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Tight deadline
By Erik Olson, Flextronics Design -- Design News, September 9, 2002
Company: Flextronics Design is a business unit of Flextronics with design centers positioned in strategic markets worldwide. Expertise is available in all facets of engineering including industrial design, mechanical design, embedded system design including hardware and software, IC design including FPGA and SOC ASIC design, RF design, PCB layout, design validation testing, tooling, prototyping, test development, compliance and regulatory test engineering. For more information about Flextronics Design visit www.flextronics.com/design.
Project Location: The Americas
Project Description: A control panel subassembly for a consumer white good. The control panel included numerous injection-molded plastic components and two printed circuit board assemblies (PCBA). With 12 weeks remaining prior to the production ramp, the client requested a major redesign of the assembly. The redesign changed the manufacturing process from snap fit construction to parts that would be retained by heat staking. This changed the architecture of the product from "floating" buttons to ones that were rigidly attached.
Engineering Challenges: The entire assembly structure needed to be redefined to reflect the new design direction. This included designing new attachment and alignment features in all of the components. The customer already had a considerable investment in production injection molds, so engineers worked diligently to ensure that all of the new features could be incorporated in the existing tooling. The mold for the main bezel of the assembly had a different draw direction than the component molds, complicating the design of the heat-staking features. The alignment features for the buttons, lights pipes, and PCBA housing to the main bezel were also challenging, due to the different draw angles. The holes in the bezel for the different components were machined on a computer numeric controlled (CNC) machine to improve cosmetic issues. Since the new design required that the assembly components be attached to the bezel, the CNC process would need to be held to very tight tolerances.
Project Solution: To guarantee that the schedule would be met, several engineering disciplines from different locations within Flextronics had to efficiently collaborate. A project manager coordinated all of the necessary activities. This position was critical because each design change needed to be quickly communicated to the different teams to check for feasibility. The feedback to the design team allowed them to make intelligent decisions that minimized the impact of their changes. All plastic components and the PCBA layouts needed alterations. The extent of the changes required at least six weeks of mold modification lead-time. This only left five weeks for the design team and one week for troubleshooting the new design. Manufacturing engineers presented different options on how to heat-stake the components to the bezel. They also needed to design and build assembly fixtures for the production line. Mechanical design teams from one location worked closely with the electrical engineers from another location to communicate necessary PCBA changes. Tooling engineers proposed different design options based on the existing mold designs. As the changes to the part models were being implemented, tooling engineers concurrently updated the mold designs to provide quick transfer to the mold makers. Product verification engineers from Flextronics Design and the customer were also included on the design team. They provided feedback on alignment schemes and developed quality fixtures for first article reports and on-going process inspection based on GD&T principles.
Project Results: Concurrent engineering and excellent communications were the prime contributors to the success of the project. Creative use of draft angles and alignment principles allowed the design engineers to solve the problems created by the different draw directions. All of the new features were included without adding any extra mold actions and only one of the molds could not be salvaged. The tooling engineers made this achievement possible by the innovative use of a wire electrical discharge machine. This allowed sections of the core and cavity to be replaced to add new features without compromising the integrity of the mold. All of the molds were delivered on time allowing a week for de-bugging of the assembly. The manufacturing team designed and built custom heat-staking machines that allowed for efficient assembly. With the support of the product verification team the design engineers were able to implement features for precision alignment to the CNC machining fixture. This enabled the assembly to meet quality goals. Quick communications between the teams, facilitated by the project manager, allowed the various sub-projects to get started while design changes were still being implemented. In the end, engineers met the improbable production ramp.
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