Papers by Keyword: Laser Drilling

Abstract: Motivated by a desire to improve hole quality during drilling Polymethyl methacrylate (PMMA) samples using a continuous CO₂ laser. This research presents a theoretical and experimental investigation to optimize input parameters of laser drilling such as laser power and exposure time for different thicknesses 1-3 (mm). Hole quality characteristics such as depth, inlet diameter, and heat affected zone (HAZ) were considered process results and examined with a microscope. Design Expert software has been used to get a detailed understanding of a laser drilling process owing to the confluence of multiple factors that impacts the results. depending on the Box Behnken Design (BBD) of tests software; 17 experiments were applied to explore the effect of laser factors on the micro-hole drilling process. Statistical analysis technique (ANOVA) was used to study the influence of laser drilling process factors including power, exposure time of different thicknesses on HAZ, depth, and entrance diameter. Quadratic regression models were employed to model the processing of many hole variables. Experiments were optimized using the defined goal model as a function to get the optimal hole. The data received were confirmed using verification tests, and a considerable increase in hole quality was realized. The proposed technique is perfect for reducing the HAZ and entrance hole diameter for the ideal depth hole. The laser parameters were changed in different combinations of 2-6 (W) power and 0.1- 0.3 (s) exposure duration, on the various thickness. The obtained values indicated that raising the drilling parameters increases the depth, entrance diameter, and HAZ. The sample thickness has a great impact on hole characteristics; increasing the sample thickness reduces the inlet diameter, and heat-affected zone (HAZ); increasing the thickness leads to an increase in hole depth. The results showed that the highest depth of 1mm thick was 0.99(mm) with 437(µm) diameter and 85(µm) HAZ. 1.9(mm) depth with 435(µm) diameter and 32(µm) HAZ was obtained at 4.99(W) and 0.1(s) on 2(mm) thickness. while as in 3(mm) thick, depth is equal to 2.8(mm), 472(µm) diameter, and 20(µm) HAZ was attained. COMSOL Multiphysics 5.6 software was used to apply virtual experiments and obtain the ideal conditions from the parameters' combination that improves the quality of the hole, which is the main goal of this research. Which is in good agreement with the test results. The findings and procedure of this research have not been presented elsewhere.

Abstract: Nimonic 263 is an alloy with superior mechanical strength and creep resistance at high temperatures and pressure, good formability, and corrosion and oxidation resistance. Due to their high beam density and very short pulses which reduces the heat affected zone (HAZ) Nd:YAG lasers are very suitable for materials drilling. In this paper, the Nimonic 263 sheets, thickness of 2 mm, are laser drilled with various parameters. The influence of laser drilling process on microstructural changes along with the geometrical characteristics are analysed and discussed.

Abstract: In laser processing of surfaces, typically to impart some texture or to drill shallow holes, it is necessary to correlate pulse properties (wavelength, power, beam radius and quality, duration) and material properties (reflectivity, melting temperature, conductivity, diffusivity) mainly with the depth of the formed crater. Crater shape is assumed to be paraboloidal and its maximum diameter is assumed to be uniquely related to its depth. An empirical and an analytical model are suggested to this end. The former entails construction of Artificial Neural Networks from experimental measurements, whilst the latter entails modification of established models from literature. Both types of models are exemplified in this paper drawing on data from available literature.

Abstract: Both superalloy GH2135 and stainless steel 420J1 were used as test materials to be processed by LASERTEC 80 PowerDrill three-dimensional solid laser processing center. The microstructure of the hole was investigated by super depth of field microscope and laser scanning microscope. The front and back orifice diameter, orifice deposits and thermal effect of accumulation zone were studied. The single factor test method was used to study the influence of pulse energy, pulse width and repetition frequency on the quality of micro holes. The results showed that the front and back diameter of the holes all increase with the increase of pulse energy from 0.4J-3.9J. And the front and back aperture are increase with the increase of pulse width from 0.9ms-1.9ms. Meanwhile, the variation of the aperture and pore taper is more noticeable with the repetition frequency changed from 10Hz-60Hz. The results revealed that pulse energy is one of the biggest influence factors, large pulse energy can lead to small hole taper within a certain range, and short pulse width can reduce orifice debris and splash. Both the recast layer and microcrack were existed in the two kinds of metal materials. The quality of holes drilling in GH2135 is better than 420J1.

