Sheet metal polishing is an important technology in metal surface treatment. It is widely used in automobiles, home appliances, architectural decoration, precision instruments, and other fields. It is mainly used to improve the appearance quality, corrosion resistance, and functionality of metal workpieces. The following is a detailed analysis of sheet metal polishing technology:
1. The purpose of sheet metal polishing
Aesthetics: Eliminate surface scratches and oxide layers to obtain mirror or matte effects.
Functionality:
Reduce surface roughness (such as food machinery needs to prevent bacterial adhesion).
Improve corrosion resistance (it is easy to form a dense oxide film after polishing or facilitating subsequent electroplating/spraying).
Process connection: provides a good substrate for subsequent treatments such as electroplating, anodizing, and painting.
2. Classification and process of common polishing processes
1. Mechanical polishing
Tools: polishing wheel (cloth wheel, hemp wheel) + grinding paste (emery, aluminum oxide, etc.).
Process:
Rough polishing: Use a hard polishing wheel + coarse abrasive (such as W40) to remove deep scratches.
Medium polishing: Change to soft wheel + fine abrasive (such as W10) to reduce roughness.
Fine polishing: Use a velvet wheel + mirror paste (such as W1) to achieve an ultra-light surface of Ra≤0.01μm.
Applicable materials: stainless steel, aluminum, copper, and other metals with good ductility.
2. Electrolytic polishing (electrochemical polishing)
Principle: The microscopic protrusions on the metal surface are dissolved by electrolytes to achieve a leveling effect.
Advantages:
No mechanical stress, suitable for thin-walled parts or complex structural parts (such as medical devices).
It can improve surface corrosion resistance (form a passivation film).
Parameter control: voltage (5-20V), temperature (50-80℃), time (1-10 minutes).
3. Chemical polishing
Principle: Use acidic/alkaline solution to selectively corrode surface protrusions.
Features:
Simple equipment suitable for batches of small parts (such as hardware accessories).
High environmental pressure (waste acid needs to be treated).
4. Ultrasonic polishing
Application scenarios: Precision polishing of tiny holes and complex grooves (such as mold cavities).
Auxiliary medium: micron-grade abrasive suspension + high-frequency vibration (20-40kHz).
III. Key control factors for sheet metal polishing
Factors Influence and optimization measures
Material properties Stainless steel (304/316) needs to prevent over-polishing and deformation; aluminum alloy is easy to stick to the wheel and requires low speed.
Surface initial state Forged parts need to be sandblasted to remove the oxide skin, and stamped parts need to be deburred.
Process parameters The mechanical polishing speed is recommended to be 1200-3000 rpm, and the pressure is 0.1- 0.3MPa.
Environmental cleanliness Dust will cause secondary scratches, and it is recommended to operate in a dust-free workshop.
IV. Common problems and solutions
Orange peel texture: Due to uneven pressure or too coarse abrasion, the hardness of the polishing wheel and the tool path need to be adjusted.
Edge over-polishing: Use masking tape to protect sharp corners or use magnetic polishing (for small parts).
Rust after polishing: Stainless steel needs to be passivated immediately after polishing (such as nitric acid soaking).
5. Industry application cases
Automotive industry: Stainless steel exhaust pipes need mirror polishing (Ra≤0.05μm) to improve aesthetics.
Electronic equipment: Matte polishing of aluminum alloy shell (Ra 0.2-0.4μm) takes into account both touch and anti-fingerprint.
Architectural decoration: Copper plate is chemically polished and aged to form a retro texture.