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The reason why the bearing has common defects in grinding
**The Common Causes of Bearing Defects During the Grinding Process**
In the grinding process, bearings are often subjected to high-speed rotation using a grinding wheel. If not properly operated and adjusted according to the manufacturer's instructions, various defects may occur, affecting the overall quality of the bearing.
During fine grinding, the surface finish is critical. Visible grinding marks can often be observed with the naked eye, which usually appear as interlaced spiral patterns. These spiral traces are primarily caused by an uneven grinding wheel surface, where some areas are concave or convex. As the workpiece or grinding wheel reciprocates, these irregularities create visible patterns. The pitch of the spirals depends on the speed of the worktable and the rotational speed of the workpiece, as well as the alignment between the grinding wheel axis and the guide rails of the worktable.
Common causes of such spiral marks include:
1. Poorly dressed grinding wheels without proper chamfering.
2. Excessive lubricant on the workbench guide rails, causing it to float.
3. Machine inaccuracy or improper adjustment.
4. Excessive grinding pressure applied during the process.
Detailed reasons for the formation of spiral marks include:
- Insufficient rigidity in the V-shaped guide rail, leading to misalignment during grinding.
- Unstable workbench speed during dressing, resulting in inconsistent grinding.
- Poor rigidity in the workpiece itself.
- Accumulation of debris or metal chips on the grinding wheel surface.
- Inadequate dressing of the grinding wheel, leaving bumps or irregularities.
Another common defect is the fish-scale pattern on the workpiece surface. This occurs when the grinding wheel is not properly dressed, becomes dull, or has oil and waste on its surface. Additionally, a weak diamond cage or poor-quality diamonds can lead to uneven trimming, contributing to this issue.
Other defects include straight wave patterns on the workpiece surface, resembling sine waves. These are typically caused by excessive clearance in the grinding wheel spindle, too hard a grinding wheel, poor static balance, or improper feed rates. Radial runout from worn bearings can also contribute to this issue.
Burn marks on the workpiece surface are another serious problem. They can result from a grinding wheel that is too hard or too dense, excessive feed rate, insufficient coolant supply, or improper dressing of the wheel. Other factors include incorrect grinding speeds, unstable oscillations, and deep burns from rough grinding.
To detect burn marks, regular pickling of the workpiece is recommended. After pickling, the surface should be inspected under an astigmatism lamp. A normal surface appears evenly dark gray, while burn marks show dark black patches or cracks along the grinding direction.
Surface roughness issues can arise due to low grinding speed, fast feed rate, or improper wheel dressing. A thick or soft grinding wheel, incorrect dressing speed, or poor-quality ultra-fine kerosene can also contribute to this problem.
To ensure high-quality grinding results, it is essential to maintain proper machine conditions, use suitable grinding wheels, and follow correct operating procedures. Regular maintenance and inspection of the grinding equipment can significantly reduce defects and improve the performance of the final product.
**Related Bearing Knowledge:**
- Types of Bearings and Their Markings
- Grease Filling Machines for Bearings
- Imported Sliding Bearings
- Common Faults in Rolling Bearings
- Analysis of Rolling Mill Bearing Devices
For more information, visit China Bearing Network.
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