Skeleton arc additive manufacturing with closed loop control

Abstract

Wire Arc Addtive Manufacturing (WAAM) is a promising direct energy deposition technology to produce high-value material components with a low buy-to-fly ratio. WAAM is able to produce thin-walled structures of large scale and also truss structures without any support. To manufacture complex parts, process reliability and repeatability are still a necessity and this often leads to long developing times. In this paper, a method is proposed to automatically manufacture complex truss structures with point by point arc additive manufacturing and a six axis robot. Computer aided manufacturing (CAM) software is designed to manage (i) material deposition at intersections and (ii) collisions between the part under construction and the torch. Because it is difficult to model the deposition process, the bead geometry is monitored using video imaging. Image treatment program detects the contour of the deposit and computes its current position. With this position, the CAM software corrects the geometry of the part for future deposition. Simple case studies are tested to validate the algorithm. Two solid free form geometries designed by topology optimization are manufactured with this skeleton arc additive manufacturing process.

Continuous three-dimensional path planning (CTPP) for complex thin parts with wire arc additive manufacturing

“…In this work, a six-axis robotic arm holds the welding torch. The robot is controlled with six degrees of freedom (X, Y, Z, RX, RY, RZ) which are the three translations and the three rotations linked to the Cartesian frame [17]. Figure 7 shows a diagram of the six-axis robot with a vertical cross-section of the workspace, the dimensions of this workspace allow the manufacture of workpieces of the size of a meter.…”

A practical fabrication strategy for wire arc additive manufacturing of metallic parts with wire structures

“…In WAAM, the welding pool that provides the surface tension can counter gravitational forces during the welding process. For each deposit, the Eotvos number reported in [8] is used to represent the gravity force effect relative to surface tension, expressing as: where and ∆ are obtained from Table I. is defined as the characteristic length.…”

“…In recent years, WAAM has been integrated with industrial robotic systems or computer-aided manufacturing (CAM) systems, allowing it to perform multi-axis freeform deposition in threedimensional space [7], such as wire structures fabricated in ref [8]. Wire structures are skeleton-like components composed of many interconnected support struts.…”

“…A significant difference between the fabrication of wire structures and others (such as thin-walled or solid structures) is that the material is successively added in a point-by-point manner [8] instead of continuous bead deposition layer-by-layer [13]. Therefore, to successfully implement WAAM for producing wire structures, an accurate point-by-point bead model is required to predict and control the forming shape of each deposition and, ultimately, the geometry of the final part [14].…”

“…Non-layerwise slicing methods are widely developed in AM of complex structures [16]. For the deposition strategy of the wire structures, Radel et al [8] reported that struts could be fabricated through depositing material point-by-point in space with acceptable fabrication efficiency.…”