# Comparison of Current Five-Point Cylindicity Error Separation Techniques
## 4 Conclusions
Measurement of cylindrical profile was performed with the measuring system made up of two V-blocks and a displacement probe. During measuring, two cross-sectional profiles that contact two V-blocks control the radial and tilt error motions of the measuring system, yielding repeatable error motions of the measuring system in each revolution. This makes the measured cylindrical profile immune to the error motions of the cylinder. 2. Error motions of the cylinder are removed, whereas, the carriage straightness error motions will directly impact the measurement accuracy of cylindrical profile, which would weaken the theoretical completeness. 3. Detecting full harmonic components of sequential cross-sectional profiles is dependent on selection angular values of the probe and V-block. Therefore, to ensure good anti-interference capability, angular value of the probe should be carefully selected so as to obtain large transfer function \(\Omega(p)(p=0,2,\cdots,15)\). 4. The measurement uncertainty was assessed through statistical testing. The expanded uncertainty reached 19% compared to the results obtained with the highly accurate radial method. This EST was verified in practice using a model test stand, not on a large roller. 5. It is a portable system, and is suitable for in situ measurement. 6. During measurement, it is crucial to avoid the measuring system rotating around and moving in the \(Z\)-axis of the cylinder. How to decrease the impact from straightness deviations of the guideway is crucial to measurement accuracy. 7. Compensation for the straightness deviations of the guideway was proposed to improve the measurement accuracy. In the authors' opinion, however, it may be a good solution to diametrically arrange the second probe in the axial direction of the original probe. Summing up, the parallel four-point scan technique is recommended for on-machine measurement cylindricity of large rollers, where spindle tilt error motions are negligible. Diametrical arrangement of the second probe in the axial direction of original probe will make the V-block scan EST be the most prospective technique for short roller. However, it is worth noting that, in actual multipoint EST, the main factor of impact on measurement accuracy is the inconsistency of characteristics between multiple displacement probes; therefore, probes should be carefully chosen. [PERSON] and [PERSON] conceived and investigated; [PERSON] designed the experimental system and performed the experiments; [PERSON] simulated, analyzed and wrote; [PERSON] modified. **Funding:** This research was funded by [National Natural Science Foundation of China] grant number [51475132 and 51475133] and [Natural Science Foundation of Anhui Province of China] grant number [1508085 ME81]. **Acknowledgments:** This study has been supported by the National Natural Science Foundation of China (Grant Nos. : 51475132, 51475133) and the Natural Science Foundation of Anhui Province of China (Grant No. : 1508085 ME81). The authors would like to thank the other members of the research team for their contributions to this study. **Conflicts of Interest:** The authors declare no conflicts of interest.