How to Weld Plastic | Step By Step

Plastic welding is a technique for joining softened thermoplastic surfaces with heat. When compatible thermoplastics are heated, a molecular bond is formed, resulting in the formation of plastic. The surfaces must be pushed, heated, and pressed, and then cooled during the production process.

In this article, we will guide you on how to weld plastic step by step and the techniques and tips of welding plastics with advantages and disadvantages.

Because of the heating techniques used, there are many different types of plastics available. Aside from the welding procedure, a variety of additional elements have an impact on the polymer quality. For example, how weld able are the foundation materials?

Before beginning the welding procedure, take some time to ensure that the fundamental components are flexible enough to create the desired end product.

Because of its extensive use, which spans from simple to sophisticated, plastic manufacture is unavoidable. Essential plastics include disposable tableware, vinyl toys, and light storage jars, and the most advanced versions have medical equipment, internet connections, and building pipes.

How To Weld Plastics – Step By Step

It can be challenging to make a correctly mixed plastic, especially if you’re a newbie. This process, however, can be finished rapidly if the procedures mentioned below are followed.

1. Get your workstation in order by cleaning and organizing it

Make sure your workspace is well-ventilated: The first step in any welding project is to protect yourself. Before you begin, put on safety equipment and make sure you’re working in a well-ventilated location. Wear long-sleeved clothing and heat-resistant gloves to stay safe.

To remove particles from the plastic, wash it with soap and warm water: Eliminating all impurities from the plastic eliminates any weak spots during welding. After washing the plastic, dry it with a clean or lint-free cloth.

To remove persistent stains from plastic, use a liquid solvent. One of the most effective liquid solvents is Methyl Ethyl Ketone (MEK).

Label the polymers you’ve correctly selected: You’ll see that each of the polymers has its letter if you look around. These letters are used to identify the plastic type.

The letters PP stand for polypropylene, PVC stands for polyvinyl chloride, and PE stands for polyethene chloride. Using these letter IDs as a starting point, choose the best rod for the specific type of plastic. For example, if you’re linking polyethene, you’ll need a polyethene rod.

Use a welding rod test kit to see if your rod is safe to use: If you’re not sure what kind of plastic you have, use a welding rod test kit. These rod test kits can identify several sorts of plastics. To carry out this test, use a rod that closely mimics the chosen polymers during the testing process. Next, fix one end of the rod to a clean plastic surface by heating it. See what happens if you remove it from the rod with a pair of plastics.

If the rod and the plastic stay together, they are made of the same material. Because only one rod can be compatible with the plastic, welders must carefully inspect the reference letters before beginning the process.

Remove any artwork off the plastic with a piece of 80-grit sandpaper: By rubbing the sandpaper back and forth across the plastic’s surface. Using a sanding wheel or an abrasive disc connected to the sandpaper may help you save time and effort. Paint scrapers can also be used for this exercise.

To hold the joints in place, clamp and tape the plastic pieces together: Make sure you’ve made the desired joint before turning on your torch. Place the plastic parts on a workbench and firmly press them together. The components are then secured to the table with C-clamps. To keep the pieces together, wrap a piece of foil around them. To get the most remarkable results, don’t cover the region that will be welded.

2. Joining the Pieces of Plastic

Before using the welding gun, warm it up for at least 2-3 minutes: Different plastics melt at different temperatures. As a result, your welding temperatures should be matched to the materials you’ll be welding. Temperatures between 2000°C and 3000°C (3920°F and 5720°F) are ideal.

If the plastic is subjected to greater temperatures, it may melt ineffectively. In extreme circumstances, these plastics can completely burn. It’s important to remember that welding plastics like PP requires a welding gun temperature of 3000C or 5720F. PVC should be melted at 275 degrees Fahrenheit (527 degrees Fahrenheit), while PE should be melted at 265 degrees Fahrenheit (509 degrees Fahrenheit).

Tack-weld the loose plastic ends together: Melt the loose plastic ends to keep them together. This can be done by applying heat with a tack-welding nozzle on a welding gun. As soon as the plastic begins to melt, join the pieces together. During the welding process, this step prevents the plastic from sliding about unnecessarily.

Using pliers, snip the welding rods’ ends: Holding the pliers diagonally against the rod. If you don’t have pliers, a trimming knife will suffice. Trimming the end of a rod increases the chances of a smooth and stable weld.

When you start welding, it also prevents a vast plastic bubble from forming. Allow the welding gun to cool down before replacing nozzles or inserting a new welding rod. Make sure the gun is heated to the right temperature before you start welding again.

Insert a welding rod into the welding gun’s speed nozzle: The nozzle’s purpose is to keep the rod from moving about while welding. You’ll need to get a nozzle for your handgun as soon as possible if it doesn’t already have one. After attaching the nozzle to the plastic welding gun, insert the rod into the other opening at the top. The cut end should be placed first, as it will be the side used when welding begins.

Contacting the attached nozzle while it is still hot can result in severe burns. Feed the rod through the other aperture with the speed nozzle during welding. You can also use pendulum welding to melt the rod if the welding is in a tight space. Pendulum welding takes longer than welding with a speed nozzle. Therefore welders should be aware of this.

