Step by Step: The Film Insert Molding Process

Project planning takes “know how,” and sometimes it’s helpful to know how a production process works when designing your decorated plastic part. Details like when the decoration is applied, how silk screening works, what happens in the injection mold cavity — having at least a basic understanding of all of these processes can help with planning for designs and timelines.

Plus, we enjoy talking about them!

So if you have a project on the way and want to know more before enlisting the help of an in-mold labeling manufacturer, here is a step-by-step overview of the film insert molding process so you can follow along.

The Film Insert Molding Process

1. Printing

At Sanwa, we use a silk screen process for printing — similar to how a screen printed shirt is made. We have stencils with very small holes that allow ink to pass though. A design is “burned” into the screen using an emulsion, and each color or layer gets its own screen (sometimes up to 20 screens). The combination of screens creates the completed graphic design. This allows us to keep our quality high and ensure proper graphic registration.

Printing Patent: We have a patented solution for preventing rust or discoloration when using silver inks. Standar colors (like white, black, etc.) can be made from basic materials, but metallic colors like silver or gold have to have some metal inside. If the edge of a part has silver exposed, over time it could rust. At Sanwa, we have a patented process to prevent this.

2. Forming

Next, we use “high pressure forming” in which heat and pressure are used to bend the printed film without cracking the printed ink or plastic.

Our patented forming method allows for superior quality and registration. With forming, there can be stretching, which could create off-center graphics. To address this, we have developed countermeasure methods to produce tolerance parts. The forming allows the printed film to form to the injection mold cavity shape. This small detail in the process allows for greater quality, the option for edges and corners to be wrapped without resin showing, and can prevent light from leaking out of the non-wrapped areas (like sides edges and corners).

3. Injection Molding

Once the silk screen printed graphic has been formed, it is placed into the injection mold cavity — this is where the molding process begins! Speed, pressure, and temperature are all important factors when producing a high quality molded part, and we have over 40 years of experience dialing in our processes to ensure the very best results.

Forming & Molding Patent: We also have a patented insert molding method in which no resin layer is seen and no wrinkle is generated by the film. This special thermoforming process allows us to deliver flawless three-dimensional parts for our customers consistently.

And There’s Still More…

Of course, the above just covers the production process and doesn’t include the various other steps along the way when manufacturing molded plastic parts. At Sanwa, our larger process includes prototyping and evaluating, research, testing, and trials — all before we get to the mass production phase.

Learn more about what it takes to get your product created with this timeline.

And we invite you to be in touch if you have questions. Responsiveness and education are at the heart of our philosophy, and we’re always happy to be a resource when it comes to creating high-quality decorative plastic parts.