Introduction of precision grinding system for super surface treatment

Our country mainly uses sandpaper, abrasive belt, PVA grinding wheel and even grinding paste to process external cylindrical fine grinding or fine polishing. Sandpaper and grind paste require skilled technicians to operate, and the efficiency is very low. Although the abrasive belt and PVA grinding wheel are efficient in large-area processing, the ultra-precision grinding effect is not very satisfactory due to the limitations of the tool itself and the machine. At present, foreign countries such as the United States and Japan have successfully developed precision grinding systems for grinding thin films, making the polishing effect of processed products more precise and consistent.

The precision grinding system of 3M company in the United States is mainly based on a film coated with abrasives and continues to be processed in a single direction. The contact surfaces for grinding and polishing are all unused high-precision abrasives. Because the abrasive will not be reused, it avoids the disadvantages of different polishing effects between the end and the end of the workpiece that occur during general fine polishing. The advantages of the 3M precision grinding system also include ensuring that the shape of the workpiece itself does not produce swings or vibration marks, the grinding wheel is easy to replace, easy to operate, it can save up to 50% of the working time, and the polishing effect is more precise (<0.025~μm).

The abrasive film is an abrasive tool with tens of μm fine abrasive particles uniformly coated on a polyester film substrate with a thickness of about 25~100μm with a synthetic resin binder.

The structure of the abrasive film has four major elements:

(1) Substrate: Polyester film 857 (PET), with high tensile strength in vertical and horizontal directions, small flexibility, toughness and uniform thickness. The thickness standards of the substrate are: 25, 50, 75μm. With the current automation requirements, longer films are needed, and thick films are not satisfactory, so there are 7, 10, 12, 23, 27, 30, 37μm series. (Guide: The latest method of maintenance of CNC protection products)

(2) Abrasive grains: Al2O3, SiC are mainly used in Japan, as well as Cr2O3 (grinding head), CeO2, synthetic diamond single crystal, polycrystalline, FeO, etc. The particle size needs to be fine and evenly distributed, which requires strict control of the particle size distribution and no large particles. There are four kinds of abrasive particles produced by 3M precision grinding in the United States: Al2O3, SiC, artificial box corundum, and CBN. All abrasive grains are finely screened, and there will be no rough patterns when used. The products are waterproof, and can be dry or wet.

(3) Binder: mainly polymer resin and dozens of compound additives. Commonly used are propylene, epoxy, and urethane. The first two are harder, the latter is softer. It is generally required to coat the film twice. The first application is to increase the adhesion of the film.

(4) Coating; mainly use electrostatic method and roller coating method. In the electrostatic method, the binder is phenol. The base material is polyester film. The abrasive is A12O3 and SiC. The roller coating method is mainly by means of printing technology, the abrasive and the binder are mixed and roller coated, and the coating thickness is controlled by the roller, that is, the gap of the roller is adjusted. There are also kneading methods, sintering methods, electroplating methods, and Ni plating methods.

The heat-resistant temperature of Japanese abrasive film is the temperature of the polymer adhesive material used, about 25O℃. Grinding is based on the principle of wet processing. The coolant is water and oil. General water can meet the requirements (such as tap water). Pure water is used for precision processing, and kerosene is used for aluminum alloy grinding.

The precision grinding system using grinding film will be the trend of polishing and finishing in the future, it is more advanced than the belt tool. It can improve production capacity and efficiency, with high pass rate, good quality, broaden production range, and accurately control the entire grinding process. The remanufacturing rate is low, and employees can take up their jobs after a little training. It can be said that the fine polishing industry will be the world of abrasive film tools in the future.

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