Honing technology principle
This process not only allows for a large machining margin (honing was used for polishing in the 1950s), but is also an effective method for machining parts with high precision dimensions, geometric shape accuracy, and surface roughness.
Honing features :
1.High machining accuracy
In particular, some small and medium-sized optical through hole, the cylindricity of up to 0.001mm.- parts with uneven wall thickness, such as linkages, have roundness up to 0.002mm. For large holes (with a diameter of less than 200mm), the roundness can also be up to 0.005mm. If there is no ring groove or radial hole, etc. The straightness within 0.01mm is also possible. The accuracy of honing is higher than that of grinding. The bearing supporting the grinding wheel is located outside the honing hole during grinding, so there will be deviation. Honing can only change the shape accuracy of the processed workpiece. Some necessary measures should be taken to change the position accuracy of the part.If use the panel to improve the verticality of the end face of the part and the axis (the panel is installed on the stroke arm, adjust it to be perpendicular to the rotating spindle, the part can be processed by leaning on the panel).
2.Good surface quality
The surface is cross mesh, which is beneficial to the storage of lubricating oil and the maintenance of oil film. With a high surface support rate (the actual contact area between the hole and the shaft and the ratio of the matching area between the two), it can withstand greater load and wear resistance, thus improving the service life of the product. The honing speed is low (it is tens of percent of the grinding speed), and the oil stone is in contact with the hole, so the uniform grinding pressure of each grinding particle is small, so the heat value of the workpiece is small, the surface of the workpiece almost no thermal damage and metamorphic layer, deformation is small. The honing surface is almost free of inlaid sand and extruded hard layer. The grinding pressure is higher than the cutting pressure of honing. The grinding tool is in line with the workpiece and has higher relative speed. As a result, high temperature will be generated in local areas, which will lead to permanent damage to the surface structure of parts.
3.Wide processing range
Main processing of various cylindrical hole: light through hole. Holes with axial and radial breaks, such as holes with radial holes or grooves, keyway holes, spline holes.Blind holes. Multi-step hole, etc.In addition, special honing head can also be used to process conical hole, elliptical hole, etc. However, due to the complicated structure of honing head, it is generally not needed. The cylinder can be honed with the external honing tool, but the margin of division is much smaller than that of the internal honing. It can process almost any material, especially diamond and cubic boron nitride abrasive applications. It also improves the efficiency of honing.
The cutting process of honing
1.Constant press feeding honing
Constant pressure feeding, feeding mechanism with constant pressure to the hole wall, divided into three stages.
The first stage is the shedding cutting stage
At the beginning of the honing process, due to the roughness of the hole wall, the contact area between the oil stone and the hole wall is small and the contact pressure is large. The protruding part of the hole wall is quickly ground. And because of the large contact pressure on the surface of the stone, together with the chip of the stone binder wear, so that the bond strength of the particles and binder drop, so that some of the particles in the cutting pressure of their own fall off, the surface of the stone is exposed new grinding particles, this is the sharpening of the stone.
The second stage is the crushing and cutting stage
With the honing process, the surface of the hole becomes more and more smooth and the contact area with the oilstone becomes larger and larger. The contact pressure per unit area decreases and the cutting efficiency decreases. At the same time cut the chip is small and fine, these chips on the wear of the binder is also very small. Therefore, the oil stone grinding grains fall off very little, at this point grinding is not by the new grinding grains, but by the grinding grain tip cutting. As a result, the tip of the abrasive particles load is very large, the abrasive particles are easy to break, break and form a new cutting edge.
The third stage is the blocking cutting stage
As the honing process continues, the contact area between the stone and the hole surface becomes larger and larger. The extremely fine chips accumulate between the stone and the hole wall, which is difficult to remove, causing the stone to block and become very smooth.Therefore, the cutting ability of the stone is very low, equivalent to polishing. If honing continues, the oilstone is blocked seriously and the adhesive blockage occurs, the oilstone completely loses its cutting ability and generates severe heating, which will affect the hole accuracy and surface roughness. Finish the honing as soon as possible.
2.Quantitative feeding honing
In quantitative honing, the feeding mechanism expands the feeding at a constant speed so that the abrasive grains are forced to cut into the workpiece. Therefore, the honing process only exists the shedding cutting and the breaking cutting, it is impossible to produce the blocking cutting phenomenon. When the cutting force of the oil stone becomes blocked, the feed is greater than the actual grinding amount, and the honing pressure is increased, so that the abrasive particles fall off and break, and the cutting effect is enhanced. When honing with this method, in order to improve the hole accuracy and surface roughness, the honing can be finished without a certain time.
3.Constant pressure - quantitative feeding honing
When the oil stone enters the cutting stage, it is converted to quantitative feed honing to improve the efficiency. Finally, honing without feeding can be used to improve hole accuracy and surface roughness.