陶瓷喷嘴Nd:YAG激光精密打孔应用研究

通过在陶瓷喷嘴上进行激光打孔的多种工艺参数试验，分析了激光能量、脉冲宽度和激光频率等对打孔质量的影响，摸索出了一套切实有效的激光打孔工艺参数，较好地解决了小孔锥度问题，加工出了合格的陶瓷小孔样品。并对激光加工工艺参数进行了多因素分析，探讨了多种加工工艺参数对加工小孔锥度的影响。     

激光小孔加工实验研究及工艺仿真

通过单因素试验分析了激光器电压、脉冲宽度、重复频率、聚焦条件、辅助气体等因素对小孔加工效果的影响规律。借助MATLAB神经网络工具箱和遗传算法工具箱,建立了基于BP神经网络和遗传神经网络(GA-BP)的激光打孔加工工艺仿真模型,利用两种模型分别对不同加工参数下的小孔孔径进行了仿真和预测。结果表明,经遗传算法优化后的BP网络模型具有更好的预测精度。     

宝石的激光打孔、切割和检验

一、激光打孔机原理、参数及工艺要求我厂激光打孔机是宝石打孔的专用设备,是以钕玻璃为工作物质的固体激光器。工作频率为每秒50～70次,完成一个打孔需1～2次脉冲,脉冲宽度在0.5～2毫秒,输出能量为1～2焦耳。为了获得不同能量和不同激光束进行有效打孔光学谐振腔在一定的要求范围内(选择),打小孔粒子的腔长800毫米,打大孔粒子的腔长520毫米,构成谐振腔的两个反射镜,1.06微米波长,透射率为50％、95％的平面反射镜分别为φ20毫米,聚光器采用椭圆柱形聚光器,为了使工作物质吸收光谱及脉冲氙灯发光,光谱相匹配,聚光器采用银板反射镜镀层,工作时谐振腔聚光器用冷水冷却,聚光器长度:170mm、长轴720mm、短轴6.2mm,     

激光打孔温度场的数值分析与仿真

根据激光打孔的特点及实际加工环境建立其数学模型,对激光打孔过程的温度场利用有限元法和有限差分法进行了数值计算,并通过ANSYS进行仿真得到小孔的孔深、孔径的时间特性以及随激光能量的变化曲线,为激光打孔参数的选取提供了依据。     

激光在加工中的应用

使用透镜可把激光的高强度光聚焦在试样上,因此可以熔化并蒸发掉试样的材料,从而加工出小孔。激光切割功率的这种简单过程是非常易于实现的,但从一台机床的观点来看,仍然存在着一些问题。首先,尽管在设计射束过程中的考虑是非常充分的,但用这种方法加工出来的原始“小孔”在形状上常常是不规则的。对于成功的操作来说,激光能的持续时间是很严格的。在连续或高重复脉冲输出的情况下,沿选择的通路移动激光射束便可进行切割和焊接。(基于同一理由,用脉冲能量来打孔是最容易的,因为普通机械打孔采用重复的或周期性的力。要达到高功率,断续地施力比连     

激光加工微小孔内表面粗糙度的测量

采用激光打孔方法分别加工出直径为 0 2mm、0 2 5mm和 0 3mm的微小孔 ,应用剖分法直接接触式测量得到所加工微小孔的内表面粗糙度 ,并使用反射式显微镜进一步直接观察验证。该测量结果可用于熔融快速原型机喷头的微小孔内表面粗糙度的确定 ,也可用于研究纺丝机、喷墨打印机等类似微小孔时参考     

超短脉冲电流微细电解加工技术研究

利用电化学腐蚀方法,在自制的电解加工机床上连续实现微细工具电极的制作和工件的加工,通过试验研究了超短脉冲的电压幅值和脉冲宽度对侧面加工间隙的影响。结果表明,减小脉冲宽度,降低加工电压,可以提高微细电解加工的精度。利用优化的加工参数,进行了微小孔加工、微细直写加工以及成形电极微细加工的实验。     

皮秒激光CVD金刚石膜打孔温度场仿真

建立了皮秒激光在CVD金刚石膜打孔时的瞬态热传导三维物理模型并利用ANSYS对过程进行了仿真,分析了温度场的空间变化规律以及温度场随时间变化趋势,将仿真值和实验结果进行了对比,在此基础上研究了激光能量,脉冲宽度,重复频率等对打孔品质的影响。     

激光切割钢板时高质量切缝起点的工艺参数

激光切割往往是在最初的切割位置打一个小孔,然后再进行切割,而小孔则会赞成切割质量的下降。一种新的激光切割方法可以避免类似火山口状的起始切割孔,切割起点可以和后序切割质量一样。先用脉冲激光束,然后用连续激光束（功率按一定斜率上升）对板材打孔的同时进步板材的加速移动,这种加工参数可以在激光器内进行预先设置。各种厚度的低碳钢和不锈钢其起始切割参数均是一定的,欲得到最好的切割 使加速度较小（1m/s^2）,对于1mm厚的低碳钢和不锈钢薄板在材加速的同时功率按设定斜率变化其打孔质量优于厚板。与正常切缝比,在切缝起始1mm处可发现轻微的质量变化。这种现象可以用切割起始时速度变化来解释。     

信息

90033用激光加工喷雾器针阀体 吉林工业大学研制的喷雾器针阀体激光打孔机于去年11月份通过省级鉴定。由于有激光电源储能电容充电采用闭环自动控制、脉冲氙灯按临界阻尼状态放电并进行预电离、激光脉冲采用超声调制、工艺参数确定方法合理等,保证了激光打孔的精度、表面质量及稳定性。用该机在 18CrNiWA材料上加工φ0.25～0.3mm、深1～ 2mm的孔,其孔径精度可控制在0.02mm范围之内(IT8—9级),几何形状精度可达B级,表面粗糙度Ra0.04μm以下,成品率可达95%以上。台架试验和雾化高速摄影试验表明,激光打出的喷孔达到了12V150LA发动机性能…     

毫秒激光金属打孔的解析和实验

研究了用毫秒脉宽的长脉冲激光单个脉冲打深孔的成形过程和打孔速率.首先,由切割法得到了1 ms脉宽的Nd:YAG高斯激光对厚铝板打孔时孔的形貌,激光能量为7.9和28.9 J时,对应的孔深分别为1.849和2.975 mm.根据实验建立了轴对称模型,通过热传导方程得到了固相温度的解析解.然后,假设物质一旦熔融就离开孔,由...     

Statistical analysis of repeatability in laser percussion drilling

This study investigates the effect of six parameters in the repeatability of drilled holes in laser percussion drilling process by means of statistical techniques. Peak power, pulse width, pulse frequency, number of pulses, gas pressure and focal plane position were considered as independent process parameters. Experiments were designed with the aim of reducing the number of required experiments. The response surface method was used to develop the models for required responses. The significant factors in the process were selected based on the analysis of the variance (ANOVA). The experiments were conducted in mild steel sheet with a thickness of 2 mm. Each experiment was repeated 35 times in order to investigate the repeatability of the process. The equivalent entrance diameter, percentage of standard deviation of entrance diameter (%STD Eq Dia), circularity (ratio of minimum to maximum Feret’s diameter) and its standard deviation (STD circularity) were selected as process characteristics. The %STD Eq Dia and STD circularity, respectively, show the repeatability of equivalent diameter and circularity in the process. The results show that the process of drilling smaller hole diameters is more repeatable than drilling larger holes. Pulse width, gas pressure, focal plane position, peak power and number of pulses, respectively, have significant effect on the repeatability of hole diameter and circularity. Pulse frequency has no significant effect on the repeatability of the process.     

An investigation of practical application of variable spindle speed machining to noncircular turning process

The present study investigates the effects of four controllable variables on the metallurgy and drilling velocity of laser percussion drilled acute (30° to surface) blind holes in 2 mm thick flat pieces of nickel superalloy—CMSX-4 material. Design of experiment and statistical modelling were used in the experimental study to understand parameter interactions. Pulse energy, pulse width, pulse frequency and gas pressure were chosen as the independent process variables. The response surface method was used to develop the models for each of the responses: physical characteristics of wall and bottom recast layer and drilling velocity (function of material removal rate). A central composite design was chosen as it offered the most economical number of experiments for the required information. The significant process factors in each model were identified based on the analysis of variance and the models were checked by complete residual analysis. It was found that high pulse energy and short pulse width gave the maximum drilling velocity and lowest recast layer thickness at the hole bottom, whereas low pulse energy and short pulse width minimised the wall recast layer thickness.     

Analysis of silicon via hole drilling for wafer level chip stacking by UV laser

For stacking wafers/dies, through-silicon-vias (TSVs) need to be created for electrical connection of each wafer/die, which enables better electrical characteristics and less footprints. And for via hole processing, chemical methods such as DRIE (Deep Reactive Ion Etching) are mostly used. These methods suffer the problems of slow processing speed, being environment-unfriendly and damage on the existing electric circuits due to high process temperature. Furthermore, masks are also needed. To find an alternative to the methods, researches on the laser drilling of via holes on silicon wafer are being conducted. This paper investigates the silicon via hole drilling process using laser beam. The percussion drilling method is used for this investigation. It is also examined how the laser parameters- laser power, pulse frequency, the number of laser pulses and the diameter of laser beam- have an influence on the drilling depth, the hole diameter and the quality of via holes. From these results, laser drilling process is optimized. The via hole made by UV laser on the crystal silicon wafer is 100μm deep, has the diameter of 27.2μm on the top, 12.9μm at the bottom. These diameters deviate from the target values by 2.8μm and 0.4μm respectively. These values correspond to the deviation from the target taper angle of the via hole by less than 1°. The processing speed of the laser via hole drilling is 114mm/sec, therefore, etching process can be replaced by this method, if the number of via holes on a wafer is smaller than 470,588. The ablation threshold fluence of silicon is also determined by a FEM model and is verified by experiment.     

