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Plastic welding seems counterintuitive. Typical welding by using metals uses high heat and electricity to fuse pieces of metal together. When it comes to plastic, it seems like the plastics would melt before they are able to join. Fortunately, that is not the case in this very little known field. So what exactly is plastic welding?
Plastic welding is a technique used for semi-finished plastic materials that uses heat to weld the softened surfaces of materials for various purposes by using multiple techniques such as the following:
- Laser welding
- Spin welding
- Infrared welding
- Hot plate welding
- Vibration welding
- Ultrasonic welding
Not all plastic is made the same; therefore, different techniques must be used to keep softer plastics from becoming damaged. Contrariwise, higher heat is used for plastics that have a more solidified makeup and need hotter temperatures to be softened for fusion. Various different products and materials use plastic welding in order to simply join two pieces of plastic together. All of the techniques above, though different, generate heat to melt the plastic and fuse pieces together.
Common Plastic Welding Techniques And How They Are Used
Plastic welding has tons of purposes. Between all the various techniques for performing the trade, there is a multitude of different uses. We will go over each type of plastic welding and give an overview as to what each is used for.
Laser Welding Plastics
Laser welding is most prominent in the automotive industry. By using lasers to generate the proper heat, a welder can meticulously weld two pieces of plastic together to form the right parts for an automobile. Laser welding of plastic is also an important aspect of the medical product and tool world. The benefit of lasers is how precise the technique can be, giving the welder a unique ability to weld intricate plastic pieces. Other types of plastic welding don’t give the welder as much of an edge to be meticulous. Also, laser welding is an important part of the electronic packaging industry as well.
Spin Welding Plastics?
Spin welding is another form of plastic welding used in the automotive industry. By spinning plastic pieces to generate heat through friction, two pieces of plastic can be fused together. The fast spinning of plastic pieces will immediately generate heat once contact is made. Some of the car parts that this technique is used for are fuel filters, check valves, truck lights, aerosol cylinders and tank floats.
Infrared Welding Plastics
Fabricating complex parts at high speeds with low costs is the name of the game in infrared welding (IR welding). Although this technique is solid when it comes to efficiency, the application isn’t necessarily as widespread as other techniques. The most common items that IR welding is used in are CO detector filters, medical IV-bags, high-speed cut & seal film, brake fluid reservoirs for vehicles, and PE pipes used in natural gas transmission.
Plastic Hot Plate Welding
Also known as fusion welding, hot plate welding is a technique used to fuse pieces that are a few centimeters in length up to 1.6 meters. Again, this is an application that is used within the automotive industry for tail light housings, certain fuel tanks, cases & lids of car batteries, carburetor floats, washer fluid reservoirs, and coolant reservoirs. This process is also used outside of the world of cars to fuse plastic piping together as well.
How Does Vibration Welding Plastics Work?
One of the quicker techniques used in welding plastic is through vibration welding. By vigorously vibrating pieces of plastic, the proper heat is generated to weld plastic pieces together. This technique is useful for small applications, along with larger ones. Some of the items that use vibration welding are instrument panels, intake manifolds, glove boxes, armrests, taillamps, power tools, surgical instruments, filters, and home appliances.
Here’s a demonstration of vibration welding plastics.
What Is Plastic Ultrasonic Welding?
This technique can sometimes be confused with vibration welding, but rest assured that ultrasonic welding is actually different. Vibration welding is performed by rubbing the pieces together to generate heat, whereas ultrasonic welding is performed by vigorously jackhammering one piece into the other. Although this sounds counterintuitive, the vibration is so fast it will generate the right heat. This application is used in smaller products such as electronics housing, packaging, brackets for parts such as intake manifolds and automotive acoustic padding.
What do the different plastic welding techniques look like?
How Does a Plastic Welder Work?
Through the various types of plastic welding that can be performed, each welder will work differently to generate the correct level of heat to perform the job. Some applications will not work for others and vice versa. Bigger items can require certain applications, and smaller, more intricate items will require a different technique. Let’s cover some of the ways plastic welders work.
