Abstract
Here we present the raster method of final abrasive treatment of surfaces. Here we describe the theoretical foundations and patterns of raster processing method. We also describe the kinematics of lapping and polishing machine Rastr 220. For pieces of brittle composite material based on graphite, we have designed and manufactured a universal multipiece arrangement. The number of simultaneously machined pieces and their location in the device shall provide an even lapping wear. For this purpose, the axis of rotation of the tool shall be offset about its axis of symmetry to 5-15 mm. The device of larger diameter at the lapping should provide for periodic lapping bleed of the pieces by a certain amount. However, from the viewpoint of surface grit, a high lapping bleed of the pieces is not desired. In the process of lapping, the device shall be fully loaded with pieces. In case of impossibility to meet these requirements, it is necessary to periodically change the position of pieces in it. The device allows to compensate for different height of processable workpieces, to provide for their self-aligning on the tool surface, and to place the pieces evenly over the surface of lapping. The experimental testing of the treatment process on the machines with raster kinematics of the tool working movement was carried out. The comprehensive studies of precision treatment process for high-precision pieces made of composite materials based on siliconized graphite of grade (GAKK 55/40) were conducted. The requirements for working planes of the pieces are the following: Ra not more than 0.1 µm, flatness deviation not more than 0.6 µm. An estimation method for surface indulation was offered, and common technological advice on the implementation of raster lapping process for siliconized graphite pieces on the machine Rastr 220 was developed.
Highlights
Reliability and durability of mechanisms and machines containing nodes with different mechanical seals is largely dependent on the quality of surface finishing for high-precision workpiece surfaces
The multipiece arrangement for simultaneous treatment of three parts was designed and manufactured for lapping of rings made of siliconized graphite
The lapping and polishing machine "Rastr 220" does not require the additional production spaces, it is easy in maintenance and adjustment, and can perform both group and routine treatment of pieces
Summary
Reliability and durability of mechanisms and machines containing nodes with different mechanical seals is largely dependent on the quality of surface finishing for high-precision workpiece surfaces. One of the final methods of precise flat surfaces treatment is the abrasive lapping. Sometimes only this technique is possible, especially in the lapping of pieces made of solid composite materials, such as ceramics, cemented carbide, glass, ruby, siliconized graphite and others. In the production environment with the small output or rebuilding of pieces such as mechanical seals, the finishing shall be made by repeated manual lapping. This technology is very time-consuming and requires professional skills. This finishing operation allows to obtain a surface with the grit of Ra=0.004-0.16 μm and deviation from the desired geometric shape up to 0.1-0.3 μm. (Reznikov, 1977; Shalnov, 1972)
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