Abstract
Hole drilling in Ti6Al4V titanium alloy is challenging due to its poor machinability resulting from high-temperature strength and low thermal conductivity. Therefore, an evaluation of the helical milling process is carried out by comparing the thrust force, surface roughness, machining temperature, burr size, and hole diametrical accuracy with the conventional drilling process. The results indicate the advantage of the helical milling in terms of the lower magnitude of thrust force. The holes generated using helical milling displayed a superior surface finish at lower axial feed conditions, while higher axial feed conditions result in chatter due to the tool deformation. Also, the absence of a heat-affected zone (HAZ) under dry helical milling conditions indicates the work surface formation without thermal damage. Besides, a significant reduction in the size of the burrs is noted during helical milling due to lower machining temperature. Analysis of the hole diameter reinforces the capability of the helical milling process for processing H7 quality holes. Consequently, helical milling can be considered a sustainable alternative to mechanical drilling, considering its ability to machine quality holes under dry machining conditions.
Highlights
Properties like high strength to weight ratio, fatigue life, yield strength, relatively high resistance to corrosion and temperatures, unique to titanium alloys make them a desirable material in many manufacturing industries [1,2]
High axial thrust force can result in tool deformation, vibration and affect the diametrical accuracy and surface finish of the processed holes [29]
The thrust force developed during the drilling and helical milling is analyzed
Summary
Properties like high strength to weight ratio, fatigue life, yield strength, relatively high resistance to corrosion and temperatures, unique to titanium alloys make them a desirable material in many manufacturing industries [1,2]. Titanium alloys are used explicitly as structural materials [3], where a considerable number of holes are required for assembling the fuselage by employing bolts or rivets. A report briefs that around 180 000 holes are processed in a single Airbus 380 wing box [4], and in an aircraft assembly, hole-making comprises 40–60% of the total material removal process [5,6]. Conventional drilling is the most acclaimed process for making holes for structural assembly. Implementation of dry machining is beneficial as it is a sustainable process that can reduce production costs and increase productivity [7]. The machining of titanium alloys poses several challenges. From the material point of view, titanium alloys demonstrate very poor machinability due to their high reactivity leading to cold welds and premature tool failure [6]. The low thermal conductivity characteristics can lead to a rapid
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