Additive vs. Subtractive Manufacturing: A Comparative Life Cycle and Cost Analyses of Steel Mill Spare Parts
, Nuria Baladés 2, Juan J. Gallardo-Galán 1, Antonio J. Gil-Mena 3 and David L. Sales 4,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study presents a comprehensive comparative analysis of environmental and economic performance between conventional subtractive manufacturing (CNC) and a hybrid additive-subtractive approach (WAAM-CNC) for producing a stainless steel support block used in steel mills. The authors employ Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) to demonstrate the hybrid route’s environmental advantages, including a 49% reduction in average environmental impacts and 70% material savings. While the work is methodologically sound and addresses a critical industrial challenge, several revisions are required to enhance clarity, validate assumptions, and contextualize findings within broader sustainability goals.
1. Specify why ReCiPe 2016 was selected over other LCA methodologies (e.g., IMPACT 2002+). A brief comparison would strengthen reproducibility.
2. Clarify how “negligible” WAAM spatter and emissions were quantified. If based on assumptions, cite literature supporting this simplification.
3. Define “solid-envelope ratio” upon first mention (Introduction) to aid non-specialist readers.
4. WAAM is a method with metal melting process, which is different from the solid-state additive manufacturing, such as linear friction welding and friction stir welding. What are the advantages of the additive manufacturing method with metal melting process compared with the solid-state forming techniques? The author needs to make relevant description in the section of introduction, which should refer to the following papers:
[1] https://doi.org/10.1016/j.cja.2024.09.002
[2] https://doi.org/10.1016/j.cja.2024.03.039
[3] https://doi.org/10.1016/j.matchar.2024.114257
5. Expand abbreviations like “PA-WAAM” in the abstract to ensure clarity.
6. Discuss how the hybrid approach aligns with Industry 5.0 goals (e.g., human-centric automation, circularity) to emphasize its strategic relevance beyond cost and emissions.
Author Response
Please see attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript proposed an interesting environmental and economical analysis about the realization of a specific steel tool using both traditional CNC manufacturing or an hybrid AM-CNC manufacturing. The paper has a relevant interest in the manufacturing industry as sustainability represent an important goal. The novelty is evident and English is appropriate. The analysis is well conducted and results are coincise but precise, adding value to the existing literature. Some minor issues follow:
- LCA is an extremely important tool for the evaluation of the sustainability in manufacturing processes in general. Please add a small paragraph about it in the introduction. Some other manufacturing sectors in which LCA was used are: composite production (i.e. https://doi.org/10.1016/j.jmapro.2023.01.068) or coating manufacturing (i.e. https://doi.org/10.1007/s00170-023-12796-x)
- A single piece was chosen as a functional unit. Please provide some more informations to support it. In example, the demand of the pieces is sufficiently low to use additive Manufacturing? The conventional manufacturing can have some economies of scale for larger lot sizes?
- Which version of Ecoinvent Database was used?
- How the disposal of the removed mass and residual fluids was treated?
- Lines from 386 to 420 should be moved to section 2, a new subsection can be useful.
- Please use bullet points in the conclusions
- Future developments derived from this manuscript could be added in the conclusions
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
