Injection molding is a broad term used to describe one of the most important processes in the manufacturing industry. It’s a process where a typically metal tool is made, then molten plastic is injected into the mold and ejected. The process repeats to produce thousands of identical parts. It’s safe to assume that every large-volume plastic part on the market has come from an injection-molding machine, because the benefits of using injection molding for production are numerous. These include low cost per part, short cycle times, a large range of materials, and consistent, in-tolerance parts.
There are various sub-processes that add further capabilities to this already versatile technology. This article will specifically explore insert molding vs. overmolding and the advantages of each.
Insert molding is a subset of injection molding techniques where a metal part is inserted into the mold prior to the actual injection molding. The insert is precisely positioned inside the mold either manually or by a robotic arm. The mold then closes and plastic is molded over the insert, creating a single part.
One of the most common applications for insert molding is the creation of metal attachment points for fasteners. Fasteners are typically used if the overall assembly is designed to be disassembled or if the insert molded component must be attached to a different material or component. Metal threaded inserts molded into plastic reduce risks of damage during installation.
Insert molding can also be used to eliminate the need for fasteners completely by including the necessary metal parts in the mold, thus firmly securing the parts into a single bonded component.
A insert molded threaded insert
Insert molding is a versatile process that has numerous benefits, some of which are listed below.
Despite the many benefits of insert molding, there are also a few disadvantages that need to be considered before choosing to use this sub-process.
Overmolding is essentially a type of insert molding. However, overmolding vs. insert molding is, as the name suggests, plastic is molded over another molded part. The first component is made inside an injection mold and it is then placed into a second mold to add the over-molded material. This technique is often used to combine multiple plastics for either practical or aesthetic purposes. For example, one might use different durometer plastics to mold a softer plastic over a more rigid one to make a part easier to grip. Using multiple colored plastics in an overmolded part can also distinguish the product from other brands. This is regularly done on the handles of tools like screwdrivers, power drills, or toothbrushes.
An overmolded handle on a power drill
Overmolding is a versatile process that has numerous benefits:.
Despite the many benefits of overmolding, there are also a few disadvantages that need to be considered before deciding to use this process.
Injection molding, which includes the sub-processes insert molding and overmolding, is a versatile and low-cost manufacturing production process that is used in the large majority of consumer products. Injection molding often results in the lowest cost per part when compared to other manufacturing techniques like CNC machining and even 3D printing.
Once injection molding is chosen for a specific application, the next step is often whether to use insert molding, overmolding, or just stick with plain injection molding. When trying to weigh the advantages of the processes, it is important to accurately define the product application. Each of these processes has specific use cases that are suited to different product types. It can be difficult to gauge which process will best suit your particular product, so it’s good to get expert advice early on. Contact a Xometry representative to leverage decades of vast manufacturing expertise. We will help steer your design decisions in the right direction so that you can choose between insert molding vs. overmolding, or just injection molding.