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Peer-Review Record

Maintenance Strategies for Industrial Multi-Stage Machines: The Study of a Thermoforming Machine

Sensors 2021, 21(20), 6809; https://doi.org/10.3390/s21206809

by Francisco Javier Álvarez García^*

and David Rodríguez Salgado

Reviewer 1: Anonymous

Reviewer 2:

Helen C. (Nelly) Leligou

Reviewer 3: Anonymous

Sensors 2021, 21(20), 6809; https://doi.org/10.3390/s21206809

Submission received: 13 September 2021 / Revised: 6 October 2021 / Accepted: 12 October 2021 / Published: 13 October 2021

(This article belongs to the Special Issue Multistage Manufacturing Processes in the Industry 4.0 for Zero-Defect Products)

Round 1

Reviewer 1 Report

Dear authors,

Overall impression:

The article is very interesting but there are many flaws in terms of a thorough preparation.

The first section is very broadly researched, but it needs more visible clarity. The case study in section two needs to be detailed further. In section three more clarity needs to be added, e.g.: optical clarity needs to be established, figures need to be improved and explained in more detail, sources need to be added and argumentation need to be improved. In section 4 it should be concluded having the specific character of “multi-stage” in mind. There should be added a comment on further research”.

Detailed remarks:

For the comment numbers (Comment No) please see attached PDF. Please comment on each comment number.

