An experimental analysis of minimum chip thickness in micro-milling of two different titanium alloys

Micro-milling is a micro-mechanical cutting method used to obtain complex and three-dimensional micro geometries. Micro-cutting tools are used in the manufacturing of micro-components and the type of workpiece is also important for good surface quality and minimum burr. In this study, micro machinability of Ti6Al4V alloy which is used most frequently in micro-component production is compared with Ti5553 alloy. Micro-milling of Ti5553 alloy and comparison of the minimum chip thickness with Ti6Al4V were performed for the first time in this study. Using different cutting parameters, the variation of surface roughness, burr width, and cutting forces were investigated. The cutting tests were carried out on a specially designed and high-precision micro-milling test system using a TiCN-coated two-flute end mill of 0.6 mm diameter. According to the results, minimum chip thickness is approximately 0.3 times the edge radius of the cutting tool and does not vary with the alloy type. At feed rates smaller than the minimum chip thickness, both the cutting forces increase and the surface quality decreases. For both alloys, reduced feed rate and increased depth of cut lead to increased burr width. The burr widths in Ti6Al4V alloy are higher. At the end of the study, the limits of the cutting parameters where plowing occurred for the both alloys are clearly determined. In addition, the limits of the cutting parameter causing plowing have been confirmed by cutting forces, surface roughness, and burr formation.

Experimental investigation of top burr formation in high-speed micro-milling of Ti6Al4V alloy

Miniaturization with superior quality product of super alloy is the demand of the industry. Ti6Al4V is the demanding super alloy due to its excellent material properties, although this super alloy is known for poor machinability in terms of burr formation, low tool life, and poor surface finish. Therefore, being a popular super alloy, it comes under the difficult-to-cut material. In the current work, burr formation on the machining of Ti6Al4V has been studied. Experimental investigation and characterizations of top burr formation on Ti6Al4V alloy using end milling process were carried out. A scanning electron microscopy identifies the burr formed on the machined surface. A new technique has been introduced to measure the top burr width (i.e. equivalent width) accurately. Equivalent burr width calculated as the ratio of total area of burr generated to the total height. It was observed that equivalent burr width in up milling was increased by 120%, while in down milling, it was decreased by 50% as the speed varies from conventional to high speed. Furthermore, the effects of different cutting parameters and tool parameters on top burr formation have been analyzed to establish correlation among them.

A Study on Micro-Milling of Aluminium 6061 and Copper With Respect to Cutting Forces, Surface Roughness and Burr Formation

In the present study, micro-milling of aluminium 6061 alloy and copper was undertaken. TiAlN coated two-flute flat end milling cutters of 0.5 mm diameter were used for conducting micro-channel milling experiments with minimum quantity lubrication (MQL) as the cutting environment. The effect of process parameters namely cutting velocity (vc) and feed per flute (fz) on the cutting forces, surface roughness and burr width are reported. RMS values of longitudinal feed force (FX), transverse cutting force (FY) and vertical thrust force (FZ) were measured and the maximum values for Al 6061 are 0.33 N, 0.16 N and 0.21 N respectively, and the same for copper are measured to be 0.11 N, 0.17 N and 0.22 N respectively. Average surface roughness along the milling direction (Ra) at the bottom surface of the micro-channel was measured. Smoother surfaces were generated at lower feed per flute in both the materials. Ra is found to be varying from 28.2 nm to 86.9 nm for Al 6061, and for copper, the range is from 4.9 nm to 32.7 nm. SEM images of the micro-channels were analysed and top burr width was measured in both up-milling and down-milling directions. Higher feed per flute produced smaller burrs in both up-milling and down-milling directions. Maximum burr width for Al 6061 is measured to be 12.86 μm and 15.28 μm in up-milling and down-milling direction respectively, and for copper, the same are measured to be 12.84 μm and 20.46 μm respectively.

