Energy-efficient high-performance deep hole drilling using twist drills

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Dry cutting and minimum quantity lubrication (MQL) have the potential to reduce the energy consumption of machining processes. The elimination of cooling lubricant in metalworking can generate various environmental and economic benefits, but it also increases the requirements with regard to the cutting technology. In many cases, the machining of deep holes is an exclusion criterion for the introduction of dry and MQL techniques. The high heat input, caused by the inner cutting zone within the workpiece, and particularly the challenging chip evacuation in case of high length-to-diameter ratios are two problems in deep hole drilling, which can originate insufficient process reliability and thus a decision against the introduction of dry machining or MQL. Based on the fundamental investigations in deep hole drilling of aluminium casting under MQL, different solutions are transferred to new applications and optimized in this knowledge transfer project. The main objective is to enable the energy-efficient high-performance MQL deep hole drilling for complex components made of steel, which is still one of the most important structural materials. HPM Technology from Münsingen works on the MQL technique and develops a new MQL mixing nozzle plus device as well as new cooling strategies. Thereby the low cooling effect has to be enhanced by innovative fluids without reducing the good lubrication capability of common MQL. High-performance twist drills with a length-to-diameter ratio of up to l/D = 60 are developed particularly for the application under MQL by the second project partner Miller from Altenstadt. The technological process development at the ISF is linked to an innovative method for simulation-based compensation of the resulting straightness deviation, which is often a critical quality feature in deep hole drilling operations. The close collaboration with the industrial partners allows both, holistic and detailed analysis of the demanding deep hole drilling process and the corresponding components. The developed solutions should enhance the current state of the art and enable wide industrial application of the high-performance deep hole drilling under energy-efficient MQL. To eliminate the existing obstacles regarding the MQL, the developments are validated on complex demonstrator parts.