Laser Welding
The “trench” of a laser weld is never going to end up any deeper than 2mm. The precise laser beam generates heat and uses a programmed machine to make the exact weld to form two pieces together. The melts that are created using the laser are formed together to create the proper seal, thus creating a great plastic weld.
Spin Welding
Spin welding is a technique that’s specific to circular joints. The reason being that the pieces generate heat by slowly being formed together while they are spinning quickly. Once the pieces make contact, the friction immediately begins generating heat, and the plastic melts just enough to form the two pieces together. Once the joint is set, the piece is left to cool so the joint can solidify.
Here’s a spin welding video tutorial that shows how to do it and what it looks like.
Infrared Welding
Infrared welding is similar to laser welding in the sense that heat is generated without contact. Although an IR beam isn’t visible, its presence generates heat within the plastic to soften it before welding. This technique is also one that (like all forms of welding) requires special care as IR beams are a form of radiation, which can be dangerous.
Hot Plate Welding
Hot plate welding immediately gives the impression of manufacturing in high numbers. Essentially this technique involves cutting a plate to the exact shape of the pieces you’re welding. So, once cut, a welder can continuously weld a multitude of the same pieces. Once the plates are heated, the plastic pieces are then also heated and immediately fused together to be left to cool.
Vibration Welding
As mentioned, vibration welding uses a technique that rubs the plastic pieces together so fast that they generate enough heat to melt. Once formed together with a solid joint, the pieces get cooled and are ready to go. The rubbing that is used in this form of plastic welding moves the pieces from side to side to generate heat. This is an important distinction that helps differentiate vibration welding from ultrasonic.
Ultrasonic Welding
The pieces used in ultrasonic welding are held together under pressure while creating friction (unlike friction welding, mind you) through a motion similar to that of a jackhammer. By rigorously ramming two plastic pieces together, heat will be generated to melt the plastic together. It takes a high rate of vibrations and friction to generate the heat, but the pieces held under pressure will fuse together to create the proper joint.
What Types of Plastic Can be Welded?
There is a handful of different plastics that can be welded together using the above techniques. Each type of plastic has specific applications that it’s used for, but the following types all have the ability to be welded together.
Polypropylene
Again, the automotive industry plays a part in the world of plastics. Polypropylene plastic is used in many automotive applications. It can also be used to manufacture Tupperware, living hinges, textiles, plastic dishes, and more.
This type of plastic was created in 1951 by a pair of Phillips petroleum scientists named Paul Hogan and Robert Banks. By 1957 it had become so well-known in its popularity that it began being used in many different products. It’s still used consistently to this day and has been a reliable plastic ever since it was created.
High-Density Polyethylene
Being a plastic that is commonly recycled to be used again in other products, high-density polyethylene (HDPE) has been a great application for products made from plastic. It’s been used in plastic bottles, corrosion-resistant piping, geomembranes, and plastic lumber, to name a few. The most attractive characteristic of HDPE is that it’s lightweight, but it is also durable. With an impact-resistant quality, a product made from HDPE can be dropped on the ground without worry.
HDPE is also long-lasting, and weather-resistant hence uses such as plastic lumber. It resists mold, corrosion, insects, and it doesn’t rot. So, HDPE is the perfect material for underground piping. It will resist the elements while helping to transfer fluids from one location to another. And it makes for the perfect plastic to be used in welding because of its malleable nature.
Polyvinyl Chloride
Polyvinyl chloride (PVC) is the third most used synthetic plastic polymer, and for good reason. It’s been used in various different products for years, the most notable being PVC piping. Having replaced metals that can corrode over time, any home will have PVC piping as part of the system that helps to transfer liquids and waste. Any building for that matter will utilize PVC in its construction.
But the uses don’t stop there. PVC has also been used in plastic toys for years. It’s also been utilized in manufacturing plastic packaging for various products. It can also be seen being used in other building materials such as doors and windows. Don’t forget vinyl siding either. Although it’s easier to name the material “vinyl”, the siding is actually going to be made from PVC materials.
