Investigation of compliant fixed abrasive machining of internal surfaces using flexible tool
Vohra Moiz Sabbir
Date of Issue2017-03-29
School of Mechanical and Aerospace Engineering
With increasing demand of more complex, aesthetically appealing and high performance products, it is very essential to develop more prominent and efficient machining technologies. Additive manufacturing can create more complex, curved and intricate geometries for robust product designs. There is a need to develop novel finishing technologies for such products which cannot be finished using conventional techniques. Compliant tools such as abrasive coated cloth, paper and flap wheels are commonly used in manufacturing finishing processes especially in aerospace and precision engineering industry. Although such tool has been well proven for polishing, the mechanical behaviour and material removal mechanism of these tools have not been understood or documented completely. The aim of this project is to investigate the capabilities of fixed compliant abrasive tool for finishing internal channels using flexible tool. The finishing process was designed and its experimental setup was assembled. Experiments were conducted to investigate the effects of internal abrasive finishing on surface roughness by varying different parameters. The trials were conducted on aluminium straight cylindrical channels of circular and elliptical cross sections. Experimentally, it was observed that the finishing technique was able to polish the internal surfaces of circular cross section using PFERDS Polistar tool, whereas it was unable to machine complete periphery of elliptical channels due to lack of backup pressure while machining. Average surface roughness (Ra) value was found to be in the range of 0.8 IJ.m - 1.5 IJ.m depending on tool speed, bend radius of flexible shaft, feed rate, abrasive grain size and the density of abrasive grains on the tool. Temperature rise during machining did not significantly affect the surface roughness or damage the abrasive grains of Polistar tool. It can be concluded that the aforesaid finishing technique using flexible shaft is a plausible method to polish internal channels using compliant abrasive tools. However this project is limited to use PFERDS Polistar abrasive for circular and elliptical straight cylindrical channels only. Further research needs to be done to analyse its accessibility and applicability for more complex internal geometries and use of custom designed compliant tools.