Consider This When Designing Parts Which Require Overmolding

Overmolding is a specialized process of injection molding which incorporates the molding of one material (overmold) on top or around another (substrate). You see this today in many of your everyday hand held tools and devices. This option typically gives the end user a better grip or more comfortable feel while utilizing the given instrument or device.

More and more engineers are looking overmolding as a viable option for their new designs. As in sports the professionals make it look easy but you bet it isn't as easy as it looks. There a many key factors that need to be considered when designing an overmolded plastic part and we will briefly discuss them here on this page. We will also provide you with links to professional guidelines to help you get it right the first time and therefore save yourself effort, time and money.

The more simplistic your substrate geometry is the easier it will be to overmold it. Obviously if you have convex or concave parabolic shapes it will be difficult to create tool steel to shut off on these surfaces making it very tough to mold without flashing (leaking) plastic out of the cavity. Keep the substrate design as simple yet elegant as you can. remember that the injection molding process takes place with high pressures so good seals and part orientation are the key to success.

It is also a good idea to know how many of these parts are you going to manufacture. Typically this process is used on high end electronics and tools which the end user will pay a premium for. It is also used in the toy industry but typically only very high volume toys. In manufacturing plastic parts the cost of the mold must be considered as it is often overlooked and can be a big suprise if you haven't purchased tooling before. you want the cost of the tooling to factor out of the unit cost and this means you will be looking at high volume applications to get your ROI on that mold or molds which is most oftern the case. If it is a plastic over plastic application you need to consider that is a minimum of two cavities to get the job done.

If you would like to speak to us regarding overmolding please contact us. Please see the links below that will give you some ideas on what else to look out for when designing and overmolded part.

GLS Design Guide: