High-efficiency and precision cutting of glass by selective laser-assisted milling

As a hard and brittle material, glass is difficult to precisely cut with high efficiency. Although various attempts at ductile cutting of glass with high cutting depth have been reported, the low efficiency of the cutting process remains problematic. In order to achieve high-efficiency and precision cutting of glass, this paper proposes selective laser-assisted milling (SLAM). In this method, a fiber laser that has a wavelength out of the absorption band of glass is absorbed only into the small area where the black-body coating is put, and the selectively heated area is removed with a cutting tool. The experimental results of this study have demonstrated that SLAM reduces the arithmetic average of the roughness profile by 74% compared with conventional cutting. An observational analysis of the generated chips revealed that the application of SLAM changed the morphology of the chips from the crack type to the quasi-continuous type. These results demonstrate the feasibility of the high-efficiency and precision cutting of glass.     

CO2连续激光弯曲硼硅酸盐玻璃薄片实验研究

利用CO2连续激光对硼硅酸盐玻璃薄片进行了弯曲试验,研究了激光功率（P）、扫描速度（V）、扫描次数（n）及样品宽度（d）对弯曲效果的影响,并简要分析了弯曲现象产生的原因。给出了弯曲加工的P,V范围图,获得多组可以成功弯曲玻璃样品的工艺参数。实验结果表明,采用CO2连续激光可以对硼硅酸盐玻璃薄片进行弯曲加工,弯曲角度可达24°以上。     

CO2 laser cutting of stained glass

This paper covers the CO₂ laser cutting of stained glass using a Ferranti MF400 CNC laser cutting machine. The report examines the various laser cutting parameters required to generate a cut surface in glass which will require minimal post-treatment to be carried out, and also investigates the degree of geometrical intricacy that can be attempted, together with the associated limitations, in cutting 2D glass components. The experimental procedure used to obtain the necessary information for a preliminary database on the laser cutting of stained glass is also detailed. Finally, the implications and applications of the investigative work are examined for commercial situations through construction of a simple 2D test artefact.Notation f pulse frequency (Hz) - k thermal conductivity (W/mK) - P laser beam power (W) - Pl pulse duration (10^–5 s) - Pr pulse ratio - Ps pulse separation (10^–5 s) - P shield gas pressure (bar) - R _a surface roughness (m) - t _s substrate thickness (mm) - V cutting speed (mm/min) - V _opt optimum cutting speed (mm/min) - w kcrf width (mm) - angle of deviation (deg.) - wavelength (m) - d perforation depth (mm)     

Experimental investigation on the CO2 laser cutting of soda-lime glass

Journal of Mechanical Science and Technology - This study reports on complete glass cutting using a single CO2 laser beam with a low power of several tens of watts. In this study, the morphological...     

微细立铣削切削振动试验研究

基于45钢微细立铣削试验,分析了微细立铣削切削振动的基本特征,研究了直槽立铣加工时铣削参数对振动加速度和振动位移量影响的基本规律.研究结果表明:在同样的切削工况下,微细立铣削的切削振动远大于大直径立铣刀铣削的情况;铣削参数是振动加速度的主要影响因素,振动加速度随铣削参数的增加都呈上升趋势,但轴向切深H和转速n对振动加速度的影响比进给量f更显著;在一定的参数范围内,减小主轴转速n和增大轴向切深H能够减小振动位移量的大小.     

Experimental study on operating temperature in laser-assisted milling of silicon nitride ceramics

Operating temperature plays a significant role in laser-assisted milling (LAMill) of silicon nitride ceramics. Understanding the features of temperature variation can improve the performance of LAMill. Based on the analysis of operating temperature, this paper aims to provide guidelines on parameter selection for LAMill from three aspects: laser?Csilicon nitride interaction mechanism, effect of parameters on temperature, and evaluation of surface quality of the machined workpieces. First, the laser?Csilicon nitride interaction mechanism is explored via heating experiments. It is found that the formation of silica bubbles at the thin top layer of the workpiece can slightly increase the temperature of silicon nitride workpieces due to the heat energy released from the oxidation process. Then, the trends of temperature variations in LAMill are obtained through a parametric study. The key parameters such as laser power, laser beam diameter, feed rate, and preheat time are highlighted. At last, the surface quality of the machined workpieces under different operating temperatures is evaluated in terms of edge chipping, surface finish, and surface residual stress. It is shown that high operating temperature leads to low cutting force, good surface finish, small edge chipping, and low residual stress. In addition, the temperature range for brittle-to-ductile transition should be avoided since the cutting force decreases slowly due to the rapid increase of fracture toughness.     

