May 2023 Volume 5

FORGING RESEARCH

Assessing the defect locations and, if defects were few and in accessible locations, attempting to excavate the defect regions and perform localized material deposit repairs. But, due to limited resources in this project the decision was made to use a second end-of-life tool and redesign the approach in a manner to simplify requisite tool paths. The approach with the second tool was to remove create a hollow cylinder by fully removing the teeth and cutting to a depth that is defined by the root region in the skim cut illustrated in Fig. 2. This required roughly double the volume of material to be removed, but provided the opportunity for a single continuous helical tool path to be utilized to build up the cladding. A steel backing plate (later machined off) was used to help define the surface of the tool. The build time was dramatically reduced, as expected. Macroscopically, the build appeared uniform and of high integrity. However, sectioning revealed internal defects even with the simpler toolpaths and this also rendered the die inappropriate for EDM and the intended in-plant trials. The defects were of a different morphology, but still rendered the tool unserviceable. A photograph of the deposit appears in Fig. 6. A typical defect that were revealed are shown in Fig. 7. As in Fig. 5, the surfaces revealed by the EDM are those of the pieces removed from the tool. The mating surface in tool itself showed identical defects – and the massive tool was simply less easy to manipulate and therefore photograph.

Fig. 7: Defects identified in the cladding build-up using the continuous helical path. In contrast to the extended high aspect ratio defects observed with the axial toolpaths, the defects observed in this case were equiaxed and generally widely separated. EDM was suspended after locating these defects in multiple teeth in the die. The work plan was carried out with immense contributions from both Lincoln Electric and Presrite, at CWRU technical discussions involvedGirishPadhy on a regular basis.We succeeded in establishing feasibility of 718 rebuild followed by heat treatment that could be EDMed, and tested two strategies for toolpathgeneration.However, at this point, we concluded that success in rebuilding through laser hot wire claddingwould require a systematic set of parameter optimization trials that would require a large scale effort. Our attention then turned to refurbishing and refreshing a CWRU campus facility for arc-based freeform welding. Our goal for this task was to provide the campus with a low- cost student-user-friendly freeform welder to encourage students a platform for hands-on experience rebuilding surfaces, and Lincoln Electric donated a 4' x 4' plasma cutting table (Torchmate® 4400 - A 4x4 CNC Plasma Cutting Machine) and a MIG Welder (Powerwave 300c). This donation was made specifically to allow the feasibility of integrating two off-the-shelf commercial devices to create a low-cost gantry-based freeformwelder system. Rebuilding of forge dies may be a problem well-suited to the capabilities of the CNC table since it is capable motion across a large area (4' square) with modest vertical throw (6" or 0.5'). Using two robust commercial machines is particularly well-suited for student use.This facility was installed as part of an earlier project, but was in need of complete refurbishment, testing, and creation of an operating manual to permit a wider array of users to make use of it. A photograph of the integrated device examples of built parts demonstrating its capability are shown in Figs. 8 and 9. Two teams of students worked on its refurbishment. In both cases they worked under the joint supervision of McGuffin-Cawley and Girish Padhy. The first team, Ian Suddarth and Liam Crowley, worked through a summer and identified problem areas and ordered hardware. They rebuilt custom pieces used to mount the welder to the table. At the conclusion of the summer they had restored the full range of motion, but inconsistencies in operation were noted. The second team, Steve Kellogg and Courtenay Mackey, worked during the academic year. They contacted Torchmate technical staff to resolve lingering issues and restored full functionality. Notably, Kellogg showed initiative in working closely with TorchMate to other creative pursuits. FreeformWelder

Fig. 6: End-of-life 718 tool after wired EDM to form a hollow cylinder and rebuild using a continuous helical path.

FIA MAGAZINE | MAY 2023 88