Ultrasonic assisted nano-fluid MQL in deep drilling of hard-to-cut materials

Abstract

This paper presents a new method of combining Minimum Quantity Lubricant (MQL) with ultrasonic assistance in deep hole drilling processes for difficult-to-cut materials, using internal coolant tools. A small amount of lubricant as 90 mL/h was provided directly into the cutting zone during deep drilling under ultrasonic vibrations exerted on the tool. A comparative experimental study was implemented for two types of drilling processes: conventional drilling (CD) and ultrasonic-assisted drilling (UAD). For each set, three different methods of lubricant feeding methods were applied, including flooding, MQL, and MQL with graphene nanoparticles. A continuous drilling process using a through-hole drill bit (D = 5 mm, L = 8D) for AISI SUS 304 stainless steel was implemented to validate the effectiveness of the proposed approach. The results show that the approach proposed can overcome the bottleneck in deep drilling using MQL, providing a higher production rate, longer tool life, and better machining performance in terms of cutting forces and processing ability. Using the newly proposed method, continuous drilling can be done in critical machining conditions, which are typically recommended by the tool manufacturers. The results are promising to expand to deep hole drilling of other hard-to-cut materials.