9 Ways to Join Plastic: How Does Plastic Overmolding Compare?

9 Ways to Join Plastic- How Does Plastic Overmolding Compare

Do you know what the global plastic market size is? Almost 593bn USD. We know that plastic is manufactured in the form of small plastic palettes.

So have you ever wondered how smaller pieces turn into huge plastic products like toys, utensils, chairs, switches, and more?

You will get the answer to this question by learning how to melt the plastic together. Almost 9 ways to join plastic are used by manufacturers to transform plastic into amazing products.

Are you also a manufacturer looking for useful ways to melt the plastic together? If so, then you are at the right place. This article aims at discussing the ways to join plastic with a comparison of different over-molding processes.

4 Plastic Joining Welding Methods

Procedures like injection molding don’t always work to make something out of plastic. Sometimes you need to join two plastic pieces to make a product.

But how to melt the plastic together?

With several welding options in the market, melting and joining plastic has become easier and more convenient.

Check out these mostly used plastic welding methods for joining plastic. As a manufacturer or customer, these methods will certainly help you.

Ultrasonic Welding

Some plastics are highly rigid and make every joining process a failure. However, the only way to join them is by adding vibrational pulses and pressure.

This forces the plastic structure to lose itself and attach firmly to another plastic piece. That’s what ultrasonic welding does for joining the plastic—the extensive vibration and pressure cause the plastic materials to rub vigorously.

The rubbing creates heat and helps to melt the plastic together and join it. The biggest benefit of using ultrasonic welding is the quickness and versatility of the process. You don’t have to wait hours before getting the result, and a few minutes are enough.

Ultrasonic welding is so useful that it can help insert metal into the plastic component.

Pros of Ultrasonic Welding

  • Quick interaction with high creation rates
  • Solid bond strength and airtight fixing
  • It requires no extra materials

Cons of Ultrasonic Welding

  • Restricted to specific kinds of plastics
  • Costly hardware cost
  • Restricted joint plan adaptability

Spin Welding

Joining circular parts requires a particular welding procedure because of their geometrical shape. Spin welding is a procedure where surface friction joins plastic, resulting in a circular welding joint on the plastic surface.

Both plastic parts are held firmly using tools and then rotated or spun at high speeds. An extensive speed and force heat the rubbing parts, ultimately melting the plastic.

While spinning at high speed, more pressure is applied to help the materials bond together better. The main component in this procedure is the frictional heat produced by rubbing off the two plastic pieces.

Pros of Spin Welding

  • Practical cycle
  • The similarity between different plastics
  • Great joint strength

Cons of Spin Welding

  • Restricted to a roundabout or tube-shaped parts
  • Restricted joint plan adaptability
  • Surface completion issues

Vibration Welding

Plastic parts are irregular in shape and composed of different materials and are usually very difficult to join. The reason is the varying melting points and pressure-bearing capacity of these plastics.

When extensive vibration is applied to the two parts, it creates a frictional heat that helps with melting and bonding. The pressure also adds up by forcing the two pieces into one, making an unbreakable joint.

The joints created with vibrational welding can differ in strength. The resultant joint can be stronger or weaker depending on the cycle times and plastic materials used.

Pros of Vibration Welding

  • High bond strength
  • A large variety of plastic similarity
  • Great joint plan adaptability

Cons of Vibration Welding

  • Slow cycle with low creation rates
  • Costly gear cost
  • Restricted to level or somewhat bent parts

Hot Plate Welding

A heated plate is used for melting the two plastic pieces to join them. The temperature of the plate and the duration for which the pieces remain in contact with the plate differs.

The intensity of the hot plate dissolves the plastic material, and the strain from the plate melts the plastic part together.

Once the prescribed period is completed, the plate is removed from between the plastics. The resultant bond is highly strong and permanent.

Pros of Hot Plate Welding

  • The similarity between a wide range of plastics
  • Savvy process
  • Great joint strength

Cons of Hot Plate Welding

  • Slow interaction with low creation rates
  • Restricted joint plan adaptability
  • Restricted to level or somewhat bent parts

Advanced Plastic Joining: Infrared, Thermal, and Overmolding

Advanced Plastic Joining- Infrared, Thermal, and Overmolding

After plastic welding, come the advanced plastic joining methods. They indirectly use heat, adhesion, and other procedures to join the two plastics. Here are three advanced procedures for joining plastics.

Infrared Welding

Intensified infrared beams are used for instantly heating the plastics and joining them. The quickness is what today’s manufacturers require and infrared welding offers this.

Both parts of the plastic are held together with rigid force. The plastic pieces have the infrared emitting platen near them for the procedure. The platen emits beams into both parts of the plastic. These beams are usually in the form of a line or circle.

When the procedure is completed, the platen is removed and plastic pieces are left to resolidify by applying pressure. Complex and irregularly shaped plastics joinwith infrared welding. Places where strong hermetic seals are required have the best solution of infrared welding.

The best thing is there are no additional additives required in the process.

Laser Welding

When a clean joint is required for joining plastics you need laser welding. Laser welding is not only for plastics, in fact countless materials can be joined using it. Because of the constant evolution of the products and a need to make more products, laser welding has evolved.

