Inner diameter coating system COAXid

COAXid – Direction-independent powder feed for complex inner surfaces

The inner coating head COAXid is based on the coaxial principle of powder feed. Apart from simple rotation-symmetrical internal coatings, the principle, especially, enables the local, generative build-up of 3-D structures on inner surfaces. The head is modularly constructed and can be combined with different optics for solid-state lasers (fiber, disk and rod lasers). Exchangeable norm segments allow a variable adjustment of the immersion depths. The media supply (powder, gas, cooling water) takes place in a protected way inside of the segments.

Surface coating and generated 3 D moulds at a cylindrical surface
© Fraunhofer IWS
Surface coating and generated 3 D moulds at a cylindrical surface


The main application fields of these heads are coatings in welding positions with difficult accessibility. The multi beam principle of the powder feed allows coatings at vertical walls even in over-head positions. It is no problem anymore to repair defects at tube`s inner walls, to coat internal areas of housing-shaped components, or even to repair hard surfaces at extruder tubes or to coat deep lying engravings in the mould and tool making.

Technical data

  • variable immersion depths 1000 mm, > 1000 mm with additional guide pulley
  • minimum internal diameter: 100 mm
  • coaxial supply of commercial metal and hard metal powder
  • powder mass flow (Stellit): up to 50 g/min
  • weld seam widths: 1.5 to 4 mm
  • disc, fiber, rod solid-state laser with max. 3 kW