{"title":"Abnormal melt pool behavior in overhead wire arc-based directed energy deposition","authors":"Hongbo Liu, Hui Chen, Jun Xiong","doi":"10.1016/j.jmapro.2025.07.020","DOIUrl":null,"url":null,"abstract":"<div><div>Overhead wire arc-based directed energy deposition (WADED) is a key technique for the in-situ fabrication of overhanging components. However, humping and dripping frequently occur during overhead WADED since gravity acting on the melt pool may make it detach from previous layers. This study investigates gravity-induced humping and dripping phenomena in overhead WADED of thin-walled low-carbon steel parts. The droplet transfer behavior of four gas metal arc (GMA) variants, i.e., continuous current GMA (CC-GMA), cold metal transfer (CMT), pulsed GMA (P-GMA), and CMT plus pulse (CMT + P), is comparatively analyzed during overhead deposition. Among the four variants, CMT + P can produce the best forming quality due to its highly stable droplet transfer. The melt pool geometry ratio <em>D</em>, defined as the product of melt pool length and height divided by the square of melt pool width, is proposed as an index to evaluate the probability of humping and dripping defects. A process window for overhead WADED using the CMT + P process is established. The effects of travel speed (TS), wire feed speed (WFS), and a constant WFS/TS ratio on the melt pool behavior during overhead deposition are explored. When <em>D</em> is below 2.0, stable melt pools and defect-free surfaces are produced. When <em>D</em> is greater than or equal to 2.0 but <3.9, humping is more likely to form with increasing TS or WFS. Dripping occurs when <em>D</em> is greater than or equal to 3.9, especially at lower TS or higher WFS. When the WFS/TS ratio is kept constant, humping and dripping defects occur more easily as WFS and the corresponding TS increase. This study lays a solid foundation for defect-free overhead WADED of complex overhanging structures.</div></div>","PeriodicalId":16148,"journal":{"name":"Journal of Manufacturing Processes","volume":"150 ","pages":"Pages 1164-1177"},"PeriodicalIF":6.1000,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Manufacturing Processes","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1526612525007881","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MANUFACTURING","Score":null,"Total":0}
引用次数: 0
Abstract
Overhead wire arc-based directed energy deposition (WADED) is a key technique for the in-situ fabrication of overhanging components. However, humping and dripping frequently occur during overhead WADED since gravity acting on the melt pool may make it detach from previous layers. This study investigates gravity-induced humping and dripping phenomena in overhead WADED of thin-walled low-carbon steel parts. The droplet transfer behavior of four gas metal arc (GMA) variants, i.e., continuous current GMA (CC-GMA), cold metal transfer (CMT), pulsed GMA (P-GMA), and CMT plus pulse (CMT + P), is comparatively analyzed during overhead deposition. Among the four variants, CMT + P can produce the best forming quality due to its highly stable droplet transfer. The melt pool geometry ratio D, defined as the product of melt pool length and height divided by the square of melt pool width, is proposed as an index to evaluate the probability of humping and dripping defects. A process window for overhead WADED using the CMT + P process is established. The effects of travel speed (TS), wire feed speed (WFS), and a constant WFS/TS ratio on the melt pool behavior during overhead deposition are explored. When D is below 2.0, stable melt pools and defect-free surfaces are produced. When D is greater than or equal to 2.0 but <3.9, humping is more likely to form with increasing TS or WFS. Dripping occurs when D is greater than or equal to 3.9, especially at lower TS or higher WFS. When the WFS/TS ratio is kept constant, humping and dripping defects occur more easily as WFS and the corresponding TS increase. This study lays a solid foundation for defect-free overhead WADED of complex overhanging structures.
期刊介绍:
The aim of the Journal of Manufacturing Processes (JMP) is to exchange current and future directions of manufacturing processes research, development and implementation, and to publish archival scholarly literature with a view to advancing state-of-the-art manufacturing processes and encouraging innovation for developing new and efficient processes. The journal will also publish from other research communities for rapid communication of innovative new concepts. Special-topic issues on emerging technologies and invited papers will also be published.