Optimized Robotic WAAM

This chapter summarizes a PhD thesis introducing a methodology for optimizing robotic MIG (metal inert gas) to perform WAAM (wire and arc additive manufacturing) without using machines equipped with CMT (cold metal transfer) technology. It tries to find the optimal MIG parameters to make WAAM using a welding robot feasible production technique capable of making functional products with proper mechanical properties. Some experiments were performed first to collect data. Then NN (neural network) models were created to simulate the MIG process. Then different optimization techniques were used to find the optimal parameters to be used for deposition. These results were practically tested, and the best one was selected to be used in the third stage. In the third stage, a block of metal was deposited. Then samples were cut from deposited blocks in two directions and tested for tension stress. These samples were successful. They showed behavior close to base alloy.

Various welding processes for joining aluminium alloy with steel: Effect of process parameters and observations–a review

The versatile aluminium alloys and steel are being used in automotive engines (exhaust systems), pressure vessels (flanges), turbine rotors, boilers (bonnet) and in many applications. The collective effect of these two metals created a revolution and are being utilized in most of the sectors wherein joining of these two dissimilar materials are always a major challenge faced by the manufacturers. Initially, the rivets were widely used for joining dissimilar materials owing to easy installation and flexibility, but the joint interlock fails and sudden ruptures occurred when exposed to higher load. Hence, numerous welding processes like metal inert gas welding, friction stir welding, friction stir spot welding, advanced laser welding, advanced cold metal transfer welding and hybrid welding techniques have been introduced in order to conquer the above problem because of residual stresses, cracks, distortion, and undercuts. Moreover, an appropriate standardization with controlled process inputs is still an uncertainty in joining the dissimilar materials. Hence, a detailed review on joining the dissimilar metals based on aluminium alloy and steel by various welding processes and influence of their parameters on the properties have been summarized in detail which would be a reference for manufacturing industries in the coming decades.

Deposition Geometrical Characteristics of Wire Arc Additive Manufactured AA2219 Aluminium Alloy With Cold Metal Transfer Pulse Advance Arc Mode

A cold metal transfer pulse advance (CMT-PA) arc mode was employed in this paper for the additive manufacturing of Al alloy. The effects of process parameters on the surface morphology and effective width percentage were investigated. And a deposition width model was built by the multiple linear regressions. Based on the principle that the volume of sample is equal to that of filler wire, a deposition height model was simultaneously derived. The results show that the process parameters affect the trends of droplet spreading in horizontal direction and molten pool tangential direction by changing the heat input and arc force. The disparity between two trends directly determines the final deposition geometrical characteristics. The influences of three factors on the effective width percentage show a trend of first increasing and then decreasing. So it provides a process window of good deposition forming. Using the optimal parameter in the window, the effective width percentage reaches to 83% and machining allowance is only 0.8 mm, which significantly improves materials utilization and reduces manufacturing costs. Besides, the error rates of deposition width and height models are less than 4% and 6%, respectively. Two models can facilitate manufacturing different size parts and make a profit for the actual production.

On the Effect of Heat Input and Interpass Temperature on the Performance of Inconel 625 Alloy Deposited Using Wire Arc Additive Manufacturing–Cold Metal Transfer Process

Relatively high heat input and heat accumulation are treated as critical challenges to affect the qualities and performances of components fabricated by wire arc additive manufacturing (WAAM). In this study, various heat inputs, namely 276, 552 and 828 J/mm, were performed to fabricate three thin-wall Inconel 625 structures by cold metal transfer (CMT)-based WAAM, respectively, and active interpass cooling was conducted to limit heat accumulation. The macrostructure, microstructure and mechanical properties of the produced components by CMT were investigated. It was found that the increased heat input can deteriorate surface roughness, and the size of dendrite arm spacing increases with increasing heat input, thus leading to the deterioration of mechanical properties. Lower heat input and application of active interpass cooling can be an effective method to refine microstructure and reduce anisotropy. This study enhances the understanding of interpass temperature control and the effectiveness of heat inputs for Inconel 625 alloy by WAAM. It also provides a valuable in situ process for microstructure and mechanical properties’ refinement of WAAM-fabricated alloys and the control of heat accumulation for the fabrication of large-sized structures for future practical applications.