Calibration of a 3D-ball plate

The presented 3D-ball plate is used for testing machine tools with a workspace of 500 mm × 500 mm × 320 mm. The artefact consists of a 2D-ball plate which is either located by a kinematic correct coupling on a base plate or on a spacer. The spacers are placed between the base plate and the ball plate and are also kinematic coupled to the other elements of the artefact. The kinematic couplings provide a high repeatability of the measurement setup. Because of the specific application the known calibration procedures for 2D-ball plates are not applicable.A calibration method for the pseudo-3D-artefact on a coordinate measuring machine (CMM) is presented, with the aim to minimise the influence of geometric CMM errors. Therefore a computer simulation is used to analyse the effects of these disturbing errors on the calibration of the ball plate and the spacers. Using a reversal method, the plate is measured at four different horizontal positions after rotating the ball plate around its vertical axis. A couple of the CMM errors, e.g., a squareness error C0Y between the X- and Y-axis of the CMM, can be eliminated by that method—others have to be determined with additional measurements, e.g., the positioning errors EXX or EYY of the X- and Y-axis, respectively. The paper also contains a measurement uncertainty estimation for the calibration by use of experiments, tolerances and Monte Carlo-simulations. The achieved uncertainty for ball positions in the working volume is less than 2.1 μm (coverage factor k = 2).     

Analysis based on microcontact mechanism for the roughness dependent stick–slip motion

The stick–slip behavior occurring between an indenter with its round tip treated as a rigid sphere with a radius of 300 nm and the (1 0 0) Si specimen was considered. The characteristic slip distances were observed in the stick–slip behavior under small normal loads. A statistical evaluation of microcontact on the basis of Fourier cosine series was proposed to evaluate the dominant scales of roughness under different normal loads. The experimental results showed the elastic deformation exhibited in the contact between the indenter and the specimen when the contact load was smaller than 40 μN. The characteristic scales of roughness obtained by the proposed method revealed good agreement with the experimental results of slip distance under different contact loads. Through the proposed method, the roughness dependence of the stick–slip behavior can be further understood quantitatively.     

Diagonal in space of coordinate measuring machine verification using an optical-comb pulsed interferometer with a ball-lens target

This paper presents a new optical method of coordinate measuring machine (CMM) verification. The proposed system based on a single-mode fiber optical-comb pulsed interferometer with a ball lens of refractive index 2 employed as the target. The target can be used for absolute-length measurements in all directions. The laser source is an optical frequency comb, whose repetition rate is stabilized by a rubidium frequency standard. The measurement range is confirmed to be up to 10 m. The diagonals of a CMM are easier to verify by the proposed method than by the conventional artifact test method. The measurement uncertainty of the proposed method is also smaller than that of the conventional method because the proposed measurement system is less affected by air temperature; it achieves an uncertainty of approximately 7 μm for measuring lengths of 10 m. The experimental results show that the measurement accuracy depends on noise in the interference fringe, which arises from airflow fluctuations and mechanical vibrations.     

Wear behaviour of dental enamel at the nanoscale with a sharp and blunt indenter tip

Two different diamond nanoindenter tips, a rounded conical (～1200 nm radius) and a sharp cube corner (20–50 nm radius) were used to abrade bovine enamel. Square abraded areas (2 μm × 2 μm, 5 μm × 5 μm, 10 μm × 10 μm) were generated with loads that varied from 50 μN to 500 μN depending on the indenter tip. In addition normal and lateral forces were simultaneously measured along 10 μm single scratched lines with the sharp cube corner tip. SEM (scanning electron microscopy) and TEM (transmission electron microscopy) were also used to characterise the worn areas and debris. Two different wear mechanisms were observed depending on the geometry of the tip. The rounded tip generates a predominantly elastic contact that mainly compresses and plastically deforms the superficial material and generates severe shear deformation within the sub-surface material which, under certain conditions, fractures and removes material from the sample. The sharp tip cuts into and ploughs the enamel creating a wedge or ridge of material ahead of itself which eventually detaches. This sequence is repeated continuously for every passage of the sharp indenter tip. The different mechanisms are discussed in terms of abrading tip contact angle and enamel microstructure.     

A motorized 5 m tape comparator for traceable measurements of tapes and rules

A motorized 5 m tape comparator was constructed in TUBITAK UME for calibration of tapes and rules up to 5 m length in one set-up and further lengths in multiple set-ups. The system is a practical development and provides a cost effective solution for calibration of tapes in which the highest grade’s accuracy requirement in OIML R35-1 e.g. is 600 μm for 5 m length and 1100 μm for 10 m length. It is mainly composed of 6 m rail system, mechanical parts, optical units and an integrated 6 m incremental linear encoder as a reference measurement axis for traceable measurements. The rails are kinematically located on a heavy marble construction and a motorized carriage, which employs a camera for probing of the scales on the tapes, is moved along the rails during the measurement. The image of the scale taken by the camera is viewed on the monitor screen together with the running software. The operator can perform the probing process by simply moving the carriage over the measured scales (tapes or rules) using a joystick. The carriage movement is measured by the incremental linear encoder previously calibrated by a laser interferometer and the software automatically takes the measurement results from the incremental linear encoder, applies correction values previously defined and determines the length of the tapes and rules as well as deviations from nominal lengths. The estimated expanded uncertainty of the steel tape measurement is U = 54 μm in one set-up (for 5 m length) and U = 77 μm in two set-ups (for 10 m length) at the confidence level of approximately 95%. Uncertainty budget for calibration of the device itself and for calibration of the test tapes are explained in detail. The results of extensive experimental work and analysis are provided by demonstrating application of science and technology of measurement and instrumentation. Investigations for long term stability of the system are given with the reported test results for the years of 2003-2011 and participated intercomparison results to validate the device scientifically are illustrated.     

