Designing a Laboratory Cam Profile Measuring Machine to Validate Follower Displacements

Round 1

Reviewer 1 Report

The authors present is a knife-edge disk cam mechanism teaching apparatus, built around a commercial dial indicator.  

There are several cam-follower mechanism demonstrators available on the market or/and described in literature (please Google "experimental cam mechanism analysis").  

The authors should compare theirs with these, such as with: 

https://www.tecquipment.com/cam-analysis-machine

https://www.indiamart.com/proddetail/cam-analysis-machine-4989940648.html

https://sunlabtech.com/cam-mechanism-2/

Research has also been done on experimental cam analysis, and on using motion simulation software such as Working Model 2D.  

The reference list is very modest and should be expanded.  

Student perception of the use of the apparatus in classroom setting should be documented in the paper. 

Engineering drawings should not be included in the paper, rather offered to the interested reader upon request.  

Adding a capability to offset the line of sliding of the follower would enhance the paper a small amount.  

Plots in Excel should not include titles as these are repeated in the figure caption.  

Author Response

Authors: Thank you for taking the time to review our manuscript and for your thoughtful suggestions. Please see our detailed responses to your suggestions.

• The author’s present is a knife-edge disk cam mechanism teaching apparatus, built around a commercial dial indicator. There are several cam-follower mechanism demonstrators available on the market or/and described in literature (please Google "experimental cam mechanism analysis"). The authors should compare theirs with these, such as with:
  • https://www.tecquipment.com/cam-analysis-machine
  • https://www.indiamart.com/proddetail/cam-analysis-machine-4989940648.html
  • https://sunlabtech.com/cam-mechanism-2/
  • Authors: Thank you for providing the references. The machines listed above were researched and compared to the ones presented in the article. The comparisons and corresponding references were added to the article.
• Research has also been done on experimental cam analysis, and on using motion simulation software such as Working Model 2D.
  • Authors: Working model 2D can be greatly beneficial to simulate the cam motion and aid in cam design. However, the scope of this article focuses primarily on the experimental validation of cam shapes.
• The reference list is very modest and should be expanded.
  • Authors: References to other cam analysis machines were added. We believe it is the nature of articles within the scope of this Hardware journal that the main focus is on the laboratory equipment design and implementation.
• Student perception of the use of the apparatus in classroom setting should be documented in the paper.
  • Authors: Thank you for this suggestion. The machine was conceptualized with educational objectives in mind, intended primarily for instructional demonstrations and laboratory applications. Integration of the machine into classroom settings has not been realized as of yet but there are plans to have students use the equipment in the future.
• Engineering drawings should not be included in the paper, but rather offered to the interested reader upon request.
  • Authors: Other papers published in the Hardware journal include drawing packets. The authors believe that including a drawing packet aligns with the following goal of Hardware: “The aim of Hardware is to provide a means to share the designs of instruments and devices and therefore requires that any design files employed in the construction of the devices are made available in the original editable source format in an open license as supplementary information.”
• Adding a capability to offset the line of sliding of the follower would enhance the paper a small amount.
  • Authors: Offsetting the line of the sliding follower has been considered and added to the further modifications that could be added to the apparatus. We encourage the reader to explore other follower options. The main goal of the cam measuring machine was to validate the 3D printed cam profiles. The point follower perpendicular to the rotating axis of the cam is the simplest method to measure the cam profile.

Comments on the Quality of English Language

• Plots in Excel should not include titles as these are repeated in the figure caption.

Authors: Thank you for this suggestion. The titles in the Excel graphs have been omitted.

Reviewer 2 Report

The article describes the engineering procedure of creating laboratory equipment for the cams measuring. Cam types and motion shape diagrams are described. Chapter 3 contains instructions for assembling the laboratory equipment.

The article is educational rather than research in nature. The research problem is not described. The scientific hypothesis is not stated.

However, the content of the article is in line with the goals of the Hardware journal. The content of the article is clear and understandable. Pictures and drawing documentation are at a good and comprehensible level.

