MTouch: an automatic fault detection system for desktop FFF 3D printers using a contact sensor

Desktop fused filament fabrication (FFF) 3D printers have been growing in popularity among hobbyist and professional users as a prototyping and low-volume manufacturing tool. One issue these printers face is the inability to determine when a defect has occurred rendering the print unusable. Several techniques have been proposed to detect such defects, but many of these approaches are tailored to one specific fault, use expensive hardware, and/or use machine learning algorithms which can be sensitive to ambient conditions making them unreliable. This paper proposes a novel, low-cost system, named MTouch, to accurately detect millimeter-scale defects that tend to make prints unusable. MTouch uses an actuated contact probe designed with a low-power solenoid, magnet, and hall effect sensor. This sensor is used to check for the presence, or absence, of the printed object at specific locations. The MTouch probe demonstrated 100% accurate readings, which was significantly higher than the 74% achieved using a repurposed commercially available bed leveling touch probe (the BLTouch). Additionally, algorithms were developed to detect common print failures such as layer shifting, bed separation, and filament runout using the MTouch probe. In head-to-head testing against a commercially available print defect detection system (The Spaghetti Detective), the MTouch was able to detect faults 44% faster on average while only increasing the print time by 8.49%. In addition, MTouch was able to detect faults The Spaghetti Detective was unable to identify such as layer shifting and filament runout/jam.