During Centerless Cylindrical Grinding, the workpiece is placed between a guide wheel and a grinding wheel. One grinding wheel performs the grinding, while the other, the guide wheel, acts as a transmission mechanism. The workpiece is securely supported by a support plate. Notably, the guide wheel's axis forms an angle θ with the grinding wheel, perpendicular to the workpiece. This design not only drives the workpiece's rotation but also facilitates its feed motion.

During the centerless grinding process, you may encounter a variety of grinding defects. To help you better understand and address these challenges, we have organized the following common grinding defects and their corresponding elimination methods:

1 Parts are not round

Causes:

(1) The guide wheel is not rounded or not rounded enough;

(2) The number of grindings is insufficient or the ovality of the previous process exceeds the standard;

(3) The grinding wheel is worn and blunt;

(4) The grinding amount is too large or the cutting speed is too fast.

Solutions:

(1) Re-trim the guide wheel until the intermittent sound stops;

(2) Increase the number of grindings appropriately;

(3) Re-trim or replace the grinding wheel;

(4) Reduce the grinding amount and reduce the cutting speed.

2. Parts angular shape (polygon) problem

Causes:

(1) Improper adjustment of the center height of the part;

(2) Excessive axial thrust on the part causes the part to press against the stop pin and cannot rotate evenly;

(3) The grinding wheel is unbalanced, causing vibration;

(4) The center height of the part is set too high.

Solutions:

(1) Carefully adjust the center height of the part;

(2) Reduce the inclination angle of the grinding machine guide wheel, for example, adjust it to 0.5° or 0.25°, or check the balance of the fulcrum to solve the problem;

(3) Balance the grinding wheel;

(4) Appropriately reduce the center height of the part.

3. Vibration marks on the surface of parts

Causes:

(1) Unbalanced grinding wheel causes machine vibration;

(2) Improper center position of parts causes parts to jump during processing;

(3) Grinding wheel is worn or improperly dressed, resulting in its surface being too smooth;

(4) The guide wheel rotates too fast.

Elimination methods:

(1) Carefully balance the grinding wheel to ensure its stable operation;

(2) Properly adjust the center position of the parts to reduce the jumping phenomenon;

(3) Properly dress the grinding wheel to increase its surface roughness;

(4) Reduce the rotation speed of the guide wheel to reduce vibration.

4. Taper appears on the parts

Causes:

(1) The height difference between the front guide plate and the guide wheel busbar is too large, or the front guide plate is tilted toward the guide wheel, resulting in a smaller front size of the part;

(2) The height difference between the rear guide plate surface and the guide wheel busbar, or the rear guide plate is tilted toward the guide wheel, resulting in a smaller rear size of the part;

(3) Other factors may also cause taper at the front or rear of the part.

① Taper problem of the grinding wheel itself: If the grinding wheel is not properly trimmed during the dressing process, it may have a taper.

② Wear of the grinding wheel and guide wheel surface: As the use time increases, the surface of the grinding wheel and guide wheel will inevitably wear, which will also affect the size of the part.

Elimination method:

(1) Adjust the position of the front guide plate to ensure that it remains parallel to the guide wheel busbar to eliminate the problem of smaller front size.

(2) Adjust the guide surface of the rear guide plate to make it parallel to the guide wheel busbar and on the same straight line to solve the problem of smaller rear size. ① Adjust the grinding wheel's tilt angle during the correction process based on the orientation of the part's taper.

② Also, pay attention to the proper fit between the grinding wheel and the guide wheel to ensure surface wear is within a manageable range, thereby ensuring accurate part dimensions.

5. Parts with large center and small ends

Causes:

(1) The front and rear guide plates are tilted evenly toward the grinding wheel, causing the center of the part to be larger than the ends.

(2) The grinding wheel is trimmed into a drum shape, with a convex center and concave sides, which can also cause this problem.

Solutions:

(1) Adjust the front and rear guide plates to keep them level and avoid tilting to one side.

(2) Re-trim the grinding wheel to ensure that it is cylindrical and avoid trimming it into a drum shape. When trimming, the allowance for each modification should not be too large to avoid affecting the dimensional accuracy of the part.