Kusatsu Factory, Japan

The Kusatsu Factory employs mixed flow cell lines for ultra-high-mix low-volume production. Because simply automating such cell lines in their entirety cannot improve productivity or quality in any cost-effective way, we took a more nuanced approach: we scientifically analyzed and evaluated the operating conditions of each process and how the tasks were being carried out in order to determine which tasks to automate or aggregate. Based on our conclusions, we built semi-automated mixed flow cell lines that enable optimal human-machine collaboration to more than double cell line productivity.

Effectively improving efficiency and quality in ultra-high-mix low-volume production requires that production site operations be examined from a bird’s eye view to pinpoint the most problematic processes so that targeted changes can be made. At the Kusatsu Factory, data collected from all machines in the printed circuit board (PCB) mounting line is aggregated to create big data, which is analyzed to visualize operation status. Improvement points were traditionally identified by veteran workers with a deep understanding of the products and the lines for producing them. The new visualization system boosted productivity by 30% with 1/6 the time spent on improvement activities. We are now working to reduce the defect rate down to ppb levels.

The Kusatsu Factory’s PCB mounting line employs i-BELT, a service for utilizing production site data. It collects data from the PLC as each PCB is sequentially processed by the solder printer, high-speed mounter, multi-function mounter, and reflow furnace, and demonstrates how it transitions over time using a visualization tool. The data is analyzed to investigate factors that negatively impact line utilization rates and pinpoint how the line can be balanced for effective improvement.

Although mixed flow cell lines for ultra-high-mix low-volume production are generally difficult to automate, we are actively automating those parts for which automation is effective. At the Kusatsu Factory, the following processes, for example, have been automated: LED lighting inspections, rotary switch inspections, pick & place of individual parts, and appearance inspections of assembled items. Intra-facility transport of completed products has also been automated using mobile robots.

Appearance inspections of products were traditionally conducted visually by veteran workers. Not only were these tests effort-consuming and inefficient; their results could be erratic depending on the skills and conditions of the inspectors. At the Kusatsu Factory, sensory inspections have been automated using a system that quantifies inspection points, inspection items, and defect criteria, and learns them in detail through image processing. The automated inspections are more precise and consistent than those conducted by veteran workers.