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78 SMT007 MAGAZINE I JULY 2018 sure and water flow, and once nailed down, a tubing cut list was developed to make sure that all tubing was cut to appropri- ate lengths for the preferred rout- ing. The customer validated the process. While computer model- ing of this type of routing seems efficient, a routing that looks great on the computer screen can turn out to be an inefficient order of operations on the production line based on the obstacles that oper- ators encounter during the assem- bly process. Having a combination of computer modelling and hands- on trial builds meant nothing was missed and that the order of opera- tions was fully optimized. Initially, the project was planned as a batch build process in several dedicated work cells, however, the volumes quickly outgrew that model. Our team utilized Lean manufacturing principles to redesign production flow from a cellular manufacturing process to a single conveyorized production line that integrated subassemblies with final assembly. Lean manufacturing principles were a core part of this redesign effort. In the original process, cables, harnesses, PCBAs and subassemblies were assembled separately and pulled from stock. Final units were assembled sequentially by a pair of production operators. The redesigned line has seven "feeder" work cells where production operators build elec- tronic subassemblies consisting of multiple PCBAs, an onboard computer and associated harnesses; the fluidics; heating elements, cool- ing elements and additional subassemblies. In total, there are over 800 line items, seven custom PCBAs and 37 custom cables. At each station, operators add their subassembly to the base unit as it moves down the conveyor line. Programming, serialization, functional test, burn-in and crating are located at the end of the line. As part of this process, a 17-page device history record (DHR) is created and electroni- cally filed for future use. The continuous flow line minimizes materi- als and product transport by stocking materi- als and subassemblies near point-of-use. Oper- Figure 1: The units involve complex electromechanical assemblies. Figure 2: Operators add subassemblies as the units progress down a conveyorized line.

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