Gradually glide the speed gun over the plastic: Beginning at the top of the crack or where the two pieces of plastic should be joined. Hold the gun at a 45-degree angle while connecting the nozzle’s edge to the plastic to complete the welding procedure.

Heat the plastic until it melts while pressing the welding flame along the junction. With your other free hand, slowly insert the rod into the joint. In this case, the plastic will melt rather than burn. If you notice a color shift, try increasing the torch’s speed.

During pendulum welding, swing the welding gun back and forth: At a distance of about 2.5cm above the joint or fracture, tilt the gun at a 45-degree angle while positioning the welding rod from the opposite side at a 45-degree angle. Carry on like this until the welding is finished.

Instead of a plastic heating gun, you can use a simple propane torch. The propane torch comes in handy for joints that a speed nozzle can’t reach. Make sure you’re controlling both the torch and the welding gun simultaneously to obtain the best results. To help the plastic melt more slowly, keep swinging the torch at a fast pace.

3. Putting the Finishing Touches on the Weld

Allow at least 5 minutes for the plastic to cool before continuing to work with it: Before dealing with the plastic, allow it to cool to room temperature. The advantage of welded plastics is that they cool quickly. Passing the fused plastic close to your body is the simplest way to see if it has cooled to the right temperature. When there is no heat, it is ready for you to continue working on it.

Before the Weld cools completely, double-check that it is in good shape. If the welded plastic isn’t smooth enough, use more welding rods. Place your Weld in a safe place, preferably on a heat-resistant surface, until it cools fully.

Sand the welded joint: For consistency, use 12-grit sandpaper to smooth down the rough ridges. After sanding, the plastic and joint will be leveled. It also prevents scratches on the surrounding plastic. A rotary tool coupled to a sanding wheel can help welders speed up the sanding process. Make sure you sand carefully because plastics are sensitive and easily scratched.

Finish the plastic with 180/320 grit sandpaper: Grain sandpaper can smooth off the Weld. High-quality grits are produced using sandpapers with grits of 180 and 320. Even though such grit sandpapers are lightly abrasive, welders must use extra caution since they can still scratch the plastic.

Sanding with 180/320 grit sandpapers should be done the same way that sanding with 120 grit sandpaper. Rub the Weld until it is silky smooth and uniform in appearance. Start with lower grit sandpaper and work your way up to higher and finer grits as you sand the combined plastics. The higher grit sandpaper can be saved for the final phase. It’s worth mentioning that sandpaper with a lower grit is often rougher than sandpaper with a higher grain.

5 Techniques of How to Weld plastic

There are several solutions available if you’re looking to figure out how to weld plastic. These methods are distinguished by their heating procedures, and internal and external heating are the two types of heating.

The following are the most common ways for welding plastics:

Ultrasonic Welding: This method includes re-forming or joining thermoplastics using heat generated by high-frequency acoustic vibrations. The process is completed when high-frequency electrical energy is converted into high-frequency mechanical motion. When paired with other external elements, automatic movement produces frictional heat at the welds’ contact points. The heat forms a molecular bond between the welded components, allowing them to come together.

Radio Frequency Welding: Radio Frequency Welding employs radio waves to connect metals, similar to ultrasonic welding. The approach uses high-frequency electrical energy or radio waves instead of acoustic vibrations. One of the most prevalent methods for connecting plastics is radiofrequency welding, and it takes between 2 and 5 seconds to perform this method.

Hot Air Welding: Hot Air Welding, often known as gas welding, is a welding procedure that involves the use of hot gas. The hot gas is generally generated after the air in the welding gun has been electrically heated.

Laser welding: In laser welding, two portions of the welds are pressed against each other. A laser beam is then passed over the joining line to solidify the plastic and create a permanent bond. This approach has a turnaround time of 3-5 seconds.

Vibration Welding: This technology welds by generating heat through friction. To produce friction, the components to be melted or connected are rubbed together at a certain amplitude and frequency. Continuous vibrations will eventually generate heat. The thermoplastics at the junction melt due to the heat, forcing the pieces to fuse. It takes 1 to 5 seconds for this process to complete.

Advantages to Welding Plastics

• It’s simple to prepare the work surface.
• Plastic welding does not necessitate the use of any consumables.
• Weld plastics are incredibly light.
• Plastic welds can be used to create leak-tight or airtight sealing.

Disadvantages to Welding Plastics

• The importance of material compatibility cannot be overstated.
• A wide range of welding processes needs difficult-to-form junction configurations.
• Welding is more expensive than other readily available options.

Consider These Tips When Purchasing a Plastic Welding Machine

The instruments you employ at work will always identify your profession. If you use a good welding machine as advised, you will get high-quality final items. When looking for one, keep the following points in mind.

Quality

Examine the welding machine to check if it complies with the global welding standards of the DVS (German Welding Society). Robust, structural, and molecular welding are prioritized in the DVS standards.

Guarantee

Your welding equipment should come with a warranty to protect you from early malfunctions, repairs, or even the cost of replacing it.

Support

Examine the customer service system of your supplier. Examine the time between the customer’s induction and the delivery of the machine.

Conclusion

Learning how to weld plastic is a creative process that has become the go-to method for manufacturing almost anything. These items play a significant role in our day-to-day existence. The plastic business has employed millions of people, providing them with a source of income and a way of life.