Shaft Grinding Defects and Solutions

Through grinding of centerless grinding machine is a grinding process in which the workpiece is pushed into the grinding zone from the front of the machine tool onto the supporting plate and guide plate, and then through the grinding zone from the back of the machine tool. It is mainly suitable for processing cylindrical and disc-shaped parts, and other parts such as short cones can be processed through special changes. In this processing process, improper selection and adjustment of grinding wheels, guide wheels, pallets, guide plates, feed and lead rollers, and cutting fluid will cause grinding defects, which will affect the processing accuracy.

Spiral pattern appears on grinding surface

1.  The protruding ends of the grinding wheel are “outwardly convex”. The elimination method is to dress the convex surface more when the grinding wheel is dressing.

2.  The pallet has cracked, resulting in sharp edges or the surface is not polished or rough. The method of elimination is to polish the pallet or replace it with a new pallet.

3.  When the lead-out roller is used for the lead-out of the workpiece, the speed of the roller is inappropriate or the adjustment of the feed roller is incorrect. The speed of the rollers should be adjusted appropriately.

4.  Grinding wheel bond hardness is uneven. A new grinding wheel must be replaced.

Chatter marks on the surface

1.  The grinding wheel or some other parts are not balanced, and the grinding wheel is not clamped correctly. The grinding wheel and chuck should be rebalanced, and the clamping method should be paid attention to when installing the grinding wheel.

2.  The center of the workpiece is too high. The pallet should be lowered.

3.  The pallet installation is not strong. The pallet should be reinstalled or reinforced.

4.  The pallet support slope is worn or bent. The pallet should be ground.

Irregular scratches on the surface

The main reason for this phenomenon is the problem of the cutting fluid, which may be that the cutting fluid is not clean or the lubrication performance of the cutting fluid is not good. If it is the former, you can replace with a new cutting fluid or increase the filtering device of the cutting fluid; if it is the latter, replace the cutting fluid with good lubricating performance.

Surface burn

1.  The cutting depth is too large, the cutting speed is too fast, the cooling is not enough, and the grinding wheel is too hard or dull. The cutting depth should be reduced, the cutting speed should be reduced, the cutting fluid flow should be increased, and a softer grinding wheel should be used to dress the surface of the grinding wheel.

2.  Improper amount of grinding. When burns occur when the amount of grinding is small, the longitudinal feed rate should be increased; when burns occur when the amount of grinding is large, the amount of feed should be reduced and the number of grinding should be increased.

The workpiece produces a polygonal shape

1.  The inclination angle of the guide wheel is too large, and the workpiece runs poorly during processing. The solution is to reduce the inclination of the guide wheel. If the feed speed is to be kept constant, the speed of the guide wheel should be increased.

2.  The roundness error of the blank is too large. Generally, the roundness error of the blank cannot exceed 50% of the grinding allowance. The solution is to improve the roundness of the workpiece before grinding, or multi-pass grinding on a centerless grinder.

3.  The guide wheel runs poorly, and the guide wheel must be trimmed to maintain good contact between the guide wheel spindle and the bearing.

4.  The imbalance between the grinding wheel and the guide wheel is too large, and the grinding wheel should be rebalanced.

The diameter of both ends of the shaft is smaller than other places when grinding

The main reason for this situation is that the rigidity of the grinding wheel or the guide wheel is insufficient, which causes the load to change. In addition, the change of cutting depth will also cause machining errors, which requires readjusting the grinding wheel or guide wheel bearing.

The axis of the long workpiece is not straight

This situation is caused by poor adjustment of the machine tool and the feeding mechanism, and the workpiece itself is not straight before processing, the solution is as follows:

1.  Carefully adjust the machine tool and the feeding mechanism.

2.  The workpiece should be straightened before processing, and stress-relieving heat treatment is also required. The workpiece must be straightened during two grinding.

3.  Increase the flow of cutting fluid.