Roundness Instrument Research Articles

Research on the Roundness Approximation Search Algorithm of Si3N4 Ceramic Balls Based on Least Square and EMD Methods

This paper aims to obtain the best shape accuracy evaluation algorithm for silicon nitride ceramic balls after lapping, and to extract the initial signal of the ball surface to improve the accuracy and reliability of the algorithm. The research methods of this paper are as follows: Firstly, an analysis of the uniform envelope of the lapping trajectory of ceramic balls is carried out to verify whether the lapping trajectory after processing can achieve a consistent envelope on the balls' surface. On this basis, it is found through experiments that the standard deviation SD between the roundness deviations of different contour sections is small. The value is maintained at approximately 0.03 μm, and the roundness deviation can approximately replace the spherical deviation. Then the different contour sections of the sphere are sampled by the Taylor roundness instrument. Considering the uncertainty, the sampling points of different contour sections are averaged and used as the original signal of the sphere surface. Then the EMD method is used to process the signal to be detected on the sphere surface. The initial signal of the sphere surface is extracted by judging whether the number of ripples Kc obtained by decomposition is greater than the critical value. Then the initial signal is used as the input value of the approximation algorithm. Through the roundness deviation approximation algorithm based on the least square method, the given minimum approximation domain range is finely processed. The divided fine points are used as the center of the circle to intersect with the initial signal. The maximum, minimum, and range of each circle are calculated to obtain the roundness error based on the minimum circumscribed circle, the maximum inscribed circle, and the minimum region method. Finally, the calculated values are compared with those obtained by the traditional algorithm. The experimental results of this paper show that the algorithm is consistent with the roundness error measured by the instrument, compared with the mainstream evaluation criteria. In summary, the conclusions can be drawn as follows: Through a large number of experimental cases and comparative experiments, the algorithm has high accuracy and reliability. The research results of this paper have essential reference significance for accurately evaluating the shape accuracy of ceramic balls in actual production.

Feasibility Study of a Piezo Actuator as a Potential Standard in Calibration for Roundness Instruments

The paper presents experimental data that show the possible application of a piezo actuator in the role of calibration standard that can serve as an alternative route to currently available methods like gauge blocks or flick standards. First, the experimental setups for interferometric and roundness instruments measurements were described. Next, the experiments using an interferometer for calibration of the piezo actuator were shown. Finally, the application of a piezo actuator to calibrate the roundness instrument, to state the correction factor for the roundness probe, and to relate it to the unit of metre, assuring the traceability of future measurements was performed. Detailed procedures of simulating grooves and then processing the data were described and the calibration curve was obtained using regression analysis. The estimation of uncertainty provided by different factors during the measurements was given to fulfil as closely as possible real calibration procedures taken up in the measurement laboratories. Finally, the limitations of the presented procedures were presented and discussed.

Research on Grinding Parameters of Parts with Same Clamping Mode and Different Sizes

Aiming to study the influence of ultra-precision grinding parameters on the accuracy between the same clamping method and different workpiece sizes. This paper mainly analyzes the difference between the measurement precision of different parts by the same measurement method and the measurement precision of the same parts by different measurement methods. Therefore, the influence of grinding parameters on grinding precision is reflected. For the same part, it is concluded that the coaxiality error coincidence degree at end A and end B reaches 90.32% and 95.27%, respectively by using precision three-coordinate measuring instrument and Mahr roundness instrument. The coincidence degree of end A and end B verticality error reached 97.54% and 91.08%, respectively. For parts with different sizes, the Mahr roundness meter is used for measurement. The analysis shows that the coaxiality coincidence at end A and end B is the highest, reaching 98.36% and 92%, respectively. And from the analysis, the errors are mainly reflected in the factors such as jig and fixture and grinding process.

A virtual parallel two-point roundness error measurement system

As a typical artifact in machining, the roundness of shaft artifacts is an important tolerance standard. How to measure with high precision in ultra-precision machining is a difficult point. At present, the three-probe method is the most widely used method to measure spindle rotation error and artifact roundness error, which has the advantage of on-machine measurement, but the three-probe method has the critical problem of harmonic suppression. To completely separate the spindle error when measuring the roundness of the artifact, a new virtual parallel two-point measurement system is proposed in this paper. The probe is fixed on the flexible hinge stage, which is driven by a voice coil motor so that the measurement function of two probes can be realized only by using a single probe. Detailed numerical analysis and simulation analysis have been carried out to verify that the method can completely separate the spindle error in theory. Finally, the accuracy of the measurement system is tested through experiments. The new method results are compared with the single-point scanning method without error separation and the high-precision roundness instrument Talyrond 585LT. The comparison results show that the new method can separate the rotation error of the spindle and can improve the roundness measurement accuracy.

