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Design for Machining
Published in Helmi Youssef, Hassan El-Hofy, Non-Traditional and Advanced Machining Technologies, 2020
Valve spools, fuel injector plungers, seal rings, piston rods, valve stems, cylinder heads, and spherical valve seats are typical applications. Holes or pins as small as 0.8–300 mm in diameter can be lapped. Flat WPs having an area from 6 to 1300 cm2 can be lapped successfully. For one-of-a-kind fabrication, hand lapping is used. Automatic lapping machines are available for mass production at high rates of 3000 piece/h. Steel and CI are most frequently used by lapping. Glass, aluminum, bronze, magnesium, plastics, and ceramics can also be finished by lapping. Soft materials are less satisfactory for lapping, as the abrasive grits are embedded in the lapped surface.
Detector Fabrication
Published in Alan Owens, Semiconductor Radiation Detectors, 2019
Crystal surfaces “as-cut” are very rough. For almost all detector applications, the crystal surface must be optically flat to ensure uniformity and reproducibility in its mechanical and electrical characteristics. To achieve such a finish, crystals are usually lapped and polished using a purpose-built machine as shown in Fig. 6.3. Lapping is a machining operation, in which two surfaces are rubbed together with an abrasive between them. The crystal to be processed is one surface and is known as the workpiece. In the lapping machine, it is held in a metal chuck between two rings while pressed onto the second surface (known as the lap) which is usually a rotating wheel. Abrasive slurry flowing on to the wheel serves two functions – abrasion and lubrication. A weight on top of the workpiece provides the load and a micrometre is used to gauge how much material is removed. Depending on the machine, the rings may be kept stationary while the disk rotates or they may be moved in a reciprocating sliding action. Crystals are lapped first in coarse carborundum (SiC) powder followed by fine carborundum powder. Polishing then takes place in several steps, first, in coarse alumina (Al2O3) emulsion (3 μm), followed by in fine (0.05 μm) alumina emulsion. This procedure results in an optically flat surface with a mirror finish. For soft materials, where mechanical damage can extend several hundred microns into the crystal, it is usually recommended that the crystal be cut into thick slices and polished to the required thickness to remove the damaged layer.
Abrasive Applications of Diamond
Published in Mark A. Prelas, Galina Popovici, Louis K. Bigelow, Handbook of Industrial Diamonds and Diamond Films, 2018
K. Subramanian, V. R. Shanbhag
Lapping is the process of finishing work materials by applying a loose abrasive slurry between a work material and a closely fitting surface, called a lapping plate. When loose abrasive is used to machine the work material, it may slide, roll, become embedded, or do all three, depending on the shape of the abrasive grain and the composition of the backup surface.
Experimental studies on reflective finishing of aluminum sheet by CNC abrasive lapping
Published in Materials and Manufacturing Processes, 2023
Lapping process generally carried out on the specially designed lapping machine with loose abrasive particles used to remove the material from the surface of workpiece. U. Heisel and J. Avroutine analyzed the lapping mechanism and how the movement of the abrasive grains between the lap plate and the workpiece during the lapping process has a significant impact on the mechanisms of surface development and removal rate.[3] Ahn, Y., and Park inferred that more mass concentration of abrasives increases the metal removal rate but decreases the surface quality after lapping the ceramics.[4] Sergey N. Grigoriev et al. shows that the lapping decreases Rt value on Al2O3/TiC and SiAlON Ceramics.[5] The lapping process can also be used to get the precise surface on ceramic balls.[6] The lapping process plays a significant role in optical glass polishing. The different abrasives slurries, its concentration, abrasive grit size, lap load affects the surface quality of fused silica samples.[7] The lapping the optical glass influenced by the abrasive grains and it wear.[8]
Effect of rotational speed ratio between platen and work piece on lapping processes
Published in Machining Science and Technology, 2020
Tufa Habtamu Beri, Yang Ling, Min Liu, Wei Hang, Julong Yuan
As can be revealed from the literature, variables that have been considered in the study to affect lapping process so far includes, abrasive grain size, types of abrasive, concentration of abrasives, viscosity of the compound, lapping pressure, lapping speed, lapping time, and lap material/disc material. However, a trajectory analysis of a single fixed abrasive particle embedded in lapping plate shows various paths from simple and uniform to complex paths for rotational speed ratio between lapping plate and workpiece. The authors assume these trajectory path variations will have an effect on the material removal and surface quality of lapping process. Therefore, the purpose of this paper is to conduct effect of lapping process by introducing rotational speed ratio between lapping plate and workpiece as new input process parameter. In the study, at first trajectory study analyses of single fixed abrasive particle embedded in the lapping plate were presented under different rotational speed ratios between lapping plate and workpiece. Then experimental investigation was conducted to study the effect of the rotational speed ratios on silicon wafer.
Development of magnetically assisted lapping process for nano-finishing of alumina balls
Published in Machining Science and Technology, 2019
Partap Singh Samra, Sehijpal Singh, Lakhvir Singh
Moreover, finishing of ceramic balls with high quality, good efficiency and low cost is critical to their widespread application. Most of the research is carried out using conventional lapping and magnetic float polishing. London (1990) has developed an apparatus for low stress polishing of balls which helps in reducing total machining time. Sato (1994) has designed a ball lapping machine capable of solving the problems in the conventional technique with regard to machining accuracy, operability and circulation. The process of conventional lapping has its own disadvantages such as: The process uses high loads (∼10 N per ball), low polishing speeds (∼50 rpm), and diamond abrasive. It takes a considerable long time (6–16 weeks) due to lower speeds. Furthermore, the use of abrasive under heavy loads results in scratches, pits and micro cracks in the surface of the polished balls.