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Technological operation 50 – grinding
Figure 1 shows a technological sketch for 50 technological operation – finished machining of a cylindrical outer surface (final geometric dimension). According to the principles of the technical drawing, very thick lines mean surfaces machined in a given technological operation.
|Cut No:||Description of the technological cut:|
|10||Grinding surface Ø50h6 as shown.|
A grinding machine was used as a technological machine.
It stands out among others the following methods of longitudinal grinding of external cylindrical surfaces:
- The workpiece performs rotary and feed motion along the axis (the sleeve class object moves feed along its axis). The grinding wheel performs rotary and transverse feed motion.
- The workpiece only rotates, and the grinding wheel rotates as well as longitudinal and transverse.
The workpiece rotates. The grinding wheel performs rotary motion and transverse feed motion. As part of cross grinding, shape grinding is also distinguished, where the only difference is the profile shape of the abrasive disk.
An important issue is the selection of grinding wheels and machining parameters to obtain the desired quality effects of grinding. The grinding wheels are selected based on:
- type of machining: roughing or finishing;
- the type of workpiece material being subjected to this operation.
These are the basic selection criteria at the initial stage of abrasive disk selection. In addition to them, among others the size of the contact surface of the grinding wheel with the workpiece is taken into account. The larger the diameter of the abrasive disk and the object, the larger the contact surface. The consequence is difficult crumbling of already blunted abrasive grains. A small diameter workpiece requires a abrasive disk with greater hardness than a shaft with a decidedly larger diameter.
The hardness of the abrasive disk also depends on the type and technical condition of the grinder itself, including the rigidity of its construction. If the rigidity of grinder is not very good and the vibrations occur in connection with it, it is recommended to use grinding wheels with higher hardness.
The grinding operation of a specific cylindrical surface is the last technological operation associated with the machining of a sleeve class part as part of a technological process using only conventional machine tools. Further technological operations are:
- 60: final technical control;
- 70: washing, drying, maintenance and packaging.
The final technical control is the final verification of the obtained quality parameters: the accuracy of the geometric dimensions and the condition of the surface layer of the machined surfaces (roughness, hardness if heat or thermo-chemical treatment is involved). Due to the nature of the hardness measurement, selected items may be subject to verification, not all of them. The visible trace of the indenter may disqualify the item for functional reasons. As a rule, hardened surfaces are ground and carrying out a hardness measurement on such a surface leads locally to a significant deterioration of roughness, which can have a very adverse effect, especially in the context of cooperation between different parts.
Washing, drying, conservation and packaging seem to be slightly neglected but have a significant impact on the durability of manufactured items.
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