Modeling, quantification, and mitigation of uncertainty propagation in two-step roundness measurements

Error separation (ES) techniques can eliminate the systematic error caused by the rotary table, and thus, overcome the accuracy limit of state-of-the-art roundness instruments. However, up to now, no rigorous and effective approaches are available for evaluating the measurement uncertainty in ES techniques. To achieve the highest precision of ES techniques, this paper investigates the uncertainty in the two-step roundness measurements, including modeling, quantification, and mitigation of the uncertainty propagation. First, the law of propagation of angle uncertainty is analytically derived by calculating the partial derivative of the Laplace transform of roundness function with respect to the angle. Based on the uncertainty propagation law, the measurement uncertainty can be evaluated quantitatively. Moreover, for inhibiting the uncertainty propagation, approaches are proposed, which not only eliminate the suppressed harmonics completely but also reduce the measurement uncertainty substantially. Finally, Monte Carlo simulations and test measurements are both performed for verification.

General Aviation Pilots Transition to Advanced Cockpit Technologies and Adult Learning

Pilots for many years have received training on the round instrument gauges. Can they now safely make the transfer to the new cockpit technologies? Studies show a cognitive deficit with pilots over the age of 40 making transitions to these advanced cockpits. Older pilots as well as older adult learners in general absorb and retain information differently than our younger counterparts. The training and instructional programs are now geared towards a one size fits all. According to the literature, problems seem to surface affecting older pilots. This article addresses these concerns.

Human Factors Regarding Age in Single Pilot Transitions to Technologically Advanced Aircraft

The purpose of this research is investigating the relationship between computer simulated instruction and pilot performance in the transition to technologically advanced aircraft. With the advent of computerized glass cockpits in modern aircraft a problem has arisen of the ability of aging pilots and the human factors involved. These pilots for many years have received training on the round instrument gauges and the question is, can they now safely make the transfer to the new cockpit technologies? Studies show a cognitive deficit with pilot's age 40 years and older making transitions to these advanced cockpits. SPSS statistical software will be used to analyze data looking at specifically Spearman's Rank Order Correlation. This non-parametric statistic will be used to compare one group of under age 40 pilots and one group over age 40 pilots and their ability to transfer to more technologically advanced aircraft.

Wear Measurement on Chain Joint Components Using a Roundness Instrument

Driving and timing chains are widely used machine elements which are continuously improved regarding wear and energy efficiency. Especially for timing chains, reducing wear is of high importance as it is critical for the function of the combustion engine. To achieve this goal, the wear in the chain joint has to be measured precisely which is usually done by measuring the length of the entire chain. With this method, no information about the distribution of wear between the contacting bodies, pin and bush, is available. An additional measuring and analyzing technique using a standard roundness instrument is developed with which more detailed information about the wear in the chain joint is obtained. With this method, unworn chain joint components are characterized and the wear on worn components is measured and compared for pins with different surface treatments. Furthermore, approaches to use the measured data in simulation and calculation are presented.

Famous lines in history: Langer lines.

The orientation of surgical incisions over the skin iswidely considered to affect scarring and the final cosmetic outcome for patients. Whenmost surgeons visualize lines on the skin surface to guide such incisions, it is Langer lines (alsoknownasskincleavageor tension lines) thatmost readilycometomind.KarlLanger(1819-1887),themanbehindthefamouslines, was born in Vienna, Austria, where he spentmost of his life and later becameprofessor of anatomy at Joseph’s Academy. In 1861, Langer began publishing a series of 5 articles detailing his seminalwork on the physical andmechanicalpropertiesof theskin. In thefirstof thesearticles,Langer creditedDupuytrenandMalgaigne for their earlierobservations. In 1834, Dupuytren reported seeing a youngmanwhohad attempted to commit suicidebystabbinghimselfover theheart3 times.Thepatient claimedto haveusedaroundawlasthe instrument,buthedidnotfashionroundstab wounds onhis chest. This ledDupuytren to study thematter in cadavers anddiscover thata round instrument indeedproduced linearcleftswhen thrust throughtheskin.Healsonoticedthat thesecleftshaddifferentorientations in different parts of thebody.Malgaigne confirmed these findingsandobserved fromhisexperienceasa surgeon that the retractionof wounds differedwith the direction of incisions. Langer went on to use sharp conical spikes to produce wounds all over the body of a large series of cadavers—of different ages and body constitutions—toanalyze the relationshipof each small cleft to thenext. He further attempted to shed light on wound retraction and the tension in human skin bymaking small circular incisions all over the bodies of cadavers and documenting in the directions in which the resulting woundsnarrowedandbroadened, if at all. Bywayof these incredibly meticulous efforts, Langer was able to draw his famous lines. Unfortunately, Langer’sworkwas largely unappreciated and ignored during his lifetime. In fact, because his original publications were written in the classical scientific German of his era, with hints of his local Austrian dialect, it was not until 1978 that a translation of his work wasmade available to the English-speaking world. Today, elective surgical incisions may not follow Langer lines in all body areas, andother guides, such as relaxed skin tension lines running perpendicular to the direction of muscle contraction, may serve patients better. However, the concept of skin tension lines has helped improve the practice of surgery and forensicmedicine, and Langer’swork hasbeen instrumental inourunderstandingof themanyfascinatingproperties of the skin.

