Welding Plastic: Methods, Materials, and Important Aspects
We work with plastic daily and know welding is an important part of many manufacturing processes. But which methods work best, and which materials are suitable for welding? Here, we'll go through the most common methods for welding plastic, and discuss material properties and common problems that can arise.
Methods for Welding Plastic
There are different methods for welding plastic, but the most common are hot gas welding, extrusion welding, and friction welding. Hot gas welding uses a gas flame to heat the plastic to its melting point, after which it's shaped and joined. Extrusion welding uses an extruder to melt and shape the plastic, while friction welding uses pressure and friction to melt and join the plastic.
We have experience working with these methods and find that hot gas welding is one of the most flexible. But which materials can be welded with this method?
Materials Suitable for Welding
Some of the materials that are best suited for welding are HDPE, UHMWPE, PP, and PVC. These materials have a relatively low melting point and are therefore easier to weld. PVDF is another material that can be welded, but it requires a higher temperature and careful control of the process.
But what happens if we try to weld materials such as POM-C or PTFE? These materials are difficult to weld due to their high melting point and low ability to bond to each other. PTFE can't actually be welded at all, due to its extremely low coefficient of friction and high melting point.
Why are some materials so difficult to weld? There are things that can be done to improve weldability, such as using a different welding method or adding a weld-improving component to the material.
Preparation of Joints
An important part of welding is the preparation of the joints. It's important that they are clean and dry, and that they have the right shape and size to be joined. We often use a joint milling machine to cut the joints, and then we clean them with a brush and cleaning fluid.
If the joints aren't properly prepared, it can lead to poor welding and the joints won't last over time. It can also lead to damage to the material, or the welding won't be strong enough.
Testing of Welds
When the welding is complete, it's important to test it to see if it's good. We often use a combination of visual and mechanical tests to check the quality of the welding. We look at the appearance of the welding and check if it's straight and even. We also test the strength of the welding by subjecting it to load and seeing if it holds.
If the welding isn't good, it may need to be redone or repaired. In some cases, it may be necessary to replace the entire material.
Common Errors That Can Occur
There are several common errors that can occur during welding. A common error is that the welding gets too hot, which can lead to damage to the material or the welding not being strong enough. Another common error is that the welding gets too cold, which can lead to the welding not being strong enough.
We've also seen that welding can become porous, which can lead to it not being strong enough. This may be because the material doesn't have the right properties, or the welding process hasn't been managed properly.
When Welding Is Better Than Bonding
Sometimes welding is preferable to bonding. Welding is often better when the material is thick, or when the welding needs to be very strong. Bonding may be better when the material is thin, or when the adhesive is stronger than the weld.
If we can't decide whether to weld or bond, it may be helpful to try both methods and see which works best.
Welding plastic is a complex process that requires accuracy and experience. With the right material, the right method, and the right preparation, welding can be very good. Do you have questions or concerns about welding plastic? Please contact us!
Want to discuss your needs for welded plastic components?
Welding Plastic: Methods, Materials, and Important Aspects