Easier, faster, cheaper — three keywords associated with meeting aggressive time-to-market demands, particularly in the evolving electronics design world. And a critical component of meeting those demands is producing a prototype that does not involve complicated processes, is rapidly manufactured, and does not cost a fortune for low-volume orders. In other words, “easier, faster, cheaper.”
Overmolding is one prototype-producing process that offers manufacturers an opportunity to rapidly design products for many me-too markets where brand distinction becomes nearly as important as the product itself. While overmolding prototypes is not a new process, being able to create engineering-grade parts appropriate for end-use applications with speed and at reasonable costs has been a challenge.
We sat down with Becky Cater, Proto Labs’ Global Product Manager for injection molding, to discuss overmolding, the key considerations for designers, and how the process fits into the time-to-market equation.
What is the advantage of overmolding for prototype development and why would be considered appealing to makers of consumer electronics, for instance?
Overmolding is the process of incorporating multiple materials into a single molded part. The use of multiple materials can enhance a product’s functionality by adding a soft-touch for improved grip or adding a softer material for improved vibration or slip resistance. Overmolding can also enhance a product’s aesthetics by incorporating the use of multiple colors for branding or product differentiation. When the part is ultimately destined for mass production in overmolding, being able to prototype using the same production materials and manufacturing process allows designers to test parts that are an accurate representation of their final part. The rapid overmolding process can support customers through initial prototyping and into low-volume production.
What should a designer consider before choosing to overmold? (i.e. material, cost, number of units needed?)
Once designers have determined the need for a multi-material molded part, there are a few options for manufacturing those parts. One option would be to mold individual parts out of each material and then use a secondary method like adhesives or fasteners to attach the parts. Although the initial cost of this method can be lower than manufacturing an overmolded part, the additional cost, time and complexity of the secondary attachment process can quickly outweigh the initial savings. Overmolding streamlines the manufacturing process by fully integrating multiple materials into a finished part in a single process. If overmolding is the best fit, material compatibility is an important consideration as not all materials adhere equally well to each other. Adding a mechanical interlock can help ensure the finished overmolded part functions as intended. Lastly, it is helpful to collaborate with a molder who can offer design tips regarding wall thickness, gating, and ejection, and molding shutoffs in order to achieve an optimal overmolded part.
Optimizing product development and new product introduction processes are critical in dynamic market segments such as consumer. How can overmolding contribute to shortening these processes?
New product development frequently goes beyond simply form, fit and functional testing. Consumer products often require marketing and consumer feedback and having early design parts that accurately represent production parts can provide valuable feedback. Waiting for sample parts off of expensive production tooling can take months and can lead to product launch delays if design changes are ultimately needed. Using rapid overmolding for initial samples and design iterations can save valuable time and money by accelerating the speed at which designers can iterate to a final design. Once the design is finalized, rapid overmolding can also be used to provide on-demand end-use parts as production ramps. This minimizes the risk of needing to purchase large quantities of parts before the market demand has been fully proven.
Say a designer want to lay down the first portion of her product, add electronics, and overmold it to hold it all down. Is overmolding a good fit for embedded circuitry (i.e. PCB assemblies, cable assemblies, other sensitive electronics)? If so, what are the advantages to using overmolding and what are the challenges from both the design and manufacturing end?
Rapid overmolding is best suited for molding robust parts. Sensitive parts such as PCB assemblies and other electronics can be easily damaged during the molding process due to mold retention and molding temperatures and may not be an ideal fit for rapid overmolding. In addition to molding plastic over plastic, non-sensitive parts such as metal inserts can be manufactured with rapid overmolding as well. Substrates such as threaded inserts, simple metal insert forms, bearings, and bushings are common. Adding these types of metal inserts increases the durability, functionality, and longevity of plastic parts while taking advantage of the lightweight nature of plastic materials. The design and manufacturing challenges in overmolding include material compatibility considerations, designing proper gating and ejection, and part retention (making sure the part stays in place during the molding process).
Why has — at least to-date — overmolding been considered a difficult process to introduce at scale?
Historically there have been very few options for fast, cost-effective prototyping or low-volume production of overmolded parts. The overmolding process has typically required a large financial investment in tooling, leading it to only be viable for very high volume applications. Tooling lead time has also been prohibitive, with traditional molds often taking several months to manufacture.
How does your recently announced automated, rapid overmolding manufacturing service address those challenges, and what are the customer requirements should they decide to take that route with you?
With the introduction of rapid overmolding, the overmolding process is now more accessible to a broader range of industries and applications. Proto Labs has developed proprietary software that automates the front end quoting and manufacturing processes and allows us to offer cost-effective, quick-turn overmolding. Overmolded parts are now available in a matter of weeks versus months with traditional tooling, and in the same production-grade materials. For customers interested in having a part produced with our rapid overmolding process, the first step is to upload your substrate, overmold, and combined assembly 3D CAD files on our website. Once the files are uploaded, we’ll provide an interactive quote with detailed design for manufacturability (DFM) feedback within a few hours. From there, our application engineers can discuss material compatibility and mold design with you to help optimize your part design for the rapid overmolding process.