Matching Measurement Strategy and Form Error Compensation for Freeform Surface Machining Based on STS Turning

Round 1

Reviewer 1 Report

In this paper, a surface matching measurement strategy based on the least squares principle and iterative precision adjustment is proposed and verified by simulation and experiments.However, this paper has some problems, and all the following should be addressed before publication:

 

1. The experimental results before and after compensation processing are compared, and the effectiveness of this method is demonstrated. However, the comparison of the processing effect between the compensation processing and the traditional processing method was not carried out. Description of traditional processing methods is missing. The differences and advantages of this compensation method over traditional methods are not presented. The description of innovation in this method is insufficient.
2. The rotation and translation matrices are obtained by the least square calculation according to the best matching condition. The best matching condition is defined as the sum of the distance between each point on the measured surface and the corresponding projection point on the theoretical surface are all in their minimum. When the figure error exceeds the tolerance, the obtained surface figure error will be used to compensate the tool cutting path. However, PV is used as a surface figure error to judge the machining result. Why the criterion changed to PV value should be explained in article.

3.After the third compensation processing experiment, the PV decreased from 352nm to 335nm, and the RMS increased from 23nm to 34nm. For freeform optical systems, imaging quality is particularly important. The imaging quality of a freeform optical system is usually determined by RMS. Therefore, the RMS after compensating machining is increased, which cannot explain the advantage of this method.

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Reviewer 2 Report

The paper is clearly and comprehensibly structured. The general quality of the figures is good.
Some of the formatting in the paper is inconsistent and some of the wording should be revised.

Anyway, main issues are the following:

In general, the form error compensation by measurement, comparison with the nominal surface and generation of a compensated machining program is nothing new and has been applied, specifically in optics manufacture. Particular systems are commercially available. Therefore the novelty of this approach must be strongly emphasized and made absolutely clear. So far, it seems to be another application of form error compensation.

In section 2 should be mentioned the name of the processing program that has been modified. Or, is this a self-developed software tool ? If so, there should be a more detailed description or a reference to publications.

In the "Simulation Study" it is described that an ideal free form is modified by coordinate transformation and then matched by the developed algorithm. Obviously, the final matching should then always result in the total omission of the form error (form error =! 0). However, higher deviations occur in the results. Is there an explanation for this? Why can't the algorithm undo the coordinate transformation completely ? These questions must be answered to enable a better assessment of the algorithm.

Furthermore, it should be described how the error compensation is derived from the form errors calculated by the algorithm. There is no information about this in the paper. However, this is necessary to better understand the experimental part.

The experimental part of the paper could also include a comparison of the developed algorithm with an already common solution for error compensation. The comparison would allow a more precise evaluation of the potential of the developed algorithm and could possibly reveal further advantages. In addition, the question should be answered how often the algorithm has been investigated experimentally. How many repetition were performed ?

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Reviewer 3 Report

Paper is original and significant. 

Modeling is supported by appropriate measurements.

English usage needs work.

A few items that stand out (but not all):

line 41 and 42 do not make sense.

line 72 should be micron not micro

line 84 "was" seems not to be necessary

Fig 8b is confusing.  Should have a closeup of the freeform surface.

Author Response

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Reviewer 4 Report

Please refer to the attached reviewer report for more details.

Comments for author File: Comments.pdf

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Round 2

Reviewer 2 Report

The manuscript has been modified and slightly amended. But still the main issues mentioned in the first review are not answered properly:

"In the "Simulation Study" it is described that an ideal free form is modified by coordinate transformation and then matched by the developed algorithm. Obviously, the final matching should then always result in the total omission of the form error (form error =! 0). However, higher deviations occur in the results. Is there an explanation for this? Why can't the algorithm undo the coordinate transformation completely ? ". 

And: "Furthermore, it should be described how the error compensation is derived from the form errors calculated by the algorithm. "

Lastly, the error compensatuion of surfaces by measurement and re-manufacturing is a standard in optical industry. Therefor a comparison - at tleast in the experimental section - with a commercial tools should be shown and the advantages (if  sifnificant) of the seld developed method shoud be clarifies.

The modificatiopns given by now do not answer my questions satisfyingly and are not my understanding of a thorough revision.

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Round 3

Reviewer 2 Report

The manuscript has been modified succesfully and the explanations are are mostly helpful. Thanks !

The revision is nearly done, but the new paragraphs, especially the one on page 5 ("As shown in Fig.5, ...") needs some language alterations; the following phrases are unclear::

"... the matching error is different respectively ..."

"... is small than that ... " - smaller than that ???

"And even coordinate transformations in six directions, the simulation results are tiny, .. " ???

"... which verified ... " - which verifies ??

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