高速铣削过程中表面粗糙度变化规律的试验研究

在高速铣削试验的基础上,研究切削速度与进给量对加工表面粗糙度的影响。     

Tribological and mechanical investigation of SiO2 and Si3N4 coatings on fused silica and borosilicate glass

Amorphous SiO₂ and Si₃N₄ plasma‐enhanced chemical vapour deposited (PECVD) coatings were deposited on two different substrate materials (fused silica and borosilicate glass), with three coating thicknesses (0.1, 0.5, and 1.0 μm). The mechanical properties (hardness and elastic modulus) were determined by depth‐sensing indentation, with loads from 700 mN down to 0.1 mN. Tribological behaviour was studied in instrumented oscillating sliding tests at room temperature with a ball‐on‐flat arrangement, in which the coated disc was tested against an alumina ball, at a load of 1 N. Interpretation of the measurement of hardness and modulus of the coatings has to take into consideration the influence of layer thickness and the effect of the substrate. Tensile film stress and crack generation were only observed for Si₃N₄ on fused silica above a threshold thickness. Friction and wear measurements show that the coating has an effect on friction, while wear is affected by the thin coatings only for a short running‐in phase. The morphology of the wear scars indicates that the coatings have good adhesion. Despite crack generation, delamination effects were not observed. Indentation patterns similarly showed excellent lateral homogeneity of the mechanical properties over the entire film surface, and indicated that load‐displacement curves may be used to characterise the system.     

高速铣削过程中表面粗糙度变化规律的试验研究

在高速铣削试验的基础上 ,研究分析切削速度与进给量对加工表面粗糙度的影响。试验数据表明 ,切削速度的提高有利于改善加工表面粗糙度 ,当切削速度超过某一范围后 ,随切削速度的进一步提高 ,加工表面粗糙度的降低并不明显 ,有时还会使表面粗糙度增加。根据试验结果 ,对具体工件材料与刀具材料匹配选择合理的切削速度与进给量范围 ,可以获得最小加工表面粗糙度值     

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.     

An experimental investigation on the machining characteristics of microscale end milling

This paper discusses an experimental approach to assess the machining characteristics in microscale end milling operation through a systematic experimentation procedure. Microchannels were machined on brass plates using a carbide end mill of 1?mm diameter to analyze the effect of chip load (feed per tooth) and cutting speed on the surface roughness, specific cutting pressure, and cutting forces during microend milling operation. The tangential and radial components of forces were analyzed with the help of a three-dimensional model using the force signals acquired through KISTLER dynamometer. Feed per tooth and the interaction of cutting speed and chip load were identified as the critical parameters affecting the surface roughness of microchannel. Applying the concept of elastic recovery on the side wall surface of microchannels, the minimum chip thickness during the above micromilling operation was evaluated as 0.97???m, and the result was validated by the drastic increase in specific cutting pressure and erratic behavior of cutting forces below a chip load of 1???m.     

An investigation on worn surfaces of chopped glass fibre reinforced polyester through SEM observations

The wear mechanisms of chopped strand mat (CSM) glass fibre reinforced polyester (CGRP) composite subjected to dry sliding against smooth stainless steel counterface (R_a=0.06 μm) were studied using a pin-on-disc technique. The effects of normal load (30-90 N), sliding velocity (2.8-3.9 m/s) and sliding distance (0.7-3.5 km) on friction and wear behaviour of the CGRP composite in two different CSM orientations (parallel and anti-parallel) were measured. The worn surfaces of the CGRP composite specimens for each specific test condition were examined using scanning electron microscopy (SEM).Sliding in P-orientation exhibited lower friction coefficient at lower load and higher speed compared to AP-orientation. Meanwhile, sliding in AP-orientation exhibited (15%) less friction coefficient at higher load compared to P-orientation. At higher range of all tested parameters, AP-orientation exhibited less mass loss (16%) compared to the P-orientation.Interestingly, SEM observations showed various wear mechanisms that predominated by abrasive nature. Damage of different features in the matrix and CSM glass fibre associated with higher values of load, speed, and sliding distance such as micro- and macro-cracks in the matrix, interface separation, fibre debonding and fracture, and different sizes of fractured fibres were evident.     

