Performance of laser assisted micro-milling (laμmill) of titanium alloy using micro ball end mill

Laser assisted milling technique turns to be complicated and unpredictable when the machining size is scaled to micro level. Furthermore, less has been reported on the application of ball end mill in laser assisted micro milling. This study was carried out to evaluate and clarify the machining characteristics of micro ball end mill in laser assisted micro milling of titanium alloy Ti6Al4V. Finite element method (FEM) simulation of preheating was used to determine the machining parameters and the cutting tool to laser beam distance. The performance of laser assisted micro milling using micro ball end mill was evaluated via experimental works using various feed, feed rate, depth of cut and cutting speed. The cutting force, tool wear, chip pattern, burr and machining surface conditions were compared between conventional micro milling and laser assisted micro milling. Machining simulation was also carried out to study and collect the supportive evidence to explain the chips formation mechanisms. The laser heating simulation model was built and validated to determine the cutting tool to laser beam distance. When the feed rates ranging from 52.5 to 210 mm/min, the workpiece temperature at machining region was increased from 128 °C to 178 °C when the cutting tool is located at 0.6 mm from the laser. At this condition, the creation of heat affected zone and melted zone were successfully avoided. This study has proven that laser assisted micro milling reduces the cutting force approximately 5 to 20 %, depending on the feed and depth of cut applied. However, it is also found out that the chip pattern has a strong correlation with tool wear rate and surface roughness. It was observed that loose arc chips were produced at the feed and depth of cut of 3.0 x 10-3 mm/flute and 0.02 mm, respectively. This type of chip is preferable due to less chip blocking, rubbing and chip compression effect. It is also proven that laser assisted micro milling technique is more effective when the workpiece temperature is increased to approximately 250 °C compared to 180 °C

Evaluation of glass welding by ultrashort pulse laser

It is considered that fusion welding should be the most promising technique in glass joining, since joining can be accomplished without any intermediated layer and mechanical contact. High precision, small heat-affected zone (HAZ) and small shock-affected zone (SAZ) makes ultra-short pulsed laser capable to perform the process with minimal damages to the surrounding area. However, there are still a lot of things to be clarified in this process, since glass materials are veiy sensitive to temperature gradients and available in different thermal properties. In this study, molten zones created by high ultra-short pulsed laser in borosilicate glass (Schott D263) and fused silica were evaluated. Laser irradiation was done inside the glass some micrometers below the top surface under various processing conditions. Molten zone was observed visually and its strength was measured using bending test. Actual fusion welding of two glass plates was also successfully demonstrated and evaluated by strength measurement. The influence of polarization, feed rate v, incident laser power Win and pulse repetition rate Rp to molten zone strength and appearance were discussed. Main conclusions in this study are as follows:- a) There was no obvious influence to the molten zone appearance by the difference of beam polarizations. b) Incident laser power played the most important role in controlling molten zone size. Molten zone size increased with the increment of laser power. c) Cracks and bubbles were effectively reduced by selecting the proper pulse repetition rate. Low pulse repetition rate led to cracking at the surrounding area of molten zone and high pulse repetition rate caused cracking in the bottom area of molten zone. d) Measurement of mechanical strength had proven that low feed rate offered wider applicable pulse repetition rate with no fatal strength decrement of molten zone by ultra-short pulse laser. Keywords: Ultra-short pulse laser, borosilicate glass, fused silica, molten zones, heat effected zone (HAZ), fusion welding, feed rate, polarization, pulse repetition rate

Tool wear propagation in Ti6Al4V laser assisted micro milling using micro ball end mill

This paper presents an experimental study of laser assisted micro milling of Ti6Al4V using micro ball end mill. Tool wear propagation was observed and compared between conventional and laser assisted micro milling to evaluate the effectiveness of laser assisted machining technique in Ti6Al4V micro machining. It is confirmed that laser assisted micro milling technique managed to improve the tool life even when using micro ball end mill tool. The tools in laser assisted micro milling served different tool wear mode compared to conventional micro milling. The maximum flank wear in laser assisted micro milling reduced for approximately 50 % at machining distance of 6000 mm when the laser pulse width is increased from 1 to 2 ms

Comparison between Dry, MQL, and Cryogenic Cooling Technique on Surface Integrity of Burnished Surface

Environmental concerns has contributed towards higher demands for green products. Therefore, various machining conditions, such as dry and near dry machining have been introduced to resolve the cutting fluid problem. However, the application of cryogenic cooling still not well understood especially for burnishing process. It is essential to initiate a study on the effect of cryogenic cooling technique to substitute other techniques to improvement burnishing process. Carbon dioxide is used as the cryogenic gas under supercritical state, and compare with dry and minimal quantity lubricant. Solid carbide burnishing tool is used with a diameter and corner radius of 16 mm and 1 mm, respectively. The result shows that burnishing process under cryogenic condition recorded less burn mark and better tool wear than dry and MQL conditions. In addition, cryogenic condition exhibits significant grain refinement and surface hardness. In conclusion, the performance of carbon dioxide gas under supercritical state outperformed other coolant conditions