Author Response

Authors: Thank you for taking the time to review our manuscript and for your thoughtful suggestions. Please see our detailed responses to your suggestions.

• The article describes the engineering procedure of creating laboratory equipment for the cams measuring. Cam types and motion shape diagrams are described. Chapter 3 contains instructions for assembling the laboratory equipment.
• The article is educational rather than research in nature. The research problem is not described. The scientific hypothesis is not stated.
  • Authors: The apparatus presented in the article serves as a low-cost alternative to other laboratory cam profile measuring machines. It does not answer a defined research problem with a hypothesis but provides an alternative solution to measuring cams. The authors believe that the article presented aligns with the goal of the Hardware journal of providing low-cost alternatives using 3D printed methods to otherwise costly equipment.
• However, the content of the article is in line with the goals of the Hardware journal. The content of the article is clear and understandable. Pictures and drawing documentation are at a good and comprehensible level.
  • Authors: Thank you for evaluating our work and for your feedback.

Reviewer 3 Report

At first glance, the article is very interesting due to its economic aspect: a proposal to build a cam measurement station for approximately USD 250 instead of purchasing a professional station for approximately USD 4,000. After taking a closer look at the article, however, I had a lot of doubts, which I will list below.

The article is formally correct, but in terms of content it gives the impression of an essay on "Basics of machine design" mixed with very detailed DIY instructions. This is undoubtedly very inspiring in the area of basic engineering teaching, especially at the bachelor's level, where it allows students to be provided with such a low-budget solution for laboratory work before allowing them to work in truly metrological positions, where a certain technical culture of service is required. The proposed solution may be very interesting for engineering schools, but I assess its industrial or scientific usefulness as poor.

Subsections 2.1 to 2.5 are overly extensive and, in my opinion, duplicate the content contained in virtually every available textbook on "Basics of Machine Design" on the topic of the synthesis of cam mechanisms. I recommend reducing unnecessary mathematical considerations and citing one of the popular textbooks. This will certainly be beneficial for the reception of the article.

The station itself is completely manual with metrological solutions known since the 19th century. The authors did not perform any validation of the station in terms of the uncertainty of the measurement path, but immediately started testing the cams obtained by 3D printing, which inevitably result in significant manufacturing inaccuracies. As a result, the actual waveforms presented in the charts compared to the theoretical waveforms are a mixture of the actual inaccuracy of the cams and the measurement uncertainty of the station itself.

Therefore, I strongly recommend that the authors validate the measurement station using reference cams or other cams previously measured on validated metrological stations. Only then, with a measurement profile of the station, will it be possible to assess its suitability for any real, even didactic, measurements. The ideal solution would be to measure these cams produced on a 3D printer at a professional, validated metrological station and then compare the waveforms with those obtained from the proposed station. Then it will be possible to reliably assess the usefulness of the proposed solution.

A minor note: I suggest moving the reference to citation [2] from line L22 to a position on line L19 just after the name Yousuf. The description will be much clearer, because in its current form the reference to Yousuf looks orphaned.

Author Response

Authors: Thank you for taking the time to review our manuscript and for your thoughtful suggestions. Please see our detailed responses to your suggestions.

