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74 SMT007 MAGAZINE I MAY 2022 by Zac Elliott SIEMENS Throughout this series of articles, we have looked at the benefits of implementing a digital thread for electronics manufacturing. In this edition, I would like to close the loop (pun very much intended) on the lean digital thread and dis- cuss closed-loop manufacturing. What is Closed-Loop Manufacturing? In closed-loop manufacturing (CLM) the systems and business processes used to design, plan, man- ufacture, and use a product are connected, thus enabling continuous improvement and self-organi- zation of production processes. Each step along the value chain constantly feeds data back to the pre- ceding stages so that simulations can be refined, and decisions improved. At the same time, data is automatically pushed forward to the downstream processes, to ensure production plans and manu- facturing processes are up to date. This creates a continuous cycle to improve quality, efficiency, and profitability. The Role of the Digital Twin Closed-loop manufacturing depends on the abil- ity to share information between different business processes using a digital twin. A digital twin is sim- ply a virtual version of a product that can be used to simulate and test how a device will be built and used in the real world. There are several digital twins for a given product: to be placed into an X-ray machine in order to confirm the solder connection of the compo- nent to the PCB. Final inspection also includes the "fit up" with a header that will plug into the receptable on the board to make sure that the connector will function properly and has not been damaged in the rework process. While the rework of high density SMT con- nectors with ground planes is challenging, the right process with the right controls in place and completed with properly trained personal will provide for a high yield. SMT007 Bob Wettermann is the prin- cipal of BEST Inc., a contract rework and repair facility in Chicago. For more informa- tion, contact To read past columns or con- tact Wettermann, click here. • Digital twin of the design: The digital twin of the design is all the data that can be used to visualize and simulate the final end-product. This includes the mechanical and electrical designs, schematics, etc. • Digital twin of the process: The digital twin of the process defines the manufacturing sequence and steps needed to build the product. This includes the machine technol- ogy, recipes, work instructions, and other information needed to simulate and improve the manufacturing flow. • Digital twin of production: The digital twin of production includes all the data aggregated during the manufacturing process of a device, including all records of test results, traceability, parametric readings from assembly equipment and the environment, and any exceptions encountered during manufacturing of the device. Having multiple versions of the digital twin allows specialized software to be used during the various stages of the manufacturing flow. Software that is optimized to design a PCB is not the same software that is optimized to collect the test results from an ICT machine that tests the PCB. Each type of soft- ware has completely different inputs and outputs. But they don't work in isolation. The design informa- tion is needed to develop the ICT test protocol and the aggregated test results can be used to improve the product design. To read the entire column, click here. COLUMN EXCERPT: Lean Digital Thread Closing the Loop on Manufacturing

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