Large format additive manufacturing (LFAM) systems are machines that produce very large parts, way larger than the more typical 6 in. to a foot sized parts. Large parts are often multiple feet in length or width.
Large format additive systems typically use pellet feedstock fed from an extruder. The extruder is often mounted on an X/Y gantry or a multi-axis robotic arm. Most LFAM systems are not enclosed in heated chambers, so the best material resins show good melt strength and minimal shrinkage upon cooling to avoid sagging and warpage. In many cases, carbon fiber-, glass fiber- or mineral-reinforced resins are used to combat warpage and improve dimensional stability.
In the process of developing resins for large format printing, organizations like Oak Ridge National Laboratory and SABIC have evaluated a range of reinforced polymers based on ABS, PC, PEI and polyphenylene sulfide (PPS).
LFAM is typically performed under ambient conditions, so it’s important to consider the thermal history of the chosen material. If layers are added too slowly, layers may not adhere or develop strong adhesion. But if layers are added too quickly, the part can deform under its own weight from excess heat build-up. Materials with low coefficient of thermal expansion (CTE) and good melt strength tend to be good candidates for this process.