2. Ultrasonic cleaning

    Ultrasonic cleaning uses a transducer to convert electrical energy into high-frequency mechanical vibrations, generating a large number of tiny bubbles in a liquid medium. The instantaneous impact force released when these bubbles rapidly form and collapse (i.e., the cavitation effect) can effectively remove contaminants adhering to the surface of the workpiece and into its tiny pores. Because the cleaning process is non-contact, ultrasonic cleaning is particularly suitable for precision parts, complex geometries, and workpieces with blind holes, and it can achieve a high degree of automation.

Its main limitation is that it must rely on a liquid medium, making it unsuitable for handling large workpieces or materials that should not come into contact with liquids. Furthermore, the wastewater generated requires proper treatment. In addition, ultrasonic cleaning has certain requirements regarding the suspension method of the workpiece and the formulation of the cleaning solution, and the overall operating cost is at a moderate level.

3. High-pressure water jet cleaning

    High-pressure water jet cleaning uses a booster pump to pressurize water to hundreds or even thousands of bar, creating a high-speed water jet that impacts the workpiece surface. The kinetic energy and impact force of the water jet remove dirt, rust, and coatings. This method does not use chemicals, produces no chemical waste, and offers rapid cleaning, making it suitable for surface treatment of large-area equipment and building structures.

However, high-pressure water jets pose a certain risk of physical damage to the substrate surface, especially if the high-pressure parameters are not set correctly, which may cause surface roughening. This method consumes a large amount of water, making the construction cost of the wastewater collection and purification system considerable, and it is difficult to achieve high-precision selective cleaning of precision workpieces.

4. Sandblasting and shot peening cleaning

    Sandblasting and shot peening are the most traditional industrial surface treatment methods. They use high-speed airflow or centrifugal force to propel abrasive particles (such as quartz sand, steel shot, glass beads, etc.) onto the workpiece surface, removing rust, old coatings, and oxide scale through mechanical impact and grinding force. This method has strong cleaning power and is especially suitable for removing heavy rust and thick coatings. The equipment structure is simple and the initial investment cost is low.

Its core drawback is that the cleaning process causes irreversible roughening of the substrate surface, making it unsuitable for precision-machined parts or workpieces with strict surface roughness requirements. Furthermore, abrasive blasting generates a large amount of dust, posing a threat to operator health and the environment, and abrasive consumption is also a continuous operating cost.

5. Dry ice cleaning

    Dry ice cleaning is a relatively advanced physical cleaning method that has become increasingly popular in recent years. Its principle combines the mechanical impact of solid CO₂ particles with sublimation expansion: dry ice particles impact the contaminant layer at high speed, simultaneously sublimating into gaseous CO₂, causing a sudden expansion in volume of approximately 800 times, thereby peeling the contaminants off the substrate surface. Because dry ice sublimates without leaving any residue and does not damage the substrate surface, dry ice cleaning can be performed online directly at production temperatures, making it one of the few traditional methods capable of online operation.

However, the biggest bottleneck for dry ice cleaning lies in the cost of consumables. The production, storage, and transportation of dry ice all require special conditions, resulting in a significantly higher unit cleaning cost compared to other methods, typically several times the operating cost of laser cleaning. Furthermore, the cleaning process generates considerable noise, and the low-temperature conditions impose certain limitations on some materials and operating environments.

6. Laser cleaning

    Laser cleaning is a new generation of precision cleaning technology based on the principle of light-matter interaction. Its core mechanism involves irradiating the workpiece surface with a high-peak-power pulsed laser beam. Contaminant layers (such as oxides, mold release agent residues, rubber deposits, and grease) have a higher absorption rate for specific wavelengths of laser light, rapidly absorbing the laser energy and undergoing evaporation, sublimation, or peeling. Meanwhile, the substrate, due to its extremely low absorption rate for that wavelength, experiences only a very slight temperature rise, thus preserving its surface integrity. This "selective cleaning" mechanism is the fundamental technological advantage that distinguishes laser cleaning from all other methods.

By precisely adjusting the laser's wavelength, pulse width, repetition rate, and energy density, operators can achieve micron-level precision control over the cleaning depth and area, making it suitable for precision cleaning of various materials such as metals, rubber, and ceramics. The laser cleaning system can be seamlessly integrated with PLC and SCADA automation control systems, supporting fully automated, 24-hour continuous online operation. It also digitally records key parameters for each cleaning process, meeting the traceability requirements of Industry 4.0 quality systems.