Page 19 - MetalForming November 2009

features to the dies to achieve through- put and quality specifications. After the robot drops the blanks in the die station, actuators built into the die fine-tune blank location to ensure dimensional repeatability. We also provided a regis- tration fixture for the pick-and-place blank destacker. After the destacker stages a blank for the robot, the fixture crowds the blank into a corner to register
the datum point and locate the edges, to ensure the robot grabs the part exactly where it’s supposed to.
“Originally, we had thought about designing a simpler setup where the robot would do it all,” adds Webb— “destacking and press load/unload. Cycle time was an unacceptable 10 sec. So, we added pick-and-place units to destack and prestage the blanks, and takeaway
chutes at the end of each press line.” To make its presses automation- friendly, HON added new controls and redundant PLCs, one dedicated to com- municating with the robot and one to operate the press. It also added an HMI panel near the robot control panel to
allow cell setup from one location.
In addition to the improvement in operator safety and ergonomics upgrade, Coffman also notes an improvement in part quality since the move to robotics. “We’ve reduced our scrap rate by 95 percent,” Coffman says, “because we’ve eliminated misfeeds or otherwise incor- rect blank placement in the dies. This also has resulted in more reliable just- in-time delivery of parts to our assem- bly lines. Now, rather than potentially being a bottleneck to the assembly process, our press lines stay six parts
ahead of the assembly lines.”
All told, this editor appreciates hearing
about a process-improvement oppor- tunity that starts out focused on safety and ergonomics and winds up improv- ing quality and productivity too. MF
One Powerful Lean Tool: 3P
3P production-preparation processes such as the press-automation project undertaken at The HON Co. plant in Cedartown, GA, focus on eliminating waste through product and process design. Lean consultants suggest that the best way to tackle such projects is to involve a diverse group of people in a series of brainstorming sessions to identify and discuss alternative ways to meet a specific goal, such as improving ergonomics or increasing throughput. The team should comprise designers, engineers from multiple disciplines, operators and operations managers. Typically, these projects, which start with a clean sheet of paper, result in bigger paybacks than do the incremental improvements resulting from kaizen events. The focus is on project management and waste reduction, or elimination.
Once the 3P team has selected its preferred solution to the task at hand, it then works to demonstrate the flow of raw material to finished product, using diagrams and sketches. Then, as did the press-automation team at HON, it constructs a prototype to simulate the process to verify that it will operate as designed and produce the expected results. Finally, the team develops an implementation plan, complete with resource requirements and assignment of responsibilities.
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