Reduction of Work-in-process

This factor has become one of the most powerful cost factors in reduction of manufacturing cycle time as well as having a direct impact on the cost of quality.

A manufacturer of complex electro-optical devices manufactures a product which, when assembled, carries a value of approximately $50,000, and produces 50 assemblies per month. Ten to fifteen adhesive bonds are required in each of the subassemblies which go into a complete product, and a total of approximately 100. When using both RTV and epoxies for these bonds, each bond or seal required two to three days to set up before it is tested, and sequential assembly is necessary. The total cycle time of the product was four months.

The use of UV curable adhesives reduced the cycle time of a subassembly to 2 hours, and the total product cycle time to 4 days. The work-in-process product value (assuming a straight-line value added rate) of 4 months was:

This example was simplified in that one-half of the finished product value (price) was used as an assumed cost, and that the product cost rises steadily from zero to full cost over the product cycle. The significance of the example is the huge amount of capital which can be tied up in work-in-process.

In this same case of cycle time reduction, additional direct savings also were achieved. Many of the bonds made previously using two-part adhesives could not be reworked if they were faulty, resulting in scrapped subassemblies. On the other hand, a fault in a UV bond could be reworked, reducing scrap and increasing yield.

Additionally, the time to detect a fault had been 2-3 days, during which time other process-related faults might continue. Detection with UV cured bonds was immediate, further reducing quality related costs.

Excerpt from: Stowe, R.W., "Some Economic Factors of UV Curing;"
Copyright Fusion UV Systems, Inc.

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