Statistical process design for hybrid adaptive layer manufacturing

Purpose - This paper discusses the optimization of the process parameters for the hybrid-layered manufacturing (HLM) process during its weld layer deposition with subsequent surface machining in attaining the desired accuracy and contour profile of the deposited weld layer thickness. Design/methodology/approach - The HLM process integrates the synergic metal inert gas (MIG) - metal active gas (MAG) welding process for depositing the metal layer of a desired slice thickness and perform the computer numerical control (CNC) machining process on the deposited layer to enhance both the surface quality and dimensional accuracy of the deposited layer. For the HLM process the weld bead geometry plays a vital role in determination of the layer thickness, surface quality, build time, heat input into the deposited layer and the hardness attained by the prototype. A feasible weld bead width and heights are to be formulated for the exterior contour weld path deposition and for the interior weld cladding. Thus, Taguchi methodology was employed with minimum number of trails as compared with classical statistical experiments. This study systematically reveals the complex cause-effect relationships between design parameters and performance. Findings - Statistical design of experiments using orthogonal arrays and signal-to-noise (S/N) ratios are performed to constitute the core of the robust design procedure. Experimental confirmations of the performance characteristic using the derived optimal levels of process parameters are provided to confirm the effectiveness of this approach. Research limitations/implications - The welding parameters such as current, voltage, arc length, wire feed rates, wire stick-out distance, shielding gas, filler wire diameter, weld speed, etc. will influence on the deposited weld bead geometry. Further investigations are to be carried out during adaptive layer deposition on the induced thermal stresses and its influence on the hardness of the deposited weld layer. Originality/value - This paper describes a low cost direct rapid tooling process, HLM. This unique methodology would reduce the cost and time to make molds and dies that are used in batch production

Hybrid layered manufacturing: direct rapid metal tool-making process

The fabrication method for direct metallic tools presented here combines synergic gas metal arc welding and computer numerical control (CNC) machining processes in order to exploit the benefits of both while avoiding their limitations. A programmable logic controller (PLC)-based low-cost three-axis manipulator is fabricated with a stepper motor driver in open-loop control. The tool head will hold the welding torch and milling cutter. At any time, either milling or welding will take place; for that the welding gun can be moved up and down with a pneumatic operation. The welding parameters such as current, voltage and arc length are controlled externally. The framework also consists of a software program which uses the zeroth-order edge approximation uniform slicing strategy to calculate each slice thickness to be deposited with the required metal as successive layers from lower to topmost layer with the welding process. Further it generates the required CNC code for machining from the top to bottom layer direction of the deposited metallic layers to attain the required contour profile shape with user specified accuracy. By attaining this cutting edge technology the manufacturers find metallic rapid prototyping to be the technique for the future