Plastic Welding: Methods and Ideal Applications

Posted by on November 5th, 2015

In the not so distant past, there were limited choices for welding plastics – i.e. gluing or vibration/ultrasonic welding; and while both have their advantages and ideal applications, they are not up to the task of handling today’s smaller and more sophisticated product designs that use plastics.

It can be confusing to compare typical plastic welding methods and determine which one is best for joining plastics in your product design application. In this post, we’re going to give you a quick Plastic Welding 101 tutorial on the pros and cons of each type of plastic joining process and provide you some guidelines on ideal applications for each.

Laser Plastic Welding

Laser plastic welding gives you flexibility when you need to weld complex, intricate, large and 3D part geometries. Sophisticated online process monitoring features help ensure higher quality control and fewer bad parts to rework. This method is also well suited for sensitive applications because it imparts minimal stress on delicate parts. That’s why laser plastic welding is ideal for welding plastics in sensor housings, tail lights, and manifolds in the automotive industry, various housings for consumer electronics applications, and perfect for joining plastics for microfluidics, catheters, and other medical devices.

Ultrasonic Welding

Ultrasonic welding is the method of choice when you need very short cycle times under 5 seconds and are working with 3D contour joints that do not need to be completely flat. However, the high resonance frequencies of ultrasonic welding will exist through the entire part and could potentially damage components outside of the weld zone. Flash, or excess melted plastic, typically protrudes from the joined plastics. This method also generates dust-like particles that may cause part contamination. Manufacturers typically use ultrasonic welding for joining plastics in mobile phone housings, bumper reinforcements, and intake manifolds.

Hot Plate Welding

Hot plate welding is a very inexpensive process in which you use handheld devices to bond less complex applications. This method is good for welding joints with simple contours rather than intricate designs. Hot plate melting is susceptible to tack – molten plastic sticking to the hot plate – and flash. The automotive and maritime industries use hot plate welding in large profile applications, such as center consoles in automobiles, glove box lids, and fishing buoys.

Friction Welding

Friction welding is also an inexpensive process using low maintenance machinery that experiences minimal downtime and low cycle time. However, designers and manufacturers are limited to welding plastic parts with only two-dimensional contours. Here, also, high mechanical load may damage surrounding parts, and friction welding generates a large amount of flash. This method can be a good choice for large profile two-dimensional applications, such as manifolds, housings, bumper reinforcements, and pipes.

High Frequency Welding

High frequency welding has the advantages of a low thermal load, a touchless process that doesn’t mar or damage surrounding parts, and minimal flash. Equipment is expensive, though, and high frequency welding machines can join only polar polymers, PVC, and PA. Users must follow strict regulations to protect against the electromagnetic radiation produced by this process. Yet high frequency welding remains a viable option for any continuous welding applications, including housings for electronics and other consumer products.

LPKF’s take: Laser Plastic Welding is for innovative designs and demanding applications

It’s good to have choices to meet your specific plastic welding requirements, but in our opinion, laser plastic welding leads the way – especially for complex applications that no other plastic joining method can accommodate. LPKF’s recent advances in transparent laser plastic welding has revolutionized the fluidics and medical device industries in particular, both of which benefit from the laser’s superior ability to join two clear plastic components. Our clear-to-clear welding technology – LPKF ClearJoining – has brought fast relief to the headache of joining clear plastic pieces, which previously required a laser-absorbing additive for any manufacturer that requires plastic clarity. The bottom line: when you need to join plastic parts for innovative devices that need extreme precision, tight weld seams, clean joints, and sterile parts, choose laser plastic welding.

How could laser plastic welding make your job easier – and your designs more innovative? Visit to learn more about our laser plastic welding solutions.To learn more about the advantages of laser plastic welding, read our blog post The Future of Laser Plastic Welding is Transparent. (It’s time to leave the adhesives behind) and watch our webinar on the general how-to’s.