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Like metals, you can fuse plastics to become a single homogenous workpiece. Since welding refers to melting two pieces of material and pressing or pounding them together to become a single piece, we refer to it as plastic welding. We call a device for fusing plastics a plastic welder.
To help you better understand how to weld plastic together, we will be discussing some principles behind plastic welding and the fundamentals concerning the use of plastic welders. We will also go over the basic steps on how to use a plastic welder.
Plastics have a much lower melting point than metals. As such, they require simpler tools that use lighter loads of electricity and produce more manageable hazards.
- What Is a Thermoplastic?
- Stages of Plastic Welding
- What Is a Plastic Welder?
- How To Use a Plastic Welder for Speed Welding
What Is a Thermoplastic?
A thermoplastic is a substance that can take any form because it becomes plastic upon heating. It hardens as it cools down, and it can repeat the formation or begin a deformation process upon repetitive heating.
One thing to consider when working with or welding thermoplastics is that you should only try to weld similar materials. Because of the developments in the plastic industry, there are so many types of thermoplastics.
Here’s a list of the most common weldable variations:
- High-Density Polyethylene (HDPE)
- Polypropylene (PP)
- Chlorinated Polyvinyl Chloride (CPVC)
- Polyvinyl Chloride (PVC)
- Polyvinylidene Difluoride (PVDF)
- Acrylonitrile Butadiene Styrene (ABS)
Stages of Plastic Welding
There are at least three primary stages involved in plastic welding. They include surface preparation, heat generation and application, and pressure application and cooling. Before we discuss the proper use of a plastic welder, let’s go over the primary stages one by one.
The first stage of any type of welding task, including plastic welding, is surface preparation. With proper surface preparation, you can achieve high-quality welds. On the other hand, if you prepare a plastic workpiece poorly before welding, expect poor results.
Heat Generation and Application
As soon as you finish cleaning your plastic workpiece, you can start the second stage of generating and applying heat. It is essential to know the correct heating temperature to avoid overdoing the melting process. The trick to determining the appropriate heat level is finding out the type of thermoplastic.
Pressure Application and Cooling
Finally, the third stage requires applying pressure over the welded area and letting it cool down until it hardens. As soon as the weld pool solidifies, the welding process is complete. Anything you do after the weld bead sets is purely aesthetic and can sometimes be damaging to the durability of the weld.
What Is a Plastic Welder?
A plastic welder is any electrical or mechanical device used to fuse two or more pieces of similar plastic material or to repair cracks or dents in a plastic workpiece. There are at least 14 welding techniques using different types of plastic welders, including:
Hot Air Welder
As its name suggests, a hot air welder uses hot gas or air to melt plastics and fuse them into a single piece. If a consumable filler is involved, you will have to feed it manually into the weld pool.
Speed Tip Welder
In a speed tip welder, a tip feeds a melting filler into the gap between two plastic pieces. A speed tip welder can have replaceable tips for functions other than pushing the welding rod.
Other Plastic Welders
The following welding devices are either more complicated to use or more expensive than the previously listed techniques. Additionally, they deliver industrial-grade welding outputs for much larger workpieces.
- Extrusion Welder
- Contact Welder
- Hot-Plate Welder
- Infrared Welder
- High-Frequency Welder
- Induction Welder
- Induction Welder
- Ultrasonic Welder
- Friction Welder
- Spin Welder
- Laser Welder
- Solvent Welder
Among the different styles of plastic welders, the speed tip welder is the most straightforward option. However, others also consider the welding rod variation of hot air welding similar to stick welding for metals and an easy enough technique. In the following section, we will be discussing the basic procedures of using a speed tip welder.
How To Use a Plastic Welder for Speed Welding
In speed welding, the plastic welder has a very similar appearance to a soldering iron used by electricians and microchip technicians. It also uses a very similar amount of electricity and wattage, and it fits a person’s hand like a marker.
Whether you need to fuse two plastic pieces or repair a crack in a single piece, speed welding is the most economical solution. It does not require heavy tools and large workspaces, and it does not produce too much waste.
Use the following procedures when working with a speed tip welder:
Setup and Cleaning
The first major procedure for using a speed tip welder is as basic as the first stage of plastic welding. Similar to any fabrication project, preparation is very important.
Consider each of the following steps when setting up a plastic welding task and prepping the materials for the project:
Step 1: Prepare a well-lit and sufficiently ventilated workspace.
