The project comprises four workpackages.
WP1 - Fundamental research on liquid lubrication in sheet metal forming
Analysis and modelling of the mechanisms of liquid lubrication in typical sheet forming operations such as deep drawing and ironing are carried out to determine film thickness in macrohydrodynamic lubrication in order to estimate the limits of lubrication, which are set by the film thickness decreasing to a minimum size equal to the of the tool surface roughness Ra. Important parameters to be quantified are normal pressure in the tool/workpiece interface, relative sliding speed and tool/workpiece interface temperature controlling the lubricant viscosity. A viscometer determining the viscosity as a function of pressure, shear strain rate and temperature is to be developed, since the ones commercially available do not allow the high pressures dealt with in metal forming.
WP2 Development of methodology for off-line evaluation of new tribo-systems
Off-line testing procedures start with numerical analysis of the production process in order to determine the main parameters governing lubrication, i.e. normal pressure, surface expansion, sliding length, sliding velocity and tool/workpiece interface temperature. The result of these calculations is input to design of the laboratory test. A numerical analysis of this test includes determination of necessary load and tool design to obtain similar pressure conditions and temperature development as in production. Finally the testing can be performed to evaluate lubricant performance. When a successful tribo-system has been found, production testing of the new system is carried out. The methodology is under development and has been applied to a first production platform at the Danish company Grundfos including a five steps progressive deep drawing tool for production of a stainless steel component, where chlorinated paraffin oil has until now been necessary to apply. It is clear, however, that a considerable amount of research and development is still to be done before a complete methodology is established.
WP3 Development and testing of tailored tool surfaces
The idea of developing tailored tool surface topographies that entrap and pressurize lubricant, which subsequently escapes by micro-hydrodynamic lubrication is to be pursued by analysing the influence of pocket geometry on the escape mechanism of lubrication. By combining pre-machining by turning or milling of hardened dies with robot assisted polishing perpendicular to the machining direction very accurate lubricant reservoirs can be manufactured. A few examples in Danish industry indicate remarkable results in raising the limits of lubrication with this new technique in deep drawing tools.
WP4 Testing of new, anti-seizure tool coating
Japanese investigations providing deep drawing tools with pure diamond coating have indicated the possibility to deep draw with no lubricant at all. Personal communications with the main developer reveals that a special ultrasonic technique had to be developed for polishing. The robot assisted polishing technology is expected to be very suited for solving this problem.