Hybrid micro-machining processes : a review

Micro-machining has attracted great attention as micro-components/products such as micro-displays, micro-sensors, micro-batteries, etc. are becoming established in all major areas of our daily life and can already been found across the broad spectrum of application areas especially in sectors such as automotive, aerospace, photonics, renewable energy and medical instruments. These micro-components/products are usually made of multi-materials (may include hard-to-machine materials) and possess complex shaped micro-structures but demand sub-micron machining accuracy. A number of micro-machining processes is therefore, needed to deliver such components/products. The paper reviews recent development of hybrid micro-machining processes which involve integration of various micro-machining processes with the purpose of improving machinability, geometrical accuracy, tool life, surface integrity, machining rate and reducing the process forces. Hybrid micro-machining processes are classified in two major categories namely, assisted and combined hybrid micro-machining techniques. The machining capability, advantages and disadvantages of the state-of-the-art hybrid micro-machining processes are characterized and assessed. Some case studies on integration of hybrid micro-machining with other micro-machining and assisted techniques are also introduced. Possible future efforts and developments in the field of hybrid micro-machining processes are also discussed

Ultrasonic Enhancement of Pulsed Electrochemical Machining

Electrochemical machining (ECM) has gained prominence in the field on precise machining and has been subjected to a lot of study in order to bring its use to commercial levels. One of the key issues of electrochemical machining is the lack of proper flushing ECM by-products. Ultrasonic assisted ECM is often used to minimize the flushing issue. This study attempts a novel variation in ultrasonic assistance of ECM by introducing ultrasonic waves in the flowing electrolyte without vibrating tool or workpiece. This ensures intense agitation in the inter-electrode gap (IEG) with relatively simpler set-up. Aluminum 6061 is used as a workpiece material to drill holes. Stainless steel tubes coated with Teflon is used as tool. The Teflon coating minimizes the effect of stray current. Use of pulsed DC current and ultrasonic vibration improves the quality of the ECM’ed holes. The intense ultrasonic cavitation disturbs the anodic reaction in IEG negatively affecting MRR. On the other hand, the de-agglomeration of ECM by-products and depassivation of anodic workpiece improves surface roughness by approximately 50% and the taper angle of the hole by approximately 75%

Ultrasonic Enhancement of Pulsed Electrochemical Machining

Electrochemical machining (ECM) has gained prominence in the field on precise machining and has been subjected to a lot of study in order to bring its use to commercial levels. One of the key issues of electrochemical machining is the lack of proper flushing ECM by-products. Ultrasonic assisted ECM is often used to minimize the flushing issue. This study attempts a novel variation in ultrasonic assistance of ECM by introducing ultrasonic waves in the flowing electrolyte without vibrating tool or workpiece. This ensures intense agitation in the inter-electrode gap (IEG) with relatively simpler set-up. Aluminum 6061 is used as a workpiece material to drill holes. Stainless steel tubes coated with Teflon is used as tool. The Teflon coating minimizes the effect of stray current. Use of pulsed DC current and ultrasonic vibration improves the quality of the ECM’ed holes. The intense ultrasonic cavitation disturbs the anodic reaction in IEG negatively affecting MRR. On the other hand, the de-agglomeration of ECM by-products and depassivation of anodic workpiece improves surface roughness by approximately 50% and the taper angle of the hole by approximately 75%