Comeragh Composites is a specialist technical consultancy based in Belfast, Northern Ireland, with dedicated expertise in delivering systems for polymer and composite manufacturing projects. The company’s engineering team recently collaborated with Additive Flow for a challenging project involving a metal and polymer over-molded component.
The component is for a child car seat: specifically, it is a hook for retaining the seat within a car. Four of these critically functional components are deployed within a single base unit that is locked into the car and catches the actual seat that the child sits in. Each component was manufactured from connecting two parts, the inner part made from steel and over-molded in a polymer material. Typical production volumes for this individual component are 40,000 per year for the OEM, with the potential to roll it out for other models.
The engineering brief was to manufacture this multi-material, multi assembly hook more cost-effectively without compromising performance or safety. Competition from low-cost manufacturing economies is constantly driving this re-engineering approach — with the alternative being to consider relocating manufacturing — to maintain profit margins. Moreover, reducing costs and maintaining or improving safety requirements are generally considered to be incompatible. But this does not always have to be the case. By engaging with Additive Flow, Comeragh was able to find a solution that not only met the brief but added significant value in other ways as well.
The main priority was safety performance (equal to or above requirements), while cost reduction was targeted as a required outcome. However, once the human thinking was removed, Additive Flow’s FormFlow software was able to exploit the workflows and deliver a single-polymer composite material, injection-molded part that could be manufactured at a reduced cost while adhering to all safety requirements.
The original iteration of the component involved manufacturing a metal steel inner part that was then fully over-molded with a polymer material to meet the safety requirements. The manufacturing processes involved were proving complex and costly, as well as time consuming.
Additive Flow deployed the multi-property optimization capabilities of its FormFlow software to consider the use of a single composite polymer material and eliminate the metal part. To this end, Additive Flow conducted a structural simulation on the original model, which quickly identified that a direct conversion to a single polymer material was not possible. However, by considering the well understood properties of the polymer PA66 with 30% glass fiber, FormFlow analyzed various other orientations of the component and produced results demonstrating the impact of fiber alignment. Results show a 30% difference in stress and a 58.4% difference in displacement – highlighting the need to understand orthotropic behavior and deal with it.
Additive Flow’s leading multi-property optimizer then allocated different orientations of the fiber within the part, to be delivered by different inlets within the injection molding process. This is especially powerful for this product, as the two forces acting upon the component are perpendicular. Additive Flow’s software Formflow optimized the properties simultaneously with geometry, to align with these different mechanical load cases while optimizing weight within the safety factor.
From this, Additive Flow subsequently ran a series of optimizations for a single material (multi-property) component that operated within the material stress constraints as the original dual-material component, with a weight reduction of 60%. Furthermore, by allocating the different orientations of the fibers, the results then informed Comeragh engineers as to how to best position the inlet for the injection molding process to ensure optimal production of the component.
Production of the new single material component optimized by FormFlow resulted in significantly reduced costs – which were cut in half. The cost-per-part of the original dual-material component was €2–2.50 compared with the cost-per-part of the new single-material component at €1–1.50. This translates to an annual cost reduction of €40,000 (10,000 units / 4 components per unit). In addition, the injection molding process greatly simplified the end-to-end manufacturing process, while also contributing to the simplification of the supply chain and increasing the recyclability of the component, making it more sustainable at end-of-life.
Findhan Strain, Director at Comeragh Composites, commenting on the outcome of the collaboration with Additive Flow, said: “There is an obvious cost benefit to running an optimization of this nature. However, another significant benefit for us is the supply chain simplification: now we no longer need to buy in metallic components, deal with suppliers and potential quality issues, or manage the movement of the metal material across the factory floor with a machine operator preparing it for over-molding. Now, with the PA66 single material injection molded component it is much easier to control the process.
He continued: “A further benefit is the enhanced suitability of the part within a circular economy approach. Although PA66 with 30% GF is not yet easy to recycle, it is easier than steel over-molded with another polymer such as POM. This is particularly relevant when considering an over-molded part that has a low residual value but would require notable effort to recycle. Undertaking these types of design activities are relevant now and will only increase in importance in coming years.”
“I would also add that while some of these benefits are a bit more difficult to quantify financially, they add really significant value for us, for volume manufacturing applications.”
Alexander Pluke, CEO of Additive Flow, further commented on the project: “I think what this project shows is that the optimization algorithms that we have developed at Additive Flow do not just apply to additive technologies but translate easily and effectively to injection molding processes. It is important to consider materials that we’ve known about and have a good understanding of — and to question why we are not deploying them in a way that is actually possible to improve manufacturing outcomes — regardless of process — in terms of the parts themselves, manufacturability, sustainability and recyclability. I also specifically believe that the multi-property capabilities of FormFlow offer interesting opportunities to really harness the orthotropic strengths of materials in the right way – as we have demonstrated here. Cutting costs and increasing sustainability seems like a win-win.”