What methods are available for polishing plastic moulds?

Plastic mould polishing basic procedures To obtain high quality polishing results, it is most important to have high quality polishing tools and auxiliary products such as oil stones, sandpaper and diamond grinding paste. The general process of polishing plastic moulds is as follows: 1, fine polishing fine polishing mainly uses diamond grinding paste. If the polishing cloth wheel is mixed with diamond abrasive powder or paste, the usual order of polishing is 9μm (#1800) to 6μm (#3000) to 3μm (#8000). 9μm diamond abrasive paste and polishing cloth wheel can be used to remove the hairline abrasion marks left by #1200 and #1500 sandpaper. This is followed by polishing with sticky felt and diamond abrasive paste in a sequence of 1μm (#14000) to 1/2μm (#60000) to 1/4μm (#100000). Polishing processes requiring a precision of 1μm and above (including 1μm) can be carried out in a clean polishing room in the tooling workshop. For more precise polishing an absolutely clean space is required. Dust, smoke, dandruff and spittle may ruin the high-precision polished surface obtained after several hours of work.2, rough polishing by milling, EDM, grinding and other processes after the surface can be selected at 35 000-40 000 rpm rotary surface polishing machine or ultrasonic grinding machine for polishing. Commonly used methods include the removal of the white EDM layer using a wheel with a diameter of Φ3 mm, WA # 400. This is followed by manual oilstone polishing, strips of oilstone with paraffin as lubricant or coolant. The general order of use is #180 ~ #240 ~ #320 ~ #400 ~ #600 ~ #800 ~ #1000. many mould makers choose to start with #400 in order to save time. 3. Semi-fine polishing Semi-fine polishing mainly uses sandpaper and paraffin. In practice, #1500 is only suitable for hardened mould steels (52 HRC and above) and not for pre-hardened steels, as this may cause surface burns on the pre-hardened parts. Singular finishing is done with abrasive paste, 8000, 10,000 to achieve a mirror finish.

Ultrasonic polishing

The workpiece is put into the abrasive suspension and placed together in the ultrasonic field, relying on the oscillating effect of ultrasound, so that the abrasive is ground and polished on the surface of the workpiece. The ultrasonic process has low macro forces and does not cause deformation of the workpiece, but the tooling is more difficult to produce and install. Ultrasonic machining can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibration is then applied to agitate the solution, so that the dissolution products on the surface of the workpiece are detached and the corrosion or electrolyte near the surface is uniform; the cavitation effect of ultrasonic waves in the liquid can also inhibit the corrosion process and facilitate surface brightening.

Fluid polishing

Fluid polishing is to rely on the high-speed flow of liquid and the abrasive particles carried by the workpiece surface to achieve the purpose of polishing. Commonly used methods are: abrasive jet processing, liquid jet processing, hydrodynamic grinding, etc. Fluid power polishing is driven by hydraulic pressure, so that the liquid medium carrying abrasive particles flowing at high speed reciprocally across the surface of the workpiece. The medium is mainly made of a special compound (polymeric substance) with good flow through at low pressure and mixed with abrasives, which can be made of silicon carbide powder.

Mechanical polishing

Mechanical polishing is by cutting, material surface plastic deformation to remove the convex part of the polished and smooth surface polishing method, the general use of oil stone, wool wheel, sandpaper, etc., mainly manual operation, special parts such as the surface of the rotary body, can use the rotary table and other auxiliary tools, the surface quality requirements of high can be used to ultra-precision polishing method. Super-finishing polishing is the use of special abrasives, in the polishing fluid containing abrasives, pressed on the surface of the workpiece being processed, for high-speed rotary movement. With this technique a surface roughness of Ra0.008μm can be achieved, which is the highest of the various polishing methods. Optical lens moulds are often used in this way. So the mirror surface processing of precision moulds is still mainly mechanical polishing.