Effect of Coating and Polishing of Cutting Tool on Machined Surface Quality in Dry Machining of Aluminium Alloy

Surface quality is one of the major concerns in any machining process. To achieve the higher surface finish, mostly concentrated on machining parameter optimisation. This study has been carried out to study the effect of coating and polishing of flute surface of the solid carbide (WC-Co) endmill cutters on machined surface quality obtained during dry machining of Aluminium alloy 24345WP. Experiments were conducted on Aluminum workpieces with Ø6 mm 2 flute end- mill cutter with and without coating/polishing and their effect on surface quality studied for linear as well as areal surface roughness parameters using white light interferometery. The study concludes that polished flute tool, despite their non-sharp cutting edges, gives considerably better surface finish due to its lowering of chip tool friction. This was also supported by the results obtained from scanning electron microscopy of the cutting tool edge as well as optical microscopy of the obtained machined surface.

Experimental and theoretical investigation into simultaneous deburring of microchannel and cleaning of the cutting tool in micromilling

High material removal rate, high resolution and reproducibility of micromilling make it a suitable process for making microfeatures on different materials. However, existence of unwanted protrusions or surface irregularities on the machined surface known as burrs demands some post-processing to make it qualify for end use. In addition, clogging of materials on the flute surface increases the effective edge radius and tool loading during polymer machining. In the present work, a new strategy is demonstrated for simultaneous deburring of microchannel and cleaning of cutting tool during micromilling of polymethyl methacrylate. The performance of the process has been further evaluated by milling of microchannels in oxygen-free high conductivity copper workpiece. Burr formation, surface roughness and tool loading have been found to be significantly reduced by using the proposed method. A theoretical study of the process has also been carried out to understand the mechanism of the proposed method.

THE EFFECT OF THE DOUBLE-DECK FILAMENT SETUP ON ENHANCING THE UNIFORMITY OF TEMPERATURE FIELD ON LONG-FLUTE CUTTING TOOLS

In the present study, a double-deck filament setup is proposed for the hot filament chemical vapor deposition (HFCVD) method and an optimization method is presented to determine its optimal geometry that is able to produce a highly uniform temperature field on the whole flute surface of long-flute cutting tools. The optimization method is based on the finite volume method (FVM) simulation and the Taguchi method. The simulation results show that this double-deck filament setup always produce a highly uniform temperature distribution along the filament direction. Comparatively, for the temperature uniformity along the drill axis, the heights of the two filament decks present virtually significant influence, while the separations between the two filaments in either deck exhibit a relative weak effect. An optimized setup is obtained that can produce a highly uniform temperature field with an average temperature of 834°C, a standard deviation (σ) of 2.59°C and a temperature range (R) of 11.75°C. Finally, the precision of the proposed simulation method is verified by an additional temperature measurement. The measured temperature results show that a highly uniform temperature fields with σ/R = 9.6/35.2°C can be generated by the optimized setup and the deviation of the simulated results from the measured actual temperatures are within 0.5–3.5%, which justifies the correctness of the simulation method proposed in present study.

THE EFFECT OF THE GAS INLET ON THE FLUID FIELD DURING FABRICATING HFCVD DIAMOND-COATED CUTTING TOOLS

In the present study, the fluid field in a process of fabricating diamond coated cutting tools using the hot filament chemical vapor deposition (HFCVD) method is investigated using the finite volume method (FVM), in which the effects of the inlet height, gas initial velocity, inlet radius and arrangement are illustrated in terms of the gas velocity magnitude and vector distribution near the filaments and the flute surface of cutting tools. In the simulations, the coupling effect of the temperature and the gas field is also considered by simultaneously calculating the temperature distribution. The simulation results suggest that either shortening the distance between the gas inlet and filaments, or increasing the gas initial velocity is helpful for the reactive gas arriving at filaments surface and being dissociated. Furthermore, increasing the inlet area is able to significantly increase the velocity of gas field around the filaments, as well as produce a much more uniform gas velocity field. Based on this conclusion, two novel multi-inlets setups are proposed to further improve the generated gas field and the simulation results show that the most superior gas field can be achieved with the one including 8 larger central inlets and 24 smaller outskirt inlets. Finally, an actual deposition experiment is carried out and its result indicates that adopting the optimized such inlet arrangement could generate a highly uniform and homogeneous growth environment on whole deposition area.

The Performance of Small Diameter Twist Drills in Deep-Hole Drilling

This paper investigates the performance of small diameter high-speed steel twist drills drilling boreholes with a depth of ten times the diameter into carbon steel AISI 1045 using minimum quantity lubrication. The performance of small twist drills is determined, first, by their deep-hole drilling capability, i.e., in how far the cutting forces can be kept at a noncritical level by maintaining the chip disposal, and, second, by their tool life. This work shows that both the deep-hole drilling capability and tool life of small drills are strongly dependent on their geometry, in particular the size of the chip flutes, and the flute surface topography.

Modeling Chip-Evacuation Forces in Drilling for Various Flute Geometries

In this paper, a chip-evacuation force model is presented to predict the torque and thrust required to evacuate the chips during drilling for various flute geometries. The model considers the chips in the flutes as granular solids and determines the chip-evacuation thrust and torque from the normal and lateral pressure distributions in the chips that fill the flutes. The model requires two coefficients of friction that are established via a calibration procedure. The critical depth for the process is determined by setting a threshold value on the chip-evacuation torque, which is based on the onset of chip-clogging. The effectiveness of the chip-evacuation force model in determining the chip-evacuation thrust and torque and predicting the critical depth has been assessed via a set of validation experiments using both standard and parabolic drills. The parabolic drill produced lower chip-evacuation forces and increased critical depths relative to the standard drill. While the standard drill has a modestly larger effective flute cross-sectional area for most of the flute length, the parabolic drill has a significantly smaller contact area between the chips and the flute surface, which is the main reason for the superior chip-evacuation performance of the parabolic drill.