In September this year, the United States 3D printing manufacturing exhibition (Rapid and TCT) and October composite materials and advanced materials exhibition (CAMX), Thermwood company demonstrated its large-scale additive manufacturing equipment LSAM, and successfully printed the available on-site The tooling and mould for aerospace composite material molding demonstrated to the public its low-cost and rapid response composite manufacturing capabilities.
1. LSAM equipment and key technologies
LSAM is a large-scale thermoplastic composite material manufacturing equipment. Its standard model is equipped with a fixed workbench and a movable gantry. The gantry is equipped with an extrusion type 3D printing head and a traditional milling head, so that the parts are on the same equipment It can complete the increase and decrease of material manufacturing to avoid errors caused by re-fixing the parts.
LSAM uses a two-step "near net-shape" production process. First, print out parts that are slightly larger than the final size layer by layer, and then perform finishing to trim the parts into the final size and shape. If the double gantry structure is adopted, the 3D printing of one part and the milling of the other part can be performed at both ends of the worktable at the same time, thereby further improving efficiency.
The key technologies of LSAM include the following aspects: First, advanced printing system design. Most of the heat of the print head extruder comes from the heated barrel rather than the friction generated by the rotation of the screw and the printing material. Compared with the traditional design, the heating is more uniform and there is no need to replace the screw to process different composite materials;
The print head uses a special alloy to support a processing temperature of up to 450°C; the polymer melt pump is driven by a servo to control the flow to form a uniform output; its uniquely designed pressure roller can achieve no gaps between the printing layers, and the bottom of the part is printed to a special adhesive On the board, cooling stress and part warping can be eliminated; the second is strong temperature control.
LSAM integrates a temperature control system. When loading a printed material file, the area temperature and pressure limit of the material will be automatically set. The system can realize real-time temperature measurement and control, synchronized with the extruder and melt pump, and automatically Complete the adjustment of the feed speed;
The third is process software suitable for additive manufacturing of large parts. It has functions such as corner pullback compensation, which can realize the programming of complex parts and automatically adjust it according to the printing characteristics of the LSAM equipment.
2. Boeing verifies the feasibility of LSAM
According to a report on the Compositesworld website on October 18, 2021, the Boeing Research and Technology Laboratory and Thermwood have completed a project funded by the US Navy. Composite tooling has verified its feasibility as a low-cost, rapid manufacturing method to replace traditional tooling manufacturing methods.
In the manufacturing process, LSAM used 277kg of thermoplastic resin material, which took 7 hours and 26 minutes to complete the printing, and replaced the milling head to complete the final processing within 53 hours. The tooling size and surface quality met the design requirements.
After many times of autoclave process cycle tests, the vacuum retention, dimensional stability and high temperature durability of the tooling can meet the requirements. This project proved the ability of LSAM equipment to add and subtract materials on a single platform for composite tooling. Compared with traditional manufacturing methods, it can save about 50% of the cost and shorten the manufacturing cycle by 65%.
In addition, according to previous reports on the Compositesworld website, Thermwood has also cooperated with Boeing and successfully printed a 3.6-meter-long Boeing 777x trim tooling using the vertical layer printing (VLP) patented technology. Hours, verified the large-size, low-cost and rapid manufacturing capabilities of LSAM equipment.
LSAM equipment, with its patented 3D printing technology and the design idea of adding and reducing materials, provides the ability to complete 3D printing and precision milling of parts on one device, with low cost and short cycle manufacturing advantages.
The LSAM equipment of Thermwood Company has been used to produce solidified molds for aerospace composite materials, which shows that the current large-scale composite parts manufactured by foreign materials have reached the level of industrial application, which is worthy of attention.