How to Weld Plastic: Strength, Use Case & Step by Step Guide

Last Updated on June 7, 2020 by Gary Hargrave

Have you ever thought, “Is there really any way to weld plastic?” Well, many of us certainly have and some of you still might be wondering how do we actually do that? Well, this guide has been produced only to demonstrate this process by using a Step-By-Step comprehensive approach.

So just stick to the end.

What Is Plastic Welding Used For?

As the name suggests, this process is used for joining all types of plastic materials. But most frequently, it is used for repairing and joining broken parts together. Besides, plastic welding can also be applied to manufacturing a variety of plastic-made products.

Is Plastic Welding Strong?

This is a very common question. But the answer is, if a welder knows his stuff and do the whole process efficiently while keeping all the critical factors (we’ll learn about them shortly) in mind, it can be way stronger than the base material itself which is very interesting!

What Types Of Plastic Can Be Welded?

Well, there are basically five types of plastic materials that can be welded. They include polycarbonate, polypropylene, nylon, acrylic & acrylonitrile butadiene styrene or ABS.

how to weld plastic

How to Weld Plastic?

Plastic welding doesn’t require having a large number of tools and equipment in order to get started. Instead, only a handful number of tools and gears will do. Let’s learn about all of them in particular:

What Are the Required Gears

Personal Safety Gears

  • Welding Glasses: welding glasses are mainly designed to protect the welders’ eyes. Although welding materials such as aluminum, steel will require you to wear an auto-darkening welding helmet & mask, plastic welding doesn’t produce harmful lights meaning you don’t require all those fancy lists of extra gears.
  • Welding Sleeves: well, long sleeve dresses are very good for welding any material. Plastic welding isn’t as much fire-intensive as welding steel and aluminum. But the fact is all types of welding processes will produce a high amount of heat over materials which can really harm your skin and body if subconsciously get touched. So wearing full sleeve clothes will ensure complete protection.
  • Welding Gloves: as we know, our hands and wrists are the only body part to stay in the closest proximity from the arc. Besides, any type of accidents can happen if a welder works without wearing gloves. On the other hand, gloves also help the welder to effortlessly hold tools and equipment which basically get hot after using for several hours.
  • Welding Boots: welders’ feet are the only body part that usually needs to stand for long hours without taking any rest. But that doesn’t mean wearing comfortable boots would be enough. You need to buy a shock-resistant pair of boots that are specially manufactured while keeping welders in mind.

Welding Tools

  • A Plastic Welder: well, like every welding process, plastic welding requires a separate welder to do the work. They basically come in with different functionality and power capacity. The more power wattage/amps it has, the higher the amount of heat it can produce to join thicker materials. Just make sure it features standard airflow to efficiently conduct the melting operation.
  • Rod Testing Kit (RTK): plastics can be of many types like stainless steel. Every welder must find out the unique code of their stainless steel in order to get the appropriate filler metal. Similar to that, you can only weld plastic materials by using the exact filler rod of that type. For this, we need to use this rod testing kit or (RTK) in order to identify the exact code of our plastic material.
  • Filler Rod: after you’re sure about what type of plastic you’re going to weld, you need to buy the exact similar type of filler metal for that. This can be of polypropylene, polyethylene or polyvinyl chloride.
  • Sandpapers: sandpapers are extremely essential for plastic welding. As with welding any material, it needs to get well cleaned before putting torch over it. The surface of your plastic may have unwanted paint which can be rubbed off by using this sandpaper. We’ll need 80, 120 & 180-grit sandpapers for applying on different stages.
  • C-clamps: these are extremely essential for welding any type of materials because they hold all the workpieces firmly in place with the welding table or the surface you’re working on so that, they don’t accidentally move aside during welding securing your whole project.
  • Angle Trimmer: this angle trimmer will be used to cut down the tip of your rod into angles so that it ensures an effective and stable weld of your plastic materials.

