Surface processing by laser ablation

Laser ablation is the process of removing material from surface by irradiating it with a laser beam. 4JET has industrialized the advantages of touchless precision cleaning in a variety of different industrial applications. Particularly pulsed lasers are used for these processes.

Examples for laser ablation

Laser Paint Stripping
Bauteil nach KTL-Entlackung

Component after cathodic dip paint removal
Bauteil nach KTL-Entlackung

Rotating optics enable cathodic dip paint removal
of the internal surfaces of cylinders with small
diameters

To provide components with high-quality corrosion protection, they are coated in cathodic dip paint. In certain areas, such as the bearing seat of wheel hubs, it is not possible to apply a cathodic dip paint on the component. Usually, the components were masked accordingly prior to painting. However, this is very time consuming and there is no guarantee that the cathodic dip paint will not seep under the mask. This is where the benefits of using laser to remove cathodic dip paint are apparent. The component is first coated fully with paint. A pulsed solid state laser then selectively removes the cathodic dip paint layer in the respective areas, leaving them exposed. The layers below the cathodic dip paint, such as zinc phosphate, are not affected.

Laser Coating Removal

Residue free laser coating removal of a PA tube

Initially galvanic coated tubes for clutch and brake systems are coated completely with a PA or PVF layer. After cutting to length the plastic layer has to be removed from both endings of each tube. Mechanical ablation causes damage to galvanic coating or plastic residues remain on the tube which may cause contaminations in the hydraulic system. Whereas lasers operate touchless and remove the thin PA or PVF layer completely down to the galvanic coated tube without causing any damage.

The principle of laser ablation

The pulsed and focused light meets with energy densities of several J/cm² and peak powers in the MW range on the surface that is to be processed. The instantaneous application means that the energy cannot dissipate, and it virtually blasts off the coating in a small area. The area of impact corresponds with the size of the laser beam spot on the surface. The penetration depth depends upon the application with just a few µm per pulse. By repeating this process several tenthousand l times per second, the surface can be gradually cleaned pulse by pulse. Using optical scanning systems, the laser beam spots are placed side by side in order to process a larger continuous area.

Organic surface layers and metals can be removed. Due to the comparably poor absorption of short-wave light in organic surface layers, the removal sometimes does not happen by layer-wise ablation “from top to bottom”, but by absorption of the laser radiation into the substrate and therefore underneath the layer that is to be removed.

The matter that is blasted off – generally fine dust and gas – is suctioned off locally and piped to a filter. During the short duration of the pulses, the substrate – such as an aluminum vulcanization mold – absorbs virtually no laser light. As a result there is no thermal effect upon the substrate. Organic materials in particular are therefore easy to remove from surfaces. Furthermore, mineral layers such as oxides and ceramics can also be processed.

Essential benefits of laser ablation

  • Dry process with no need for solvents or abrasive materials
  • No consumable materials to be disposed of
  • High process reliability and repeatability
  • Compact footprint
  • Selectivity of the process – the processing areas can be precisely defined unlike wet processes, and can be reduced to the areas that are to be cleaned
  • No mechanical or chemical impact upon the substrate

Depending on the application and requirements we develop customized laser ablation machines. Besides the customer-tailored, core laser process, we deliver total solutions including handling solutions, ancillary processes and quality control.