The Issue of Contactless Setup before Measuring Process

Increasing demands on productivity of measurement and control processes deal with high demands on speed, reliability and repeatability of all the preparatory steps that precede the measurement itself. These activities are still productivity needed and the productivity effect is multiplied by a technological downtime carrying them considerable economic impact, direct value added product. A typical case is the initial adjusting of the turntable of roundness instrument and measurement of the surface parameters in a hole with small diameter. This title deals with these issues.It describes the issue of compensation contact setting of roundness machine by contactless method including performance model and philosophy of determining measurement uncertainty. The initial proposal will be modified for specific task of CNC measuring parameters in the small diameter holes.

Calibration of Flick standards

Flick standards or magnification standards are widely used for an efficient and functional calibration of the sensitivity of form measuring instruments. The results of a recent measurement comparison have shown to be partially unsatisfactory and revealed problems related to the calibration of these standards. In this paper the influence factors for the calibration of Flick standards using roundness measurement instruments are discussed in detail, in particular the bandwidth of the measurement chain, residual form errors of the device under test, profile distortions due to the diameter of the probing element and questions related to the definition of the measurand. The different contributions are estimated using simulations and are experimentally verified. Also alternative methods to calibrate Flick standards are investigated. Finally the practical limitations of Flick standard calibration are shown and the usability of Flick standards both to calibrate the sensitivity of roundness instruments and to check the filter function of such instruments is analysed.

Greenhouse Facility Management Experts Identification of Competencies and Teaching Methods to Support Secondary Agricultural Education Instructors: A Modified Delphi Study

In this study the Delphi technique has been used to develop a list of educational competencies for preparing secondary agricultural education instructors to effectively manage their school greenhouse facilities. The use of specialized facilities in agricultural education requires appropriate preparation of agricultural education teachers. The Delphi technique uses an anonymous panel of experts for suggestions and assessments aiming at consensus. Thirteen experts from multiple schools and universities took part in the investigation. The study used a series of three web–based questionnaires to determine competencies that teachers need to know, to be able to perform, and to identify effective teaching methods for teachers to obtain these competencies. The first round instrument consisted of three open–ended questions, and a series of questions to validate the background of the members of the panel. In the second round, respondents were asked to rate each competency and teaching method using a seven–point Likert–type scale. Median scores and interquartile values were calculated. Panel members were sent a copy of their individual responses as well as the group responses for review. In the third round, panel members were requested to indicate their level of agreement with each item using a five–point Likert–type scale.

The IMGC calibration setup for microdisplacement actuators

For the calibration of piezo-capacitive displacement actuators, we use an interferometric setup with subnanometric resolution. In order to minimize the periodic nonlinearity effect of the laser interferometer, the optical path difference is changed in steps of /spl lambda/, obtained from a computer-based loop control of the out-of-phase difference between the reference and the measuring signal of the interferometer. Experimental results show an expanded uncertainty of about 0.7 nm +0.1/spl times/10/sup -3/ L. The calibrated actuator is then used as a transfer standard at the nanometer level, both for testing the nonlinearity of the laser interferometer and for calibrating the linear variable differential transformer (LVDT) probe of the Istituto di Metrologia "G. Colonnetti" (IMGC), Torino, Italy, roundness instrument (used for measuring silicon spheres for the Avogadro constant).

An intercomparison of roundness measurements between ten European national standards laboratories

An intercomparison of high-accuracy roundness measurements has been carried out with the participation of the national standards laboratories of ten European countries. The circulated artefacts were a hemispherical glass standard and a steel disc. A total of eight roundness profiles were examined, two on the hemisphere and six on the disc. The eccentricity between external and internal surfaces of the disc was determined, and the effect of various measuring conditions evaluated. While the overall results show a satisfying agreement for almost all laboratories, room for further improvements still exists. The uncertainty limit was mainly due to the spindle errors of the roundness instruments used in each laboratory. These instruments were proven to be of a good quality at the 0.1 μm level. Below this limit, best results were reported by those laboratories where error separation techniques were available.

High-precision measurement of small balls

Spindle compensating high-precision roundness techniques have the resolution required for measuring modern precision miniature workpieces but their accuracy has been considered only at radii of tens of millimetres. As the performance of such instruments decreases with decreasing radius, it is not clear that their precision is adequately maintained. An investigation of the sources of systematic error shows that current designs are usable, in this context, down to radii of around 1 mm. An implementation using a calliperlike stylus on a turntable roundness instrument is described and evaluated on balls of this size.

High precision measurement of gyro rotor sphericity

Quartz gyro rotors with a sphericity of better than one part per million are needed for the Relativity Gyroscope Experiment. This paper describes the measurement techniques that are employed to ensure that this requirement is met. The basic measurement is a surface irregularity map, generated with the help of a computer-aided roundness instrument with a measurement uncertainty approaching 2.5 nm. Analysis and plotting of the data, and the impact of the results on gyro performance, are discussed