Micro-milling of unreinforced and reinforced polypropylene

It is essential to determine the micro-machinability performance of polymer and glass fiber–reinforced polymer composite in order to effectively utilize the polymer and its composite as an engineering material at the micro-scale world. However, a literature survey revealed that not much work was done on the micro-milling of polymer and its composite. In the light of literature surveys, it can be said that the novelty of this study is to investigate the micro-milling performance of polypropylene and glass fiber–reinforced polypropylene manufactured with plastic injection molding process. The tests were performed at different feed rates and spindle speeds and the effect of these parameters on tool wear, burr width and micro-milling forces was investigated. In general, it was concluded that wear and forces in micro-milling of reinforced polypropylene composite were higher than that of unreinforced polypropylene. Micro-milling forces increased with feed rate and spindle speed for both materials. The lowest top burr size and force values were obtained at the feed of 50 mm/min and the spindle speed of 20,000 r/min. Unreinforced polypropylene gave better performance with respect to glass fiber–reinforced polypropylene composite from micro-machinability aspect.

Investigation of Burr in High Speed Microdrilling

This paper discusses burr in microdrilling that affect forms and functions of parts. The effects of microdrilling parameters on burr length and width are identified. The experiment was conducted using Mikrotools DT110 machine with one millimetre diameter of HSS on copper workpiece. Burr heights in terms of burr length and burr width were measured by using scanning electron microscope. The data was analyzed using Taguchi method to find the optimum micro-drilling process parameter for minimizing the burr height. The relationship among spindle speed, feed rate and burr has been developed. It is found that feed rate is the most influential factors on the burr height. The desirability of getting the minimum burr height is 72% and the optimum parameters are 30000 rpm spindle speed and 0.2 mm/min feed rate.

Grey Prediction on Sheared Edge Quality in Precision Blanking Process for Micro IT Parts

Sheared edge quality of micro IT parts is an important standard to evaluate product quality. In this paper, a prediction model of sheared edge quality based on grey prediction is studied. By mapping the stroke and the burr width to be the time increment and the eigenvalue of grey system, the grey prediction model was established. The dynamic regularity of burr in actual production was attained from the precision blanking experiment and the prediction of burr width was performed. The results show that the model can predict burr width accurately and needs less sampling data. Thus, it is fit for the requirement of manufacturing.

Effect of Carbon Nanotube (CNT) Loading on the Thermomechanical Properties and the Machinability of CNT-Reinforced Polymer Composites

The machinability of carbon nanotube (CNT)-reinforced polymer composites is studied as a function of CNT loading, in light of the trends seen in their material properties. To this end, the thermomechanical properties of the CNT composites with different loadings of CNTs are characterized. Micro-endmilling experiments are also conducted on all the materials under investigation. Chip morphology, burr width, surface roughness, and cutting forces are used as the machinability measures to compare the composites. For composites with lower loadings of CNTs (1.75% by weight), the visco-elastic/plastic deformation of the polymer-phase plays a significant role during machining, whereas, at loadings ≥5% by weight, the CNT distribution and interface effects dictate the machining response of the composite. The ductile-to-brittle transition that occurs with an increase in CNT loading results in reduced minimum chip thickness values and burr dimensions in the CNT composite. The increase in thermal conductivity with the increase in CNT loading results in reduced number of adiabatic shear bands being observed on the chips and reduced thermal softening effects at high cutting velocities. Thus, overall, an increase in CNT loading appears to improve the machinability of the composite.

Effect of Carbon Nanotube (CNT) Loading on the Thermo-Mechanical Properties and the Machinability of CNT-Reinforced Polymer Composites

The machinability of carbon nanotube (CNT)-reinforced polymer composites is studied as a function of CNT loading, in light of the trends seen in their material properties. To this end, the thermo-mechanical properties of CNT composites with different loadings of CNTs are characterized. Micro endmilling experiments are also conducted on all the materials under investigation. Chip morphology, burr width, surface roughness and cutting forces are used as the machinability measures to compare the composites. For composites with lower loadings of CNTs (1.75% by weight), the visco-elastic/plastic deformation of the polymer phase plays a significant role during machining, whereas, at loadings ≥ 5% by weight, the CNT distribution and interface effects dictate the machining response of the composite. The ductile-to-brittle transition and reduction in fracture strength that occurs with an increase in CNT loading, results in reduced minimum chip thickness values, burr dimensions and cutting forces in the CNT composite. The increase in thermal conductivity with the increase in CNT loading, results in reduced number of adiabatic shear bands being observed on the chips and reduced thermal softening effects at high cutting velocities. Thus, overall the increase in CNT loading improves the machinability of the composite.