Experimental investigation and numerical analysis for machinability of alumina ceramic by laser-assisted grinding

Alumina (Al₂O₃) ceramic has been widely used in various fields, but it has certain difficulties in machining as a hard and brittle material. While laser-assisted grinding (LAG), an alternative and novel method for fabrication of alumina ceramic, can utilize laser beam to locally heat the workpiece before the ceramic is removed, thereby reducing fracture toughness and keeping the surface integrity. In this paper, a thermal model is established to study and understand the processing mechanism of the LAG process. Meanwhile, an orthogonal experiment is designed and implemented to optimize the grinding process. Then, by analyzing the surface topography, the advantages of LAG are strongly proved. It is found that the temperature modelling results matches experimental results well. The processing parameter that has greatest impact on surface roughness is laser power, followed by grinding depth and wheel speed, and feeding speed at last. The optimal surface roughness value can be obtained by certain processing parameters. Also, compared to conventional grinding (CG), the removal method of alumina ceramics alters from brittle fracture to plastic fracture. Overall, this study clearly elucidates that LAG of alumina ceramic is a very promising machining method, and can be potentially utilized for various industrial, aerospace and automobile applications.     

An experimental study on the machining characteristics in ductile-mode milling of BK-7 glass

Glass is considered as one of the most challenging materials to machine because of its high hardness coupled with high brittleness. The challenge, in machining such a brittle material, lies in achieving the material removal through plastic deformation rather than characteristic brittle fracture. It has already been established that every brittle material, no matter how brittle it is, can be machined in ductile mode under certain critical conditions. The critical conditions are material specific, and hence, every material tends to show unique behavior in terms of critical conditions during machining process. This paper outlines the results of an experimental study to determine the critical chip thickness for ductile–brittle transition, chip morphology, and the effect of cutting speed on the critical conditions in peripheral milling process of BK-7 glass. It is established experimentally that the cutting speed affects the chip morphology, machined surface quality, and critical conditions due to possible thermal effects in such a way that ductile–brittle transition phenomenon is facilitated at high cutting speeds.     

A study on penetration fracture characteristics of glass plates subjected to impact loadings

In this study, a comparison between theoretical solutions and experimental results are examined for fracture conditions in the case of float glass plates subject to static loadings. The ranges from fracture-generated initiations to critical penetration energies are confirmed according to the impactor mass under high velocity, and an analytical method is presented to determine the fracture strength and penetration strength. Also, fracture patterns are investigated according to impact velocities.     

顺逆铣对表面粗糙度影响的轨迹包络几何分析和实验验证

顺铣和逆铣作为铣削加工中的两种铣削方法被广泛地使用,通常认为:精加工用顺铣,粗加工用逆铣,顺铣能获得较好的表面粗糙度和几何精度。通过对立铣刀侧铣平面、凸凹圆弧面时,刀具旋转运动和进给运动的轨迹包络几何,计算出顺铣、逆铣时不同的残留高度,得到逆铣加工得到的表面粗糙度优于顺铣。然后通过实验:采用顺铣和逆铣两种方法对平面、凸凹圆弧面进行加工,对表面粗糙度进行对比和数据分析也证实了逆铣加工得到的表面粗糙度要优于顺铣。     

半球形屋面结构风荷载特性试验研究

球形屋面网壳结构是常用的大跨结构屋面形式.在同济大学TJ-3大气边界层风洞中,通过1∶200比例的刚性测压模型,研究了A,B两类风场下半球形屋面结构表面的平均以及脉动风压分布特征.试验结果表明风场类型对平均风压分布影响较小,但对脉动风压分布会有相对较大的影响.同时通过研究子午线上平均及脉动风压分布,表明结构顶部的突出圆顶（采光顶）将增大结构局部风荷载,设计时需特别考虑.最后给出了适合工程应用的分块体型系数,以供结构工程师设计参考.     

Experimental research on machining characteristics of SiC ceramic with end electric discharge milling

Silicon carbide (SiC) ceramic has been widely used in modern industry. However, the beneficial properties of SiC ceramic make machining difficult and costly by conventional machining methods. This paper proposes a new process of machining SiC ceramic using end electric discharge (ED) milling. The process is able to effectively machine a large surface area on SiC ceramic at low cost and no environmental pollution. The effects of emulsion concentration, emulsion flux, milling depth, copper electrode number, and copper electrode diameter on the process performance such as the material removal rate, electrode wear ratio, and surface roughness have been investigated. In addition, the microstructure of the machined surface is examined with a scanning electron microscope, and the material removal mechanism of SiC ceramic during end ED milling is obtained.     

四轴数控重磨球头立铣刀端刃的实现问题研究

球头立铣刀的应用越来越广泛，其质量好坏直接影响到加工对象的表面质量、精度及加工效率。目前，刀具用户对球头立铣刀用钝后的重新修磨，依靠手工进行，其精度无法保证，如何有效解决它的修磨问题十分迫切。本文从工作实际出发，就如何进行快速、准确、高质量的刀具修磨工艺和编程技术进行研究，对具体地如何实现球头立铣刀端刃的重磨和夹具设计问题进行讨论。