4. INJECTION MOLDED PART DESIGNS

A. Problem/Issue

Over the years we have designed many components and assemblies to be injection molded. The method is often used because of low cost in moderate volumes. Many times the piece part costs allow a mold to be made in volumes as low as a few thousand per year. The mold material can be tailored to match the intended life of a part. One example is a laser measurement product for a major manufacturer of circuit board assembly machinery. They needed a complex component that: 1) had smooth surfaces 2) did not reflect light 3) was strong enough to withstand 30 G's force 4) could withstand ten million cycles 5) did not creep substantially 6) was an electrical insulator 7) cost less than a dollar in volumes of 6,000/yr. with limited mold cost and lead times. Their "shopping list" was significant.

B. Analysis

We contacted a compounder and researched similar applications. We researched literature, accepted industry pracitces, and trade journals. We were looking for an ideal material coupled with a mold that would meet their cost objectives. We also did a search of local and regional mold makers that quoted reasonable lead times.

C. Solution/Results

We found a 30% glass filled black Ultem material to fit the need. A mold was constructed using the shrinkage of the material to enable a precise part to be molded. The set-up and processing had to be closely controlled as well to ensure the tolerances they required. The 2 part mold with 2 angled slides was completed in 8 weeks and parts were made and tested. The parts are still used today and the material is being expanded in other product lines as well.