Enhanced processing speed in laser drilling of stainless steel by spatially and temporally superposed pulsed Nd:YAG laser radiation

Percussion drilling through holes in stainless steel (1.4301, 5, 8, and 10 mm in thickness) was performed with the superposed radiation of two pulsed Nd:YAG lasers. Holes were drilled with flash lamp pumped Nd:YAG slab-laser radiation with a pulse duration of 0.5 ms superposed with diode-pumped solid-state (DPSS) laser radiation with a pulse duration of 17 ns. The drilling efficiency is improved by the spatially and temporally superposed radiation of the two lasers. With the superposed laser radiation, drilling through stainless-steel samples at a maximum aspect ratio of 60 is performed up to four times faster with the reproducibility of the drilling time improved by a factor of six in standard deviation.     

Experimental investigation of surface and geometrical characteristics of rotary ultrasonic drilling of soda glass

Edge-chipping, surface roughness and dimensional accuracy are crucial quality aspects of drilled holes in hard-to-cut material such as glass, ceramics and carbon fiber reinforced plastics. In this article, an experimental study was conducted to investigate the quality measures of holes produced by rotary ultrasonic drilling (RUD) and conventional drilling. Edge-chipping width at tool exit side, the surface roughness (Ra and Rz), out-of-roundness, cylindricity error and hole conicity were the main responses when drilling soda glass using diamond abrasive tools and a cutting fluid. Statistically designed experiments were carried out for rotary ultrasonic and conventional drilling (CD) at two levels of tool feed rate (0.6 and 6?mm/min), spindle speed (3,000 and 8,000?rpm) and tool particles-concentration. Analysis of variance was used to define the significant factors and their interactions and build models for predicting the responses. The results showed that reducing the chipping, surface roughness and roundness error. The normal tool concentration showed a substantial effect in improving the surface quality and reducing the hole-geometrical errors.     

Ceramic to metal joining by using 1064 nm pulsed and CW laser energy source

A novel joining method for ceramic and metallic layers is proposed using laser drilling and surface tension driven liquid metal filling. A high intensity laser beam irradiated a 500 μm thick ceramic filter, and the irradiated laser drilled the ceramic layer. The pulsed or CW laser transmitted through the ceramic layer irradiated the bottom metallic layer; the molten metallic layer then filled the drilled ceramic holes by the capillary force between the liquid metal and ceramic layer. As process variables, average laser power, pulse duration, and the number of pulses were used. The scattering optical properties were also studied for both green and red lasers. There was no significant difference between the colors and the estimated extinction coefficients were ?26.94 1/mm and ?28.42 1/mm for the green and red lasers, respectively.     

Laser hole cutting in Kevlar: modeling and quality assessment

Machining of Kevlar laminates with conventional methods results in poor end-product quality and excessive specific energy requirement for machining. However, laser machining has considerable advantages over the conventional methods due to precision and rapid processing. In the present study, laser hole cutting into Kevlar laminates with different thicknesses and properties is carried out. The laser output power, frequency, and cutting speed are varied during the hole-cutting experiments. The specific energy requirements for cutting, thermal efficiency of the cutting process, and kerf width are formulated and predicted for various laser parameters and Kevlar properties. The cut quality is associated with the damage size around the holes cut and statistical analysis is carried out to examine the affecting parameters on the damaged size. It is found that specific energy requirement is significantly lower than that of the conventional drilling method. The damage size is affected significantly by the laser irradiated power. The quality of holes, as judged by the percentage of damage size around the cut edges cut by a laser beam, is considerably improved compared to the conventional methods.     

High-speed drilling of small-diameter holes by core flat drills

Examples are presented to illustrate the high-speed drilling of small-diameter holes (up to 10 mm) by core flat drills: holes (diameter 7 mm) in a discharge valve; and the drilling two-part holes consisting of a cylindrical section (diameter 3.8 mm) and conical section (base diameter 10 mm) in a metal housing.     

Ablation drilling of invar alloy using ultrashort pulsed laser

Drilling a hole in Invar alloy is accomplished by using a nanosecond pulsed Nd:YAG laser. However, this process has a few problems, such as heat effect and poor edge quality. Therefore, the ablation properties of the Invar alloy were investigated by using an ultrashort pulsed laser, which is a regenerative amplifier Ti:sapphire laser with a 1 kHz repetition rate, a 184 fs pulse duration, and a 785 nm wavelength. To study the ablation characteristics of the Invar alloy, we measured the ablation shape, width, and ablated depth at the energy fluence of a single pulse. The optimal condition for hole drilling is a z-axis transfer depth of 4 μm, a circular feed rate of 0.2 mm/s, and a pulse energy of 26.4 μJ. A fine circular hole without burrs and thermal damage were obtained under the optimal processing conditions. The ultrashort pulsed laser system is an excellent tool for micro-hole drilling in Invar alloys without heat effects and poor edge quality.