When it comes to plastics, the process is similar, and takes part in three stages. Firstly, the surfaces are prepared before heat and pressure is applied and, finally, the materials are allowed to cool to create fusion. Joining methods for plastics can be separated into external or internal heating methods, depending on the exact process used. There's also another, more inexpensive way of welding plastics together known as solvent welding. This refers to a process in which a solvent or solvent blend with no dissolved polymer is used to create a joint between two thermoplastic parts. This no-heat process uses pressure to form a chemical bond between pieces of plastic, though the welded joint is often weaker than the individual parent materials.
In wood welding, the process differs quite significantly. Unlike metal and plastic welding which uses a heated filler to create a joint, wood welding uses heat generated from friction to join the materials. The materials to be joined are subjected to a great deal of pressure before a linear friction movement creates heat to bond the workpieces together. This is a fast process which allows wood to be joined without adhesives or nails in a matter of seconds.
Welded joints come in a number of different flavours, depending on their final use and application. In a butt joint, the connection between the ends or edges of two parts makes an angle of 135-180° inclusive in the region of the joint. T-joints, as their name suggest, form an almost perpendicular joint. Corner joints occur at 90 degrees to each other, mimicking the corner of a box. In a lap joint, the connection between two overlapping parts makes an angle to one another of 0-5, while cruciform joints form a kind of cross-like shape with two flat plates being welded to another flat plate at right angles to each other. Welds can also be divided according to the placement of the filler material, the area filled, and the technique used. These cover the full gamut of welding types including full penetration welds, partial penetration welds, single side welds, double side welds, single run welds, and multi-run welds.