What is overmolding and 2k injection molding


There are very similar between over-molding and 2k injection molding, simply explain there is two point difference.

1, overmolding is using normal injection molding machine to produce the parts, which means move the first part (substrate part) to the subsequent mold (over mold) and molding to get the final part. 2K injection molding is using the 2K injection molding machine to produce two or three materials (colors), molding process is compalex but fast, efficient, and high quality.

2, compare to overmolding and 2k injection molding, 2k injection molding has high quality and high production efficiency, but since the 2k injection molding machine is too expensive, so sometimes use over-molding to replace it.

Blow is the relation to overmolding and 2k injection molding.

What is overmolding?

Overmolding is an operation in which two or more mediums (substances) are merged to form an ending molded product, over-molding needs to make two separate molds, one is substrate (first mold), the second mold is called over mold, but if the substrate is metal parts or brass parts, this type of overmolding we normally call insert molding, and insert molding only need one mold to finish the process. The over molding materials majorly used are thermoplastics and rubber, or the same material but different colors. During overmolding, the activity that happens is either mechanical or chemical which leaves the two substances bonded.


Over molding process is producing the molded part (substrate) from the first mold and move it to another related over mold, the substance can be used to combine the surface molded with the molding substrate. The molded material can otherwise be put back to the surface it was extracted from and the overmolding substance added.

Advantages of overmolding

  1. Compare to 2k injection molding, overmolding is more easy to make, you can use a normal injection molding machine to make 2 or 3 different colors in one molded part, or make two or three different materials in one ending part.

  2. For some small quantity of two-color molding parts projects, you do you not need to invert or hire 2k injection molding machine, use overmolding process is the best and low cost to meet customers requirement.

  3. It increases the design diversity and also exalts the end product towards many materials composition.

  4. There are less secondary activities or processes carried out on the end products. This reduces any cost of labour. Also, after manufacture, no more costs are incurred.

  5. The parts have a high level of stability and constitution since after being left to mechanically inter-lock they become one.

  6. Product overmolded using plastics have high resistance to vibrations and shock due to the plastic resins having been structured perfectly.

  7. The plastic molding components are more reliable because there is no bonding at the manufacturing stage.

  8. The end products are of desired quality such as firm components and eye-catching designs.

    Metal insert overmolding

Disadvantage of overmolding

  1. Since overmolding process is moving the first molded substrate part to another over mold, so the tolerance is not as good as the 2k injection molding process.

  2. the production capacity is not as efficient as 2k injection molding, because working on the overmolding you need use robot or manual jobs to put the substrate into the over-mold, this will take time and the molding parameter sometimes is not stable, especially two or more substrates in one over mold, this cold caused more issue and increased the waste rate, and this waste is double (substrate and overmold).

  3. With overmolding, there are less available choices in terms of plastic compatibility.

  4. There are no secondary practices carried out on the end products of overmolding. Activities and adjustments come to a full stop when the molding material becomes cold.

  5. In cases where products are scarce, it is expensive to run such an operation. Sincere you need use person to put the substrate into overmold, so the cycle time is increased and the production cost is increased accordingly.

What is 2k injection molding? (Two-shot injection)

2k injection molding is a manufacturing process used when referring to molding two materials/colors into one plastic part. This plastic molding technology blends two materials or two different colours materials into one ending plastic part by using 2k injection molding machine.

2K injection molding

The chemical bonding process involved in this process takes place because they are able to merge two or more material into one part. When using 2k injection molding technology process, the material selection will be the key point factor to the success of the project or not.

This is an industrial activity that entails directing two totally opposite polymers into a ready product.

Differences between the 2K injection molding and overmolding

Overmolding is for some small scale production volume compared to the 2k injection which is majorly large production scale.

With the overmolding process, for another process to happen, the material used to mold must get cold to be removed whereas.

With 2K injection molding it is different. The polymer is usually still hot and flexible; hence more operations can still be carried out.

Once an object is made using overmolding it is locked mechanically with the other substances whereas it forms a chemical bond that entails its molecules bonding in 2k injection molding.

The 2K injection molding procedure can house diverse ideas such as the use of many different materials thus high-quality end product, opposed to the 2K injection molding procedure, the overmolding activity can have some compatibility issues more so plastics.

When overmolding, you are restricted to overmolding a metal with a plastic a few cases of a plastic and a plastic.

While in 2K injection molding there is a wide range of materials that can act as the molding substance or be molded on.

Advantages of 2K injection molding

The parts are strongly fitted and molded thus components or rather end products become more durable.

The appearance in terms of aesthetic value or beauty is high since many colours can be blended in the molding stages.

There are reduced costs since all manufacturing procedures are completed in the injection stage.

Finally, custom made products can be made to suit the user’s preferences

Disadvantages of 2K injection molding

When such a process is introduced at once, the mold cost is expensive, and you must run this mold in the 2K injection molding machine, this machine is expensive than the single color injection molding machine, it becomes expensive compared to introduction through bits and bits. Ultimately, this idea is outweighed by the fact that the expenses will be recovered due to the lack of labor cost and assembly costs.


You may have question when do you need to use overmolding and when should you use 2k injection molding process, there is some simple suggestion,

  1. If the quantity is not so high, maybe only a few thousand or ten thousand, then use overmolding process, this will save some mold cost for you.

  2. If you need over a half million of parts, then 2K injection molding is the best process to save cost for you.

  3. some of the parts only can use overmolding and some of parts can be done by double injection molding process only, this is depending on the part structure, if you can not sure about this, you are welcome to send your data to [email protected], we can check this for you and offer you a price for your reference.

Looking for over molding or 2k injection molding service?

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We will offer you the most competitive price at high-quality plastic tooling and plastic parts for the long-term business relationship, we will suggest you which is the best injection molding process for your products.

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