The Step By Step Process to Weld Plastic

  • Put On Your Safety Clothes: as discussed earlier, there are basically four major gears a welder need to wear before initiating the process. This includes welding safety glasses for protecting eyes, welding sleeves for the upper body, welding gloves for hands & wrists and finally, welding boots for protecting the feet from the fire and hot metals.
  • Determine The Appropriate Type Of Plastic: as said earlier, you’re required to do this by using your rod testing kit which will ultimately reveal the exact type of your plastic material by which you can determine the filler metal and what amount of heat you need to apply with your welding gun.
  • Clean The Areas To Be Weld: now we already have sandpapers in hand. Welding plastic without appropriately cleaning can be a bad idea as it may face you with serious quality issues right away you’re done with your welding. This is also true for welding other materials. Sandpapers which have 80-grit can effectively do this task.
  • Clamping: clamping workpieces is one of the most overlooked and critical tasks many welders do which results in serious destruction to their work. We’ll simply use the C-clamps to attach them with our workpieces after which we’ll verify whether they have been firmly attached or not. This is a process worth spending time on. So never rush on it.
  • Preheating The Welding Gun: now we need to simply set the temperature on the welding gun and leave it switched on for 2 minutes. This will preheat the gun. Now you might be wondering, what number of temperatures you should select for your certain type of plastic?
    Well, there are three most common types of plastic materials naming polypropylene, polyethylene, and polyvinyl chloride or PVC. For polypropylene or polyurethane, we’ll use 300° Celsius. For polyvinyl chloride or PVC, we’ll choose 275° Celsius. Lastly, for polyethylene, we’ll choose 265° Celsius.
  • Trim The Filler Rod: now it’s time to trim the filler rod. We can use either any trimming knife or an angle trimmer to do this task. Now begin trimming the tip of your filler rod into a pointed finish. This will diminish the appearance of plastic bubbles after you initiate the process and also provide you with an efficient and stable weld of your plastic materials.
  • Track Welding: we’ll do this task before attaching any filler rod into the gun. Tack welding is basically a temporary means to hold your parts in place by applying heat over them. You just need to melt the end areas of your workpiece joint by applying heat over them.
  • Attach The Rod With The Welding Gun: now it’s time to attach this rod with our actual welding gun. For this, we’ll need to have an open area on the speed nozzle of the gun. If your welding gun doesn’t come with this feature, you can buy only the nozzle separately for using filler rods. Now attach the nozzle with your gun and put the filler rod inside it in order to feed it during welding.
  • Perform Speed Welding: well, this time we’ll initiate the actual work. There are basically two common types of plastic welding naming speed welding and pendulum welding. For speed welding, we need to hold the welding gun into a 45° angle and running it over the joint while feeding the filler rod. Just make sure you touch the nozzle edge with the joint while doing it.
  • In Case Of Pendulum Welding: pendulum welding is a completely unique approach of joining plastic materials especially if you don’t have any speed nozzle or even the welding gun itself. You can perform this process just by using a propane torch. Just hold the torch or nozzle from one inch above the joint, and put your filler rod at a 45° angle while doing a back and forth heating towards the plastic to melt and join them together.
  • Allow It to Cool Down: now after you’re done with the main process, you’re required to let it cool for 5-10 minutes. Just make sure you do all of your corrections before it gets solidified and you need to be very fast in doing that because plastic cools down very faster.
  • Provide A Final Finish With Sandpapers: finally, we’ll grind the ridges of the joint and give it a clear finish by using sandpapers. For grinding ridges and applying the final finish, we’ll use 120 grit and 180 grit sandpapers respectively.

Measures to Ensure Safety

As with welding using any process, accidents can anytime happen. Although plastic welding is a bit safe to work with, having a fire extinguisher near your workplace will ensure overall safety inside your working area.

Final Words

Learning how to weld plastic is a topic worth spending time on. Many of us including some welders still don’t know how to properly do it. Hence, this guide will be helpful for all the aspirants out there. Thanks for reading the whole post. Stay along with us for our upcoming welding-related guides and articles

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