Transitioning from Single Cavity Design to Multi-cavity Tooling

The Problem: Starting a new design, making sure it works and integrating it into production.

The Solution: Apple Rubber works with customers from the initial design phase — from single cavity or prototype stage to transition into a multi-cavity production tool — with full process validation.

Apple Rubber prides itself on having an extensive staff of rubber engineers. Our engineers are versatile, and can go from assisting with actual part design to aiding in the modification to assure robust performance and finally, assuring seamless full-scale production assembly. Our customer came to us with a standard o-ring design. With engineers’ assistance and using our O-Ring Gland Calculator at applerubber.com, we assured him that his o-ring had the correct compression. We looked at both concentric and eccentric conditions to do a tolerance stack up. These ensure that, regardless of whether the design was shifted in the application, the correct compression will be maintained on the o-ring to assure sealing.

Through this process, one problem that we identified was the gland volume was less than the volume of the o-ring. This caused higher compression and potential leak paths. We recommended at least an 85% volume fill.

Our customer then received all the mating components to do functional testing. With our in-house tool making, we are able to make a single cavity tool with high precision to match certain dimensions and tolerances. We then noticed that other components were out of specification, so this caused our o-ring to fail in the applications. Using the O-Ring Gland Calculator again, we were able to assist our customer in changing the o-ring to meet their design with actual dimensions of the mating metal and plastic components. O-Ring tooling is typically cheaper than changing plastic tooling. With the new o-ring, our customer was able to function test the new design, and verify that it passed. Knowing our customer was using the o-ring for a disposable application, we knew automation assembly was going to be very important. Many assemblers use vibratory bowl feeds to try and feed silicone o-rings. This causes the silicone material to produce static electricity as it is vibrated, which means the o-rings will stick together. Therefore, for the prototype tooling, we added a blast bead surface to help rough the finished surface of the o-ring. We also provided a coated o-ring to test. Testing this early in the design phase helps with a later phase of biocompatibility testing, because more changes will not have to be made then, which would slow the rest of the process.

With the higher durometer, the bead surface was all that was required to feed the automation equipment. Now that we had reached the production stage, we designed a multi-cavity tooling to fulfill the customer’s current projections and 10-year projection. We completed the production tooling by providing a full process validation IQ OQ PQ. Installation qualification (IQ) was completed on the equipment that was being used to run the mold. Operational Qualification (OQ) was run varying the major processing factors. Runs were done at the high and low limits of all identified machine settings. Performance qualification (PQ) was competed by measuring all o-rings to look at CPK and PPK. Once qualified, we are able to provide millions of o-rings to our customer.