Friction and Wear Behavior of Deep Drawing Tools Using Volatile Lubricants Injected Through Laser-Drilled Micro-Holes

Gerd Reichardt,Paul Reichle,Rudolf Weber,Jakob Barz,Kim Riedmüller,Georg Umlauf,Thomas Graf,Manuel Henn,Mathias Liewald,Günter E M Tovar

doi:10.1007/s11837-021-05028-8

Gerd Reichardt, Paul Reichle + Show 8 more

Open Access

https://doi.org/10.1007/s11837-021-05028-8

Copy DOI

Abstract

In deep drawing processes, the use of lubricants is mandatory in order to prevent wear on tools and surface damage to the formed sheet metal components. Here, frequently used lubricants are synthetic and mineral oils, emulsions, and waxes. However, these conventional lubricants have to be applied to the sheet material prior to the forming operation and removed afterwards by cleaning processes. Additionally, the lubricants often contain substances that are harmful to the environment and to human health. To counteract these economic and ecological disadvantages, research is currently being conducted on a novel tribological system. For this, volatile media such as liquid carbon dioxide and gaseous nitrogen are being used, and are introduced directly into the friction zones between the tool and the sheet metal material during deep drawing under high pressure through special laser-drilled micro-holes. This paper covers the latest investigations and findings regarding the design of flow-optimized micro-holes, the laser drilling process, the friction characterization on tool radii, and the tool wear to be expected when using the lubrication medium CO2.

Highlights

As part of the research in the field of sheet metal forming, both tool and lubricant manufacturers are often focusing on approaches for generally reducing the amount of lubricant required on the sheet metal materials
One approach being investigated in this context is lubrication with volatile media, such as nitrogen (N2) or carbon dioxide (CO2), which are introduced directly into the contact zone between the tool and the sheet metal material under high pressure via laser-drilled micro-holes
A numerical investigation of the CO2 flow in micro-holes integrated into a deep drawing tool shows a dependence between the type of the microhole and the condition of the lubrication media in the forming zone

Summary

INTRODUCTION

As part of the research in the field of sheet metal forming, both tool and lubricant manufacturers are often focusing on approaches for generally reducing the amount of lubricant required on the sheet metal materials. In the case of small droplets, this cooling effect leads to temperatures around 195 K which can surmount the heat of crystallization causing CO2 to shift to its solid state This forming of dry ice is the reason why previous investigations showed a lower coefficient of friction if liquid CO2 was used instead of its gaseous state.[10] the goal of designing the micro-holes of the deep drawing tool is to combine a sufficient supply of lubricant into all areas of the forming zone with a high amount of dry ice formation, in order to ensure a satisfactory lubrication. The positioning of the focus of the laser beam for the individual micro-holes at any position and angle on the surface of the forming tool was significantly simplified by the use of a five-axis coordinate transformation This feature allowed for a precise movement in the direction of the beam with static inclination and rotational angles of the galvanometer-scanner during the drilling process by compensational, simultaneous movement of all three Cartesian axes. Test setup for endurance tests directly from the coil with volatile lubricants

Experimental Results of the Tribological Investigations

CONCLUSION

CONFLICT OF INTEREST