Understand the core differences between Insert Molding and Overmolding. This guide covers their definitions, unique advantages, and how these specialized injection molding techniques can enhance part durability, reduce assembly costs, and improve product functionality.
Insert Molding
The idea about insert molding is that one part or piece is specifically manufactured to fit inside a larger injection molding design, as an inner piece or component.
So the original part or “insert” is handed over to another assembly space, and it gets integrated into the bigger injection molded component. The plastic molding flows around the original piece to encapsulate or connect with it in some way. The finished product is composed of that original piece, or multiple pieces, precision molded into the larger plastic product.
Experts commonly cite examples such as metal knives or scalpels with injection molded plastic exterior pieces, or items like screws or fasteners molded into the surface of a plastic design.
Over Molding
In over molding, the process is very similar in some ways. Over molding happens when one original piece is injection molded, and a secondary injection molding process goes over top.
One way to think about this is in a project that involves manufacturing of a plastic utensil or consumer product with more than one plastic surface. The original part is injection molded first, and the secondary part is poured over it. That’s why they call this over molding.
Think of a plastic item like a mop, toothbrush or snow scraper for your car, with an original solid plastic body and a soft grip injection molded piece around the handle. This is one of the most common uses of over molding, and is a good example of how this process works. This article from Composite World also goes into detail on modern over molding processes and how valuable these have become to the manufacturing community.
However, the reality is a bit more nuanced. Individual products may be made with multiple plastics, or a combination of plastic and metal, composite, or different types of polymers or acrylic materials. So it really make sense to evaluate insert molding and over molding on a case-by-case basis.
