With a wide range of high surface demmand plastic products‘applications increasing,especially such as optical lenses and CD, they require the appearance of the surface of the plastic mold cavity often to achieve the degree of mirror-polished, thus polishing requirements are very high. plastic mold polishing also has other advantages, such as ease of stripping , reduce injection cycles of plastic parts. Thus plastic mold polishing process is a very important step as to whole plastic mold manufacturing.Plastic mold polishing has 5 methods :
- mechanical polishing :mechanical polishing is finished by cutting and removing the protrusions and get a smooth surface, polishing method generally uses Whetstone, wool wheel, sandpaper, etc., mainly by manual.some special parts with rotors surface need use the turntable and if the other tools require high surface quality ,it may need ultra-precision polishing. ultra-precision polishing adopt a special abrasive, the polishing liquid containing abrasive pressed against the surface of the workpiece to be machined with high speed rotation. this technique can achieve a surface roughness Ra0.008μm which is the highest precision polishing methods. Optical lens mold often use this method;
- chemical polishing: chemical polishing is to allow the material in the chemical medium with convex portion get dissolved firstly, thereby to obtain a smooth surface. The main advantage of this method is that this method does not require complicated equipment, the complex shape of the workpiece can be polished, many workpiece can be polished simultaneously , high efficiency. main problem is how to formulate the proper chemical polishing solution. Chemical polishing the surface roughness is general 10μm;
- electrolytic polishing: electrolytic polishing and chemical polishing have the same basic principle, namely by selectively dissolve the small convex portion on the surface , so as to smooth the surface. Compared with chemical polishing, it can eliminate the influence of cathodic reaction .
Electrochemical polishing process is divided into two steps: (1) macro-leveling :Solubility spreads to the electrolyte material ,refine rough surface geometry, Ra> 1μm. (2) Micro flat; anodizing, surface brightness increase, Ra <1μm;
- ultrasonic polishing :the workpiece soaked into the abrasive solution and placed in an ultrasonic field together, for the ultrasonic oscillation, the abrasive on the workpiece surface could grind and polish. Ultrasonic machining force is small, so as not to cause deformation of the workpiece, but the tooling fabrication and installation are difficult. Ultrasonic polishing may combine with chemical or electrochemical method. After the etching solution and the electrolysis, the solution was stirred and then ultrasonic vibration is applied, so that the solute on the surface would fall off ;
- fluid polishing:fluid polishing is a method that high-speed flow liquid and its carrying abrasive wash surface to achieve the purpose of polishing. Common methods: abrasive jetting polishing, liquid jetting polishing, hydrodynamic grinding. Hydrodynamics grinding is driven by hydraulic fluid carrying the abrasive medium to reciprocate through the workpiece surface;
- Magnetic polishing:Magnetic polishing is to use magnetic abrasive form an abrasive brush in the magnetic field of the workpiece grinding. This method is with high processing efficiency, good quality, easy to control the processing conditions, . If using a suitable abrasive ,surface roughness can be achieved Ra0.1μm.