Comment No	Comment
1	Language expression
2	"Conventional" not clear
3	Not clear, what "first case" is
4	Source(s) missing
5	Is there a logical relation between "single-stage" and "first case"?
6	Definition multi-stage unclear
7	Example for multi-stage missing
8	Orthographical mistake
9	Language expression
10	Language expression
11	"Alternative" not clear. Relation to "multi-stage"?
12	Refer to later definition of MTTR
13	Language expression
14	"Based on the above" not clear
15	"Desing S3-RF" not clear. Typo?
16	Language expression
17	Layout change: DBT is styled like a sub title, but all the other approaches weren't styled like "DBT" -> create subchapters with enumerations?
18	Blank space
19	Strive for a clear optical structure: the maintenance strategies should be associated clearly with paragraphs
20	Language expression
21	Logical link: machine learning <-> security?
22	Language expression
23	"based on computational data" not clear
24	"behavioural models" not clear
25	"the real model" not clear
26	Source [37] is not related to multi-stage
27	EDT not explained in details
28	Layout change: DBT is styled like a sub title, but all the other approaches weren't styled like "DBT" -> create subchapters with enumerations?
29	Section 1 should be structured more clearly e.g. with subchapters
30	The paragraph should be shifted to the section 2 where the setup is explained
31	The specific character of "multi-stage" must be detailed and worked out more intensively
32	Language expression
33	Missing labels in Figure 1 / Bullet points must be found also in Figure 1
34	Missing scale in Figure 1
35	"4.3-7-10" not nice
36	Missing consistency: ";" <-> ","
37	Missing consistency: ";" <-> ","
38	Language expression
39	PLC: all abbreviations must be explained at first usage
40	Missing consistency: Origin <-> Source
41	Consistency/Not clear: consequence of its failure <-> "Failure" in Table 1
42	Consistency: usage of capital letter "Static"<->"static"
43	Consistency: usage of blank space bevor "/"
44	Orthographical mistake
45	Consistency: usage of "."<->","
46	Not clear: "are one of many multi-stage machines"
47	Put step numbers in flag symbols
48	Consistency: "." used
49	Language expression
50	Shaft to be identified in Figure 1?
51	Language expression
52	Language expression
53	Unclear: favourable resolution
54	Source(s) missing
55	Consistency: writing of Multi Stage Thermoforming Machine
56	"the fixed value of MTTF" not clear
57	Unclear: "several strategies" - more than 1 - why?
58	Language expression
59	Language expression
60	Not clear: "market values"
61	-
62	Source(s) missing
63	Not clear what "has its own time values" means. Is this related to line 221ff?
64	Language expression
65	Source(s) missing
66	Top border line of Figure 3 missing
67	"i" should be indexed in Figure 3
68	Consistency: usage of capital letter "Motor"
69	Consistency: usage of capital letter "Cutter"
70	See 55
71	"on the supply of components" is not clear
72	"substituting the supply time …" is not clear
73	Main message of Figure 3 is the difference between IPPM and PPM - this must be pointed out in more details
74	Consistency: usage of capital letter "Efficiency"/"Availability"
75	Highlight "Peristaltic pump" if this is really the only mentionable point of Table 3
76	Why pointing out only "Peristaltic pump" in Text for Table 3
77	Orthographical mistake
78	Orthographical mistake
79	see 68
80	see 69
81	"electronic components" and "mechanical components" from text are not found in Figure 4
82	Language expression
83	Language expression
84	Language expression
85	Language expression
86	Language expression
87	Difference between "expected time" and "known from experience"?
88	Orthographical mistake
89	Language expression: expression = equation?
90	Please improve figure 5
91	Where SA1…SA6 to be found in Figure 5?
92	Language expression: Setup instead of conceptualisation?
93	Consistency: usage of capital letter "Humidity"
94	Consistency: usage of capital letter "Thermoformer"
95	Not defined: WIKA
96	Not defined: HGC
97	Consistency: usage of "items" in Table 1<->"Components" in Table 4
98	Unclear: The adoption of this …"
99	Language expression
100	See 89
101	Not clear: "command and signalling"
102	Brackets around "7 and 8"?
103	"do not apply for this model" - why?
104	"Where MTBFi is the …": not a full sentence
105	MTTRi: please use index for "i"
106	100 machine cycles: why?
107	Language expression
108	Difference R(t,i) in (9) and R_((t,i)) in text?
109	What is Ofi_i?
110	Language expression
111	Language expression
112	Blank space
113	"its shutdown" not clear - language expression?
114	"is evaluated": language expression
115	"x" is for cross product in (10)
116	Source(s) missing for "c" is 0.67
117	"may have" not clear
118	Blank space
119	"was used for all "j" sensors": why?
120	SA1…SAn -> use index: SA₁
121	San. -> why "."?
122	Avoid these few words in new line (STEP2, STEP6, STEP8)
123	Blank space
124	Blank space
125	costi -> blank before index in (11)
126	Language expression
127	Language expression
128	"that very moment": not clear
129	"coordinated manner": not clear
130	Language expression
131	proved to be efficient
132	Why Item with capital letter? Consistency with item/component?
133	Language expression
134	See 90
135	Setup instead of conceptualisation?
136	Language expression
137	Language expression
138	Language expression
139	ACZ not defined, Z is index?
140	Use Index for Sai
141	Consistency: usage of capital letter "behaviour map"<->"pattern of behaviour"
142	The Study has been developed by evaluating…: not clear
143	EP / Acz
144	AC.1 to AC.8: Why "."?
145	Not clear: using the encoder assessment scale
146	In short…: not clear
147	Language expression
148	Language expression
149	Any learning: not clear
150	"Proposed DBT" on next page
151	"EP1000)." not nice in new line
152	See 120
153	Use symbol for arrows
154	Blank space
155	Font in equations is italic style, why - (14)?
156	Language expression: "is other than" - "is different from"
157	Language expression: "as to whether"
158	Language expression: "this is"
159	Language expression: reflect
160	measurement scale has been assessed: not clear
161	Language expression: only thing
162	…has its own relationship. Proof?
163	See 97
164	Language expression: without fail
165	failure?
166	See 120
167	"Very precise": not clear
168	See 55
169	Is there a column "DBT false" not visible?
170	All the "1" in the table are not vertically aligned
171	strategies have been tested: test conditions? "Unexpected failures can be detected with ALOP and DBT": where can i see that in the table?
172	Consistency with item/component?
173	See 120
174	Typo: SA2 and SA3 with index or not, see 120 also
175	See 120
176	Language expression: expression = equation?
177	Top border line of Figure 7 missing
178	Top border line of Figure 8 missing
179	"Comparison" - "Comparative values": consistency
180	What shall i see exactly in the two figures 7 & 8? Please describe in detail in text
181	of Availability values?
182	significance need to be proven. It is a statistical term.
183	Not clear: Given the results
184	Language expression: is interesting
185	Language expression: "could be an avenue"
186	See 120
187	Language expression: to do so
188	dmax / dmin: use index
189	Please come back to the specific character of "multi-stage" in this conclusion
190	What is the further research?
191	Consistency: second name in bibliographic data abbreviated?
192	Blank space
193	Full or abbreviated first names in bibliographic data?
194	Blank space

