What is Plastic Welding?

Plastic – it is versatile, lightweight, and durable, and can be molded into just about any kind of shape you can think of. However, even the best of things can break down, either from overuse, rough use, or age. One of the best things about plastic is that when it does break, it can be welded back together and resume its functionality. Hence, the importance of plastic welding.

What is Plastic Welding?

The method of welding parts of plastic together is referred to as plastic welding. Plastic welding can be carried out on pieces of plastic made of the same kind of plastic or even to join different types of plastic pieces together. There are various techniques of plastic welding, some of which are given below.

Different Types of Plastic Welding

Hot Gas Plastic Welding: This is a method of plastic welding wherein a specially designed hot air welding gun, which produces a hot air jet is used to soften the plastic parts that need to be welded, along with the plastic filler rod. The hot gas plastic welding technique is used for the manufacture of smaller sized items, which include plumbing fittings, chemical tanks, and so on. The type of plastic on the welding rod and the plastic pieces being welded have to be the same, or at least very similar, the only exception being when PVC and acrylic are welded together.

Ultrasonic Plastic Welding: In this type of plastic welding technique, low amplitude high frequency vibration – 15 kHz - 40 kHz – is applied, which results in producing heat, due to the friction it creates between the pieces of plastic being joined. The interface between the two parts is designed in such a way so that the energy is concentrated in order to achieve maximum welding strength. This plastic welding process is fast and can be done over long periods of time without interruptions.

Friction or Vibration Plastic Welding: In this, the two parts of plastic to be welded are rubbed together at a higher amplitude and lower frequency compared to ultrasonic welding. The friction that is thus caused, plus the clamping pressure that is applied results in creating the heat required to melt the surface of the interface between the two pieces, which results in a welding that is very strong. The friction applied can be either orbital or linear, hence the design of the two pieces being welded should allow for this movement.

Plastic Welding via Lasers: In this technique, one of the pieces to be welded has to be transmissive towards the laser and either a coating on the other piece or the other piece itself has to be absorptive of the laser. The two pieces are placed together under pressure and then a beam of laser is applied along the line of the joint. The laser beam goes through the top part and then is absorbed by the bottom part or the special absorbent coating, which results in generating sufficient heat to soften the surfaces of the two plastic pieces being welded.

Thermoplastic Welding: In contrast to laser welding, which focuses a beam of light on the edge of the pieces being joined, the technique used is known as through-transmission. In this method, the laser beam goes through a part, which is transparent to the wavelength of the laser, usually near infrared, and then is absorbed by a part that is colored carbon black or any other color. This results in the absorbent part melting, thus conducting heat on the transmissive part, causing the two parts to be welded together.