Metal polishing

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Metal polishing

Currently, the commonly used polishing methods include the following:

1. Mechanical polishing
Mechanical polishing is a finishing process that removes the raised areas on a surface through cutting and plastic deformation, thereby producing a smooth finish. It typically employs tools such as oilstones, wool wheels, and sandpaper, with manual operation being the primary method. For special parts—such as surfaces of rotating bodies—auxiliary equipment like rotary tables may be used. When exceptionally high surface quality is required, ultra‑precision lapping and polishing can be employed. This technique involves using specially designed abrasives that are pressed against the workpiece’s surface while immersed in an abrasive‑containing lapping fluid, subjected to high‑speed rotational motion. By utilizing this method, it is possible to achieve… A surface roughness of Ra 0.008 µm is the highest among all polishing methods. This technique is commonly used for optical lens molds.

2. Chemical polishing

Chemical polishing is a process in which, within a chemical medium, the microscopic protrusions on a material’s surface are preferentially dissolved relative to the recessed areas, thereby producing a smooth finish. The primary advantages of this method are that it requires no complex equipment, can be used to polish workpieces with intricate shapes, and allows for the simultaneous polishing of numerous parts, resulting in high efficiency. The key challenge in chemical polishing lies in formulating the appropriate polishing solution. The surface roughness achieved through chemical polishing typically ranges on the order of several… 10 µm.

3. Electropolishing

The basic principle of electrolytic polishing is the same as that of chemical polishing: it relies on the selective dissolution of the microscopic protrusions on the material’s surface to achieve a smooth finish. Compared with chemical polishing, it can eliminate the influence of cathodic reactions and delivers superior results. The electrochemical polishing process consists of two steps: ( 1) Macro-level leveling: Dissolution products diffuse into the electrolyte, reducing the geometric roughness of the material’s surface. 2 ) Micro‑level leveling: anodic polarization, resulting in improved surface brightness.

4. Ultrasonic polishing

The workpiece is immersed in an abrasive suspension and placed within an ultrasonic field. Under the oscillatory action of the ultrasonic waves, the abrasive particles abrade and polish the workpiece surface. Ultrasonic machining exerts minimal macroscopic forces, thereby avoiding deformation of the workpiece; however, the fabrication and installation of tooling can be relatively challenging. Ultrasonic machining can be combined with chemical or electrochemical processes. By superimposing ultrasonic vibration to stir the electrolyte or etchant, dissolution products are removed from the workpiece surface, ensuring uniform distribution of corrosive or electrolytic species near the surface. Moreover, the cavitation effect of ultrasound in liquids can suppress corrosion, promoting a brighter, smoother surface finish.

5. Fluid polishing

Fluid polishing relies on a high‑velocity liquid stream carrying abrasive particles to scour the workpiece surface, thereby achieving a polished finish. Common methods include abrasive jet machining, liquid jet machining, and fluid‑dynamic lapping. Fluid‑dynamic lapping is driven by hydraulic pressure, causing a liquid medium loaded with abrasive particles to flow at high speed back and forth across the workpiece surface. The working fluid is typically formulated from a special compound that exhibits good flow characteristics at relatively low pressures, with abrasives added; silicon carbide powder is often used as the abrasive.

6. Magnetic abrasive polishing

Magnetic abrasive polishing utilizes magnetic abrasives that, under the influence of a magnetic field, form an abrasive brush to perform grinding on the workpiece. This method offers high processing efficiency, excellent quality, and easy control of processing conditions, while also yielding favorable workpiece surface characteristics. By selecting appropriate abrasives, the surface roughness can be achieved at Ra 0.1 µm.

Polishing, surface, method, abrasive, machining, ultrasonic, chemical polishing

Shenzhen Industrial Exhibition and the 21st Shenzhen Machinery Exhibition

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Shenzhen Industrial Exhibition and the 21st Shenzhen Machinery Exhibition

A MIM Engineer’s Daily Routine