Common defects and solutions for centerless grinder products

A centerless grinding machine is a type of grinding machine that does not need to use the axis of the workpiece to perform grinding. It is composed of three mechanisms: grinding wheel, adjusting wheel and workpiece support. Common grinding defects and elimination methods of centerless grinders are organized as follows:

1. The parts are not round
cause
(1) The guide wheel is not rounded
(2) The number of grinding is small or the ellipse of the previous process is too large.
(3) Blunt grinding wheel
(4) The amount of grinding is too large or the amount of knife is too large

Elimination method
(1) Re-repair the guide wheel, and stop after the rounding of the guide wheel (generally, the repair will stop until there is no intermittent sound)
(2) Increase the number of grinding appropriately
(3) Re-repair the grinding wheel
(4) Reduce grinding amount and heavy knife speed

2. The parts have edges (polygons)
cause
(1) The part center height is not enough
(2) The axial thrust of the part is too large, which makes the part tightly press the stop pin and cannot rotate evenly
(3) Unbalanced grinding wheel
(4) The part center is too high
Elimination method
(1) Accurately advance the center of the part
(2) Reduce the inclination angle of the grinder guide wheel to 0.5° or 0.25°. If the block cannot be resolved, check the balance of the fulcrum.
（3）Balance grinding wheel
(4) Properly reduce the height of the center of the part

3. Vibration marks on the surface of the part (that is, fish spots and straight white lines appear on the surface of the part)
cause
(1) Vibration of the machine tool caused by the unbalanced surface of the grinding wheel
(2) The center of the part moves forward to make the part jump
(3) The grinding wheel is blunt or the surface of the grinding wheel is too polished
(4) The rotation speed of the guide wheel is too fast
Elimination method
(1) Carefully balance the grinding wheel
(2) Properly lower the center of the part
(3) Grinding wheel or increase the dressing speed of the grinding wheel appropriately
(4) Reduce the guide speed appropriately

4. the parts have taper
cause
(1) The front part of the part is small because the front guide plate is too low or the front guide plate is inclined in the direction of the guide wheel.
(2) The rear part of the part is small due to the low surface of the rear guide plate and the bus bar of the guide wheel or the tilt of the rear guide plate toward the guide wheel
(3) Taper at the front or rear of the part due to the following reasons
①The grinding wheel is not trimmed correctly, and it has a taper.
②The surface of the grinding wheel and guide wheel is worn
Elimination method
(1) Properly move the front guide plate and adjust the front guide plate to be parallel to the bus bar of the guide wheel
(2) After adjustment, the guide surface of the guide plate is parallel to the generatrix of the guide wheel and is in a line.
①According to the direction of the part taper, adjust the angle of the grinding wheel in the modification of the grinding wheel
②Grinding wheel and guide wheel [Metal processing WeChat, the content is good, worthy of attention]

5. the part center is big and the two ends are small
cause
(1) The front and rear guide plates are evenly inclined to the side of the grinding wheel
(2) The grinding wheel is trimmed into a drum shape
How to eliminate
(1) Adjust the front and rear guides
(2) Modify the grinding wheel, and the margin for each modification should not be too large

6. there is a ring thread on the surface of the part
cause
(1) The front and rear guide plates protrude from the surface of the guide wheel, so that the parts are scraped by the edge of the guide wheel at the exit or entrance.
(2) The support ratio is too soft, and the grinding cutting is embedded in the support surface to form a protruding burr, and the surface of the part is carved into a thread
(3) The coolant is not clean, there are chips or grit inside
(4) Due to the large amount of grinding at the exit, it is scraped by the edge of the grinding wheel.
(5) The center of the part is lower than the center of the grinding wheel, and the vertical pressure is larger, so that the sand and chips stick to the branch hair
(6) Blunt grinding wheel
(7) Too much allowance in one grinding or too thick grinding wheel repair, extremely fine thread line occurs on the surface of the part
Elimination method
(1) Adjust the front and rear guides
(2) Replace the branches with lubricated surface and higher hardness
(3) Replace the coolant
(4) Round the edge of the grinding wheel, and finally make the 20mm at the exit of the part do not grind
(5) Properly advance the height of the part center
(6) Grinding wheel
(7) Appropriately reduce the amount of wear and slow down the speed of modification

7. cut off a small piece from the front of the part
cause
(1) The front guide plate protrudes from the surface of the guide wheel
(2) The front face of the grinding wheel and the guide wheel are not in a straight line, and there is a big difference.
(3) Too much grinding at the entrance
Elimination method
(1) Move the front guide a little bit back
(2) Replace or modify the longest of the two
(3) Reduce the amount of grinding at the entrance

8. The middle part or the tail part of the part is cut badly. There are the following kinds of cuts:
1. The cut is rectangular
cause
(1) The excellent guide wheel surface of the rear guide plate prevents the rotation of the parts and the grinding of the trekking surface.
(2) The back support pad was extended too long, and the polished parts did not fall off, which prevented the polished parts from rotating and advancing
Elimination method
(1) Move the rear guide plate back properly
(2) Reinstall the support pad [Metalworking WeChat, the content is good, it is worth paying attention]
2. The cut is horn-shaped or many micro-shaped marks
cause
(1) The rear guide plate is behind the surface of the guide wheel
(2) The center of the part advances too high, causing the part to jump at the exit
Elimination method
(1) Move the rear guide slightly forward
(2) Properly reduce the center height of the part

9. the surface brightness of the part is not zero enough
cause
(1) The inclination angle of the guide wheel is too large, causing the parts to move too fast.
(2) The wheel modification speed is too fast, and the modification of the wheel surface is not bright
(3) The modified guide wheel is too thick
Elimination method
(1) Decrease the angle of inclination
(2) Reduce the modification speed and modify the grinding wheel from the beginning
(3) Rebuild the guide wheel