How to effectively clean the internal channels of metal 3D printed parts?

一, Physical cleaning technology: a development that goes from vibration to fluidisation in many ways
1. High-pressure jet cleaning from both sides
High-pressure jet technology employs compressed air to wrap metal particles of the same type and pulse jet the parts from different angles. The impact force then peels off the powder inside the pores. For instance, the TCB-100 powder cleaning system from Zhejiang Tuobo Environmental Protection Technology Co., Ltd. can get rid of channel powder that is 0.5mm or larger in diameter. It does this by making the workpiece rotate 360 degrees in three dimensions using a servo motor, along with high-pressure spraying and vibration devices. The system has a recovery rate of over 90%. This technology works well with titanium and aluminium alloys, and it can cut the time it takes to process one piece to less than 10 minutes.
2. Technology for fluidisation with vibrations
Vibration fluidisation technology uses high-frequency vibrations (1000–3000 Hz) to retain powder particles in a fluidised state. This reduces friction between particles and lets powder shed with the help of airflow. The Pro-1500 powder cleaning system from Xihao Technology uses a combination of a vibration device and a dust blowing gun kit. The vibration loosens and compacts the powder, and then high-pressure blowing and powder suction equipment picks up the powder again. It can clean up to 99% of the powder from complicated spiral heat exchangers and other systems.
3. Cleaning with ultrasonic vibrations
Ultrasonic cleaning uses the cavitation effect in the liquid to generate micro jets that hit the surface of the powder and speed up its separation. Ultrasonic cleaning can be done on precise items like medical implants in alcohol or deionised water, together with multi-band ultrasonic waves (28kHz+120kHz combo) to cover powders with varying particle sizes. The surface roughness goes down by more than 30% after cleaning.
4. A global cleaning system that works with inert gas protection
For large workpieces, like parts for aeroplanes that are 1500mm 1500mm 1700mm, a sealed glove box design is needed. It should have fully automatic inert gas protection (like argon or nitrogen) and a robotic arm that can rotate the parts in multiple axes. It should also have high-pressure spraying and vibration devices to make powder cleaning safe and effective. For instance, the Huashu High Tech FS-PBS-12M rotary powder cleaning table can hold 5000 kg of workpieces and keep an eye on the oxygen level in real time using a fully closed-loop inert gas protection system to stop powder from oxidising and exploding.
二, Chemical cleaning technology: a specific response to get rid of the problem of powder sticking
1. Technology for dissolving chemicals
Surface engineering business REM has released a new chemical dissolution technology that selectively dissolves unmelted powder using precisely prepared chemicals that don't harm the molten material. This method has worked well on materials like Ti-6Al-4V (TC4) and IN-718, which can clear microchannels that are 0.5mm wide. When used with chemical polishing later, it can greatly improve the quality of the inside surface. For instance, while cleaning complicated spiral heat exchangers, chemical dissolving technique may easily get rid of powder cake-like agglomerates without damaging the channels, as can happen with physical procedures.
2. Working together to polish chemicals
Chemical polishing uses acidic or alkaline solutions to erode the surface of objects, which removes any remaining powder and oxide coatings. For instance, you can use a mixture of phosphoric acid and nitric acid to chemically polish aluminium alloy parts. You can also employ ultrasonic oscillation to make the polishing more even. To keep the channel size from changing too much due to too much corrosion, this method has to carefully control the temperature and concentration of the solution.
三, Suggestions for comparing and choosing technologies
Type of technology, situations where it can be used, pros and cons
Cleaning big workpieces with high-pressure jets, cleaning coarse channels quickly, recovering a lot of material, and cleaning microchannels (less than 0.5mm) is hard.
Cleaning complex structures with vibration fluidisation, removing a lot of powder from thin-walled cavities, causing little harm to parts, and needing to work with other technologies to treat deep powder
Ultrasonic cleaning greatly enhances the surface quality of precision components and medical implants, and is exclusively suitable for items that can be submerged in liquids.
Microchannels for chemical dissolution technology and high adhesion powder cleaning can clean places that are hard to reach by physical means, however this requires a costly neutralisation procedure.
The synergistic treatment of chemical polishing greatly increases the smoothness of objects with high surface quality standards. This may modify the size of the channel and require rigorous process control.