Methodology And Implementation Of Multi-DOF 3D Printing System Based On Robot Arm

Fused Filament Fabrication(FFF)is one of the most widely used 3D printing methods.However,due to the limitation of the freedom of printing equipment and process planning method,the traditional FFF platform can only deposit materials on a set of parallel planes.The mechanical properties are obviously different within and between layers,and it is difficult to avoid the staircase effect.These problems become the bottleneck to expanding the application of FFF further.In order to solve the above problems,a general multi-axis FFF system is constructed base on the robotic arm,which is widely used in industry.The architect extends the degree of freedom(DOF)of the equipment and improves the surface quality and mechanical properties through multi-DOF surface printing.The system provides everything from input model processing to automatic generation of robot and material extrusion control codes,supports the printing of conventional thermoplastic materials and fiber-reinforced materials,and is suitable for different robot platforms.The specific work can be divided into the following parts:1)In terms of the printing platform,the multi-axis FFF platform based on the robotic arm is designed,and the corresponding process flow is also designed.The platform takes a closed 3D mesh model as input,automatically generates the robot and material extrusion control code,and supports multi-DOF 3D printing using conventional polymer and fiber-reinforced materials.2)In terms of process planning,this paper proposes a multi-DOF space continuous path planning method.This method slices object along with the model surface,maps the sliced curved surfaces to planes,and then generates Fermat's spiral as the print path on the planes.Finally,the path will be restored to a multi-DOF trajectory.This continuous path can enhance the mechanical properties and the surface quality of the printed object and ensure the smooth printing of the robot system.3)In terms of control methods,to ensure the precise synchronous control of the position of the deposited material and the extrusion speed of the material,the platform uses the parallel control architecture of the manipulator and the extrusion system.At the same time,in order to avoid the collision with the printing workpiece,an endposition and pose planning method was designed to ensure that the material extrusion at the end of the manipulator was perpendicular to the printing surface.In this paper,a prototype of the multi-DOF FFF system was built based on the UR3 robot,and experiments were carried out respectively for the platform and the process.Experiments show that the spatial continuous path planning enables the platform to print multi-DOF continuous reinforced fiber without cutting.Compared with the traditional FFF process,the tensile load of the structure printed using curved spatial path planning increased by up to 167%.The transverse bending load increased by up to 38% in the mechanical tests for a specific bending structure.