First, the honing process principle
Honing is a special form of grinding, but also an efficient processing of finishing methods. This process not only removes large machining margins (which are still used for polishing in the 1950s), but also an efficient method of improving part size, geometry accuracy and surface roughness.
(A) honing the characteristics of processing:
1. High processing accuracy
2. Good surface quality:
3. Wide processing range:
(B) honing processing principle:
1. Honing is the use of one or more of the oil on the circumference of the honing head, by the opening mechanism (both rotary and propulsion type) will be rolling along the radial direction, so that pressure to the workpiece hole wall, in order to produce A certain face contact. While the honing head rotation and reciprocating motion, the parts are not moving; or honing head only for the rotary movement, the workpiece reciprocating movement, in order to achieve honing.
2. In most cases, between the honing head and the machine tool spindle or between the honing head and the workpiece fixture is floating. In this way, the honing head is machined to guide the hole in the workpiece. So the machining accuracy is less affected by the accuracy of the machine itself, the formation of the hole surface is basically a creative process characteristics. The so-called creation process is the oil stone and the hole wall of each other research, mutual dressing and the formation of pore walls and Whetstone surface. Its principle is similar to the two plane movement of the plate to each other on the formation of the principle of plane.
Need to note that: because the honing Whetstone using diamond and cubic boron nitride abrasive, processing of oilstone wear is very small, that is, the amount of oil as a result of the workpiece is very small repair. Thus, the accuracy of the hole depends to some extent on the original accuracy of the oilstone on the honing head. So when we use diamond and cubic boron nitride stone, honing before a good repair of Whetstone to ensure the accuracy of the hole.
(C) honing the cutting process:
1. Constant pressure feed honing: constant pressure feed, the feed mechanism with a constant pressure to the hole wall, divided into three stages.
The first stage is off the cutting stage, this constant pressure honing, the beginning of the hole due to rough walls, oil stone and hole wall contact area is very small, contact pressure, hole wall protruding part was soon to wear. And the surface of the Whetstone due to contact pressure, coupled with the chip on the wear of the Whetstone binder, so that the bonding strength of abrasive particles and binder decreased, and some abrasive particles in the role of cutting pressure under their own off, Abrasive, that is, oil from the sharp.
The second stage is broken cutting stage, with the honing of the progress of the hole surface more and more light, with the contact area of asbestos is increasing, the contact pressure per unit area decreased cutting efficiency. At the same time cut the chip small and thin, these chips on the adhesive wear is also very small. Therefore, the oil mill abrasive off very little, this time grinding is not by the new abrasive, but by the abrasive grain cutting. So the abrasive grain tip load is very large, abrasive grain easily broken, broken broken and the formation of a new cutting edge.
The third stage is the plugging stage, and the contact area of the oilstone and the hole surface is increasing when the honing is continued. The extremely fine chip is not easy to be removed between the oil and the hole wall, resulting in clogging and becoming smooth. So the oil stone cutting capacity is very low, the equivalent of polishing. If the honing is continued and the oilstone is clogged with severe clogging, the slime is completely out of cutting capacity and is hot, and the accuracy and surface roughness of the hole are affected. At this point should be completed as soon as possible honing.
2. Quantitative feed honing: quantitative feed honing, the feed mechanism at a constant rate of expansion of feed, so that abrasive particles forced into the workpiece. So the honing process only shedding cutting and cutting cutting, can not produce clogging cutting phenomenon. Because when the oil stone clogging cutting force decreased, the feed is greater than the actual grinding, this time honing pressure increases, so that the abrasive particles fall off, broken, cutting effect enhanced. In this way honing, in order to improve the hole accuracy and surface roughness, and finally can be used for honing for a certain period of time.
3. Constant pressure - quantitative feed honing: the beginning of the constant pressure feed honing, when the oil into the plug cutting stage, the conversion into a quantitative feed honing to improve efficiency. Finally, no feed honing can be used to improve the accuracy of the hole and surface roughness.
Second, the type of honing machine and selection principles
Honing machines are split and vertical. The selection principle can refer to the following aspects:
1. Different batches of different types of honing machines, such as multi-species small batch, the choice of low-power, versatile machine; if the bulk is large, the choice of high-power special machine.
2. Select the main specifications and parameters of the machine according to the workpiece aperture, hole length and dimensions.
3. According to the structure of the hole selection machine bed reciprocating mechanism performance. Such as blind hole, requiring reciprocating stroke mechanism for repeated high precision, overtaking small, should be able to adapt to manual or automatic alternately control long and short stroke; and if short hole, hole accuracy requirements are high, the choice of mechanical reciprocating travel agencies.
4. According to the hole processing allowance, shape error and hole accuracy requirements, select the expansion of the oil rolling expansion mechanism.
5. According to the number of honing the same hole, the production batch or production rhythm, the workpiece size and the number of holes in the workpiece, the number of machines selected or the number of machine tools and the form of the table. Such as large quantities of small parts, optional vertical rotary table with multi-axis machine; large or straight row of porous parts, can choose to move the table or move the honing machine. Small batch optional single shaft. Large number of optional multi-axis, a hole for several honing or several holes at the same time honing.
6. According to the hole size accuracy, pore size, structure, the degree of wear of Whetstone, honing the structure of the form, the production volume, selected size control.
7. According to the hole surface roughness, dimensional accuracy and production requirements of the beat, the choice of cutting fluid purification methods and the need to cool the cutting fluid device.
Third, direct honing new technology
Honing is a well-known, serial production commonly used in hardened surface finishing process. Honing gears can improve their noise and wear characteristics.
The honing gears can reduce the noise and prolong the service life by changing the surface structure of the teeth. Honing the surface of the gear, the formation of similar to the surface of the fish bone spine, is conducive to the root from the root surface to the pitch diameter surface to form a layer of lubricating oil film, is conducive to suppress the noise generated. The special process movement causes the honing tool to be in rolling contact with the workpiece in the corresponding direction to produce such a surface structure. The synthetic velocity component acts on the tooth surface to produce an axial cutting speed component, so that the abrasive grains of the abrasive can be kept in contact with the entire tooth surface.
The advantages of the honing process described above can be attributed to the fact that this is an economically viable processing method. In examining the economic viability of a workpiece machining process, the entire process chain must be taken into account. This is particularly important for hard gear finishing, since pre-finishing is of paramount importance. In general, the increase in processing costs is not proportional to the size of the workpiece hardness. To this end, in most cases need a good green processing methods, both to be able to effectively hardened surface processing, but also the smallest heat treatment deformation effect. This will create an ideal hardened surface finishing condition. In addition to the improvement of the pre-processing method, this hardened surface processing method is not only large enough to cut, but also to have a large size change, so as to reliably and inexpensively cut the material. This gives rise to an idea that combines the advantages of honing with the yield advantage of grinding. This leads to a way to make the idea a reality: direct honing, both the workpiece after the heat treatment directly honing.
In the pre-processing with the direct honing method, not only a high removal rate is obtained, but also the expected quality requirements can be achieved economically and with high repetition accuracy. Faster and more economical processing requirements are often required to improve the repeatability and quality of the work and to make the machine as easy as possible.
Previously, in the honing required to use artificial resin bonded alumina or carbide abrasive, electroplated CBN or diamond abrasive or composite mold.
For process control, there are several possibilities for double-sided contact, single-thread contact and single-sided contact in theory, and with or without workpiece and workpiece drive synchronization. At the same time, there is the possibility of combining these strategies together to achieve an optimized effect. In the selection of abrasive materials, must be considered to achieve the longest grinding tool life of the material. Also consider that the easy-cutting abrasive results in premature wear of the dressing abrasive.
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