- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Fewer-axis grinding methodology with simultaneously guaranteeing surface accuracy and grinding force for large optical SiC mirror
摘要： This paper presents a grinding force control strategy with simultaneously guaranteeing surface accuracy for large optical SiC mirror. A fewer-axis grinder with toric wheel is used to ensure the high stiffness during the grinding process. According to the geometric properties of the contact area at the grinding point between the grinding wheel and the workpiece, the relationship between the grinding force, the feed rate, and grinding depth is derived. Furthermore, the dynamic grinding process model is established by considering the deformation of grinding machine and contour deviation of toric wheel. The contour deviation of toric wheel is also identified by the Fourier transform and analysis of the high frequency fluctuation of grinding force. Based on the grinding principle of toric wheel and the above grinding process model, the force-controlled trajectory planning method for toric grinding is introduced. To ensure the workpiece surface accuracy and decrease the subsurface damage simultaneously, the force-controlled method by adjusting the feed rate and keeping the grinding depth unchanged is proposed. The strategy is successfully validated by grinding experiments of SiC mirror on a high-precision fewer-axis grinding machine.
关键词： Grinding process model,Toric wheel,Force control,Contour deviation
更新于2025-09-10 09:29:36
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Scratching of silicon surfaces
摘要： Nanoscale scratching of silicon surfaces is the elementary abrasive event for various machining techniques including fixed abrasive wiresaw slicing, grinding, elliptical ultrasonic cutting and single-point diamond turning. The understanding of this process is essential for improving the surface quality and reducing sub-surface damage. Nanoscratching experiments are performed using a well characterized diamond tip geometry. The finite element method is employed in order to simulate the scratching process with a continuum constitutive model developed for phase transformation in silicon (Budnitzki, M., Kuna, M., 2016. Stress induced phase transitions in silicon. JMPS 95, 64–91). The required material parameters were determined from indentation experiments in a (111) single crystal Si wafer. The simulation results agree very well with data from scratch experiments without requiring additional calibration.
关键词： silicon,scratching,phase transition,grinding,wiresawing,simulation
更新于2025-09-10 09:29:36
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Materials Science and Technology of Optical Fabrication || Material Removal Rate
摘要： This chapter covers the last of the four major characteristics of optical fabrication, material removal rate (see Figure 1.6). As discussed in Chapter 1, the macroscopic material removal rate is governed by the Preston equation (Equation (1.3)), where removal rate largely scales linearly with applied pressure and relative velocity, and all the process and material parameters are lumped into the Preston coefficient kp. The Preston equation can be applied to both grinding (which is discussed in Section 5.1) and polishing (Section 5.2). The parameters that govern material removal rate and resulting surface roughness are intimately connected. Hence, the principles of the ensemble Hertzian multi-gap (EHMG) and island distribution gap (IDG) models, as discussed in Chapter 4, can be largely applied when discussing polishing material removal rate.
关键词： optical fabrication,IDG model,material removal rate,Preston equation,grinding,polishing,EHMG model
更新于2025-09-10 09:29:36
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On-machine texturing of PCD micro-tools for dry micro-slot grinding of BK7 glass
摘要： While using diamond micro-tools for micro-grinding, tool re-clamping errors and low chip removal space from machining zone are the primary factors which cause large vibrations, higher grinding forces and poor surface quality. On-machine tool preparation and tool texturing prior to micro-grinding can reduce tool re-clamping error. It can further help to reduce the tool-workpiece contact area along with enhanced chip removal from the machining zone speci?cally essential during dry micro-grinding as usage of the cutting ?uid should be minimized or completely avoided for environmental aspects. In this study, end faces of polycrystalline diamond (PCD) micro-tools have been on-machine textured using micro electro-discharge machining (micro-EDM) process. Four types of textured tools are envisaged viz. tool with one micro-cavity at the center of the end face (T2), one micro-groove along the end face diameter (T3), two intersecting micro-grooves at the end face (T4) and four intersecting micro-grooves at the end face (T5). A new term “contact area ratio” is de?ned to explain the texture dimension on the end face of the micro-grinding tools. Performances of di?erent micro-textured tools (T2, T3, T4 and T5) with respect to a normal commercial tool (T1) in terms of grinding force, surface roughness and micro-slot quality are investigated for micro-slot grinding of BK7 glass. It is observed that micro-textured micro-grinding tool e?ciently serves the purpose of provisional chip collection in passive grinding areas of the tool whereas chip adhesion or wear on the active grinding areas signi?cantly gets reduced as compared to un-textured tools. Maximum reductions in the x and y direction forces are observed with tool type T5 compared to all other tool types. Reduction in z direction force is comparable for both tool types T2 and T3. Average surface roughness decreased from tool type T1 to type T2, T3 and up to tool type T4 whereas it again increased for tool type T5. The current study shows that textured micro-grinding tools are capable of reducing high normal forces, surface roughness and material dragging which are major concerns during micro-grinding with ?at-end poly-crystalline diamond tools.
关键词： Polycrystalline diamond tool,Micro-texture,Micro-grinding,BK7 glass,Surface roughness,Grinding force,Micro-EDM
更新于2025-09-09 09:28:46
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Materials Science and Technology of Optical Fabrication || Surface Quality
摘要： The terms “surface quality” and “subsurface mechanical damage” (SSD) are often loosely used. Here we define surface quality as a measure of the level of perfection a workpiece surface exhibits after finishing and cleaning. A perfect surface is defined as a surface free of mechanical, structural, and chemical modification relative to bulk. Note surface quality does not include surface roughness, which is treated separately in Chapter 4. In practice, there is no such thing as a perfect surface, because a variety of microscopic and molecular surface modifications may occur on or just below the surface of the workpiece. As illustrated in Figure 3.1, surface modifications include the following: ? Subsurface mechanical interactions (SSD), which may lead to fracturing, plastic flow, or densification at the surface. ? Foreign particles or residue that may be deposited on the surface as particles land or precipitate during drying. ? Chemical and structural interactions that may result from changes in surface molecular moieties or by altering the near-subsurface (Beilby) layer. These factors affecting surface quality may vary significantly in scale length, from tens of μm to Angstrom level.
关键词： etching,Beilby layer,subsurface mechanical damage,SSD,polishing,grinding,surface quality
更新于2025-09-09 09:28:46