Parts manufactured by conventional manufacturing processes (casting, forging, etc.) will not explode. However, the explosion of parts made by metal 3D printing is a potential safety hazard.
When metal 3D printing is used to manufacture parts, the problem that needs to be paid attention to in this process is the safety hazard. However, only those trapped powders that leave the processing area with the parts in the process of 3D printing metal will bring many safety hazards.
Perhaps you have seen operators and technicians wearing respirators and personal protective equipment. This is because the metal powder raw materials used in Metal 3D printing systems are usually small enough and can be easily inhaled and absorbed into the human body with breathing. In fact, some people are also allergic to nickel, which further makes the inhalation of metal powder a major concern.
Most people may not realize that once the parts made by metal 3D printing technology are taken out of the construction room and cleaned, the parts may still contain a small amount of powder materials. Because even if the metal part is completely dense, its supporting structure may not be.
Most support structures are hollow, so the powder may be trapped inside. When the components are taken out from the building board, one end of these support structures may release the metal powder trapped in the support structures into the atmosphere. This is why it is generally recommended to remove the construction substrate by underwater EDM wire cutting, so that these loose powders can be released into the water.
If 3D printed parts are not removed from the substrate using EDM processing technology, secondary cleaning operations, such as vacuuming, are required to remove loose powder trapped in the support structure. However, the difficulty of actual operation is not as easy as it sounds, because powder particles can adhere to the inner wall of the support material or partially melt onto the part surface during stress release. Even if the parts are bumped on the table many times in an exaggerated way, there may still be some powder that has not been removed.
Obviously, the method of removing loose powder from parts is very complex, and more research is needed to better understand how to use finishing technologies such as soda blasting, abrasive flow machining (AFM) and electrochemical polishing to help remove loose powder from the inside of the support structure.
Among them, abrasive flow machining technology is the latest machining method, which uses abrasive media (a flowable mixture mixed with abrasive particles) to flow through the surface of the workpiece under pressure to deburr, remove flash and grind fillet, so as to reduce the waviness and roughness of the workpiece surface and achieve the finish of precision machining. AFM is the best machining method available for complex manual finishing or complex shape workpieces, as well as parts that are difficult to be machined by other methods. The AFM method can also be applied to the work pieces that are not satisfied with the large-scale processing of rollers, vibrations and other work pieces that will be injured during processing. And the delamination regenerated after the electric discharge machining or the laser beam machining and the residual stress remaining on the machined surface in the previous process can be effectively removed.
Electrochemical polishing is also called electrolytic polishing. Electrolytic polishing takes the workpiece to be polished as the anode and insoluble metal as the cathode. Both poles are immersed into the electrolytic cell at the same time, and DC is applied to generate selective anode dissolution, so as to achieve the effect of increasing the brightness of the workpiece surface.
It should be noted that some metal powder raw materials such as titanium and aluminum are spontaneous combustion, which means that they will explode. Therefore, professional machining personnel should be careful when handling parts made of these materials, because these powders captured by the parts may be released again. If they sneak into the machine environment, they may explode under the combination of sparks or other conditions. Therefore, special care should be taken when handling and post-processing these parts, and first of all, proper cleaning should be ensured. If loose powder falls during part processing, it cannot be processed.
The progress of comprehensively understanding and diagnosing the potential safety hazards related to metal 3D printing is still in progress. If necessary, the local firefighters need to be notified in advance so that they can respond faster in case of emergency.
In addition, when 3D printed metal parts are processed on a grinding machine or a turning / milling machine, it must be ensured that the powder in these parts will not explode when sparks ignite during processing.