1, introduction

In honing process, the selection of honing process parameters has a great influence on the accuracy, surface roughness, machining efficiency and the service life of honing oilstone.

2. Honing principle

Honing is to use the principle of three plates lapping each other to process the precise surface. In grinding, honing the cutting surface of the honing stone and the surface of the machined parts are regarded as the process of mutual trimming.

3. Finishing of honing stone

Due to the manufacturing errors of honing stone, oilstone seat and grinding head body, it is impossible for honing oilstone of honing head to form a cylindrical surface with a normalization discontinuity after assembly, so as to ensure that honing oilstone and the processed surface are in good contact. Although honing oilstone and workpiece can be trimmed each other in honing process, the amount of remaining grinding is small, so it is impossible to get full trimming in the initial honing process. Especially the honing Whetstone of superhard abrasive can not be fully trimmed because of its wear resistance. Therefore, it is impossible to get the ideal machining surface and the precision can not be guaranteed. Therefore, when using a new honing stone, the honing stone must be repaired (also known as rounding) before processing. The dressing of ordinary honing oilstone is to install the honing oilstone directly on the grinding head used and take it to the external grinder for rounding, which is the most ideal. However, due to the structure of some grinding heads and other reasons, it is necessary to use a special fixture to trim the outer diameter of the grinding machine with a grinding wheel. For example, the precision requirement of honing workpiece is low, the honing head is floating connection, and the workpiece hole with waste activity or large machining allowance can also be used to directly correct rounding on the honing machine used. The finishing of superhard honing oilstone can be carried out by using carbonized silica sand wheel on the external grinder. The rotation speed of grinding wheel is 18-25m / s, the rotation speed of grinding head is 1-3m / min, the feed depth is generally 0.02-0.04mm/stroke for grinding repair, and 0.01mm/stroke for fine repair. At the same time, a large amount of coolant is needed.

4. Constant pressure expansion feed form

In the process of constant pressure expanding and feeding, although the honing head expanding and shrinking mechanism presses to the hole wall of the workpiece with constant honing oil stone working pressure, in the process of grinding, with the increase of time, all kinds of elements are not cut with fixed value, but the amount of metal grinding and honing oil stone grinding loss decrease with the increase of honing time, while the surface quality decreases with the increase of honing time Gradually smooth. The reason for this is that honing cutting is in the state of face contact, while constant pressure expansion has a strong feed follower. In grinding, the amount of cutting depends on the abrasive particles and their sharpness, as well as the abrasive particles and cutting under grinding are removed.

5. Selection of honing process parameters

5.1 selection of cutting speed and cutting cross angle

5.1.1 speed and cutting angle

The cutting speed V is composed of rotation (circle) speed V rotation and reciprocating speed v. In the honing process, due to the result of cutting movement, the abrasive grains of honing oilstone cut out cross chequer on the machining surface, and the angle of forming the chequer is called cutting cross angle θ. The angle formed by the rising reticle and the horizontal line is called the cutting angle α 1, and the angle formed by the falling reticle and the horizontal line is called the cutting angle α 2.

5.1.2 calculation of honing cutting speed

The honing cutting speed can be calculated according to the following formula: V rotation = π dn / 1000 (M / min), in which: D is the machining diameter MMN - spindle speed r / min

5.1.3 effect of cutting speed on cutting amount

In honing, the influence of cutting speed on the cutting amount (cutting amount / work cut in - indicating the sharpness of honing oilstone) is small. No matter honing casting or honing steel parts, the change of cutting speed has little change in specific cutting amount.

5.1.4 influence of cutting cross angle on cutting amount, honing oil stone wear amount and surface roughness

In honing, the cutting cross angle has great influence on the cutting amount, honing oil stone wear amount and surface roughness. With the increase of cutting cross angle, the specific grinding stone reduction increases. Of course, the roughness of the machined surface is also coarser. This is because in the process of honing and cutting, to keep the sharpness of honing oilstone depends on the surface roughness. Only sharp honing oilstone can improve the cutting amount, and if the oilstone is sharp, it must be worn. When the cutting cross angle is 0 °, the cutting efficiency is low; when the cutting cross angle is 90 °, the honing oilstone wear is large, and the surface roughness is coarse, so the cutting amount is small. Through experiments, when the cutting cross angle is about 45 °, the cutting amount is the largest. Therefore, in honing process, to improve the productivity, a cutting angle of about 45 ° should be used, and 20-30 ° can be used in finishing. 5.2 working pressure of honing oilstone and its influence

5.2.1 working pressure of honing oilstone

The so-called honing oilstone working pressure refers to the pressure exerted by honing oilstone on the surface to be processed - the pressure per unit area. It is not the value on the machine pressure gauge or other pressure values. This paper discusses the honing machine tool with constant pressure expanding feed. The working pressure of honing oilstone can be calculated according to the following formula (without considering friction and other forces). P = (D2 π P / 4bln) CTG β / 2, where p is the working pressure of honing oilstone, kgf / cm2 ≈ barb is the width of honing oilstone, MML is the length of honing oilstone, MMN is the number of honing oilstone

5.2.2 selection of honing oil stone working pressure

The working pressure of honing oilstone has a great influence on honing cutting performance, which directly affects cutting efficiency, honing oilstone wear loss, workpiece precision and roughness. When the honing pressure is high, the honing cutting amount and honing oil