Best regards,

Reviewer

Comments for author File: Comments.pdf

Author Response

We have just finished the review of our paper (Manuscript ID: sensors-1399311) titled “Maintenance Strategies for Industrial Multi-Stage Machines: The study of a Thermoforming Machine”. We sincerely appreciate the suggestions of the reviewers. We have tried to comply all the comments, which have been used to improve the quality of the original manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors propose two new predictive maintenance strategies that allow for the dynamic calculation of mean-time-to-fail (MTTF) values by logging data from strategically placed sensors in order to increase efficiency and availability. The measurements are collected either in predefined intervals or during specific machine phases which are measured by a position sensing device (encoder).

The strategies are then applied to an existing industrial multi-stage thermoforming machine in order to measure efficiency and availability and to compare against existing preventative maintenance strategies that are based on static MTTF values.

The evaluation of the algorithms on an actual machine and the collection of real-world data is very desirable. However, since the data points are limited (due to the infrequent occurrence of actual failures) it is questioned whether they are sufficient to formulate conclusive results.

The main strong point of the paper are:

a) Novel approach by using analog and digital sensors to improve predictive maintenance

b) The idea presented by the authors is both important and practical

c) The paper is overall well structured

With respect to weaknesses,

a) Some comparison points in the conclusion section are not clear and need to be rephrased

b) More datapoints would be useful in order to draw concrete conclusions

c) The literature cited can be improved with more recent publications. For example, with respect to studies based on machine learning which make it possible to work securely and prevent threats in the cloud, the following article could be relevant.

Α. Short, HC. Leligou, E. Theocharis, “Execution of a Federated Learning process within a smart contract”, IEEE International Conference on Consumer Electronics, 2021, January 10-12, DOI: 10.1109/ICCE50685.2021.9427734

Author Response

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper compares the results of diverse maintenance strategies for multi-stage industrial manufacturing machines. The authors analyze a real case of a multi-stage thermoforming machine. Two methods based on preventive maintenance, Preventive Programming Maintenance (PPM) and Improve Preventive Programming Maintenance (IPPM), are compared with two new strategies based on predictive maintenance, namely Algorithm life optimization Programming (ALOP) and Digital Behaviour Twin (DBT). The authors need to state their goals with the resulting experiments clearly. This study may raise the interest of the research community dealing with industrial maintenance.

The manuscript's structure could be improved by introducing a new section to analyze the Related Work, making it clearer the scientific goal of the study. It would be helpful to learn the positive and negative aspects of the commented related work. The authors did that somehow, but I think it may be improved. A table containing a comparison would increase the quality of the review. The description of the adopted method is not clear enough. It is expected to receive details that make the research reproducible. In fact, a methodology section would be helpful before the case study section. The Results and Conclusion section also should contain enough information for leading other groups to reproduce the proposed approach. The discussion of the results is concise and well written, but the conclusion section should be improved before publication.

Author Response

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear authors,

thank you for the accurate revision of the initial article.

The following points were noticed in the revised document:

L155 Typo „researche“
L647 „for many“: Language expression
L655 „Due to“: Language expression, “because”?
L666 Index on dmax and dmin
L674 Typo: increase
L679 Sai -> index “i”
L686 Typo „De“

Best regards,

Reviewer

Author Response

Author Response File: Author Response.pdf

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