Process Design for Deep Hole Drilling with Small Diameters Under the use of Minimum Quantity Lubrication
Within this project supported by the German Federal Ministry of Economics and Technology the single-lip deep hole drilling process with small diameters shall be qualified for the minimum quantity lubrication (MQL). Dry machining and MQL in machining technology combine economical as well as ecological advantages. Because of the reduction or abandonment of the cost related to cooling lubrication, for example the resourcing and maintenance, the elimination of workpiece and chip cleaning after the cutting process, a high cost saving potential exists. Furthermore, the health burden of the employees founded in the contact with high-additive cooling lubricants can be reduced and the compliance with legal regulations for example concerning water pollution control can be reached easier. In comparison to conventional flood lubrication, another advantage of dry machining and MQL is, that no oil or emulsion remains in the bore hole produced. Remaining oil can form a resin in the bore hole and can clog the hole, for example when a heat treatment of the workpiece after deep hole drilling is done. This effect can occur especially at bore holes with small diameters. For the realization of MQL in the single-lip deep hole drilling process, high challenges exist. Beside the cooling and lubricating of the cutting zone, in this process the coolant is the only mechanism for chip evacuation out of the deep hole. Because of that, a continuous cooling lubrication is very important for a reliable process. These challenges are reinforced in processes using tools with small diameters due to the small cooling channels, the small chip area und the usually high necessary cooling lubricant pressure. Based on further developments in the areas of MQL, tools, deep hole drilling machine tools as well as the process design is aimed. In addition, in this project advancements in the field of MQL in single-lip deep hole drilling with small diameters are intended. Here, the advantages of dry machining processes shall be utilized for deep hole drilling with small diameters. This will be carried out in cooperation with the companies HPM Technologie GmbH and TBT Tiefbohrtechnik GmbH & Co.
To reach the aim of the qualification of the minimum quantity technology in single-lip deep hole drilling with small diameters, the project is divided into several phases. At first the actual situation of deep hole drilling with tool diameters of d < 2.5 mm and an actual available MQL system will be described. Then, an optimization of the MQL technology concerning the aerosol quality, the atomization technology and the aerosol pressure will be done to reduce the risk of an unmix of the aerosol occurring at high spindle speeds. Furthermore, an adapted ventilation engineering is necessary to protect the employee for respirable parts of the aerosol. Parallel, the machine tool is also qualified for the MQL technology. A further process optimization is intended by an adaption of the tool geometry, the cutting material, tool coating and the connected effects on the thermomechanical loads and chip formation occurring in the single-lip deep hole drilling process. The advancements in the fields of MQL system, machine tool, tool and process design will be done in iterative processes on the fundament of experiments. In these experiments, an adapted process design will also be developed. The optimization in each field is based on the measurements detected in the experiments mechanical loads, surface quality, bore hole quality, impact on the subsurface zone as well as chip form.
The aim of this project is the development of a new technology for reliable deep hole drilling processes using MQL for tool diameters of d < 2.5 mm. The components developed within this project, the MQL system, the tools and machine tools as well as the process knowledge shall be brought singular and as a complete system to the marketability within this project.
- Figure 1: Process design for deep hole drilling with small diameters by optimization of the MQL technology, the tool, the process and the machine tool