Insert molding and plastic overmolding are specific fabrication processes. They principle is to inject plastic over another material such as another plastic, metal or printed circuit board. Thus, it makes the assembling process faster and more cost-effective than gluing, for instance. As a result, overmolding is widely used in plastic parts design. Next, we also use this manufacturing process to make water and air tight assemblies for electronics and electric cables and connectors.
Over-molding is categorized into 3 types: insert molding, double shot molding and co-injection molding.
Insert molding is a process that requires an insert typically made of metal. Next, this insert is placed in the tool to let the plastic flow around it. Encapsulating the insert with plastic creates a single molded plastic piece that’s generally stronger than one created using secondary assembly. Usually, we place the inserts manually into the mold. In addition, this is generally a more cost-effective way to manufacture low-volume applications or complex parts. However, automated insert molding is a better choice for part consistency. Moreover, it minimizes human error, improves efficiency, and ensures optimal cycle times.
Benefits of insert molding.
Other key cost and design benefits of insert molding include:
- Eliminating additional assembly operations such as snap fits, gluing, and the use of screws or fasteners.
- Reducing the number of required parts as well as logistics around part tracking and shipping.
- Integration of design features not which are not possible by using a single material.
Insert molding is appropriate for a wide range of applications. Thus, we use this process for the fabrication of couplings, knobs with threaded fasteners and filters. As well as complex electrical components and specific solutions.
Over-molding or Two-shot molding:
Overmolding is a manufacturing process that results in a seamless combination of multiple materials into a single part or product. In addition, it typically consists of a rigid plastic base component overmolded with a soft thermoplastic elastomer. Usually, this soft plastic is TPE or TPR. Overmolding adds value in several ways. In addition, it lowers production costs. As a result, the advantages of using overmolding are numerous.
The advantages of overmolding explained.
- It results in a soft anti slip grip that prevents dropping and at the same time it functions as a shock barrier to maximize product life.
- We create visually attractive surfaces and branded color schemes that increase shelf appeal. In this way a nicer design provides a competitive advantage.
- Over-molding reduces the number of required manufacturing steps and associated costs.
Applications of overmolded parts.
The overmolding process is extremely versatile. Common household items such as hand tools, toothbrushes and razors may have overmolded handles for better grip. In addition, overmolding is also used to bond gaskets or seals to a plastic cover. Furthermore we use overmolded parts in the manufacturing of electric cables to in-mold metal contacts and grommets. Insert molding and overmolding are somewhat similar yet they have subtle differences. It is important to talk to experts like Davantech before the start of your product development. Because we want you to benefit from out expertise and assistance. In this way, your product design has the best outcome for manufacturing your product in a cost efficient way.
At Davantech we control the overmolding technique very well. Here is what we can do for you:
- We do injection of plastic around a metal contact to make connectors or terminal blocks.
- Injection of soft plastic around an electric cable to make cable splits, connectors and grommets.
- We inject plastic around printed circuit boards to make encapsulated or watertight electronics.
- Overmolding of soft or hard plastic over metal parts to make a solid assembly between metal and plastic.
In co-injection molding we inject the hard substrate and the elastomer into the same mold. Therefore, compatibility between materials is essential and it must be carefully controlled.
Co-Injection is very expensive and difficult to control. It is used least comparing with the other two methods. The hard and soft substrates are in a fully molten state. Therefore it provides the best bonding between soft and hard parts, the molded parts quality is also the best.
Overmolding of electrical cables and metal contacts (connector overmolding).
During production of electrical cables and connector overmolding we encapsulate the wires and soldered or shrinked metal contacts with plastic.
This plastic can be softer TPE or TPR. However we also inject PP and other hard plastics around connector pins as well.
We us our vertical injection machines of 20, 25 and 45 tons for this injection molding process.
Testing of electrical cables
Our qulaity department tests all electric cables one by one before packaging. We strive to zero defects !
Over molding of printed circuits
Even printed circuit boards with electronic components are overmolded. This is to ensure water tightness.
Plastic overmolding on metal
Some metal and plastic parts require a solid assembly. Therefore, overmolding a plastic shape onto an metal part is a good solution. It is not a problem to use soft as well as hard plastic for this method. This technique ensures a tolerance free assembly where the 2 components can’t move or rotate.