The Fraunhofer Institute for Laser Technology ILT has developed a laser re-melting method for structuring metallic surfaces and polishing them to a gloss finish without the need for acids or ablation.
During the new process the laser travels over the workpiece melting the surface while the power is modulated to change the melt pool size at defined points. This power modulation causes the melt material to be redistributed creating a new undulating surface that exhibits uniformly low roughness and is left with a polished finish.
With this process resurfacing can be achieved to a structure depth of about 200µm with material processing rates of up to 75mm2/min. It is also possible to have a volume redistribution rate of 15mm³/min with each pass.
The Fraunhofer Institute for Laser Technology ILT has initially developed the process for metallic surfaces of tool inserts. The Institute has said: ‘For the first time, this selective polishing technique can now be applied on an industrial scale for both flat and freeform surfaces.’
Existing processes for surface finishing involve the use of acids for injection moulded parts and laser ablation for metals. Ablation can achieve material removal rates of 1-10 mm3/min for surface structures greater than 10µm deep. According to the Institute this process requires further treatment to remove accumulated melt residue and the laser requires about ten passes to achieve a structure depth of 200µm.