Shape-driven control of layer height in robotic wire and arc additive manufacturing

Abstract

Purpose Once an uneven substrate is aligned, traditional control theories and methods can be used on it, so aligning is of great significance for the development of wire and arc additive manufacturing (WAAM). This paper aims to propose a shape-driven control method for aligning a substrate with slopes to expand the application of WAAM. Design/methodology/approach A substrate with slopes must be aligned by depositing weld beads with slopes. First, considering the large height differences of slopes, multi-layer deposition is needed, and the number of layer of weld beads must be ascertained. Second, the change in the deposition rate is controlled as a ramp function to generate weld beads with slopes. Third, the variation of the deposition rate must be fine-tuned to compensate for the deviation between the actual and theoretical layer heights at the deposition of each layer. Finally, the parameters of the ramp functions at the deposition of each layer are determined through an optimization method. Findings First, to model the response function of layer height to deposition rate, the experiments are conducted with the deposition rate jumping from 4 to 8 mm/s and from 8 to 4 mm/s. When the deposition rate jumps from 4 to 8 mm/s and from 8 to 4 mm/s, the difference in the height of each layer decreases as the number of layer increases. Second, the variation of the deposition rate can be fine-tuned based on the deviation between the measured and theoretical layer heights because the variation of the deposition rate is proportional to the layer height when the initial and end deposition rates are near 4 or 8 mm/s, respectively. Third, the experimental results demonstrate that the proposed method is effective for single-layer aligning and aligning a substrate with one or more slopes. Originality/value The proposed method can expand the application of WAAM to an uneven substrate with slopes and lays the foundation for aligning tasks focused on uneven substrates with more complex shapes.

Interlayer closed-loop control of forming geometries for wire and arc additive manufacturing based on fuzzy-logic inference

“…In addition, an adaptive process control scheme was proposed to solve the forming issues of corner in complex-shaped components [28]. Recently, Xu et al proposed a feedforward mechanism to realize the shape-driven control of deposition height on substrates with slopes [29]. The above-mentioned schemes were designed for fabrication of MLSB components, whereas other research efforts were paid for PBP depositions.…”

Detection of the contact tube to working distance in wire and arc additive manufacturing

“…WAAM can be done in a closed-loop process as shown in [7,12,13,[15][16][17]. However, the use of external sensors limits the freedom of build degrees.…”

“…In [12] a control loop based on the layer height is established. This allows depositing an even surface on an uneven substrate.…”

“…However, this also influences the bead width. The bead width is stated to range from 4.5 to 10 mm, while the height only ranges from 1.5 to 3.1 mm [12].…”