Nowadays, metal additive manufacturing technology, especially the mainstream laser selective melting (SLM) technology, has been widely used in aerospace, high-end equipment, ships, energy, automotive, mold and other high-end manufacturing fields. With the gradual recognition of SLM processing parts technology in all walks of life, there are more and more demands for SLM additive manufacturing applications such as large format and high depth. In order to meet the processing needs of large size parts, LiM Laser has developed and mass-produced many series of equipment in recent years, including LiM-X400H, LiM-X650 series, LiM-X650H, LiM-X800 and subsequent larger size equipment.

LiM-X650H forming size: 650mm×650mm×1680mm

A device no matter how advanced, how comprehensive the function, how high precision, if the fault frequency and reliability is poor, can not work stably in the specified time, then its use value is not high, the economic effect is not good. Therefore, how to ensure the stability and reliability of SLM equipment for a long period of time while achieving large size and high efficiency processing is a great concern for users. It is also the primary responsibility of LiM laser as a product provider.

For SLM technology, large equipment research and development is not a simple geometric dimension of elongated widened, it involves multiple beam collaborative manufacturing, mechanical structure and high precision, reliable running, sent powder, powder, powder of automation control, uniform wind field and environmental stability control and guarantee continuous production, and many other difficult problem for a long period of time. So how does the LiM laser solve these difficult problems? The following is a detailed introduction by Xiao LiM.

About the accuracy and stability of the optical part

LiM laser uses internationally renowned brands IPG, Scanlab, Sill and other optical components to achieve low loss, high precision and high stability of the optical system. At the same time, a proprietary optical test platform is built to realize the long-term continuous operation and testing of 4 laser, 6 laser, 8 laser, 10 laser and above optical modules of the equipment. Finally, the optical lap area has excellent quality performance, the mechanical properties are not less than 95% of the average value of the single laser area, and the consistency difference of the mechanical properties of the whole format is not more than 5%.

Precision and stability of mechanical structures

The forming shaft of the equipment adopts high precision THK guide rail and grating ruler to make the positioning accuracy reach 0.005mm, and the forming accuracy is controlled within ±0.1mm. For high depth equipment, the forming shaft structure also adopts our company's independent research and development patent - gantry double drive structure, not only to ensure the operation of high precision, high reliability, but also to reduce the overall height of equipment, reduce equipment operating costs and other effects. In the joint of the forming cylinder of the equipment, the "zero positioning chuck" is used to separate the Z-axis drive and piston, which realizes the quick removal and accurate reset of the cylinder block, so as to realize the flexible parts taking by multiple stations and various ways.

About powder automation and sealing control

For the large size forming equipment, the automatic powder circulation system is configured to realize the metal powder addition, screening, recovery, drying, powder feeding and other fully closed automatic operations. The dense phase powder conveying technology is adopted, and the conveying efficiency is more than 10L/min. Adopt valve type quantitative powder dropping structure, double felt sealing structure, independent powder cleaning equipment and other ways, multiple ways simultaneously, comprehensive and effective improvement of powder utilization efficiency.

On wind field and environmental stabilization measures

According to the actual working conditions of each type of different equipment, the wind field test tooling is built, and the simulation calculation is carried out to realize the optimization of the wind field environment. After long-term print verification, the uniformity and stability of the large surface wind field are repeatedly tested, and the consistency of the print quality is realized. By controlling the bottom airflow of the wind direction and establishing the upper airflow of the air curtain, the problem of unequal wind field can be effectively solved by using larger surface equipment.

About the long period of stable operation of equipment

The equipment is equipped with a permanent filter, the filter element life of more than 50,000 hours, no need to replace the filter element, to ensure the continuous stability of the printing process. Cabin pressure stability control module and inert gas replacement module can keep the equipment in 100ppm oxygen content and stable pressure for a long time. In addition, equipped with powder bed monitoring module, using high-definition camera, to achieve the quality of each layer of powder laying and sintering quality monitoring, abnormal powder laying automatic powder and other measures to ensure the long-term stable operation of the equipment.

Technical improvement is only one dimension of equipment stability. In order to truly ensure the durability and reliability of equipment, every link from design and planning, manufacturing and installation, inspection and detection to use and maintenance is crucial. We will share the details next time. I am Xiao LiM. Follow me and welcome you to participate in more technology sharing.