Polishing Treatment of Plastic Molds

1.1 Mechanical polishing

Mechanical polishing is a polishing method that involves cutting and removing the protrusions on the material surface after polishing to obtain a smooth surface. It generally uses oilstone strips, wool wheels, sandpaper, etc., and is mainly operated manually. For special parts such as rotating surfaces, auxiliary tools such as turntables can be used. For surfaces with high quality requirements, ultra precision polishing can be used.

Ultra precision polishing is the use of specially designed grinding tools, which press tightly on the surface of the workpiece in a polishing fluid containing abrasives and perform high-speed rotational motion. By utilizing this technology, Ra0.008 can be achieved μ The surface roughness of m is the highest among various polishing methods. Optical lens molds often use this method.

1.2 Chemical polishing

Chemical polishing is the process of allowing the surface of a material to preferentially dissolve the concave parts of the surface that protrude in a chemical medium, thereby obtaining a smooth surface. The main advantage of this method is that it does not require complex equipment and can polish workpieces with complex shapes. It can simultaneously polish many workpieces with high efficiency. The core issue of chemical polishing is the preparation of polishing solution. The surface roughness obtained by chemical polishing is generally around 10 μ M.

1.3 Electrolytic polishing

The basic principle of electrolytic polishing is the same as chemical polishing, which selectively dissolves small protrusions on the surface of the material to make the surface smooth. Compared with chemical polishing, it can eliminate the influence of cathodic reactions and achieve better results. The electrochemical polishing process is divided into two steps:

(1) Macro leveling dissolution products diffuse into the electrolyte, resulting in a decrease in geometric roughness of the material surface, with Ra>1 μ M.

(2) Low light flat anodic polarization, increased surface brightness, Ra<1 μ M.

1.4 Ultrasonic polishing

Put the workpiece into the abrasive suspension and place it together in the ultrasonic field. With the oscillation effect of the ultrasonic wave, the abrasive is ground and polished on the surface of the workpiece. Ultrasonic machining has low macroscopic force and will not cause deformation of the workpiece, but it is difficult to make and install fixtures.

Ultrasonic processing can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibration is applied to stir the solution, causing the dissolution products on the surface of the workpiece to detach and the corrosion or electrolyte near the surface to be uniform; The cavitation effect of ultrasound in liquids can also suppress the corrosion process, which is beneficial for surface gloss

1.5 Fluid polishing

Fluid polishing is achieved by flushing the surface of a workpiece with a high-speed flowing liquid and its carried abrasive particles. Common methods include abrasive jet machining, liquid jet machining, fluid dynamic grinding, etc. Fluid dynamic grinding is driven by hydraulic pressure, which causes the liquid medium carrying abrasive particles to flow back and forth at high speed through the surface of the workpiece. The medium is mainly made of special compounds (polymer like substances) with good flowability under lower pressure and mixed with abrasives, which can use silicon carbide powder.

1.6 Magnetic Grinding and Polishing

Magnetic abrasive polishing is the process of using magnetic abrasives to form abrasive brushes under the action of a magnetic field to grind and process workpieces. This method has high processing efficiency, good quality, easy control of processing conditions, and good working conditions. By using appropriate abrasives, the surface roughness can reach Ra0.1 μ M.