7 Polishing Methods to Improve Mold Quality

In the context of increasing demand for diversification and high-end industrial products, enhancing mold quality has become particularly important, as it directly determines the final quality of the product. During the mold manufacturing process, after shape machining, surface grinding and polishing—aimed at achieving smoothness and mirror-like finishes—are essential steps. By applying appropriate polishing methods and techniques, not only can mold quality and durability be improved, but the high quality of molded products can also be further ensured.

1. Mechanical Polishing Methods

Mechanical polishing removes surface protrusions of the workpiece by cutting or plastic deformation of the material surface, resulting in a smooth finish. This method mainly relies on manual operations, using tools such as oilstones, wool wheels, and sandpaper. For applications requiring higher surface quality, ultra-precision polishing can be employed. This technique uses specialized tools in an abrasive slurry to produce high-speed rotational friction, achieving an exceptional surface roughness of Ra0.008 μm. It is widely used in polishing optical lens molds and is considered indispensable in mold manufacturing.

2. Chemical Polishing Methods

Chemical polishing involves selectively dissolving microscopic protrusions on the material surface through chemical media, creating a smooth finish. This method is suitable for complex-shaped workpieces and allows multiple workpieces to be treated simultaneously, offering high efficiency. Typically, chemical polishing achieves a surface roughness of about Ra10 μm.

3. Electrolytic Polishing Methods

Electrolytic polishing works on a principle similar to chemical polishing, selectively dissolving microscopic protrusions on the material surface to produce smoothness. However, electrolytic polishing eliminates the interference of cathodic reactions, usually resulting in superior outcomes compared to chemical polishing.

4. Ultrasonic Polishing Methods

Ultrasonic polishing is a processing method that uses ultrasonic vibrations of tool sections for polishing brittle and hard materials. In this process, the workpiece is placed in an abrasive suspension and exposed to an ultrasonic field. The abrasives grind and polish the workpiece surface under the influence of ultrasonic oscillations. Since the macroscopic force during ultrasonic processing is minimal, it does not cause workpiece deformation. However, this method poses challenges such as complex tooling design and installation.

5. Fluid Polishing Methods

Fluid polishing uses a flowing liquid carrying abrasive particles to scour the workpiece surface. Driven by hydraulic pressure, the process uses special low-viscosity compounds (polymer-like substances) as the medium, mixed with abrasives such as silicon carbide powder to enhance the polishing effect.

6. Magnetic Abrasive Polishing Methods

Magnetic abrasive polishing employs magnetic abrasives that form brush-like structures under the influence of a magnetic field, which then grind the workpiece surface. This technology is well known for its high efficiency, excellent processing quality, and controllable conditions. With proper abrasive selection, surface roughness as fine as Ra0.1 μm can be achieved.

7. EDM-Ultrasonic Composite Polishing Methods

For workpieces with a surface roughness greater than Ra1.6 μm, EDM-ultrasonic composite polishing is adopted to improve efficiency. This method combines a special high-frequency, narrow-pulse, high-peak current power source with ultrasonic vibrations, allowing electrical pulses and ultrasonic action to work synergistically. It significantly reduces surface roughness and is especially effective for rough mold surfaces produced by turning, milling, EDM, or wire-cut machining, delivering remarkable polishing results.