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Six Common Polishing Methods for Plastic Mold

Posted by: Mu Ju 2021-12-06 Comments Off on Six Common Polishing Methods for Plastic Mold

here are two main purposes for polishing the mold, one is to increase the brightness and beauty of the plastic mold. The two is to make the die easy to die out. In the process of polishing, crude oil stone is used for rough grinding of the machined mold cavity surface, grinding to the tool mark, and then using the fine oil stone to get the coarse oil stone to reach the trace, then the fine sand paper is used to grinding the surface of the fine oil stone, and then the polishing paste or the grinding paste is used. The surface of the mold cavity is finally polished and polished. Finally, the effect of bright mirror is achieved.

mold making

In daily life, our common plastic mold has six polishing methods:


  1. Mechanical polishing


Mechanical polishing is a smoothing method to get smooth surface by cutting, plastic deformation of material surface and removing the bump after being polished. In general, oil stone strip, wool wheel and sand paper are used for manual operation. Special parts, such as back body surface, can use auxiliary tools such as turntable, and the high quality of surface surface can be used for polishing and polishing. . The ultra precision polishing is a special abrasive tool, which is tightly pressed on the workpiece surface to rotate at high speed in the abrasive polishing fluid. Using this technology, the surface roughness of Ra0.008 M can be achieved, which is the highest among all kinds of polishing methods. This method is often used in optical lens moulds.


  1. Chemical polishing


Chemical polishing is to allow the material to protrude preferentially in the concave part of the surface in the chemical medium, so that the smooth surface can be obtained. The main advantage of this method is that it does not need complex equipment, can polish complex workpiece, and can polish many workpieces simultaneously, with high efficiency. The key problem of chemical polishing is the preparation of polishing solution. The surface roughness obtained by chemical polishing is generally 10 m.


  1. Electrolytic polishing


Electrolytic polishing is basically the same as chemical polishing, that is, by selectively dissolving the tiny protruding part of the material surface, making the surface smooth. Compared with chemical polishing, the effect of cathode reaction can be eliminated and the effect is better. The electrochemical polishing process is divided into two steps:


(1) the macro leveling dissolve product diffuses into the electrolyte, and the surface roughness of the material decreases, Ra>1 mu m.


(2) low light level anode polarization, surface brightness increased, Ra<1 m.


4, ultrasonic polishing


The workpiece is placed in the slurry suspension and placed in the ultrasonic field together, and the abrasive is grind and polish on the workpiece surface by the oscillating action of the ultrasonic wave. Ultrasonic machining has little macroscopic force and will not cause deformation of workpiece, but the manufacture and installation of tooling are more difficult. Ultrasonic machining can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, the ultrasonic vibration stirring solution is applied to dissolve the dissolving products on the surface of the workpiece, the corrosion or the electrolyte is uniform near the surface, and the cavitation effect of ultrasonic in the liquid can also inhibit the corrosion process and be beneficial to the light brightening of the surface.


  1. Fluid throwing


Fluid polishing is achieved by polishing the surface of the workpiece by means of high-speed flowing liquid and its abrasive particles. Common methods are abrasive jet machining, liquid jet machining, fluid dynamic grinding and so on. Hydrodynamic grinding is driven by hydraulics, so that liquid media carrying abrasive particles can flow across the workpiece surface at high speed. The medium is mainly made of special compound (polymer like substance) with good flowability under low pressure and mixed with abrasives. Silicon carbide powder can be used for abrasive.


  1. Magnetic abrasive polishing


Magnetic abrasive finishing is to use magnetic abrasive to form abrasive brush under the action of magnetic field and to grind the workpiece. This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions. With suitable abrasives, the surface roughness can reach Ra0.1 m.

PTJMould Industrial Company Limited, established in 2010, is a leading injection moulding manufacturer in China. PTJMould specializes in plastic mould production for household appliances, medical equipments, electronic equipments, safety equipments as well as monitoring system.

The company has over 15000 square metres factory. With plastic injection tooling divisions possessing different machinery and expertise, PTJMould offers tools from small and precise mobile phone parts to as big as automotive parts. Our tools are mainly exported to U.S.A., Europe, Japan and UK. PTJMould’s diversification strategy and full service has won compliment from customers all over the world.

Our mission is to provide our customers high quality moulding products and services. We aim to exceed our customers’ expectations of pricing, quality and on-time delivery. To achieve our mission, PTJMould:

  • Commits to continually improve employee skills and efficiency,
  • Provides our employees a clean and safe working environment,
  • Upgrades machine technology and support equipment through a strict maintenance program, and
  • Maintains customers’ tooling to its highest peak of performance



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