The polishing effect of sandpaper is directly related to the particle size of the abrasive.
1、 The relationship between abrasive particle size and surface roughness
The larger the particle size, the higher the surface roughness: Coarse grained abrasives (such as P80 sandpaper, with a particle diameter of about 178 μ m) will leave deep scratches on the surface of the workpiece during polishing, resulting in higher surface roughness. This sandpaper is suitable for removing severe oxide layers or deep scratches, but cannot meet the high-precision polishing requirements.
The smaller the particle size, the lower the surface roughness: Fine grained abrasives (such as P2000 sandpaper, with a particle diameter of about 10.3 μ m) can remove fine scratches left by the previous process, making the surface smoother. Actual test data shows that the surface roughness Ra value of P2000 sandpaper can be stabilized in the range of 0.4-0.6 μ m after final grinding, which is close to the polishing grade treatment effect.
2、 The influence of abrasive particle size on polishing efficiency
High polishing efficiency of coarse-grained abrasive: Due to the large size of coarse-grained abrasive particles and strong cutting force, they can quickly remove the protruding parts on the surface of the material, resulting in high polishing efficiency. However, it should be noted that the scratches left by coarse-grained abrasives are deeper and require subsequent repair with fine-grained abrasives.
Fine grained abrasive polishing has low efficiency but high accuracy: Fine grained abrasive particles are smaller and have weaker cutting forces, resulting in relatively lower polishing efficiency. But fine-grained abrasives can remove fine scratches left by the previous process, making the surface smoother and smoother, meeting the requirements of high-precision polishing.
3、 Principles for selecting abrasive particle size
Following the principle of "coarse first, fine later": In the actual polishing process, it is usually necessary to first use coarse-grained abrasives for preliminary polishing to remove the protruding parts and deep scratches on the surface of the material; Then gradually switch to fine-grained abrasives for dressing and polishing until the desired surface roughness is achieved.
Select abrasive particle size based on material hardness: For materials with higher hardness (such as quenched steel, ceramics, etc.), finer abrasive particle size is required for polishing to avoid surface damage caused by excessive cutting; For materials with lower hardness, such as aluminum, copper, etc., relatively coarse abrasive particle sizes can be used for polishing.
Avoid cross grade use: The particle size of the polishing solution should be selected at 1/10 of the mesh size of the sandpaper used in the previous process, and cross grade use is strictly prohibited. For example, if 2000 grit sandpaper (corresponding to smaller abrasive particle size) is used in the previous process, a smaller particle size polishing solution (such as 0.5 μ m diamond solution) should be selected for subsequent polishing, rather than jumping directly to a larger particle size polishing solution (such as 3 μ m diamond solution), otherwise it will reduce polishing efficiency by more than 50%.