Injection Molded Foam – How to Determine if this Process is Right for Your Project

  • May 09, 2019
  • | by Randy Millwood

Often, Designers, Engineers, and Entrepreneurs will look to the web to find solutions aimed at helping them solve a problem or do something better. We field hundreds of leads per year, and every one of them has a common goal of finding the right soft material solution. To help you figure out which one is best suited for your application we’ve assembled a few points with regards to molded foams with skinned surfaces.

What Processes Are Out There?

Injection Molded Foam is a relatively new process compared to other forms of molded foam. The process was brought about by improvements in footwear components and the transitioning from die-cut shoe outsoles to a spring-like injection molded outsole. PopFoam got its start here in the US as an R&D contractor for Nike proving out designs prior to mass production. This was when it became possible to use these machines to mold other shapes, outside of footwear. At the time, most consumer products were molded using Compression Molded Foam or Molded PU(polyurethane), now there was an alternative.

What Are The Advantages Of Each Process?

I certainly see Injection Molded Foam as a great process, I’ve been in the business since it started, but I also have no problem being honest about where it works well and where another process might work better. Most of the time several factors come into play that will steer you to the right process, and some of those are:

  • How many parts do I need and when do I need them?
  • Where and how will the parts be used?
  • Is the part used indoors or outdoors?
  • Does the part need to be cleaned or disinfected?
  • Is there a particular PMS color needed?

Generally, when considering Compression Molded Foam, you’re looking for a product that’s not overly durable and somewhat replaceable. Some examples employ laminates to improve durability, but for the most part, these are consumables aimed at ever-changing markets and meant to be replaced. Some upsides to Compression Molded Foam are – lower part cost, less tooling needed and lower volume to get started. Some downsides are – durability, appearance and heat resistance.

Compression Molded FoamPU Molded Foams come in two forms, RIM(reaction injection molded) and water blown. The water blown process makes products like sponges and Nerf footballs. These foams are not closed cell foam(meaning they absorb water), are not very durable and not UV stable. Advantages are low unit cost, less tooling needed to start and widely available. The RIM process provides a tough outer skin – which significantly improves durability. Numerous armrests for office chairs are successfully made using RIM; however, they are still open cell foam under the skin and are generally firmer in softness. Coatings and UV blockers can be added to improve durability for cleaning and outdoor applications, but they come with a cost.

foam_water_02Injection Molded Foam provides answers for a lot of these shortcomings. If you need a molded solution that can be soft, cleanable, durable, closed cell foam and available in many colors then you’re probably on the right track with Injection Molded EVA.

Does Annual Volume Play A Role?

Understanding how you start and what the end-goal is plays a big part in choosing the right process. Some applications should or can only be molded using a specific process but if you have options maybe consider how many parts are needed to get the project off the ground or to “prove out” the design. You may choose to tool up a single cavity in PU to obtain 50 parts - and that could be the right choice at this stage - but later consider and different process altogether for mass production.

Typically, PU is good to do low volume numbers – if it meets the intended use. It can be harder to scale up of you go to mass production due to equipment changes to handle the volume. Compression molded Foam can be used to supply a lower to mid-range volume application because it’s easy to tool up and can scale up reasonably well. Injection Molded Foam requires multiple tools running together to start, so it’s generally better for applications of 25,000 pcs and up per year. Another plus is how fast it can be tooled up. When your product is starting to take off, Injection Molded Foam can ramp up quickly, and by using multi-stationed machines, it can handle millions of parts.

How Are Cost Compared?

Surprisingly, the unit cost is not that far apart when you weigh in the features each process brings to the table – it’s a bit of a stepped scale. A review of the intended application, product expectation, and annual volume can reveal a path to the right process if you’re working with a good supplier. Ultimately you need to know your market, understand your customer and have a good idea of what the retail cost needs to be for your product while searching for the right molded foam process.

Randy Millwood is the National Key Account Manager at PopFoam and has been servicing the closed cell foam industry for over 20 years.

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