How to Weld Plastic – the Dos and Don’ts
Plastic welding is common across many industries and can be useful to understand when undertaking home repairs or other DIY jobs. Plastic welding requires some specialized tools, careful attention to detail and safety. This blog is a quick guide on the basics and will highlight some plastic welding tips.
Types of Plastic Welding
Plastic welding is a term that encompasses many different ways to join thermoplastic materials together. The most common methods in industrial settings are hot plate welding, high frequency welding, and vibration welding. The most common home welding technique is to use a specially designed heat gun.
Plastic Welding Safety
- You should ensure that you are working in a well-ventilated area. Your work area should be clear of any clutter so that nothing accidentally gets in the way of your weld or spills and contaminates the weld. If you are using a hand held tool, ensure you have a safe and flat surface to put it down comfortably.
- You should make sure you are familiar with the materials you are using and read the MSD sheets if needed. These sheets will list any hazardous materials in the plastic.
- You should wear protective equipment, including long sleeves and trousers, closed-toe shoes, gloves, and protective eyewear. You should consider whether a respirator or face mask is also necessary, depending on the materials involved and personal health needs.
- If you are in an area where other people are present or likely to enter, ensure everyone knows what you are doing, safe paths they can take, and any hazards that may mean they want to use a different space.
The Welding Process
This is a short guide for using heat guns for small-scale welding, for instance, if water tanks need to be repaired.
Step 1: What is the Plastic?
It is essential to know what the plastic is as you will need to use plastic welding rods of the same material. The best way to test if the plastic rod is suitable is to weld some of it to a hidden area or a test piece of the materials you are welding. If it snaps off with pliers, but some of the material remains, you have a match.
Step 2: Prepare the Surfaces
The parts that you want to weld together should be clear of any dirt or potential contaminants, including oils and even UV degradation. This is incredibly important as, firstly, any contaminant could be a fire risk, and secondly, they may make the weld fail or not take in the first place. Not only is this frustrating, but it may lead to you increasing the heat of your tool to force the weld to unsafe levels – leading to another fire hazard. Sandpaper and stiff wire brushes are good choices.
Tip: Always finish your cleaning process with warm water and a soft sponge to ensure any residue from detergents is cleared off the surface of the materials.
Step 3: V Groove and U Groove
This is where a v or u-shaped groove is made into the material at the site of the weld – this helps to ensure a strong bond for the weld.
Tip: If you are repairing your surfaces, you should drill a hole at the end of a crack to stop it from splitting further.
You may want to consider tacking the join at this point.
Step 4: Welding the Join
You should have established the type of hot air tool you need and the correct nozzle for the job. This may involve some trial and error, but your tool will have a guide to follow. If you do not think you have the correct equipment, you can browse our selection of heat guns here. You can increase and decrease the heat of your tool depending on the type of weld and material being used. Again, your tool should have a guide for you to use as a starting point.
Tip: Trim the end of the welding rod to a point to start the weld off more easily.
You should hold the welding rod to the plastic parts at a 90-degree angle to fill in the groove you have made. Place the tool underneath the rod to heat and soften it, pushing the rod steadily down and along the weld join.
A welding joint should be continuous – you cannot stop halfway through. There are fast welding tools and nozzles that are appropriate for longer welds – it is better to use the right tool for the job rather than trying to make do with what you have.
Tip: Remember the weld is not set until the material has completely cooled down!
Plastic welding is an incredibly useful skill to have and can be applied in many different circumstances and across industries. This is just a short guide; there are also many different welding techniques, such as the pendulum technique, which you may want to look into before starting your project. The more you know, the better prepared you will be!