Requirements on tools
It is necessary to control the appearance and other properties of tools before the actual coating process. We would appreciate, if the tools delivered to us for coating, met certain basic criteria. We would then be able to guarantee a quality deposition of coatings and thus customer satisfaction.
For fully functional tools it is necessary to target at the following tool characteristics:
- Surface quality
- Material properties
The surface quality could influence the deposited coatings properties.
From this view, we can divide the surface pollution into two parts:
Removable pollution – occurrence of such substances, which could be removed by additional technological modifications of a cleaning process. They are:
- Blackening
- Tool surface color marking
Non-removable pollution – application of such substances on the tool surface or such tool physical condition, which forbids a quality coating application. They are:
- Depth corrosion
- Preserving or lubricating the tools by silicon agents
Material properties
they are such properties, which are not directly connected with surface quality but with material composition or tool shape. Some material properties exclude the PVD technology use; sometimes a limited tool use can occur. For customer full satisfaction it is preferable to control the tools according to the following criteria.
Drawing temperature – the tools must be made of materials, which do not change their hardness at 400°C. In general, we are able to coat any tools made of cemented carbide or high-speed steel.
Soldered tools – it is possible to coat such soldered tools, where Cu and Ag based solder is used. In tools soldered by usual solders containing Cd and Zn, sputtering of those materials occurs during the coating process. The sputtered material pollutes the coating chamber resulting in a decrease in critical vacuum under an allowed level. Thus it is not possible to coat tools soldered by usual solders.
Tool size – it is possible to coat tools in different size coating units, distinguished by a chamber size. We are able to coat a tool of a maximum diameter of 450 mm and height of 420 mm in our largest unit.
Holes – impossibility to deposit a quality coating into holes is one of the basic limits given by the PVD technology. In general, the smaller and the deeper the hole is, the thinner the coating on its walls. Dimples and slight surface cavities can be coated with no limits.
