A decision-making model for comparing the energy demand of additive-subtractive hybrid manufacturing and conventional subtractive manufacturing based on life cycle method

Abstract

Additive-subtractive hybrid manufacturing (ASHM) holds great potential for producing lightweight and ready-to-use parts with high accuracy within a single workstation. It is viewed as a promising technology to improve material efficiency and shorten manufacturing cycle. However, the energy-efficient manufacturing is not always achieved due to the huge electrical energy consumption in the manufacturing phase. It is not a simple “yes-or-no” question that ASHM process is more energy-saving than conventional subtractive manufacturing (CSM) process for production of a given part when considering the life cycle energy demand.For addressing this problem, this paper developed a decision-making model for quantitatively analyzing and comparing the energy demand of ASHM process and CSM process. The model takes into account the whole life cycle of the part, including pre-manufacturing phase, manufacturing phase, use phase, and end-of-life recycling. The critical variables of solid-to-envelope ratio, lightweight ratio, energy consumption reduction coefficient (ERC) are embedded in the model, and their synergistic effects on energy demand comparison are comprehensively analyzed. Moreover, the electrical specific energy consumption of the manufacturing phase was extrapolated as a function of the process parameters in the two manufacturing processes, and the unique relationship between specific energy consumption and process rate, laser power of the ASHM process is established, which can improve the generality of the decision-making model.The results indicated that parts used in aerospace are more suitable for production with ASHM process due to the lightweight and extremely high ERC, which leads to less energy consumption in the use phase compared to conventional manufactured parts. In static non-moving usage scenario, when the material recycling process is not considered, the manufacturing phase in ASHM process accounts for a large amount of total energy consumption, reached about 84%, while the material production in CSM process accounts for the largest proportion, reached almost 86%. In addition, process rate in ASHM process has an important effect on the electrical energy consumption in the manufacturing phase. By increasing the process rate from 1.5 to 5.5 g/min, the energy consumption of the manufacturing phase in ASHM process was saved by 38%. This work provides a quantitative method for decision-makers to select the sustainable manufacturing process when producing a functional part.