Precision plastic mold polishing

The commonly used polishing methods for plastic molds include the following

1.1 Mechanical polishing:

Mechanical polishing is a polishing method that obtains a smooth surface by removing the protrusions after polishing through cutting and plastic deformation of the material 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 high surface 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.

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.

1.3 Electrolytic polishing

The basic principle of electrolytic polishing is the same as chemical polishing, which relies on selectively dissolving 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.

1.4 Ultrasonic polishing

Put the workpiece into the abrasive suspension and place it together in the ultrasonic field, relying on the oscillation effect of the ultrasonic wave to grind and polish the abrasive 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 and facilitate surface gloss.

1.5 Fluid polishing fluid polishing

It relies on the high-speed flow of liquid and its carried abrasive particles to flush the surface of the workpiece to achieve polishing. 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 (usually polymer like substances) with good flowability at lower pressures 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.

The basic method of mechanical polishing in plastic mold processing is very different from the surface polishing required in other industries. To be precise, mold polishing should be called mirror polishing. It not only has high requirements for polishing itself, but also has high standards for surface flatness, smoothness, and geometric accuracy. Surface polishing generally requires obtaining a bright surface.

To achieve high-quality polishing results, it is important to have high-quality polishing tools and accessories such as oilstones, sandpaper, and diamond grinding paste. The choice of polishing program depends on the surface condition after preliminary processing, such as mechanical processing, electrical discharge machining, grinding, and so on. The general process of mechanical polishing is as follows:

(1) The surface after rough polishing, milling, electrical discharge, grinding and other processes can be polished using a rotating surface polishing machine or an ultrasonic grinding machine at a suitable speed. Afterwards, manual oilstone grinding is carried out, and strip oilstones are mixed with kerosene as a lubricant or coolant.

(2) Semi precision polishing mainly uses sandpaper and kerosene.

(3) Fine polishing mainly uses diamond grinding paste.