TECHNICAL ADVICE TO MOULD MAKER
* The mould inserts should be made as small as possible.
* Avoid sharp corners.
* There must be sufficient wall thickness of the material to avoid bending stresses.
* The coolant bores should be placed in such a way that no great temperature differences (Thermic shocks) occur.

MACHINING:
* Rough machine down to max.2mm on allowance.
* Stress relieve anneal at 600-650 degree Celsius.
* Machine to finish size.
* Harden and temper to desired working hardness.
* Remove traces of grinding or if machined by erosion-polish electrolytic ally in direction of the last deformation.
* Moulds of increased precision may be finished after heat treatment.
* Mould with bigger thickness(>200mm) will need a double treatment in rough machined condition, hardening and soft annealing.

TO IMPROVE TOOL LIFE:
* Any grinding in the working area may lead to early appearance of thermo shock cracks, therefore such parts must be stress relieved annealed at below the tempering temperature.
* Eroding carburises the surface, increasing hardness and diminishing toughness. The thickness of the carburised layer depends on the consumed energy, the kind of impulse and the frequency of current. The layer appearing from eroding with inadequate finishing cannot be completely transformed (structure) any successive heat treatment. Therefore for finishing (removal of this layer) a sufficient allowance must be available (min.0.2mm).
* The contour must be drawn down in the direction of the last deformation and may be polished again, followed by stress relive annealing at 50k below last tempering temperature max. 500degrees Celsius, in an inert atmosphere.
* In case of bath nitriding, it must be taken into account that the risk of Thermo shock crack grows with n increasing nitride layer thickness. Therefore to warrant a minimum of toughness at permanent temperature load changes, this layer should not exceed a thickness of 0.1mm, i.e. the soaking time in the salt bath must not exceed 60-90 minutes. Should a repair welding become absolutely unavoidable, it will be useful to diminish the nitrogen contents in the surface layer of diffusion.

WELDING
If welding is absolutely unavoidable, the following basic rules must be observed:
* Remove the defective parts completely.
* Pre heat to 400 degrees Celsius unto the core.
* Weld under inert gas.
* Welding additives, analyze as close to welding stock as possible.
* Cool work piece down to 80degrees Celsius in calm air.
* Mark the final heat treatment in an inert atmosphere by tempering 50K below the last tempering temperature to remove the hardness in the zone affected by welding heat.
* Pre Heating of moulds: This is an absolute must for a long life of the moulds, since their toughness grows with increasing temperatures. Further more the Thermo shock stresses are reduces by a high pre heating temperature.
* Stress relieve annealing increases the life of a mould. It is recommended to carry out such treatment according to pattern to be defined by the user at fixed time intervals, as long as there are no cracks appearing in the shaping contour.