1、 Maintenance of grinding machine
1. Inspection and Scratching of Bed Guide Rail
After maintenance, the V-shaped guide rail of the bed should meet the following accuracy requirements: non straightness in the vertical plane ≤ 0.01mm/m; Non straightness within the horizontal plane ≤ 0.01mm/m; The non perpendicularity of the sliding saddle guide rail is ≤ 0.02mm/250m; Contact point requirements are 12-14 points/25mm × 25mm.
After maintenance, the bed flat guide rail should meet the following accuracy requirements: the non parallelism of the V-shaped guide rail should be ≤ 0.02mm/m; Non straightness within the vertical plane ≤ 0.01mm/m; Contact point requirements are 12-14 points/25mm × 25mm.
2. Inspection and Scratching of Sliding Saddle Guide Rail
After maintenance, the V-shaped guide rail of the sliding saddle should meet the following accuracy requirements: the non straightness in the vertical plane should be ≤ 0.01mm along the entire length; Contact point requirements are 10-12 points/25mm × 25mm.
After maintenance, the sliding saddle flat guide rail should meet the following accuracy requirements: the non parallelism of the V-shaped guide rail should be ≤ 0.02mm/m; Contact point requirements are 10-12 points/25mm × 25mm.
3. Adjustment of clearance between grinding wheel spindle and bearing shell
Paint the journal of the grinding wheel spindle, rotate it with the bearing shell, and use a scraper to scrape the surface of the bearing shell to achieve a contact point requirement of 12-14 points/25mm × 25mm. Then, adjust the installation to adjust the gap between the grinding wheel spindle and the bearing shell to 0.0025-0.005mm, which can avoid the formation of edges and circles in the workpiece during grinding.
4. Balance between the grinding wheel spindle motor and the grinding wheel
The vibration of the grinding wheel spindle motor has a significant impact on the roughness of the grinding surface, so it is necessary to perform dynamic balancing on the grinding wheel spindle motor. The grinding wheel needs to be balanced twice: first, use a diamond pen to trim the grinding wheel and then perform a rough balance; Then, use an oilstone or a grinding wheel after finishing to finely adjust the grinding wheel, and then perform another round of precision balancing.

2、 Grinding wheel dressing
In general, a grinding wheel that has only been polished with a diamond pen can only produce a surface roughness of Ra0.4-0.8 μ m on a regular grinder. In order to achieve the roughness requirement of Ra0.02-0.04 μ m on the grinding surface, it is necessary to perform two rounds of refinement and fine adjustment on the grinding wheel. The repair method can be one of the following two methods.
1. Use a diamond pen to refine, then use an oilstone to refine
The grain size of the grinding wheel is generally selected between 46 # and 80 #. Firstly, use a sharp single particle diamond pen to fine tune the grinding wheel with a small and uniform feed rate, in order to trim more equal height micro blades on the grinding wheel grains. During the finishing process, the installation of the grinding wheel dresser should be correct and reasonable, and the feed rate should be controlled at 5 μ m each time. It is recommended to choose the lowest longitudinal feed speed. During the refinement process, attention should be paid to adjusting the changes in the sound produced. If there is a uniform rustling sound, it indicates that the repair condition is normal; If the sound emitted fluctuates between high and low, or gradually increases and decreases, or even makes abnormal beeps, immediately check whether the workbench is crawling, whether the cooling is sufficient, whether the diamond pen is sharp, etc., and then make appropriate adjustments. After being refined with a diamond pen, it is further refined with an oilstone (or sand bar) to create more equal height micro blades on the grinding wheel. Oil stones need to be ground flat on a surface grinder. During fine repair, the oilstone must be parallel to the circumferential surface of the grinding wheel. The oilstone should make slight contact with the grinding wheel and slowly move longitudinally 2-3 times.
2. Refine with a diamond pen and then use a finely polished grinding wheel to refine
After finishing with a diamond pen, first adjust the taper using a core shaft with a grinding length that is basically the same as the workpiece, and then use a precision machined grinding wheel for finishing.
The fine grinding wheel can be TL60 # K~L, with a diameter of about 100mm. When precision turning the grinding wheel, install the grinding wheel on the chuck, clamp the chuck onto an automatically centering core shaft, and then press it against the two top points of the precision lathe for rough and fine turning of the outer circle of the grinding wheel, so that the outer circle of the grinding wheel is free of deviation. Then place the precision machined grinding wheel on the two tips of the grinder to perform fine grinding on the grinding wheel.
During fine repair, the headstock drives the grinding wheel to rotate, using a low speed (about 80-100r/min) and a small feed rate (about 2 μ m per reciprocating motion). The reciprocating speed of the worktable should be less than 0.3m/min. Multiple reciprocating adjustments are required. The rotation direction of the dressing grinding wheel and the dressing grinding wheel should be the same, that is, the linear velocity direction of the contact points should be opposite. The coolant should be sufficient to flush away the floating sand and prevent the residual floating sand on the grinding wheel from scratching the surface of the workpiece during grinding.
After the grinding wheel is finely and precisely trimmed, fingers can be used to gently approach the working surface of the grinding wheel in the direction of rotation and move it longitudinally. If the feel is smooth and flat like a mirror, it indicates that the grinding wheel is well trimmed; If you feel that there are abrasive particles that prick your hands, you can use a paint brush with 2/3 of the bristles removed to gently brush off the floating sand on the surface of the grinding wheel.
3. Selection of grinding quantity
When using the M131W ordinary cylindrical grinder for ultra precision grinding, it can ensure the effective achievement of the Ra0.02 μ m surface roughness requirement, and the empirical grinding amount should be selected
4. Precautions for Grinding Processing
a. During operation, close attention should be paid to the contact condition between the grinding wheel and the workpiece surface. When the surface of the workpiece comes into contact with the grinding wheel, a continuous hissing sound can be heard, and the water stains on the surface of the workpiece can be carried away by the rotating grinding wheel. At the same time, weak sparks can be seen. At this time, coolant can be added. The coolant should be a slightly higher concentration saponification solution, which must undergo strict cleaning and filtration before use. Then feed, with a feed rate of 0.005mm per pair of strokes. When the spark disappears, the grinding is completed. At this point, press the lateral feed handwheel in the feed direction to slightly press the grinding wheel into the workpiece without feeding, which is equivalent to polishing the workpiece once to further improve the surface quality of the grinding.
b. When grinding in high ambient temperatures (such as summer), the machine tool lighting should not be close to the workpiece to prevent the workpiece from expanding due to heat and affecting the grinding quality.
c. If there is surface roughness on the workpiece, it indicates that the coolant is not clean or there is floating sand on the surface of the grinding wheel. The coolant should be re filtered or the floating sand on the surface of the grinding wheel should be brushed off.
d. If there is local burn on the workpiece, it may be caused by insufficient coolant, excessive feed rate, or blunting of the grinding wheel.
e. If fine microwave patterns appear locally on the surface of the processed workpiece, it may be caused by loose spindle, motor vibration, or other reasons. Corresponding measures can be taken depending on the specific situation to solve the problem.