Coarse honing, it is also the first step of honing the cylinder hole. It is mainly used to remove the allowance, eliminate the tool mark in fine boring process, form cylindrical hole with correct geometry and basic surface roughness suitable for subsequent honing process.
Fine honing is the second step of cylinder hole honing. It mainly forms clearly visible, symmetrical and uniform net lines on the surface of cylinder hole, and forms grooves with a certain number and depth on the microscopic contour to form a certain shape, which is also the part that the cylinder hole contacts with the piston during long-term work.
The third step of cylinder hole honing is platform honing, which is the most important step in the three stage honing. A typical platform honing technique is to form a special structure on the surface of the cylinder hole, which is composed of a deep groove with the function of oil storage and a small supporting platform surface between the deep groove, has many advantages, such as: good surface wear resistance, oil film storage, the use of low friction piston rings, reduce oil consumption, reduced running-in time, reduce power loss due to friction.
The allowance of platform honing is usually 3 ~ 5mm, so that the microscopic protrusions generated by fine honing can be worn off to form a series of small platforms, which are the platform supporting surfaces. The surface roughness is very high and the contour supporting length ratio is relatively high. The use of platform honing greatly shortens or even eliminates the run-in period of cylinder hole.
Although fine honing and platform honing are two working steps, the coaxiality of fine honing and platform honing is very high in order to obtain the ideal surface platform reticulation structure. Therefore, the two stages are usually combined into one processing to achieve the realization. By designing a honing head with double feed device and two kinds of honing bars, fine honing and platform honing can be completed by one clamping, and the influence of repeated positioning error is eliminated.
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