2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Wire-fed DED: Gas and Thermal Management and Analysis
Program Organizers: Joseph Beaman, University of Texas at Austin
Wednesday 1:10 PM
August 16, 2023
Room: 412
Location: Hilton Austin
1:10 PM
A Small Volume, Local Shielding Gas Chamber with Low Gas Consumption for Laser Wire Additive Manufacturing of Bigger Titanium Parts: Alexander Barroi1; Nick Schwarz1; Joerg Hermsdorf1; Thomas Bielefeld2; Stefan Kaierle1; 1Laser Zentrum Hannover e.V.; 2Premium AEROTEC GmbH
This paper shows how additive manufacturing of large size titanium parts can be achieved by means of a mobile shielding gas chamber, without the consumption of excessive amounts of shielding gas. While welding, the oversized cover of the chamber can be slid to the sides without opening it. The laser head is only partly inserted into the chamber through the cover. This enables a small sized chamber and allows a quick filling with argon. Since the chamber has a low leakage, only small amounts of argon (5 l/min) are needed to maintain a sufficient welding atmosphere with less than 300 ppm oxygen. For large sized parts, the chamber can be repositioned on the substrate. It has flexible parts which can be fit to the already welded structures that otherwise would prevent the chamber from being put flat on the substrate. The limited build space inside the chamber requires a new welding strategy, which is suggested.
1:30 PM
Comparison of Process Control Methods for Wire-arc Directed Energy Deposition of Low Carbon Steels with In-situ Temperature Measurement: Ahamed Ameen1; Vit Janik2; Joanna Nicholas3; Xiang Zhang2; Cui Er Seow3; 1Coventry University / National Structural Integrity Research Centre; 2Coventry University; 3TWI Ltd
Additive manufacturing (AM) techniques enable the production of near-net shape parts. Wire-arc direct energy deposition (DED) can achieve a higher deposition rate among metal AM methods. Conventional arc welding requires a maximum interpass temperature to limit any reduction in mechanical properties, but this may not be practicable for wire-arc DED. In this study, two inter-pass process control methods, one with maximum interpass surface temperature and the other with constant dwell time, were adopted to deposit low-carbon steel walls while maintaining the same feedstock and heat input values. Thermocouples were inserted at three different positions in the walls during deposition, to record the thermal profiles. Testing of samples extracted from walls exhibited comparable tensile strength (~10 MPa difference) and consistent hardness values. Microstructural evaluation showed the presence of interlayer regions with alternating coarse and fine bands of ferrite grains, irrespective of interpass control method suggesting dwell time control for better productivity.
1:50 PM
Efficient Thermomechanical Simulation for WAAM using Automated GPU-based Modeling: Xavier Jimenez1; Albert To1; 1University of Pittsburgh
Simulating the wire arc additive manufacturing (WAAM) process can be challenging due to the large part size. An improved workflow that combines automation and GPU accelerated modeling using the Pittsburgh Additive Manufacturing Simulator (PAMSIM) has been implemented. Although thermal simulations are very fast, thermomechanical simulations can take 10 to 20 times more time and thus become impractical to implement before every print. This work focuses on implementation of an automated computational framework for the flash heating method combined with the temperature dependent inherent strain. The improved workflow helps to accelerate the manufacturing process of new parts using WAAM, through thermal and residual stress results at the part scale level.
2:10 PM
Inter-pass Temperature Impact in Wire-Arc Additive Manufacturing: Steven Williams1; Evan Gitto1; Bradley Jared1; 1University of Tennessee
In wire-arc additive manufacturing (WAAM), variations in bead geometry often lead to defects and unintended part geometries. Several factors influence the bead geometry including the material deposited or process inputs. In this study, ER70S-3 wire was deposited onto steel build plates at surface temperatures from ambient to 300°C using different weld parameter sets. To control build plate surface temperature, a preheat stage was designed and implemented. Then, steel beads were deposited onto the build plate surface and subsequently measured to determine their geometric properties. Initial results indicate that as the preheat temperature increases, resulting bead height decreases, bead height variation decreases, and bead width increases. Further analysis is being conducted and will be discussed to determine the impact of preheat on the resulting bead microstructure. The results of these experiments will be used to create process maps which will serve as a foundation for bead geometry control during printing.
