mechanism that, projects on demand from beneath and between the rollers to prevent this from being a problem. The rollers on this mechanism run parallel to the furnace conveyor and allow for a smooth and easy transfer of the pallets.
There are several other unique features of the Shuttleworth system. First, like the furnace, the system allows for pallet accumulation three lanes wide on a single conveyor - a sizeable cost savings over using three separate conveyors. Next, the back end of the conveyor system allows for the accumulation of several hundred pallets, to equal the entire load of the furnace. Not only does this reduce wear and damage to pallets in comparison to manually loading and unloading the cell, but it provides a reliable "safety net" for products leaving the furnace in the event of a backlog at the second robot. Finally, the entire conveyor system is modular. Each module features castor bases and quick electrical disconnects for easy access to and maintenance of the furnace and press.
"The Shuttleworth conveyor is the critical component of a completely automated system for building our complex part," said Dixon. "The fact that we can safely move these parts from the press through all of the various stages without an operator is a big deal."
How big of a deal? Although the system has been in place just since the fall of 2001, GKN has benefited from significant quality improvements and reduced labor and inventory costs. "Not only are we seeing fewer damaged parts, but by automating the system, it requires six fewer operators to run the cell. In addition, the Shuttleworth conveyor helps us speed up work in progress and reduces our inventory," Dixon said.
"Overall, the Shuttleworth conveyor allows us to produce a higher quality product for less cost. Our customers like that... we like that. Everybody is happy."
And what about those six operators who used to move everything by hand? "I've talked to them," said Dixon. "They may be the happiest of everybody. They don't miss that part of the job one bit."