How do I Choose the Best Plastic Welder?

J.T. Gale

Plastic welders are used to join thermoplastic materials together. The tool brings the plastic material up to its specific weld temperature and then joins the pieces under pressure. In selecting the best plastic welder, it is important to know the different types of plastic welders as each type of plastic requires a different joining method. Some welders are self-contained and easily portable; others require an air or gas source and are stationary units. Types of plastic welders include hand-held “stick” welders, airless welders, extrusion welders, and injection welders. Knowing the application and the material to be joined is the first step to selecting the best plastic welder for the job.

Plastic welders join thermoplastic materials together.
Plastic welders join thermoplastic materials together.

Identifying the plastic that is being welded is key to achieving a strong bond. Identifying the type of plastic can be as easy as checking out the identifying number on the material itself. Another option is to use a testing lab to help identify the plastic blend. Usually, the most accurate home test is the burn test; since each type of plastic produces a different odor when burned, burning plastic helps identify the type. Once you have identified the plastic type, you may want to keep a sample for future reference. It also is important to note that plastics will only weld with like plastics; that is, different types of plastic will not weld together.

Welders should wear helmets and gloves for protection.
Welders should wear helmets and gloves for protection.

Hand-held hot air welders, or stick welders, are a common portable plastic welder. These use a heat source to soften the plastic while a plastic rod is melted to fill the gap. The key to getting a good bond from a stick welder is to maintain a consistent downward pressure, distance between the heat source and the tool, and working speed. Features to look for in a stick welder include a way to control the air pressure, preferably from a small, portable compressor; some way to fine-tune the heat source — ones with multiple elements are a bonus; and interchangeable tips that can be selected to best fit the shape of the plastic welding application.

An airless plastic welder is like a stick welder, but uses a heating element to melt a smaller plastic rod without using an outside air supply that is blowing in heat. This type of plastic welder generally eliminates excessive welding rod buildup and can help avoid panel warpage. The final weld usually should penetrate about 75 percent of the base materials, and typically should be allowed to air cool for at least 30 minutes.

Extrusion welders are larger than the previous two units, so if space is an issue, this may not be the welder for you. This plastic welder provides a larger bead and usually is a floor-standing machine. The weight of the machine itself provides the downward pressure during the welding process.

Injection welders are both lightweight and portable — a great option if mobility is desired. Normally they are easy to use and produce a high-quality bond. The key to a decent weld with an injection welder is the ability to change the aluminum tip on the plastic welder to fit the proportions that are required.

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