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Extruded aluminum supply chains are materially inefficient with around 40% of the billet likely to be scrapped before the profile is embedded in a product. One of the largest sources of scrap is the removal due to weld integrity concerns of the tongue-shaped transverse weld(s) that forms between consecutively extruded billets. Process setting and die geometry optimization can decrease the weld length (and hence scrapped material) by modest amounts. We explore a process for significant scrap savings using profiled dummy blocks to generate shorter welds by compensating for the differential metal flow velocities across the billet cross-section as it flows through the die ports. We develop a design process for defining the profiled dummy block shape. For a given part and press, we first define an ideal dummy block shape by extracting the velocity field from finite element simulations of the conventional process and assuming perfectly rigid tooling. Next, we rationalize the tool shape using stress and deflection limits (preventing plastic deformation and interference with the container wall) and ductile damage limits for the billet to prevent cracking. We then simulate the likely effect of the rationalized dummy block design on back-end defect removal. The methodology is demonstrated for four profiles of increasing complexity. The process’ potential is evaluated experimentally using billets machined to match the ideal dummy block shape. The results show that profiled billets can achieve weld length reductions >50% for simple shapes. We demonstrate that multi-profile tooling can deliver scrap savings across a family of similar profiles.
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Characterizing Galling Conditions in Sheet Metal Stamping
Multiple experimental studies were performed on galling intiation for variety of tooling materials, coatings and surface treatments, sheet materials with various surface textures and lubrication. Majority of studies were performed for small number of samples in laboratory conditions. In this paper, the methodology of screening experiment using different combinations of tooling configurations and sheet material in the lab followed by the high volume small scale U-bend performed in the progressive die on the mechanical press is discussed. The experimental study was performed to understand the effect of the interface between the sheet metal and the die surface on sheet metal flow during stamping operations. Aluminum sheet AA5754 2.5mm thick was used in this experimentation. The sheet was tested in laboratory conditions by pulling between two flat insert with controllable clamping force and through the drawbead system with variable radii of the female bead. Comparing pulling forces during sheet metal flow through the testing setup provides information on flow resistance along the interface between the sheet and the tool surfaces. Onset of galling can be detected by the growth of the pulling force. In addition, it is defined by measurement of the surface of the tool and the scratches on the surface of the samples. Typical galling is seen as lines of sheet material deposit on the surface of the die parallel to the sheet material sliding. Most of galling is observed in the areas where lubricant can be forced out of the contact zone, such as edges of the strip, die entry radii or female bead radius.
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- Award ID(s):
- 1852112
- PAR ID:
- 10527833
- Publisher / Repository:
- SAE Mobilius
- Date Published:
- ISSN:
- 0148-7191
- Format(s):
- Medium: X
- Location:
- Detroit, Michigan, United States
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.4271/2024-01-2856
