This is sometimes accepted due to part geometry and/or mold design, but these compromises can often limit the how repeatable a process can be and significantly reduce the overall process window. This drives a process closer to the edge of the cliff and sometimes brings part quality levels hurling down that cliff. Most of these compromises can absolutely be avoided just by understanding when process development truly starts. If we understand when this process starts, we will better understand who needs to be involved in each level of development.
Process development, believe it or not, starts right at the RFQ. Once a request for quote comes in, a team should be brought together to review the potential new product. This team must include:
- Process Engineers
Involving your S.M.E.s in each of these areas upfront will greatly increase the odds of having a successful launch. These individuals should be experienced enough to look at initial part models to ensure moldability of part. Being involved in that RFQ process will also help give closer estimates on cycle times and tooling costs, both of which are very important when presenting quotes.
Process and tooling engineers should be able to identify areas of concern upfront. A good understanding of scientific injection molding and knowledge of what is required in the part design to develop this process are extremely important. These will allow for suggestions to be made to the customer to ensure a high quality part upfront and may even determine whether or not a molder is interested in producing the product.
If a potential customer is not interested in making modifications to improve process ability, you might want to rethink whether this customer is a good match for your business. Process development continues throughout the quoting and designing stages of a project, and this upfront work will absolutely reduce or eliminate any need for compromises to the injection molding process.
Profiling injection speeds before molding begins
Example: Often times processors are forced to profile injection speeds to improve the cosmetics of a part. Basically slowing the fill speed down enough to ensure that the shearing at the gate does not produce excessive heat resulting in a blemish on the part. The resulting fill time could be pushed outside of the realm of repeatability, as well as playing havoc with the orientation of the molecules as they flow.
Having an experienced process and tooling engineer involved upfront can reduce the likelihood of this result. Identifying an alternate gating location, geometry, or recommending a gate diameter to help avoid this could be a few of the recommendations.
It is important to ensure that the part and the mold are designed to run a Scientific Injection molding process. The more complex the part design, the more important it is to keep this in mind. Making adjustments to the mold after it has been built can be much more costly than designing it right up front.
Once the part design has been approved and the mold built, it can be close to impossible to correct certain errors in design. About 75% of the process development work is already completed at this point, and it will limit how robust the injection molding process can be. Understanding when this process begins will greatly improve the success of any new product launch as well as ensuring shot to shot repeatable for the future.
About the Author: Robert P. Gattshall has worked 17 years in the automotive and medical injection molding industries, including 12 years in process engineering and process development. Certified in John Bozzelli's Scientific Injection Molding for more than 10 years, Gattshall has developed more than 600 processes using scientific injection molding principles. Certified in Lean 5S and SMED, Gattshall has also trained more than 50 process technicians and engineers on the principles of decoupled molding.