MFCA considers the main material flows in all processes as well as sub materials, except auxiliary, materials. Main materials, sub materials and auxiliary materials are defined as follows (METI., 2007 and Chompu-inwai et al., 2014):
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Main materials: The principal materials in the initial process and the work-in-process from the previous process.
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Sub materials: Materials added to the main materials to form part of the company products in each process
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Auxiliary materials: Materials that are used in each process but do not form part of the company products;