What is Overmolding?
Overmolding is a process when an additional layer of material is placed on an existing part or component. Common screwdrivers, toothbrushes, cordless drills, etc., are the simplest examples of Overmolding.
Overmolding is applied to various products and is a vital part of plastic processing. The first material in the process is often called a substrate.
Let’s take another example of a screw with a T -handle. A T-handle can be attached with additional screws, but a consumer would be much happier if it is already built-in on the screw.
To do that, the screw is attached to a mold directly, and T-handle is formed chemically or mechanically.
One or multiple layers of resins can be used depending upon the material’s capability to achieve a specific thickness or look. To achieve accurate results and place the second part properly primary piece is often altered or reshaped.
The ultimate goal is to create a product that fulfils the custom function.
Although overmolding can ramp up your production speed significantly and is also cost-effective as you don’t have to manufacture two parts separately, at the same time, it is tricky to execute and requires slick to near-to-perfect command on production.
Let’s have a check on some of the applications of overmolding process –
Adding Grip and Comfort –
Generally, components with handles are difficult to maintain a grip on. As an operator, one should always choose over-molded grips over the normal ones.
It provides increased grip with better agility, especially in wet and hot conditions.
Cordless drills, toothbrushes, shaving razors, shampoo bottles, toy guns, kitchen utensils are some of the examples where overmolded handles being tremendously useful in extreme conditions.
Overmolding is highly beneficial as its applications have many possibilities. In the products where grip is overmolded it can-shaped, bent, and curved anyway depending on the product’s requirement.
Form-fitting grips created by overmolding provide impeccable grip and prevent someone’s hand from moving off the grip, which can be crucial in some professions.
Versatility of Overmolding –
As mentioned earlier also, overmolding has immense possibilities. Overmolding can be used to add colors, textures, shapes, any other operability, and usability; it all depends on consumer demand.
Overmolding can be used to manufacture innovative products with new designs for robust sales and consumer satisfaction.
Overmolding alters the physical properties of any part depending on your prospective customer’s needs.
The material used for the overmold will play a vital role in deciding the functionality of the overmold. It can be hardened for increased durability and softened for enhanced grip.
The Difference Between Overmolding and Insert Molding –
On the surface, Overmolding and Insert molding look quite similar, but there’s a subtle difference between them. Overmolding is a process where two parts are combined with each other to improve a product’s features.
The original part or substrate is produced using the injection molding process. After it is cooled, it is again fitted in an overmolding tool coated with molten thermoplastic or any other material.
On the other hand, Insert molding involves encapsulation. In this process, both the parts are molded simultaneously.
First of all, a plastic resin is poured into a mold, and a plastic part is inserted into the mold to produce an encapsulated product.
Both molding processes can be utilized for their specific purposes.
The Material Combination Used For Overmolding –
- Acrylic Thermoplastics
A commonly used plastic in industries with high impact strength and ductility. The most impressive ABS feature is its great resistance to heat, acids, oils, and even alkalis.
The ability to alloy with polymers like high-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE), high impact strength, dielectric properties, rigidness, and toughness makes ABS a must-try.
ABS is mostly used for manufacturing computer keyboards, sockets, power tool housing, and LEGO toys.
The most impressive ability of PEEK is its tremendous resistance to high temperatures and chemicals without degradation.
The material is mainly used for producing medical appliances because of its magnificent resistance to fatigue and great mechanical properties.
Apart from medical appliances, PEEK is highly utilized in industries like aerospace, automotive, electrical, and biopharmaceutical products,
Acrylic Thermoplastics –
Mostly used in medical appliances and the food packaging industry has a high resistance to UV fading and wearing out.
High-tensile strength and scratch resistance also make acrylic thermoplastics a must-try.
Its natural property of transparency, inexpensiveness, and easy availability is also responsible for its popularity among manufacturers. It is often called one of the clearest plastics available in the market.
Advantages of Overmolding –
#1 The drastic improvement of product quality and functionality. The accurate alignment and solid assembly between mating parts are responsible for quality improvement.
#2 The rigid alignment eliminates any need for adhesives in mating parts.
#3 Overmolding helps in making products more flexible for complex operations. e.g., toothbrushes, bikes, and car headlamps, etc.
Disadvantages of Overmolding –
We have talked a lot about the benefits of overmolding, but as we all know, nothing is perfect. So on the other side, there are slight disadvantages to overmolding, which I’ll discuss now.
#1 The initial cost of setting up everything is very high. Initial prototyping, designing, testing, tooling requires a lot of capital and human expertise.
#2 Overmolding follows all the injection molding rules, so any designed part should be compatible with injection molding. As the mold is made up of aluminium or iron, making design changes becomes extremely difficult.
Plastic can be added to the substrate by making the tool cavity larger by cutting away steel or aluminium.
On the contrary, when you want to take away plastic, you need to decrease the tool cavity’s size by adding aluminium or any other compatible metal.
This is a hard thing to do, and sometimes it might result in scrapping the entire part or worse. That will result in cost overruns and hurt the entire manufacturing cycle.
Interesting Read – Compression Molding Process – A Detailed Guide | Thermosets Composite Compression Molding | Types of Compression Molding | Molds Used for Compression Molding | Advantages | Disadvantages | Applications
1. What is overmolded rubber?
Ans. As an overmolding is used to mold plastic to another (usually rubber like plastic-like TPE.) That attached part si called overmolded rubber.
2. What is the difference between Two-shot molding and overmolding?
Ans. Two-shot molding and overmolding have similar applications. The only difference between them is that the former is used for large production runs and the latter is used for smaller production runs. However, before choosing any of the two options, experts should evaluate critical considerations of each manufacturing process against their project requirements to ensure they’re making the best choice.
3. What are the different types of injection molding processes?
Ans. Below are the different types of injection molding processes:
- Insert molding
- Metal injection molding
- Thin-walled molding
- Gas-assisted injection molding
- Liquid silicone injection molding
- Hit runner molding
- Thermoplastic injection molding
4. What are the types of injection molding machines?
Ans. Below are the types of injection molding machines:
- Injection unit
- Clamping unit
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Final Thoughts –
Thus, were my insights on overmolding process. The biggest advantage of overmolding lies in its ability to make flexible products with intricate designs. Looking at everything and analyzing everything before making a decision is an important part of achieving success in the injection molding industry.
I have tried to mention all the relevant details. Kindly share your reviews and thoughts about the article in the comment box.
Have a wonderful day 🙂