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As with many manufacturing theatres, there is a stream of additive processes that combine to create the finished product. The manufacture of printed circuits is no different. From the conception of the design and issuance of the procurement document, dozens of processes must take place before the PCB is shipped for assembly. Each of these processes takes time and the additive result of all these steps results in the manufacturing cycle, or lead time. Almost always, the customer just wants to know the lead time, or "When do I get my boards?"
However, in the manufacturing process steps leading to the final shipped product, there are individual cycle times within each process. From imaging all the way through final packaging, each process is allotted a predetermined amount of time to complete a given piece or full production order. In a perfect world, all individual process steps or cycle times will be completed early or on-time with the result being on-time delivery (OTD).
But, let's face it, many times Murphy makes an appearance and cycle times may increase. If this happens early in the manufacturing cycle, then the predetermined, gauged cycle time for subsequent processes is out the window. The time for those processes is now compressed or disregarded entirely and the order becomes ASAP. Did the time it took to effectively process that part miraculously compress as well? No, it did not. Now this order is competing with other orders in the same process step that were originally on-time, causing them to delay and WIP (work in process) to climb, thus resulting in the dreaded bottleneck! This is a term that sends chills through production managers and sales forces alike.
With that said, how do we combat this scenario? We streamline the process step by fine-tuning the attributes within that process. The result is reduced or optimized cycle time. This can result in the process step having "sprint capacity" to combat Mr. Murphy when he decides to make a visit. (However, in reality, once production planning finds out the process has reduced its cycle time…well you know what happens.)
Since I'm focused on quality assurance and electrical testing (ET), we will look at this scenario in the electrical test theatre.
Editor's Note: This article originally appeared in the October 2015 issue of The PCB Magazine.