In the manufacturing of large and complex plastic structures and components, it is seldom possible to mould thermoplastics into a single piece. Instead, the project is typically divided into different parts that are later joined for final assembly. While some plastics burn, others liquify and harden when cooled. In that case, a welding process can be used to melt the separate surfaces together. There are different welding methods, one of which is called extrusion welding.

What is extrusion welding?

Extrusion welding is a finishing technique used in the fabrication of plastic products. With the use of an extrusion welding gun that spits molten thermoplastic, a certified welder can join and separate parts in large plastic fabrications. A plasticized filler material is applied by pressure between the two surfaces, and as they cool down they become fused together. The way in which polyethylene responds to heating, this technique is especially effective. See the photos below for our staff extrusion welding in our factory.

Extrusion welding

How does it compare to other welding techniques?

This process was developed in the 1960s as an evolution of hot gas welding. Today, these two techniques have similar applications but extrusion welding produces stronger bonds at much faster rates. The reason is the higher volume of material an extruder can dispense in a single pass in comparison to its predecessor. Plus, it allows for better control of the welding parameters (i.e. temperature, speed, position), leading to consistency and strength improvements.

Applications

The fabrication of tanks and pipe sections especially benefits from extrusion welding, as a well-performed, sealing bond is waterproof and corrosion resistant. This welding method is ideal for large volume projects with big and/or thick geometrical parts. In such cases, it turns out to be more cost-effective than traditional techniques. For that reason, it is very popular in environmental, agricultural and water engineering applications.

Extrusion welding components

The main components needed to execute this technique are an extruder, a radiant heat source and a welding shoe. The actual process is not much different from traditional plastic welding methods. The surface needs to be cleaned and prepared, tack welding the base material parts together, then preheating until it becomes soft to guarantee the proper fusion. The extruder is the gun that feeds the bonding material, which will be in pellet or in spooled strand form. Then the radiant heat source is generally hot air that is blown through a nozzle located in the head of the weld. Finally, the welding shoe is the die, made of non-stick material, through which the filler is forced out while the technician holds it at the correct angle and pushes it forward. After welding, the parts need to cool down. In most cases, this is done in one single pass. The joint design options include butt joints (single V or double V grooves), T-joints and overlap joints. 

Extrusion welding

Recommendation

Every welding method poses advantages and disadvantages. Only a specialised team is capable of determining the most cost-effective technique for each project. The materials, the equipment, the skills of the operator, and their understanding of the industry and the different applications will determine the finishing quality of a welding process.

Contact Us!

At Industrial Plastics, we are determined to innovate our approach to fabrication by employing the most efficient technology, guaranteeing we make the highest quality plastic products available. Our experienced team is always searching for ways to improve customizability through our advanced machinery and process knowledge. We understand how imperative plastic fabrication is to many businesses. Backed by our ISO 9001 accreditation, you can put trust in Industrial Plastics fabrication. If you are in the market for plastics, contact us via [email protected] or call 1300 465 888. 

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