LASEX
Laser Armoured Screws for Extrusion


To date, state-of-the-art technology for armouring extruder screws has involved welding processes such as TIG (Tungsten Inert Gas) or PTA (Plasma Transfer Arc) in which the welding material is applied in powder form. A closely-associated process is laser CMB (Controlled Metal Buildup). This process uses a laser beam to melt the weld material instead of using an electric arc or plasma.

Working closely together with a research institute, 3S GmbH has now developed a laser CMB process for extruder screws. This process can be used to armour screws between 1 and 6 metres long and 50 to 500 mm in diameter.

Thanks to its unique technology, the LASEX process opens up a wide spectrum of materials that can be mated, which could not be realised using conventional welding processes.

This is because the laser creates a much smaller weld pool than  other processes so that fusion with the base material is more focused. This enables a higher level of hardness to be achieved.
Using a weld material with a Rockwell hardness of 55 HRC, the PTA process achieves a hardness of 50 HRC in the armour when a single layer is applied, for example. LASEX achieves a hardness of up to 57 HRC using the same materials. As a result, the LASEX process leads to an extended service life of armoured screws.

An additional LASEX advantage is that there is a lower tendency for cracks to form.  This is significant when changing colours, for example, because different coloured residues can become trapped in cracks causing discoloration of the new melt over a longer period, leading to the formation of streaks in the extruded material.