Company Chews Up the Competition with Epoxy Tooling

As part of the manufacturing of large corn chip designed to get that extra bit of dip the company uses a flexible plunger that forms the dough into a stainless steel cup just prior to frying the chip. The plunger seems like a relatively simple part but unfortunately three issues exist; delivery, cost, and durability. By rethinking the requirements some new ideas came to the table that resolved all three. Instead of doing something very conventional they chose to use a technology that wasn't necessarily high-tech but that was very efficient relative to time and cost. Replicating the part using epoxy tooling and selecting polyurethane instead of silicone resulted in a quick turnaround and at a fraction of the OEM's price.

Epoxy tooling has been around for many years and is still widely used in the cast elastomer business. It allows for fine detail and short lead-times. Generally speaking, the cost is a fraction of other tooling options. To make this work, a single new part was provided as a model. This part was replicated using a rubber mold; within four days of receipt of the model 20 additional models had been made. These new models were produced in a high hardness polyurethane to prevent any flexing or breaking during production of the tool. Each model was then attached to a common plate so that the orientation relative to a stainless steel threaded insert to be molded in the part could be maintained. The insert had to be accurately held within 1 degree of the eight fins around the diameter of the part. Models were retained in the event that additional tooling became necessary or to modify them should a new design come about.

Once the models were located on the plate a filled epoxy was cast against it and heat cured as specified. With the models removed the mold was now ready for minor secondary operations that were completed in a couple hours. From model to mold required only six business days. The part made from the new mold was an exact replica of the original. The epoxy tooling process allowed all fine detail to be picked up and the tooling is expected to produce thousands of parts.

Creating a new injection mold was considered but the limited number of parts and the lead-time for tooling caused the project to be considered unfeasible. A conservative estimate for a new single-cavity injection mold was more than double the cost of the epoxy tooling and the lead-time for creating the injection mold pushed the delivery of parts to an unacceptable point.

Moving to epoxy tooling reduced the dependency of the end-user on the original equipment manufacturer and addressed not only cost but also delivery and durability. This also presented an opportunity for the end-user to learn more about methods that can be employed to reduce lead-times and identify other areas where this sort of technology might be employed. Starting with an existing part also reduced risk, something to which we are often averse. Epoxy tooling guaranteed that the new parts would be exact replicas. No question needed to be raised about tolerance or dimensional accuracy since every model was made from the same cavity.

But other ideas were generated as well. What if a new material could be introduced that would provide better service life? The original part material was silicone rubber. Silicones are known for many of their properties but not for durability in abrasive applications such as this. The original parts were typically worn out within a few months of installation. Polyurethane was suggested as a substitute since it is very tough and could meet or exceed all other areas of the specification. Polyurethane was also a fraction of the cost of the original silicone.

Overall, the project took less than two weeks to complete the tooling and produce first articles for approval. Each line requires roughly 650 parts and a full complement of parts can be made in as little as one week. The molding operation is completely manual so there is no machine set-up or minimum quantity to produce. Even small lots of 20-60 parts are not an issue due to the relatively simple molding process. The project resulted in an overall improvement to the part and exposed the plant engineering staff to methods thought to be outdated or inappropriate for their need. They learned that there is application for every manufacturing method.