Autogenous welding
Autogenous welding: the principles
Autogenous welding is the joining of metal or plastic parts of the same kind, or which are compatible with each other, without the need for a hot external material to make the connection between the two by means of a bead or joint.
Autogenous welding involves heating the lips or edges of the materials to be joined up to the melting point, to obtain a weld that is both highly resistant and truly durable. This technique can be used to assemble parts of all sizes and volumes. Depending on the materials and welding techniques used, this welding method can produce assemblies of varying strength.
Autogenous welds are used in many industrial sectors (packaging, plastics, mechanical engineering, automobile manufacturing, etc.). They can be used to assemble thermoplastic or metal parts for the production of objects in both small and large runs, in a wide variety of formats, as well as to meet product prototyping requirements.
What materials can be joined using autogenous welding?
Materials that can be joined by autogenous welding are either metallic or thermoplastic. The choice of technology to be used for these industrial assembly operations varies according to the type of materials to be welded.
Among the metals that can be joined by autogenous welding (without the addition of material), we can distinguish :
- Steel,
- Stainless steel,
- Iron,
- Aluminium,
- Copper,
- Nickel,
- Brass,
- Tungsten,
- Titanium,
- …
Among the plastics that can be joined by filler-free welding are the following thermoplastics:
- EVA (ethylene vinyl acetate),
- PETG (Glycolized polyethylene terephthalate),
- PVC (polyvinyl chloride),
- PA (Polyamide),
- PC (Polycarbonate),
- PETP (thermoplastic polyester),
- PET (polyethylene terephthalate),
- PEEK (polyetheretherketone),
- ABS (Acrylonitrile butadiene styrene),
- PS (polystyrene),
- PMM (polymethyl methacrylate)
- PE (Polyethylene)
- PP (Polypropylene)
- …
These thermoplastics are widely used in industrial sectors such as technical textiles, medical and paramedical equipment, personal protection, advertising objects, leather goods and packaging. Matrelec supports these companies in building up or renewing their fleets of welding machines for their production and assembly lines. It offers a range of high-performance presses and welding rails capable of producing solid autogenous welds that are invisible to the naked eye.
How to make autogenous welds on plastics?
Several techniques can be used to produce thermoplastic assemblies, whether the elements to be welded are flexible, semi-rigid or rigid plastics. However, if the aim is to achieve a self-generating plastic weld, it is essential to modify the state of the material. This is achieved via molecular agitation, which is only possible with two different techniques: high-frequency welding and ultrasonic welding.
High-frequency welding is achieved using an HF welding machine, consisting of :
- a 27.12 MHz high-frequency electric field generator,
- several electrodes to create an electromagnetic field to vibrate the molecules and allow the parts to heat up,
- a pneumatic press for holding parts under pressure,
- a welding bench to hold them in place.
A high-frequency voltage is generated from an electromagnetic field, which heats up the individual parts and causes them to fuse together under pressure. A seam is formed at the junction of the materials, which after cooling becomes invisible to the naked eye and has the same strength as nearby surfaces. This process is highly effective for assembling thermoplastic parts with a high melting point, and for large production requirements, which Matrelec welding presses make possible.
Ultrasonic welding is an autogenous welding technique that is also based on molecular agitation. The main difference with high-frequency welding concerns the way in which the material is heated. The machine generates an electric current with a frequency ranging from 20 to 70 kHz to oscillate a metal part called a sonotrode. It is this oscillation that heats up low-melting plastics and creates a clean weld.