Chlorinated Polyvinyl Chloride
Although chlorinated polyvinyl chloride (CPVC) sounds like the same thing as PVC, it does have one important difference that distinguishes the two. CPVC has a higher chlorine content than PVC. This addition gives the plastic a greater ability to be malleable for the user. It is also important to mention that the temperatures the two plastics can withstand are different. CPVC has a higher heat withstanding ability at 200° F, whereas PVC tops out at 140° F.
The higher strength of CPVC makes it a great candidate for hot and cold liquid transfer. Building codes come into play in regard to PVC and CPVC applications. When it comes to transferring hot liquids, most building codes will not allow PVC because it can’t handle the heat. But they will, however, allow for CPVC to be used because it can withstand the high heat with no problem.
Acrylonitrile Butadiene Styrene
Acrylonitrile butadiene styrene (ABS) is a plastic that is most notably used in the manufacturing of Legos. ABS is solid; it is a durable plastic that can be used in various applications that require a plastic that needs to remain intact. ABS also has a low production cost, so manufacturing it is cheaper than other plastics and can be produced in high numbers. The manufacturing efficiency is also an attractive quality for ABS.
The method used in ABS is called injection molding. The liquid plastic is injected into whatever mold is needed to create the product and then cooled, so it solidifies. Its ease of manufacturing makes ABS a common choice when creating products that require plastic.
Lexan
Although Lexan isn’t typically welded together, occasionally, there will be a product or application that uses welded pieces. Kitchenware, bulletproof glass, kitchenware, and DVD’s are some of the products manufactured from Lexan. Therefore it’s not always going to need welding. In fact, when Lexan does need to be welded, solvents are used to perform the task. Special chemical compounds were created to be applied to Lexan, which then melts the plastic so it can be formed together when need be.
Is Plastic Welding Strong?
The simple answer to this question is yes; it is. But that’s because plastic welds have to be strong. Without a strong bond, pieces would fall apart and can have disastrous effects, especially when plastic piping is used in the transfer of hot liquids or chemical liquids that can be hazardous. Those welds have to be 100% reliable, or somebody will be losing their job. Without the proper plastic weld, there is not point in fusing two pieces together.
Now, some of the plastic applications that we’ve covered aren’t always going to be the strongest. For instance, if a plastic bottle or milk jug is manufactured using high-density polyethylene, the plastic isn’t going to be that durable. But that’s how those products are created by using just enough plastic to keep down waste levels while also creating a container that’s going to reliably hold liquid. But if you create Legos using ABS plastic, those pieces are going to be manufactured as solid, durable products.
When it comes to the welds themselves, they will need to be reliable. And that boils down to the proper, specific technique used to create plastic welded products. When techniques are executed properly, the welds that are created will be so reliable they will never come undone. This relates to the type of plastic, the technique, and how important it is for the joints to stay intact. Some products aren’t as important to have a durable weld, but items in the automotive and home material industries will always create durable welds that are going to last.
In fact, some plastic welding techniques can be used in repairs, especially when it comes to the automotive world. I know, we have covered a lot of plastic welding applications involving cars. But that’s the deal, cars and trucks use this trade a ton. The parts themselves are manufactured through plastic welding, repairs to the vehicle itself can also utilize plastic welding by hand. If done properly, it can be an excellent tactic for performing repairs involving plastic parts.
Last thought on welding plastics
With the various ways that we use manufacturing as a whole (and continuously evolve the world of production), there are always going to be new ways to perform tasks to increase efficiency. It keeps costs down and thus creates a better profit. And though plastic welding isn’t completely new to the world of product creation, it does have a prominent place among many different products that use it. Proper use of the trade can be used in tons of different ways that promote safety, reliable products, and save money.
Plastic is a cheap material, that is why it’s so popular. So, the propensity to find ways to fuse pieces together through welding techniques to make cost-effective products that are going to last is a no-brainer. And we believe it is within the realm of possibility to also be enlightened to the many ways that plastic is used and exactly how it’s welded together. Hopefully, we’ve been able to teach you a thing or two on the subject and enlighten our readers, because plastic welding can sound counterintuitive. Melting plastic to fuse it together? But it is a reliable craft that has been used for years and is still relied upon to this day.
