What are the basic procedures for polishing plastic moulds

Wed Feb 22 14:24:39 CST 2023

Basic procedures for polishing plastic moulds To obtain a high quality polishing result, it is most important to have high quality polishing tools and aids such as oil stones, sandpaper and diamond abrasive paste.

The general process of polishing plastic moulds is as follows.

1、Fine polishing

Fine polishing mainly uses diamond polishing paste. The usual grinding sequence is 9μm (#1800) to 6μm (#3000) to 3μm (#8000) if the polishing cloth wheel is mixed with diamond grinding powder or paste. 9μm diamond grinding paste and polishing cloth wheel can be used to remove the hairline abrasions 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 saliva froth may ruin the high-precision polished surface obtained after several hours of work.

2、Rough polishing

After milling, EDM, grinding and other processes the surface can be polished with a rotary surface polisher or ultrasonic lapping machine with a speed of 35 000-40 000 rpm. Commonly used methods include the removal of the white EDM layer using a wheel with a diameter of Φ 3 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 to save time.


Semi-finishing is mainly done with 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.

Singed finishing

Finishing with abrasive paste, 8000, 10,000 to achieve a mirror finish.