2:30 PM
Localized Shielding Gas Lens and Inert Enclosure Effects on Titanium GMAW for Wire-Arc Additive Manufacturing: Harold Walters1; Christopher Masuo1; Andrzej Nycz1; Peter Wang1; Joshua Vaughan1; Bill Carter1; Riley Wallace1; Jonathan Paul2; Jason Flamm2; 1Oak Ridge National Laboratory; 2Lincoln Electric
Depositing titanium and titanium alloys using gas-shielded metal arc welding (GMAW) presents a challenge for Wire-Arc Additive Manufacturing (WAAM) of maintaining weld quality due to the susceptibility of titanium to oxidation. GMAW utilizes an envelope of inert gas around the arc to create a small, stable environment that oxygen cannot enter to protect the weld during deposition. This standard approach falls short for shielding titanium depositions because the hot trailing bead continues to be vulnerable to oxidation during solidification. One alternative is to utilize a shielding gas device that mounts to the end effector and provides additional shielding to the trailing bead. Another alternative to this is to utilize an inert enclosure, which encompasses the entire work piece. This analysis seeks to characterize and compare the effects of utilizing a shielding gas device system to an inert enclosure for WAAM when depositing titanium beads to determine the most cost-effective process.
2:50 PM Break
3:20 PM
Prediction of Inter-pass Temperature for Large-scale Double Sided Component Fabricated Electron Beam Wire Additive Manufacturing: Guru Madireddy1; Zachary Corey2; Ron Aman2; Matt Bement3; Yousub Lee3; 1Sentient Science; 2Edison Welding Institute; 3Oak Ridge National Laboratory
Wire-based direct energy deposition (DED) technologies have been rapidly adopted for manufacturing of large structural components in aerospace and aircraft power generation industries. As the part size becomes larger, the deposition often requires expected/unexpected pauses (e.g., wire-spool change, flipping part for double-sided part) for the completion of part. The pauses lead to change of thermal profile and heat build-ups during printing and cooling that can result in inhomogeneity in distribution of defects or residual stresses. Therefore, understanding and predicting the effect of process parameters on dynamic variation of thermal profile during printing and cooling are crucial for tight control of qualifying the material/mechanical properties. In this research, we developed a part-scale thermal model for validation of inter-pass temperatures for the double-sided additive component, i.e., Droplink (> 700 mm in length). The prediction showed a good agreement in trend and values within 10% error to the pyrometer measured temperature.
3:40 PM
Process Parameters and Interpass Temperature Effects on WAAM Inconel 718: Xavier Jimenez1; Jie Song2; Yao Fu2; Albert To1; 1University of Pittsburgh; 2Virginia Tech
Inconel 718 is an alloy widely used by many industries due to its great performance at high temperatures. Wire arc additive manufacturing (WAAM) can be used to create larger parts with medium to low complexity with a reduced cost and faster manufacturing times than traditional methods. The presence of niobium in this alloy makes it prone to severe segregation during solidification which creates a liquid film and low melting-laves phases that can lead to hot cracking. This work focuses on the effect that process parameters and interpass temperature have on melt pool dimensions and the occurrence of hot cracking in MIG-based WAAM. Understanding this effect allows users to choose the most productive process parameters while maintaining geometric consistency and avoid cracking.
4:00 PM Cancelled
Shielding Gas Flow Analysis for Wire-Arc Additive Manufacturing using Schlieren Imaging: William Carter1; Christopher Masuo1; Luke Meyer1; Alex Walters1; Riley Wallace1; Andrzej Nycz1; Joshua Vaughan1; Jonathan Paul2; Jason Flamm2; 1Oak Ridge National Laboratory; 2Lincoln Electric
Proper shielding gas flow is crucial to the wire-arc additive manufacturing process. Improper shielding of the deposition process can lead to voids in the deposited material, an unstable weld arc, and excessive oxidation of the printed part. Several factors can affect the flow of the shielding gas in wire-arc additive manufacturing including nozzle design, wire stickout, gas flowrate, and the location of the nozzle over the part. Schlieren imaging, a technique that uses mirrors, a point light source, and a knife edge to view air currents, was used to examine the effects of these factors on gas coverage. Images and videos will be presented along with strategies for optimizing gas coverage under various conditions.