Abstract: A laser drilling technique named the nested-circle method is introduced in this work, in the respect of short-pulse laser processing.it is found that, as the power increases, the depth to diameter ratio of the hole will increase and the minimum number of circles can be set drilled hole reliably is reduced. Further studies have been carried out on the effect of the number of circles in the nested-circle method. Keys of settings the nested-circle method parameters—Outer circle diameter ‘D1’, Inner circle diameter ‘D2’, The Number of circles ‘R’—have been found out.

Abstract: In this paper, the technique of drilling process with picosecond(ps) laser is studiedinAl2O3 ceramics. The defocus method is used to drill the ceramic slice, which is able to improve thedrilling ratio of depth to diameter.It is found out that the best location ofthis ps-laser is about0.15mm under the lower surface of workpiece,demonstrating the difference from nanosecond(ns)-laser machinein the respective ofdefocusing.The impact of the power and the processing speed isinvestigated on the quality of the drilling. For ps-laser machine,a smaller and high qualitythrough-holeis achievable by increasing the power of laser and reducing the speed of process, withthe ratio of depth to diameter from 3.12 to 4.27.The ratio can be further increased upto 6.25,throughoptimization of these three parameters: defocusing amount, laser power and laser processing speed.

Abstract: In order to improve the machining efficiency of the CNC laser drilling, this paper presents the path optimized method based on an improved ant colony algorithm of the k-means clustering approach. The mathematical model of the path optimization is constructed, and the path optimized method based on the improved clustering ant colony algorithm is designed and actualized. The optimized path method for CNC laser drilling based on the improved clustering ant colony algorithm is tested, and the simulative and experimental result have shown that the proposed method is better performance, and the machining efficiency is greatly improved.

Abstract: The industrial relevance of bore holes with small diameters and high length-to-diameter ratios rises with the growing requirements on parts and the tendency of components toward downsizing. Examples are components for medical and biomedical products or fuel injection in the automotive industry. An adapted process design is necessary for the production of deep holes with very small diameters, especially when the conditions at the beginning of the deep hole drilling process are unfavorable. In these applications, a hybrid process consisting of a laser pre-drilling and a single-lip deep hole drilling can shorten the process chain in machining components with non-planar surfaces, or can reduce tool wear in machining case-hardened materials. In this research, the combination of laser and single-lip drilling processes was realized and investigated for the very first time. In addition, results for the machining of workpieces with non-planar surfaces are presented.

Abstract: In this paper, intermittent gas jet assisted laser drilling on stainless steel (SUS304) with a fiber laser of wavelength 1090 nm is studied. Compared with the conventionally used continuous gas jets in assisting laser drilling, the intermittent gas jet assisting can effectively increase the material removal rate. The intermittent gas jet can be modulated with the frequency to effectively reduce the over-cooling effect by the assist gas. Experimental result shows that the drilling depth and machining time can be improved. The effects of the intermittent gas jet pressures and the synchronicity of gas and laser pulses on the laser drilling are investigated and discussed. It is observed that the intermittent gas jet method obviously reduces heat loss and increases the machining efficiency during the laser drilling. Compared with result of using the continuous gas jet, laser drilling with the intermittent gas jet at 40 Hz increases the drilling depth with an improvement of 10%. It is worth noting that the intermittent gas jet method can also reduce the quantity and cost of gas while the gases such as helium and argon gases are applied.

Abstract: As the production demand for laser drilled holes continues to grow, efficient and reliable process monitoring and control techniques are required in order to improve the manufacturing efficiency and reduce manufacturing cost for ensuring quality conformance. A robust, real-time monitoring system for breakthrough and the drilling depth detection in laser drilling is proposed. The system is based on based on coaxial visual sensing technology of the working surface using a CMOS camera, coupled with microcontroller control of the drilling laser operation. The camera is installed adjacent to the entry surface of the workpiece, and the spatial extend of the laser-induced plasma at the working site is monitored as the criterion for breakthrough detection. Therefore, on-line inspection system with low cost is developed to increase productivity. Experimental results show that the proposed system successfully detects when the laser beam has broken through a workpiece, and turns off the laser automatically by feedback control.