What is Plastic Welding?

Plastic - it is versatile, lightweight, durable, and it can be molded into just about any kind of shape that 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 this synthetic material is that, when it does break, it can be welded back together to resume its functionality.

The method of joining plastic parts together is referred to as plastic welding. This process can be carried out on pieces of made of the same kind of material or even to join different types of pieces.

Hot Gas Welding: In this method, a specially designed hot air welding gun, which produces a hot air jet, is used to soften the parts that need to be welded, along with the filler rod. This technique is used for the manufacturing of smaller sized items, which include plumbing fittings, chemical tanks, and so on.

The type of plastic on the welding rod and that of the pieces being welded, has to be the same, or at least very similar, the only exception being when PVC and acrylic are welded together.

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

Friction or Vibration Welding: In this, the two parts to be welded are rubbed together at a higher amplitude and lower frequency, as compared to ultrasonic type.

The friction that is 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 joint 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 is then absorbed by the bottom part or the special absorbent coating, which results in generating sufficient heat to soften the surfaces of the two pieces being welded.

Thermoplastic Welding: 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, which is colored carbon black or any other color. This results in the absorbent part melting, thus conducting heat on the transmissive part, and causing the two parts to be welded together.