Common Polishing Methods And Working Principles

Polishing is a processing method that uses mechanical, chemical or electrochemical action to reduce the surface roughness of a workpiece in order to obtain a bright, flat surface. It is a finishing process carried out on the surface of the workpiece using polishing tools and abrasive particles or other polishing media.

Polishing can not improve the dimensional accuracy or geometric shape accuracy of the workpiece, but to get a smooth surface or mirror gloss for the purpose, sometimes also used to eliminate the gloss (matting). The polishing wheel is usually used as a polishing tool. The polishing wheel is generally made of multiple layers of canvas, felt or leather, clamped on both sides with a metal round plate, and its rim is coated with a polishing agent made of a uniform mixture of micronised abrasives and grease.

1. Ultrasonic polishing

Placing the workpiece in an abrasive suspension in an ultrasonic field, which depends on the ultrasonic vibrations. Abrasive grinding and polishing is created on the surface of the workpiece. Ultrasonic processing has low macro forces and does not cause deformation of the workpiece, but tooling production and mounting is difficult.

Ultrasonic processing can be combined with chemical or electrochemical methods. At the root of solution corrosion and electrolysis, the application of ultrasonic vibrations agitates the solution separating the dissolved products on the surface of the workpiece and averaging the corrosion or electrolyte on the left side of the surface; the cavitation of the ultrasonic waves in the liquid can also inhibit the corrosion process and favour the appearance of light.

2. Electrolytic polishing

The advantages are long mirror gloss, stable process, low pollution, low cost and good corrosion resistance. Its disadvantages are strong resistance to pollution, large investment in one-time processing equipment, large complex parts need tooling, auxiliary electrodes, large-scale production also requires cooling equipment. Suitable for mass production, important for high-grade products, export products, durable goods, its processing process is stable, relatively simple operation.

The principle of electrolytic polishing root is similar to chemical polishing, i.e. the appearance of selectively dissolved material is small and prominent, making the appearance smooth. Compared with chemical polishing, the cathodic reflection effect is obvious and better.

3. Chemical polishing

Its advantages are low investment in processing equipment, the possibility of polishing complex parts, high speed, high efficiency and good corrosion protection. Its disadvantages are poor brightness, gas spillage, the need for ventilation and the difficulty of heating. It is suitable for processing small quantities of miscellaneous parts and small parts of products with low luminescence requirements.

Chemical polishing involves dissolving the macroscopic projections of the material in a chemical medium better than a concave surface to obtain a smooth surface. The important advantage of this method is that a large number of workpieces can be polished without the need for additional equipment and several workpieces can be polished at the same time. The central issue in chemical polishing is the preparation of the polishing solution. The surface roughness obtained by chemical polishing is typically 10 μm.

4. Mechanical polishing

Mechanical polishing is the polishing method used to obtain a smooth surface through cutting processes and plastic deformation of the material surface. Oil stone belts, louvered wheels, sandpaper, sanding wheels, etc. are generally used manually, especially for the appearance of rotating bodies. Auxiliary tools such as turntables can be used, and the appearance quality requirements can be ultra-fine study and throwing methods . Ultra-fine polishing is a special kind of grinding tool . In the abrasive solution it is pressed against the machined surface of the workpiece and rotated at high speed. With this technique a surface roughness of Ra 0.008 μm can be obtained, which is often used for optical lens moulds.

5. Fluid polishing

Fluid polishing relies on the high speed flow of the fluid and the abrasive particles it carries to wash the surface of the workpiece to the polishing target. Commonly used methods are: abrasive radiation treatment, fluid radiation treatment, fluid dynamic grinding, etc. Hydrodynamic grinding is hydraulically driven to allow the liquid medium carrying abrasive particles to flow back and forth across the workpiece at high speed.

6. Magnetic grinding and polishing

Magnetic polishing is the use of magnetic abrasives under the action of a magnetic field to form abrasive brushes to grind the workpiece, this processing method is highly efficient and good quality.