Compared Overmolding and Insert Molding Process
Injection molding is an important form of the additive process used in the manufacturing industry. It involves using a metal tool to form solid parts from molten plastic. We first inject the hot liquid plastic into the mold, taking its shape. The plastic then solidifies allowing ejection of the made part. At Creatingway, we repeat this process thousands of times to produce identical parts. This form of technology suits the large volume plastic industry. It is because it comes with unique advantages when compared to other manufacturing methods. For instance, it has a short cycle time, consistent, and is low cost. Luckily, there are other sub-process that further increase the capabilities of this versatile technology. They include overmolding and insert molding. Comparative Insight of the Two while comparing their pros and cons.
What’s The Insert Molding?
Insert molding involves the insertion of a metal part before the injection molding process starts. We have to position the insert inside precisely. Thus, we use robotic arms for added accuracy and error-free placement. Afterward, the mold closes with the molten plastic molding over the metal insert. However, it only creates a single part. A common use of insert molding is in making fasteners metal attachment points. We include fasteners in an assembly design when it involves disassembly. Also, if the insert molded parts need linking to another material. Metal threaded inserts work best since they reduce damage risk while installing. Additionally, insert molding may eliminate the use of fasteners. This is if it includes the needed metal part in the mold. It then results in a single bonded part with firmly secured parts.
Advantages of Insert Molding
- Lower Assembly Cost
The injection molding machine can make thousands of parts daily. This results in a significantly lowered cost of the individual parts. We term this as achieving economies of scale. When compared to CNC machining or sheet metal fabrication, the needed assembly may pose a challenge. The use of insert molding removes the need for assembly by doing it in a single step. Thus, it maximizes on saving costs.
- Part Performance
Metal materials are heavier than plastic materials. However, plastics have the benefit of lighter weight, greater design flexibility, and reduces cost. We thus combine both materials to make one part to get the benefit of both. For instance, metal inserts offer stiffness and strength. They are also more durable to wear and tear in cyclical loading. Plastic reduces the weight of the component.
Disadvantages of insert Molding
- Increased part complexity
The designer must know the DFM principles when using custom made steel inserts. This allows easy integration of the different technologies to make one effective part.
- Multiple manufacturing technologies
The process of insert molding may involve two manufacturing processes. Custom-designed metal parts need manufacturing through a metal forming process. A common example is the use of CNC machining. However, it may significantly raise the cost of the whole process. Alternatives like die casting or metal injection molding may reduce the cost of the metal insert. Notably, making plastic parts with metal parts costs more than making plastic only parts.
What’s The Overmolding?
Overmolding has some similarities to insert molding. It involves molding plastic over another molded component. We first place the initial part in an injection mold. Then, we place it in a second mold to add the over-molded material. The technique is great in combining many plastics. It, therefore, serves an aesthetic and practical use. For instance, the use of multicolored plastics allows easy distinction between different products. Also, in overmolding rigid plastic with softer plastics for enhanced grip performance. This we see in parts like tool handles of toothbrushes, screwdrivers, and power drills.
Advantages of Overmolding
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No adhesives needed
Overmolding allows the fusion of different materials. Therefore, it eliminates the need for glue to creates permanent bonds between materials. It also increases part durability and lowers assembly costs.
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Embedded seals
Overmolding has the option of making soft mold seals into parts. For instance, an electronic may need an IP rating for longevity. We could use a part with a groove in which we could insert an O-ring later. However, it is more cost-effective to permanently seal the mold as an integral part.
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Raised material flexibility
Overmolding allows the use of many material types to make complex parts. Different properties, added haptics and visual complexity get added using this process.
Disadvantages of Overmolding
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Debonding
There is a risk of delamination when it involves bonding two different materials. It especially happens without achieving the optimal temperature range needed for bonding the material. in this case, there is an option of using mechanical interlocks for materials that do not easily bond with heat.
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Multi-step process
Overmolding parts involve two steps in the process. This increases cycle time that makes it costlier than making a single part without overmolding involved. It also needs two tools to make the overmold. However, it is a value-added solution for making two injection molded parts that would later assemble. It removes the need for later assembly. Contact Creatingway now for your overmolding and insert molding services.
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