Friction-reduced hydrodynamic sliding linear bearing with diminished inclination of tilting to increase the sliding velocity by means of optimal design of the sliding surfaces

• Applicant: Professor Dr.-Ing. Martin Dix, since 4/2021
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering ; Engineering Design, Machine Elements, Product Development ; Production Systems, Operations Management, Quality Management and Factory Planning
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 285064832

The high load capacities combined with excellent damping properties are the reasons why hydrodynamic guides (HDG) are still used in machine tools. A very high surface quality of the workpieces is achieved by damping the process forces. The HDG systems should preferably be operated in the area of fluid friction. The aim of the continuation proposal is to improve the accuracy of hydrodynamic guides during operation, i.e. constant floating behaviour independent of time and position through purposeful control of the start-up mechanisms. For this purpose, the first aspect to be shortened is the mixed friction area in the Stribeck diagram of the guide, i.e. the liquid friction area is reached at the lowest possible speed. The second aspect of the accuracy behaviour is the desired constance of the lubricating gap with fluid friction, i.e. the avoidance or minimisation of tilting of the carriage.The third criterion is the minimal increase in floating height with increasing speed, which must be determinable by the purposeful control of various mechanisms. The objective follows on from the current DFG project, in which the floating behaviour at constant speed was described only with a defined or experimentally determined initial position of the carriage. In contrast, the velocity profile of machine tools typical reversing movements always consists of 3 phases: Acceleration, constant speed and deceleration, which are in permanent repetition. Starting from the stillstand position - i.e. without a significant lubricating gap - is rather an exception, since there is not enough time between the single strokes for the oil to be pressed out of the lubricating gap. The following challenges arise from the objective, the solution of which in its entirety enables an effective design and optimal operation of the hydrodynamic guidance system:- Improvement of the measurement of hydrodynamic pressure in the lubrication gap and displacement pressure at the inlet edge- Modelling and control of the start-up process- Modulation of lubrication parameters- Adjustment of the concavity of the contact surfaceThe approach is to control and shape the start-up process in a specific way. For this purpose, the characteristics of the lubricating wedge must be mastered when starting from the initial position or after a reversal of direction. The interdependence of the three adjustable influences is particularly complex: the defined acceleration profile within the movement cycle, the lubrication and the geometry of the contact surface. The work programme dedicates one AP to each of these aspects. It is completed by work to improve the mathematical-technical understanding of the start-up and, in particular, to improve the pressure measurement system.

• DFG Programme: Research Grants
• Ehemalige Antragsteller: Professor Dr.-Ing. Matthias Putz, from 8/2020 until 4/2021; Dr.-Ing. Volker Wittstock, until 8/2020