The essence of wheel marks is that during the edge grinding process, the uneven friction and compression between the grinding wheel and the glass surface or edge leave visible marks.
Core principle: Prevention first, control from the source
Once wheel marks occur, especially on tempered glass, they are almost impossible to repair. Therefore, the focus must be placed on the prevention of the edge grinding process.
Specific Cause Analysis and Solutions
1. Selection and Maintenance of grinding wheels (the most crucial factor)
Problem: The grinding wheels are mismatched or aged
Particle size mismatch: The particle size selection of the coarse grinding, fine grinding and polishing wheels is incorrect. If coarse-grained grinding wheels are directly used for fine grinding or polishing, deep wheel marks will inevitably be left.
Poor quality of grinding wheels: The diamond particles of inferior grinding wheels are unevenly distributed, and the binder (adhesive) is either too hard or too soft, resulting in uneven grinding.
Grinding wheel wear/aging: The grinding wheel has been in use for too long, and its surface has become "passivated" or "glazed", losing its cutting ability. It only slips and rustles on the glass surface, generating a large amount of heat and scratches.
Poor dynamic balance of the grinding wheel: If the grinding wheel itself is unbalanced or installed improperly, it will jump during operation, resulting in regular and uneven wheel marks.
Solution
Follow the "from coarse to fine" principle: Ensure that the edge grinding process is complete, including at least three steps: rough grinding, fine grinding and polishing. Do not skip steps or attempt to complete it in one step.
Select the appropriate grinding wheel
Coarse grinding wheel: used for sizing and chamfering, with relatively coarse grain size (such as #80-#150).
Fine grinding wheel: Used to eliminate coarse grinding marks, with medium grain size (such as #200-#400).
Polishing wheels: Used to achieve bright edges, with very fine grain size (such as #600 and above, or dedicated diamond polishing wheels, cerium oxide polishing wheels).
Use high-quality grinding wheels: Invest in purchasing grinding wheels from well-known brands with reliable quality. Good grinding wheels have high cutting efficiency, long service life and are less likely to cause scratches.
Regularly dressing the grinding wheel: This is a crucial step! After being used for a period of time, the surface of the grinding wheel will be filled with glass powder and become smooth (glazed). The surface of the grinding wheel must be regularly cleaned with professional dressing tools (such as grinding wheel blocks or cleaning rods) to restore its sharpness and cutting ability. When operating, gently press the dresser against the rotating grinding wheel until all the diamond particles on the surface of the grinding wheel are exposed and the color darkens.
Replace the grinding wheel in a timely manner: When the cutting capacity cannot be restored even after dressing, or when the diameter of the grinding wheel is worn too small, it must be replaced immediately.
Check the installation of the grinding wheel: Ensure that the grinding wheel is firmly installed without any looseness or radial runout.
2. Adjustment and maintenance of equipment (edge grinding machine)
Problem: Improper equipment parameters or poor condition
Excessive pressure on the grinding head: Excessive pressure can cause the grinding wheel to exert excessive squeezing force on the glass, not only easily crushing the glass but also leaving deep wheel marks.
Excessive feed rate: If the glass moves too fast on the edge grinding machine, the grinding wheel will not have enough time to effectively cut and transition, resulting in rough and discontinuous wheel marks.
Cooling water issue
Insufficient water volume: Inadequate cooling and lubrication cause local overheating of the grinding wheel and glass, resulting in "thermal shock" micro-cracks and pasty glass powder. These powders will re-scratch the glass surface, forming wheel marks.
The water quality is too dirty: The cooling water contains glass debris produced during previous grinding. These hard particles will be pressed into the glass surface along with the water flow, causing random scratches and wheel marks.
Solution
Optimize process parameters
Pressure: Under the premise of ensuring grinding efficiency, use the smallest possible pressure.
Speed: Adjust the appropriate feed rate to ensure a smooth and continuous edge grinding process. For polishing edges with high requirements, the speed should be slower.
Ensure that the cooling water is sufficient and clean
Water volume: Check the water pump and pipelines to ensure that each grinding head is covered by sufficient water flow.
Water quality: Regularly clean the water tank and replace the cooling water. It is best to install a filtration system to continuously remove glass powder from the water. Maintaining clear water quality is the foundation for achieving a high-quality surface.
3. Operation techniques and skills
Problem: The operation is not standardized
Improper edge grinding (cutting depth) : Attempting to grind off too much at one time, or leaving unreasonable allowances between each process.
The Angle of the grinding wheel is incorrect: The contact Angle between the grinding wheel and the edge of the glass is incorrect, resulting in abnormal contact.
Solution
Reasonably allocate the amount of edge grinding: for instance, rough grinding removes the main allowance, fine grinding removes 0.5-1mm, and polishing only removes trace marks. Ensure that the traces of the previous process can be completely eliminated by the next process.
Check and adjust the Angle of the grinding wheels: According to the thickness of the glass and the required edge type (such as straight edge, round edge, duckbill edge), precisely adjust the Angle and position of each grinding wheel to ensure a perfect fit with the edge of the glass.
Summary: Best Practice Checklist
When wheel marks occur, please check them one by one according to the following list:
【 Top Priority 】 Inspect and repair/replace the polishing wheel: This is the area where problems occur most frequently. Immediately treat the polishing wheel with a dressing rod. If it doesn't work, replace it with a new one without hesitation.
【 Second Priority 】 Check the cooling water: Take a look to see if the water flow is large enough and if the water quality is as clean as tap water. If it becomes turbid, change the water immediately.
Adjust the equipment parameters: Appropriately reduce the grinding head pressure and slow down the feed rate, and observe the effect.
Check the grinding wheel sequence: Confirm whether the particle size combination of the coarse, fine and polishing grinding wheels is reasonable and there is no skipping. Make sure that each process really works.
Inspect the original glass sheet: Sometimes, when the original glass sheet itself has scratches or quality issues, they can be confused with edge grinding marks. Check the condition of the original glass sheet before grinding the edge.
Remember the golden rule: sharp grinding wheels + appropriate pressure + slow speed + sufficient clean cooling water = perfect and traceless edge grinding effect.
