To transform a laminated sheet in a three-dimensional shaped object through the processing of drawing is necessary to apply an axial force which, within the limits of the material molding, urges the fibers of the sheet.

The punch and the die must then win the resulting effect of lateral forces which generates a considerable friction between the walls.

The friction in turn produces wear on the surfaces of the tools, determining the end of their life and consequently the latch of the production for maintenance, with inevitable loss of productivity. To protect punches and dies from the phenomenon of wear STS has developed the HDP RED RM, PVD coating deposited with HDP (High Density Plasma) technology.

Thanks to the high density plasma HDP technology favors the deposition of a layer of considerable thickness, well bonded to the substrate, very compact and almost free from defects (droplets). The hardness values obtainable are very high (> 3000 HV) and the coefficients of friction are very low (<0.25 against 100Cr6) resulting in excellent resistance against abrasive and adhesive wear. This result is a considerable increase in tool life with the possibility also of several recoating.

As on the edges of punches and dies for blanking, also on those for drawings, it often occurs unwanted, the deposits of plasticized material called “cold welding.”
This phenomenon reduces the life of the mold and adversely affects the surface finish of the drawn pieces.

For this reason, STS, depending on the processing cycle and the materials involved, combines HDP RED RM coating with other different solutions: use of an additional self-lubricating coating, polishing of the sliding surfaces, or both solutions in combination.


The characteristics of the austenitic stainless steels sheets help to create a kind of “cold welding” phenomena where parts of the material remain “glued” to the substrate.

A similar problem is encountered during the processing of highstrength materials (HSLA, DP, TRIP …), where the situation is compounded by the effect of necking and shrinking of the molded parts.

These phenomena may be cause of premature wear of the punch or of damage to the matrix.

To overcome these criticalness STS, after careful assessment of the working conditions, is able to offer various solutions in combination with HDP RED RM such as the use of a self-lubricating coating (based Carbon or Molybdenum), or polishing of the sliding zone as well as their combination.

The chemical inertia and the characteristics of the self-lubricating layer lattice matched to the reduction of the surface roughness (Ra <0.1 micron) are the right formula to reduce wear by adhesion.


The polishing process done on the cutters and on the folding molds is a manual process which provides the sequential use of abrasive systems (stones, canvases, pastes) apt to reduce the surface roughness generated by machining (tools for removal, grinding or electric erosion) until obtaining the optimal values of Ra to prevent the process of cold welding and ensure the adhesion of the coating.

For particularly hard processing it is advisable to prepare the surface with roughness typical of a mirror lapping (Ra 0.05 micron). Thanks to the great experience gained during these years, STS can boast the ability to perform the polishing process within their production department, with their highly skilled personnel.


Given the high compression strains involved, STS proposes the interposition of a nitride layer at 700-900HV finalized to the support of the HDP RED RM coating undergoing deformation.

This layer is able to provide a gradual increase of hardness which allows the correct distribution of all the strains which are generated along the surfaces undergoing the processing.