Hybrid additive manufacturing of metal laminated forming tools
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Date
2024
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Abstract
This thesis introduces and investigates a new resource-efficient manufacturing method for rapid tooling. The presented hybrid method combines two additive manufacturing processes: sheet metal lamination and direct energy deposition (DED). In this combination, the core of the forming tool is fabricated by sheet lamination in a short time and at a low cost. The resulting step areas are compensated by laser metal deposition (LMD), which is a subset of the DED process. Three post-processing methods, milling, ball burnishing and laser polishing, are applied and compared to improve the surface roughness of the deposited areas.
The results show the essence of the two-step filling strategy, in which a bonding step should bond together the tool sheets, and in the next step, the remaining stair-step areas should be filled by LMD. The tensile strength of the fillet bonding for different process parameters and tool sheet combinations shows that the higher laser power and feed rate result in higher strength; however, the sheet thickness also needs to be considered to avoid the melt-through of the thin sheets. In the filling step, filling in the radius direction shows better surface roughness, but the nozzle life is shorter. The preheating of the die sheet to reduce the residual tensile stress shows only a 25 % reduction, which causes waviness of the deposited surface. Therefore, it can be neglected.
A semi-analytical model to analyze the stress distribution showed the possibility of using the low-strength tool sheets in a major part of the laminated tool. Deep drawing experiments are successful for two types of blanks. The wear test study shows low wear of the dies manufactured by the hybrid method in comparison with the conventional method. The feasibility of manufacturing complex geometries is demonstrated by a manufactured demonstrator.
The economic and technological advantages of the hybrid method are compared with conventional and fully manufactured tools by LMD, and the number of possible sheet combinations for tool lamination is reduced by considering cost and energy criteria.
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Keywords
additive manufacturing, rapid tooling, sheet metal lamination, laser metal deposition, deep drawing tools
Subjects based on RSWK
Rapid Tooling, Blechverarbeitung, Laserauftragschweißen, Tiefziehwerkzeug