In advanced laser welding, fiber optic bundles are used for delivering light to the wave guide. This light comes out from the laser diodes. While the waveguide is a custom tool that helps in directing the laser to the exact target place.

The laser beams help in melting the plastic and ultimately joining them together. Laser wedding is an amazing procedure because it is applicable from small to large parts.



One of the most preferred methods for joining plastics is over-molding. It’s a useful method that helps improve the overall component and design of the device as it can absorb the vibration impact.

Over-molding is a good option where insulating delicate electronics and improving chemical resistance is required.

To add different colors to the plastic, over-molding helps to mold these colors in the plastic. Different brands use this plastic running procedure as it’s a durable and custom process. It not only works for the physical benefits of the product; in fact, it is also helpful for aesthetics.

2 Simplest Way of Joining Plastic to Plastic

We’ve got you covered if you are looking for simple plastic joining methods. You may say these are the very early procedures used for joining plastics, and let’s know them, too, because they are still used today.

Solvent Bonding

Out of all methods used for joining plastics, solvent bonding is one of the easiest and simplest methods. You can say that manufacturers glue plastic to plastic in solvent bonding for joining.

This procedure is also called adhesive bonding, as the solvent acts as an adhesive. The two pieces of plastic are coated with a special type of solvent, and pressure is applied to the two parts to help the solvent work to join the pieces.

The solvent slowly evaporates and joins the plastic together. This joint is chemical. Most commonly, thermoplastics are joined with this solvent bonding process.

The other procedures used to bond the plastic are usually not good for thermoplastics. Applying extensive heat in the welding process may disturb the geometry of the thermoplastics.

Mechanical Fastening

It’s the least stable yet easy process for joining plastic together. Mechanical fasteners are used for the joining process, and two or more plastic pieces are held together with the help of mechanical fasteners.

However, one notable thing is that this procedure is suitable for only hard and strong plastics.

Plastics that cannot bear the extensive strain with the insertion of a fastener are not good for this procedure. Different mechanical fasteners can be used depending on the type of plastic and size of the product. Fasteners can be permanent or non-permanent, depending on the need.


You can join plastic to plastic using various methods. Plastic is a soft material and offers flexibility to help you join it with other plastic parts.

Some of the most common methods include:

  • Welding: it’s not the same welding as we do on metals, yet it’s a different process. It includes methods like induction welding.
  • Solvent bonding includes coating the two ends of plastics with a solvent. Then the two ends are joined together.
  • Mechanical fastening: in cases where precision bonding is not a thing to worry about, mechanical fastening is used.

Various methods are available for joining plastic together. However, it isn’t easy to label any of them as the best. Depending on the purpose, plastic, and application, different methods would prove to be best.

Some plastic joining methods are appropriate, while others might be more workable. Choosing the relatable method is important.

Standard glue might not work to glue plastic to plastic, and you will need special glue made only to join plastic. The working mechanism of these losses is unique and nonrelatable to any other glues available in the market.

Plastic glue helps in melting the plastic parts where it is applied. When the parts are joined together, this slowly hardens up again and thus joins together.

Some best plastic glues include:

  • Mr. Cements
  • Tamiya Extra Thin Cement
  • Mr. Hobby
  • Solvent burning works fast and is a very simple method for joining any type of plastic.
  • You can save hundreds of dollars on solvent bonding as it is cheaper than other bonding methods.
  • The results of solvent bonding are so amazing that no one will be able to know if there is a joint in the plastic.
  • When joining plastics, mechanical stress is obvious, which affects results. However, stress is uniform throughout the joint in the solvent bonding technique.
  • Unlike materials, the solvent bonding method is so useful that it can join.
  • Solvent bonding leaves no holes or gaps in the plastic resulting in a uniform joint.
  • Solvent bonding takes longer to join the plastic than mixing the solvents. The curing method is also time-consuming when joining plastic with solvent bonding.
  • Preparing the surface of the plastic before starting the solvent bonding process is a highly important process. It’s very time-consuming and expensive to prepare the surface thoroughly.
  • It’s an irreversible process where the plastic pieces cannot be separated again once they join.
  • This technique is dependable on the service temperature and the surrounding environment.
  • Welding is a very simple and pocket-friendly method of joining plastic together.
  • The joints of plastic welding are highly durable and exceptionally permanent.
  • Once the plastic pieces are welded together, it becomes impossible to detach them.
  • A common person cannot do the welding process. Highly professional and skilled labor who knows how to fuse plastic is required for the process.
  • Electricity remains a critical component in the procedure. There is a high consumption of electricity throughout the procedure.
  • The welding process is dangerous, so particular safety measures must be taken.


Plastic welding offers flexibility through a variety of methods that can be selected based on specific requirements. Additionally, Ultrasonic welding is a speedy and efficient process suitable for different types of plastics.

As a result, hot plate welding is an effective and cost-effective method of joining plastic spin welding and vibration welding offers great joint strength and planned adaptability.

Ultimately, the choice of plastic welding method will depend on the specific application requirements, the materials involved, and other factors such as cost and production volume.

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