Future oriented strategic technology: integrated manufacturing of large composite materials with additive and subtractive materials and its key elements

Thermowood has developed a large-scale additive and subtractive material manufacturing equipment, LSAM, and successfully printed tooling molds on site that can be used for aerospace composite material forming, demonstrating its low-cost and rapid response to composite material manufacturing capabilities to the public.

As a large-scale component additive manufacturer, Thermowood has developed a near net forming method for manufacturing parts, first using high-speed 3D printing to produce dimensions slightly larger than the required parts, and then cutting to the final size and shape. In 2017, the company signed a formal collaborative research and development agreement with the Eastern Fleet Readiness Center of the Naval Air Systems Command to collaborate on the development of large-scale additive manufacturing technology. In 2019, Thermowood collaborated with the United States Air Force Research Laboratory (AFRL) and Boeing to carry out a research project - using additive manufacturing technology to produce low-cost rapid response molds. Boeing's Auburn factory also has a Thermowood large polymer additive manufacturing system, which has a 6m printing bed and can print parts with a width of 3m, a length of 6m, and a height of 51.5m. In 2021, Purdue University established the Thermowood LSAM research laboratory for large-scale 3D printing.

LSAM Composite Material Addition and Reduction Equipment and Key Technologies
LSAM is a large-scale thermoplastic composite material additive and subtractive 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 can be completed additive and subtractive manufacturing on the same equipment, avoiding errors caused by re fixing the parts.

The LSAM 1540 equipment has a double gantry structure (workbench size 15 feet x 40 feet, 4.5m x 12m)

LSAM uses a two-step "near net forming" production process. Firstly, print the parts slightly larger than the required size at high speed, and then refine them to the final size and shape through precision machining. This is the fastest and most effective method for 3D printing large structures. By using LSAM equipment, printing and precision machining can be completed on the same machine. If a double dragon gate structure is adopted, one part can be 3D printed and the other part can be milled simultaneously at both ends of the workbench, thereby further improving efficiency.

LSAM equipment can process almost any thermoplastic composite material part, including high-temperature materials such as PSU, PESU, and PEI that need to be formed under high temperature conditions. These materials are very suitable for molds and tools that must be formed under high temperature conditions. The system integrates a liquid cooling system for drying and conveying polymer materials to maintain temperature control over important systems, which is particularly important for processing high-temperature materials, thus enabling the production of high-quality, fully integrated products. These materials are also mainly used for the production of molds and tools, most of which are used in aerospace and industrial production applications.

SAM performs 3D printing and milling on two parts separately

The key technologies of LSAM include the following aspects
One is the design of advanced printing systems. The majority of the heat generated by its print head extruder comes from the heated barrel rather than the friction between the screw rotation and the printing material. Compared with traditional designs, the heating is more uniform and does not require the replacement of screws to process different composite materials; The printing head uses special alloys that can support processing temperatures up to 450 ° C; The polymer melt pump is driven by servo to control the flow rate, forming a uniform output; Its uniquely designed pressure wheel can achieve no gaps between printing layers, and the bottom of the parts can be printed onto a special adhesive plate to eliminate cooling stress and part warping.

Screw extruder
The second is a powerful control system. LSAM integrates a control system that can monitor and adjust real-time temperature, automatically process extrusion and printing speeds. When loading the material configuration file, all parameters of the polymer, such as regional temperature and pressure limits, will be automatically set; The control system can also automatically synchronize the output of the melt pump with the machine's motion speed, ensuring absolute accuracy in size, whether the machine is accelerating or decelerating;

Temperature control pressure wheel diagram
The third is process software suitable for additive manufacturing of large parts. Equipped with corner pull compensation and other functions, it can program complex parts and automatically adjust according to the printing characteristics of LSAM equipment.

Special adhesive board
LSAM's unique printing system can produce high-strength, fully fused, vacuum sealed, and almost void free parts. It is not a laboratory or demonstration machine, but a mature industrial additive manufacturing system that is fully capable of producing large components.

Boeing verifies the feasibility of LSAM
Boeing Research and Technology Laboratory has collaborated with Thermowood Corporation to complete a project funded by the United States Navy, which involves the application of large-area additive manufacturing technology to develop composite tooling suitable for hot press tank processes, and to verify its feasibility as a low-cost, rapid manufacturing method to replace traditional tooling manufacturing methods. The manufactured hot press tank needs to be durable enough to withstand multiple curing cycles of 180 ℃ and 586Kpa.

The size of the hot press tank is approximately 1m x1m x 0.4m. Boeing uses LSAM1020 equipment and carbon fiber reinforced PESU material for part printing. The most popular material used is 277kg, which takes 7 hours and 26 minutes to complete printing. The milling head was replaced and the final processing was completed within 53 hours. The tooling size and surface quality meet the design requirements. After multiple cycles of hot pressing tank process tests, the vacuum retention, dimensional stability, and high-temperature durability of the tooling can all meet the requirements. This project demonstrates the ability of LSAM equipment to perform additive and subtractive manufacturing on a single platform for composite tooling. Compared to traditional manufacturing methods, it can save about 50% of costs and shorten the manufacturing cycle by 65%.

LSAM equipment can print composite material fixtures suitable for hot pressing tank process
In addition, Thermowood also successfully printed a 3.6-meter-long Boeing 777x dressing fixture using vertical layer printing (VLP) patented technology. The total time required for adding and subtracting materials was about 43 hours, verifying the LSAM equipment's ability to quickly manufacture large-sized, low-cost materials. At Boeing's Auburn factory, a Thermowood large polymer additive manufacturing system with a 6m printing bed was also installed.

Repair tooling for Boeing 777x
Composite material manufacturing is a strategic technology for future platforms, and developing more cost-effective tool solutions will greatly benefit production and manufacturing. Thermowood provides the ability to complete 3D printing and precision milling of parts on a single device with its patented 3D printing technology and integrated design concept of adding and subtracting materials, which has the advantages of low cost and short cycle manufacturing. With this, the company has developed the largest composite thermoplastic additive manufacturing system in the industry today, which has been applied in industries such as aerospace, military and defense, ocean and shipbuilding.

Source: Frontiers of additive manufacturing technology