Use of Lean Manufacturing Principles Enhances Quality and Productivity


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Regional EMS providers typically provide greater flexibility and responsiveness to their box build customers via use of work-cell-based batch assembly processes. Production volumes are fairly low, so the creation of dedicated continuous flow paced assembly lines is rare. However, we often see larger footprints and more complex projects with higher volumes.

Our cable, harness and PCBA manufacturing capabilities attract companies with products requiring complex subassemblies. As a result, it utilizes both work-cell-based and continuous-flow-line assembly in its box build assembly area.

One recent project example illustrates why this flexibility is important. The customer develops sports therapy devices used by trainers and professional sports teams. They had a next-generation product that increased functionality and, as a result, became mechanically much more complex. They needed a contract manufacturer capable of assisting them with development of mechanical manufacturing process instructions in addition to manufacturing the product. SAI helped develop the manufacturing process instructions as part of its new product introduction (NPI) services. The customer’s documentation for wire and cable assemblies, electronic assemblies, mechanical assemblies and cosmetics requirements is transmitted to the Aegis system and used to create visual work instructions that are utilized by the production team.

This project included cables, harnesses, PCBAs, electro-mechanical, fluidic, air and water subassemblies as well as chassis, sheet metal, plastics and hardware components. Routing the tubing in a limited chassis space was a challenge. Our team used the same process templates used in developing efficient wire and harness routing to route the fluidic, air and water lines. Trial builds were performed to ensure correct air pressure and water flow, and once nailed down, a tubing cut list was developed to make sure that all tubing was cut to appropriate lengths for the preferred routing. The customer validated the process. While computer modeling 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 operators encounter during the assembly process. Having a combination of computer modelling and hands-on trial builds meant nothing was missed and that the order of operations 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 electronic subassemblies consisting of multiple PCBAs, an onboard computer and associated harnesses; the fluidics; heating elements, cooling 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 electronically filed for future use.

To read the full version of the article, which appeared in the July 2018 issue of SMT007 Magazine, click here.

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