• At first glance, the article is remarkably interesting due to its economic aspect: a proposal to build a cam measurement station for approximately USD 250 instead of purchasing a professional station for approximately USD 4,000. After taking a closer look at the article, however, I had a lot of doubts, which I will list below.
• The article is formally correct, but in terms of content it gives the impression of an essay on "Basics of machine design" mixed with incredibly detailed DIY instructions. This is undoubtedly very inspiring in the area of basic engineering teaching, especially at the bachelor's level, where it allows students to be provided with such a low-budget solution for laboratory work before allowing them to work in truly metrological positions, where a certain technical culture of service is required. The proposed solution may be interesting for engineering schools, but I assess its industrial or scientific usefulness as poor.
  • Authors: Thank you for your feedback. The machine described in this study was specifically engineered for undergraduate instructional demonstrations and laboratory applications. It should be noted that its design and functionalities are not optimized for industrial applications. The authors believe that the article presented aligns with the goal of the Hardware journal of providing low-cost alternatives using 3D printed methods to otherwise costly equipment.
• Subsections 2.1 to 2.5 are overly extensive and, in my opinion, duplicate the content contained in virtually every available textbook on "Basics of Machine Design" on the topic of the synthesis of cam mechanisms. I recommend reducing unnecessary mathematical considerations and citing one of the popular textbooks. This will certainly be beneficial for the reception of the article.
  • Authors: The formulas presented in Sections 2.1 to 2.5 were derived by the authors and used to create profiles that were later validated with the collected data. The derivation provided eliminates the task of the reader having to search through textbooks and formulating the equations to successfully replicate results.
• The station itself is completely manual with metrological solutions known since the 19th century. The authors did not perform any validation of the station in terms of the uncertainty of the measurement path, but immediately started testing the cams obtained by 3D printing, which inevitably resulted in significant manufacturing inaccuracies. As a result, the actual waveforms presented in the charts compared to the theoretical waveforms are a mixture of the actual inaccuracy of the cams and the measurement uncertainty of the station itself. Therefore, I strongly recommend that the authors validate the measurement station using reference cams or other cams previously measured on validated metrological stations. Only then, with a measurement profile of the station, will it be possible to assess its suitability for any real, even didactic, measurements. The ideal solution would be to measure these cams produced on a 3D printer at a professional, validated metrological station and then compare the waveforms with those obtained from the proposed station. Then it will be possible to reliably assess the usefulness of the proposed solution.
  • Authors: Thank you for your valuable observation. Based on your suggestion, reference cams were fabricated and meticulously measured to corroborate the functionality and accuracy of the machine. Subsequently, the acquired data and corresponding analyses have been thoroughly integrated into the paper to enhance its comprehensiveness.
• A minor note: I suggest moving the reference to citation [2] from line L22 to a position on line L19 just after the name Yousuf. The description will be much clearer, because in its current form the reference to Yousuf looks orphaned.
  • Authors: Thank you for your feedback. The citation has been relocated accordingly.

Round 2

Reviewer 1 Report

The manuscript has been improved over its initial form. One of the relevant conclusions to emphasize is that velocity and acceleration of follower motion obtained through numerical differentiation exacerbate any measurement or data acquisition errors. 

Figure 6 is distorted.

Mechanical drawings in the appendix are too many e.g. cam drawings are irrelevant.  The authors may want instead to mention at the end of the paper that drawing of the parts with dimensions are available upon request.  

N/A

Author Response

Authors: Thank you for taking the time to review our manuscript and for your thoughtful suggestions. Please see our detailed responses to your suggestions.

• The manuscript has been improved over its initial form. One of the relevant conclusions to emphasize is that velocity and acceleration of follower motion obtained through numerical differentiation exacerbate any measurement or data acquisition errors. 
  • Authors: Thank you for your positive feedback as well as your valuable suggestion. We have included a sentence in the conclusion to emphasize this point.
• Figure 6 is distorted.
  • Authors: Thank you for this observation. We have fixed the figure.
• Mechanical drawings in the appendix are too many e.g. cam drawings are irrelevant.  The authors may want instead to mention at the end of the paper that drawing of the parts with dimensions are available upon request.  
  • Authors: Thank you for your opinion, however we feel that it is in the spirit of the Hardware Journal that the complete drawing packet be available to the reader without having to request it. Others can replicate the experiment and modify as they see fit.

Reviewer 3 Report

The authors provided a complete and comprehensive response to all submitted comments. In particular, they supplemented the article with issues of validation of the proposed position, so I have no further comments.

Author Response

The authors provided a complete and comprehensive response to all submitted comments. In particular, they supplemented the article with issues of validation of the proposed position, so I have no further comments.

Authors: Thank you for taking the time to review our manuscript and for your positive feedback.