The Difference Between Double Shot Molding and Overmolding

There are a variety of manufacturing methods used to create plastic molded products. Two methods mentioned in this article, double shot molding and overmolding, are viable manufacturing processes that offer several advantages for many plastic manufacturers. Both processes can be difficult to master since they require adherence to the very tightest of tolerances. Below, we discuss the differences and advantages between double shot molding and overmolding.

Double Shot Molding

Double shot molding, sometimes referred to as two-shot molding, is a manufacturing process used to produce complicated molded parts from two different materials by molding plastic around a preformed metal or plastic insert. The process is relatively simple; one material is injected into a mold in order to make the initial piece of the product, followed by a second injection of another material that is compatible with the initial injection molded piece. The two plastic resins then form a molecular bond and the multi-resin molded part is cooled and ejected.

Double shot molding is an ideal process for complex, multi-material, and multi-colored plastic products; specifically in high-volume production scenarios. Other advantages include:

1. Lower unit cost.
2. Reduced cost and waste associated with assembly defects.
3. Enhanced product quality.

Overmolding

Overmolding is a process of adding an additional layer of material over an already existing piece or part. This process is regularly used to manufacture parts, sub-sections of parts, and for prototype development. Typically, the substrate material (the first piece in what will be bonded and mechanically interlocked with other materials) is placed into an injection molding tool, at which point the overmold material is shot into or around the substrate. When the overmold materials solidify, the two materials become joined together as a single part.

If you are overmolding a metal part with plastic, you can really use any type of plastic. If you are overmolding a plastic part with another plastic, then there can be some compatibility issues. Your experienced molder will be able to recommend the best materials suitable for your project

Overmolding can be added to change the surface of a piece or product by adding texture, color, and incorporating necessary functionality components. Other advantages include:

1. Enhanced design flexibility and multi-material components.
2. Reduced secondary operations; assembly and labor costs.
3. Improved part strength and structure.

As mentioned above, these processes are relatively simple to understand. However, it is highly difficult to master. It requires high levels of technical expertise and attention to detail. When dealing with high-volume production scenarios, the smallest mistake can be costly. This is why it is critical to find a highly capable molding manufacturer. Once you find one, you need to involve them early on in the design phase of your part, as they can engineer value and quality into any problem areas. If you have questions or concerns regarding your part or the double shot or overmold processes, contact our experts at Midstate Mold today!