Dissimilar materials laser welding characteristics of stainless steel and titanium alloy

Welding parameters are directly influenced by the work material properties. Thermal properties such as thermal conductivity and melting point are very important to estimate the range of power required and the allowable scanning speed. However, when two or more different materials are involved, modifying lasing parameters are not enough to counter the problems such as imbalance melting region and weak adhesion of contact surface. To counter this problem, the characteristics of welding beads formation for both materials need to be clarified. In this study, comparison of welding beads constructed using the same scanning parameters were done to understand the different and similarity of melted region for the both materials. Actual welding of the both materials were done under different offset distance to obtain a balanced melting area and well mixed melting region

A study on cryogenic supercritical carbon dioxide coolant delivery technique when machining of AISI 1045 steel

The machining operation involves a material removal process and develop high temperature due to the friction force. The heat generated at the region of cutting edge has critical influences on machining process. It can increase cutting tool wear, reduce tool life, get rise to thermal deformation and might consequence to microcracks. The application of cutting fluid at the cutting zone by conventional process could overcomes the aforementioned problems to some extent via cooling and lubrication process. However, the waste of cutting fluid might be profuse and its impact on the environment. A new efficient process, cryogenic cooling using carbon dioxide gas (CO2) has been introduced on improving the cooling process. This technique is more economical in coolant usage while maintaining significant performance including cutting temperature, cutting force and surface roughness. The pulse mode of CO2 cooling spray under supercritical state has been used to corroborate the machining process by reducing the cutting zone temperature as to reducing coolant usage

Determination of heat flux intensity distribution and laser absorption rate of AISI D2 tool steel

The prediction of fluctuated temperature distribution generated by pulsed wave laser in laser assisted micro milling (LAMM) is crucial. The selection of processing parameter by minimize the effect on the processing characteristic is decisive to ensure the machining quality is high. Determining the effect of heat generated in underneath surface is important to make sure that the cutting tools are able to cut the material with maximum depth of cut and minimum defects in term of tool wear and tool life. In this study the simulation was carried by using Ansys APDL. In order to confirm the actual and distribution irradiation of temperature from simulation, an experimental was done to validate the results. The experiment was conducted by using Nd:YAG laser with wavelength 1064 nm

Numerical analysis of laser heating for laser assisted micro milling application

The promising processing techniques of micro scale parts are very important in products miniaturization and functions enhancement. Combination of two or more processing techniques gives better processing performance especially when dealing with difficult-to-cut materials. For that reason, the combination of laser beam and micro milling process has been widely studied and proven efficient in reducing cutting force and tool life extension. However, this process needs a precise temperature control in order to eliminate heat effect generated by laser beam irradiation. In this study, temperature distributions are determined numerically to characterize the melted zone and heat affected zone geometry. From the results, the estimation of tool and micro milling cutter distance together with the allowable depth of cut are determined

Numerical analysis of laser preheating for laser assisted micro milling of Inconel 718

Micro milling of super alloy materials such as Inconel 718 is challenging due to their excellent mechanical properties. Therefore, new techniques have been suggested to enhance the machinability such as pre-heating the workpiece’s surface to reduce their strength and ductility. Applying pulsed wave laser as a heat source, the prediction of fluctuated temperature distribution in laser assisted micro milling (LAMM) is crucially important. The selection of processing parameters with minimum effect on the processing characteristic is decisive in obtaining high machining quality. Clarifying the effect of heat generated underneath the laser irradiated surface is important to predict the allowable maximum cutting depth and to minimize the risk of tool wear and failure. In this study, ANSYS APDL numerical analysis was used to characterise the workpiece temperature distribution. The numerical model was validated by comparing the results with actual laser irradiation experiment. The experiment was conducted by using Nd:YAG laser with wavelength 1064 nm

Numerical analysis of laser preheating for laser assisted micro milling of Inconel 718

Micro milling of super alloy materials such as nickel based alloys such as Inconel 718 is challenging due to the excellent of its mechanical properties. Therefore, new techniques have been suggested to enhance the machinability of nickel based alloys by pre-heating the workpiece’s surface to reduce its strength and ductility. The prediction of fluctuated temperature distribution generated by pulsed wave laser in laser assisted micro milling (LAMM) is crucial. The selection of processing parameter by minimize the effect on the processing characteristic is decisive to ensure the machining quality is high. Determining the effect of heat generated in underneath surface is important to make sure that the cutting tools are able to cut the material with maximum depth of cut and minimum defects in terms of tool wear and tool life. In this study the simulation was carried by using Ansys APDL. In order to confirm the actual and distribution irradiation of temperature from simulation, an experimental was done to validate the results. The experiment was conducted by using Nd:YAG laser with wavelength 1064 nm