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The number of fasteners used in an oscilloscope top box was more than cut in half through a redesign project at LeCroy Corp. in Chestnut Ridge, NY. In total, two-thirds of all parts were eliminated from the 194-part sheet-metal chassis that was riveted together.
The design team was comprised of mechanical engineers, manufacturing engineers and a lead project engineer, who met on a weekly basis. “We were able to have the key design people be part of the regular brainstorming sessions,” says Toni Inserra, senior manufacturing engineer. “That provided invaluable real-time continuity between the mechanical engineering department and the redesign team.”
Members of the team included a senior mechanical engineer who made sure the top box and assembly satisfied all structural and customer requirements. The goals of the redesign project were to simplify manufacturing, reduce cost and make the box easier to service in the field.
A software package called DFMA (Design for Manufacturing and Assembly) was used to evaluate various iterations for ease of assembly and manufacturing efficiency at early stages of product development.
Difficult to Assemble
“The original design for the oscilloscope top box was durable, but it had an extremely low ease-of-assembly rating,” Inserra says. “There was plenty of room for improvement.” From his service background, he was able to point out areas of the product that were difficult to reach and disassemble. More often than not, those areas presented assembly difficulties, as well. “In its initial design, the equipment included sub-assemblies that could not be removed without first taking out several others,” Inserra says, “and the inside of the box was cramped for manual operations.”
One of the big developments was the replacement of rivets with interconnecting slots and “finger” tabs. This was possible due to a decision to split the top box chassis into three units to minimize interference during assembly and disassembly operations.
Another big breakthrough was use of self-clinching fasteners from PennEngineering to mount the CPU board to the chassis. “Using the PEM inserts helped us to reduce fastener count by over 50 percent in the top box,” Inserra says. The total number of fasteners in the box was reduced from 103 to 42.
Ease of assembly improved sevenfold in the new design based on a metric generated from the DFMA software. Wiring was routed in a more efficient manner and all components are easily accessible for installation or service. The new sheet-metal chassis consists of an upper and lower box and a removable front panel, eliminating awkward and constrained assembly tasks. “The new chassis makes troubleshooting in the field far simpler,” Inserra says.
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Stamped "fingers" and slots replace fasteners.
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