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Joining 3D printed parts

Joining 3D printed parts


In the previous articles we covered many scenarios where 3D printing can successfully produce parts with increasingly complex requirements. All these parts, however, were relatively small (max 300 mm for the longest side) due to the restricted size of most 3D printers. The time has come to (literally) start thinking out of the box. Using the so-called “plastic welding gun” we can join multiple small parts into a bigger one and create plastic objects that are impossible to print at once. Although there are conditions and restrictions to this method, it can surely expand the possibilities of a 3D printer.


How it works


The welding gun is a rather simple, yet ingenious tool. It uses electric current to heat up specially shaped metal wire bits. Once they are hot enough, they are pressed into the plastic which melts around the wire and holds it in place. Usually the wire bit melts both of two plastic parts, positioned next to each other and hence creates a strong metal link between them. A single wire bit may be insufficient to support the required shape so many bits are used, creating a metal seam along the two original parts. Despite the bits small size, a seam created that way is surprisingly strong – the wire bits are securely incorporated into the plastic and the wire itself (about 1 mm diameter) is impossible to tear with bare hands. There are wires with different shapes and sizes – depending on the application, geometry and load requirements can be used wider or narrower bits, almost straight or with a right angle profile.



Despite heating the wire bits up to several hundred degrees Celsius, the tool is quite safe. It uses the wire resistance to generate the heat and the actual gun itself remains cool.




As systems of all kinds become more complex, one of the best coping strategies is the modular design. Smaller components and subsystems are easier to manage, maintain, produce and replace when damaged. That approach can be implemented in the 3D printing tasks as well – multiple subsections of a large part can be printed separately and then joined with the welding gun. Having multiple printers at hand means that many of the modules can be printed at once, which effectively reduces the total manufacturing time.

A suitable object for the method, described in the article, are all kinds of machine enclosures. As modern workshops develop more and more multi axis machines and robot arms, complex geometry enclosures will be seen more often. With the ability to join multiple parts in one final object, even a small 3D printer can be used to create plastic covers for a 2 meter tall robot.

Another important note – when using the welding gun, one can join parts from different plastics. As the wire bits melt the two parts simultaneously but independently, as long as the plastic’s melting temperature can be matched by the gun, a secure joint can be made. That is clearly an advantage over other joining methods such as glueing or actual welding.



We hope this article was helpful and will let you reach new heights in your 3D printing journey. 

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