Plastic Overmolding

Plastic Overmolding

This refers to a process of molding one plastic with another plastic or metal material. The process entails the application of pressure as well as the heating of materials in the presence of suitable molten materials.

What is Plastic Overmolding?

This refers to a process of molding one plastic with another plastic or metal material. The process entails the application of pressure as well as the heating of materials in the presence of suitable molten materials.

Applications of Plastic Overmolding

Overmolding plastic parts have a wide range of applications. Below are some of the areas where they are applied;

Making Handles

Handles can be made from the plastic over-molding process. In this case, they are made thin and soft to reduce friction.

Making Automotive Parts

The knowledge can also be applied in the engineering sector in the making of parts such as buttons and interior bodies.

Medical Devices

A variety of medical devices have been made from plastic over-molding process such as surgical gloves and instruments.


A significant number of house-hold appliances have been made from plastic overmolding processes. For example, iron boxes, utensils among others.

4 Products Found.

How Plastic Overmolding Process Works

Step 1: The first step of the over-molding process entails injecting the plastic substrate into the mold until it becomes full of liquid plastic. Thereafter, the molten plastic is left to cool thus forming a hard substance as the resultant product.

Step 2: This step involves mixing a suitable plastic material such as TPE with the rigid substance initially formed after cooling molten plastic.

Step 3: This is the final step where the resultant material is allowed to solidify to form a new compound.

Plastic Insert Molding Vs. Plastic Overmolding

Plastic insert molding differs in many ways from plastic over-molding processes.

In this case, plastic insert molding involves combining molten plastic with a suitable over-molding material such as TPE at the same time.

As in the case of plastic over-molding, the molten plastic is allowed to cool before the introduction of TPE.

Types of Processes in Overmolding Plastic

Two-Short Molding: This process incorporates two distinct materials that are added subsequently by an injector. As such, this process results in the production of diverse types of products that are usually effective as well as cost-effective.

Insert Molding: In this process, the injection of plastic components such as TPE comes after the introduction of metal into the mold. It is widely spread and its especially used to improve functionality.

Injection Molding: Injection molding involves the introduction of two distinct liquid plastic into a single mold to form a rigid compound after cooling.

Combinations in Overmolding Plastic Materials

Overmolding Plastic on Metal: This entails the integration of both metallic and plastic properties by combining a metal substance with molten plastic. This results in products with desirable features such as resistance to chemicals and corrosion, enhance grip as well as vibration.

Plastic Overmold on Plastic Substrate: This process aims at improving the general efficiency and functionality of products. This is aided by introducing liquid plastic to the already existing plastic material in the mold.

Benefits of Plastic Overmolding

Improved Functionality – The process entails combining materials of different types thus integrating various properties to produce a more functional and improved product.

Better Aesthetics – The process results in the production of materials that are appealing to the eye. As such, this process is termed as flexible and customizable to suit a variety of customer’s tastes and preferences such as texture, and branding.

Time and cost-effectiveness – Overmolding process involves combing various elements to produce a single compound that serves a variety of purposes thus saving on time and costs.

Efficiency – It is efficient and effective in the sense that it performs a variety of functions at a go.

Criteria for Choosing Plastic Material for Overmolding Process

Thickness – Thickness influences the use and purpose of various thermoplastic products. For instance, products that have handles should be made soft and thin to reduce friction between the hand and the handle.

Flexibility – Flexibility refers to the ability of the thermoplastic product to assume different shapes on the application of pressure.

Mechanical Properties – This refers to key aspects such as strength and flexibility. It is therefore important to consider the mechanical properties of the resultant product before the process.

Chemical Properties – Various products of the over-molding process have different chemical compositions depending on their use.

Costs – Evaluation of the cost of production is necessary before determining the type of material to be used in the over-molding process. As such, factors such as the availability of materials as well as other manufacturing requirements will influence the type of material used in the process.

Plastic Overmolding Design Guidelines

Part Design: It is important to consider the design of the over-molded part since this will avoid inconveniences and in-effectiveness of the final thermoplastic product. Consequently, this will ensure that the product is airtight as well as efficient distribution of the molten plastic on the mold.

Compatibility Of The Material: Since the over-molding process involves the integration of various materials, it is necessary to use easily compatible materials.

Overhangs And Undercuts: The process can involve overhangs and undercuts thereby making it to be complex. As such, necessary knowledge and skills in the over-molding process are required to avoid the production of ineffective products.

The Thickness Of The Walls: The aspect of thickness and thinness of the over-molded parts should also be considered since this is determined by the type of over-molding materials.

Types of Plastics for Overmolding Process

Acrylonitrile Butadiene Styrene (ABS)

These types of plastics are commonly associated with the production of products such as electronics, and consumer-based products. They are characterized by features such as good resistance as well as adhesion.

High-density polyethylene (HDPE)

They are widely used in the over-molding process due to their ability to resist chemicals. For instance, HDPE plastic is resistant to a variety of chemicals such as alkalis, bases, and acids.

Polymethyl methacrylate (PMMA)

It has aesthetic advantages over other types of over-molding materials. Moreover, it is commonly referred to as acrylic glass since it is transparent as opposed to other materials.

Thermoplastic elastomer (TPE)

They have a wide range of applications and this can be attributed to their diverse number of properties. For example, they are strong, flexible as well as are resistant to chemicals.

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