Like in all welding tasks, choose a workspace with enough lighting and ventilation. Creating a workable surface involves producing dust and fumes that can adhere to the plastic welding area and reduce your weld quality output. A well-lit and well-ventilated work area ensures that you can get rid of all unwanted debris.
Step 2: Wear protective gear.
Aside from preparing a suitable workspace, do not forget to wear protective gear. It should include a dust mask, goggles, heat-resistant gloves, and long-sleeved clothing.
Step 3: Prepare all surfaces.
Again, before working on any surface, ensure that it is clean and devoid of all debris that can diminish weld quality. Remove paint, too, as it can mix with the weld bead and lower the overall quality of your weld.
Step 4: Secure the workpiece.
It is always easier to work on a project if you secure the workpiece using clamps, especially when fusing two separate pieces. If your materials are properly in place, you won’t have to worry about unsuccessfully hitting your mark.
Step 5: Identify your plastic or do a welding test to know the correct welding rod.
More often than not, thermoplastics will have an identification code printed or engraved onto an inconspicuous part of the product. Refer to our definition of thermoplastics and the list of the most common weldable plastics. For example, if a workpiece is a polypropylene, you will find the label “PP” somewhere.
If you can’t find an identifier anywhere and you can’t be sure what type of plastic you have, you will need a plastic welding rod testing kit. It has all the types of plastic welding rods.
Pick a rod resembling your workpiece, heat the end, and attach it to a clean spot on your plastic. Remember that only similar plastics can stay fused after welding.
Try pulling the attached rod with a pair of pliers. If it is quite difficult to detach, then it is most probably the same material.
Joining the Pieces
Fusing separate plastic pieces involves stages two and three of the plastic welding process. Both account for the second major procedure subdivision, which is enough to complete the whole plastic welding process.
Step 6: Preheat the plastic welder to the correct temperature.
Different plastics have different melting points and heat requirements for welding. Additionally, each welding technique uses a unique temperature for each type of plastic. Your speed tip welder could have a dial that changes its heating temperatures.
Step 7: Tack-weld the ends you need to fuse.
If your speed tip welder comes with a tack nozzle, be sure it is the one attached to your device before you start preheating. Then, as soon as the welder heats to the right temperature, fuse the plastic pieces by melting the ends together.
Step 8: Replace the tack nozzle with a speed nozzle and prepare your welding rod.
After securing the pieces through tack welding, replace your tack nozzle with a speed nozzle and prepare your welding rod. Using a pair of cutting pliers, trim the end of your welding rod to a diagonal before inserting it into the speed nozzle. Doing this will make filler application a lot easier.
Step 9: Decide whether to use a speed or pendulum weld.
A speed weld is where you drag the welder and the welding rod using a constant pace over the crack or area you want to join. On the other hand, a pendulum weld is useful with a tack nozzle if you don’t have a speed nozzle.
Step 10: Fix the weld as necessary.
The best time to fix a weld is while it is still a hot weld pool. Use the tip of your welder to reposition your melted filler before it hardens and cools.
Step 11: Let the weld cool and harden.
Post-Weld Finishing and Cleanup
After creating a successful weld or all of the required welds, you might think about restoring the workpiece to its former glory. The following steps will tell you how to go about completing the task with aesthetically pleasing results.
Step 13: Unplug your plastic welder and set it aside.
For safety, turn your welder off when not in use. If you are satisfied with your welds, unplug your device and set it aside to cool completely before storage.
Step 14: Sand the welded joint with semi-fine grit sandpaper.
After all the necessary welding is done, and the workpiece has entirely cooled, you can work your plastic surface with sandpaper to remove all hardened bumps. Smooth out rough parts by sanding with light pressure to make the entire workpiece consistent. A 120-grit sandpaper should do the trick.
Step 15: Use finer grit sandpaper to finish the thermoplastic surface as needed.
As you level the surface, shift to sanding with finer grit sandpaper to make the output look even neater. The higher the grit number of the sandpaper, the finer the results will be.
Learning how to use a plastic welder, particularly a speed tip welder, is like using a simplified version of a MIG welder. It involves feeding a filler material to a heating tip that fuses pieces of similar thermoplastics until it becomes a single homogenous piece.
The process uses varying amounts of electricity depending on the melting point of the plastic workpiece. However, plastic welders are entirely different devices than metal welders. They use other filling materials and use much lower amounts of electricity.
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