We've written previously about the Advantages of a Screw Extruder for Extrusion Plastic Welding. In a screw-based extruder, the turning screw grinds up the welding rod as it passes through the barrel. Both the mechanical energy of the turning screw and heat introduced along the extrusion barrel plasticize the incoming material. The barrel can be heated either with hot air or with a coil heater.
Screw Extruder with Hot Air Heating (e.g., FUSION)
This initial operation video shows you—in an easy and simple way—how to set up a Leister WELDPLAST extrusion welder. The video also demonstrates how to maintain the machine in a few steps, as well as safe and secure handling of the machine.
This initial operation video shows you—in an easy and simple way—how to set up a Leister FUSION extrusion welder. The video also demonstrates how to maintain the machine in a few steps, as well as safe and secure handling of the machine.
Plastic extrusion welders can generally be divided into two categories: screw-based extruders and non-screw-based extruders.
In both types of extruders plastic material, typically in the form of welding rod, is fed into the unit where it is melted (plasticized) and extruded out the end of the tool.
In a screw-based extruder, the turning screw grinds up the welding rod as it passes through the barrel. Both the mechanical energy of the turning screw and heaters along the barrel of the extruder plasticize the incoming material.
Non-screw based extruders use heaters alone to plasticize the welding material. The welding rod is pushed through the heat zone and out the end of the tool but is not ground up in the process.
Screw based extruders are the most common and have several advantages:
There are three essential parameters for a plastic weld: temperature, pressure, and time.
All thermoplastics have a specific temperature range for effective welding. The plastic manufacturer can often give you an appropriate range of welding temperatures for their material. However it is important to know that the perfect welding temperature for the application can vary depending on environmental conditions such as temperature or sunlight exposure. For example, if you are plastic welding in a colder than normal environment you may need to slightly increase your welding temperature.
For hand welding, the air flow temperature is the only set point to consider. With extrusion welding there are different set points for both the air temperature and the temperature of the extruded plastic
Knowing which type of plastic you're working with is a cornerstone of good plastic welding. By asking you to perform a few simple tests, such as a flame or burn test, the flow chart below will help you determine which type of plastic you have.
Click the image above to make it bigger or download a PDF copy of this chart to keep or print by clicking here.
Have questions? Your Technical Sales Representative is here to help.
Using an extrusion welder to complete your fabrication project but not sure which shoe you need? Use our chart below to identify the type of welding shoe you need:
Need help? Contact your Technical Sales Representative.
Like metal welding, plastic welding requires training and experience to become proficient. If the plastic welding procedure is not exactly right, defects can occur that will comprise the strength of the weld. Some of these defects are easily visible and others require sectioning or testing to tell if the weld is sound. Be careful not to assume a weld is strong based on how the surface looks; perform destructive tests on sample welds before you begin to ensure a good final weld.
In this article we give some of the more common defects that might be seen when welding plastics. To review proper welding technique please see our article: Using an Extrusion Welder.