3D printing technology is gradually moving into the production field, occupying an increasingly important position in the manufacture of complex parts or small batch production. Famous manufacturing users such as GE, Airbus and Honeywell have established additive manufacturing centers around the world in recent years. Multiple metal 3D printing devices are installed. In addition to these large manufacturing companies, small and medium-sized manufacturing users in some segments have also installed metal 3D printing equipment and built their competitiveness in the field of additive manufacturing. We know that there are safety production specifications to be observed in every manufacturing line or in every production workshop. Then, as more and more metal 3D printing equipment goes to the production workshop of the enterprise, what should the user do to ensure safe production? What are the safety hazards that need to be circumvented in the use of metal 3D printing equipment? In this issue, Xiaobian mainly uses powder bed laser-melting metal 3D printing equipment and its printing materials as examples to enumerate several factors that have safety hazards. Provide a certain reference for the user's safe and standardized operation of metal 3D printing equipment. Risk of use of powders and inert gases The powder bed laser-melted metal 3D printer uses a metal powder with a particle size of 10-70 microns. This type of powder material poses a risk of fire or explosion. In addition, long-term contact and inhalation of powder particles by the human body can also pose a certain health hazard. In a powder bed laser melting process, the laser locally melts the metal powder. This process is carried out in a process filled with an inert gas (argon or nitrogen) that produces oxygen in a closed environment, which is the second source of risk. In addition, a certain amount of "smoke" is generated during the laser melting of the metal powder, and these substances are deposited in the printing chamber and the filter. The particles in the smoke are finer than the metal powder itself, and the metal powder has similar safety hazards and therefore needs to be cleaned regularly. To sum up, the powder bed laser melting process has four hidden dangers in the printing process: fire and explosion, powder inhalation and contact, inert gas suffocation and environmental impact of material waste. Plastic container for storing metal powder Fire and explosion In 2014, the Occupational Safety and Health Administration introduced a case of safe production in the OSHA Occupational Safety and Health Standard. A company's metal 3D printing workplace is not equipped with compliant fire extinguishing. The equipment caused an operator to be burnt by fire. Although the fire was caused by the company's non-standard operating equipment, the incident still has a safety warning. So, what are the lessons to be learned in this incident? What causes the fire in the metal 3D printing process? As shown in the above figure, fires and explosions are usually caused by a variety of conditions, including fire, fuel, and ignition sources (left). When there are two conditions of oxygen and fuel, there is a hidden danger of fire. At this time, it is necessary to avoid the fire source. Static electricity generated in the environment may become an ignition source. In addition, hot surfaces and hot gases may generate sparks and stray currents, which may become an ignition source. Conditions that cause the explosion include: dust, oxygen, fuel, and containment (right). The dust present in the environment may explode if it encounters a fire source. Of course, even if the above conditions are met at the same time, it does not mean that it will cause fire and explosion. Only when these conditions reach a certain level will the danger occur. For example, the risk of burning increases as the particle size of the powder decreases, so in the risk control work, attention should be paid to the properties of the metal powder. Generally, aluminum alloys, titanium, titanium alloys, and the fumes produced by these metal powders are all active metals, which pose a higher risk of fire or explosion than inactive metals such as steel, inconel, bronze, and cobalt chrome. Dust inhalation and contact The metal 3D printed powder has a particle size of 10-70 microns and is at the edge of the body's respiratory system. Some scholars have shown in the research paper that after inhaling powder particles with a diameter of 10-70 micrometers, these fine powder particles can be deposited in the trachea and bronchi, and finally swallowed and discharged by the human body. Powder particles in this diameter range, It is less likely to cause damage to the human lungs, because only particles below 2 microns in diameter can reach the lungs and cause damage to the lungs. However, due to the long-term damage caused by the human body in the metal powder environment, it has not been fully confirmed. Therefore, the powder operator should still wear protective equipment such as a respirator to protect the body. Inert gas suffocation The powder bed laser melting 3D printing device uses an inert gas such as argon or nitrogen under working conditions. If the inert gas leaks for some reason, it may have serious consequences. Since neither of these gases can be detected by the human body, the victim will inhale the air containing both gases without precautions. The oxygen content in the air breathed by the human body is 21%. If the oxygen content is less than 19.5% due to the leakage of the inert gas, the human body will be harmed by the lack of oxygen. This situation is particularly prone to occur in relatively small, small operating rooms where metal 3D printing users should be aware of this potential risk and take precautions to prevent it from happening. environmental impact One of the challenges in the use of powdered bed metal 3D printers is the handling and collection of "spattered" metal powders in different parts of the equipment, which also present risks such as fire, explosion and inhalation injuries. In addition, the powder scattered in the storage may cause certain harm to the external environment. Xiaobian recommends that before using metal 3D printing equipment, in addition to fully understanding the factors related to safety production, the system should also participate in the training of printing equipment manufacturers to understand the safety operation specifications of equipment, and combine fire protection and safety production. Regulations do a good job of precautionary measures. Synthetic Crochet hair extensions are 100% handmade crochet fabrics, prefabricated loops and high-quality synthetic fibers.
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