Verification of the positioning accuracy of industrial coordinate measuring machine using optical-comb pulsed interferometer with a rough metal ball target

An optical-comb pulsed interferometer was developed for the positioning measurements of the industrial coordinate measuring machine (CMM); a rough metal ball was used as the target of the single-mode optical fiber interferometer. The measurement system is connected through a single-mode fiber more than 100 m long. It is used to connect a laser source from the 10th floor of a building to the proposed measuring system inside a CMM room in the basement of the building. The repetition frequency of a general optical comb is transferred to 1 GHz by an optical fiber-type Fabry–Pérot etalon. Then, a compact absolute position-measuring system is realized for practical non-contact use with a high accuracy of measurement. The measurement uncertainty is approximately 0.6 μm with a confidence level of 95%.     

Development and calibration of an integrated 3D scanning system for high-accuracy large-scale metrology

Quality control in advanced manufacturing requires automated and high-accuracy large-scale 3D measurement. This paper proposes a high-accuracy, low-cost 3D scanning system by integrating industrial robot with precise linear rail and laser sensor. The measuring principle and system construction of the integrated system are introduced in detail. A mathematical model is established for mapping the change of the laser sensor frame while it scans along the linear rail and a sphere-based algorithm for rail orientation calibration is introduced. Subsequently, taking the robot positioning error into consideration, an enhanced hand–eye calibration method is proposed to determine the relationship between robot end-effector and rail scanning frame. Validation experiments were performed, a maximum distance error of 0.071 mm was detected within the rail range and a mean/maximum distance error of 0.309/0.604 mm was detected in the robot volume. A large-scale scanning instance also shows that integrated robotic scanning system features high-efficiency and high-accuracy.     

Uncertainty analysis of slot die coater gap width measurement by using a shear mode micro-probing system

A shear mode micro-probing system was constructed for gap measurement of a precision slot die coater with a nominal gap width of 90 μm and a length of 200 mm. A glass micro-stylus with a nominal tip ball diameter of 52.6 μm was oscillated by a tuning fork quartz crystal resonator with its oscillation direction parallel to the measurement surfaces. An on-line qualification setup was established to compensate for the influences of the uncertainty sources, including the water layers on the measurement surfaces. The measurement uncertainty of the measured gap width was estimated to be less than 100 nm.     

Bilateral comparisons of measurement capabilities for the calibration of low nominal capacity torque measuring devices between NMIJ and PTB in the range from 0.1 N m to 10 N m using different procedures

Bilateral comparisons of the calibration of low nominal capacity torque measuring devices (TMDs) were conducted between NMIJ and PTB for the first time. A 10 N m deadweight torque standard machine (TSM) newly developed at NMIJ was compared with PTB’s two TSMs with nominal capacities of 1 N m and 1 kN m, in the range from 0.1 N m to 10 N m. The transfer measurement devices used had nominal capacities of 1 N m and 10 N m. The comparisons were made using two calibration procedures: one based on the CCM.T-K2 Key Comparison procedure and the other according to the daily calibration procedure adopted at each institute. As a result, the torque realized by the TSM at NMIJ was shown to be equivalent to that realized by the two TSMs at PTB. In addition, it was confirmed that the daily calibration procedures of both institutes yielded consistent results in the calibration of low nominal capacity TMDs.     

Improved machine tool linear axis calibration through continuous motion data capture

Machine tool calibration is becoming recognised as an important part of the manufacturing process. The current international standards for machine tool linear axes calibration support the use of quasi-static calibration techniques. These techniques can be time consuming but more importantly a compromise in quality due to the practical restriction on the spatial resolution of target positions on the axis under test. Continuous motion calibration techniques have the potential to dramatically increase calibration quality. Through taking several measurement values per second while the axis under test is in motion, it is possible to measure in far greater detail. Furthermore, since machine tools normally operate in dynamic mode, the calibration data can be more representative if it is captured while the machine is in motion. The drawback to measuring the axis while in motion is the potential increase in measurement uncertainty. In the following paper, different methods of continuous motion calibration are discussed. A time-based continuous motion solution is proposed as well as a novel optimisation and correlation algorithm to accurately fuse the data taken from quasi-static and continuous motion measurements. The measurement method allows for minimal quasi-static measurements to be taken while using a continuous motion measurement to enhance the calibration process with virtually no additional time constraints. The proposed method does not require any additional machine interfacing, making it a more readily accessible solution for widespread machine tool use than other techniques which require hardware links to the CNC. The result of which means a shorter calibration routine and enhanced results. The quasi-static and continuous motion measurements showed correlation to within 1 μm at the quasi-static measurement targets. An error of 13 μm was detailed on the continuous motion, but was missed using the standard test. On a larger, less accurate machine, the quasi-static and continuous motion measurements were on average within 3 μm of each other however, showed a standard deviation of 4 μm which is less than 1% of the overall error. Finally, a high frequency cyclic error was detected in the continuous motion measurement but was missed in the quasi-static measurement.     

Designing and producing large-volume liquid gamma-ray standard sources for low radioactive pollution measurements of seawater samples by comparison between experimental and simulation results

In order to in-situ measurement of large volume water samples, using of a portable HPGe detector was considered. Because of necessity of efficiency calibration of the detector for the geometry (100 L), the large volume standard sources were prepared. Before making large volume standard sources (100 L), the Monte Carlo method has been applied in order to optimizing the calibration procedures and in agreement with experiment results, has been caused reducing the amount of produced radioactive wastes. First, the efficiency of the portable coaxial P-type HPGe detector for 1 L liquid standard sources in Marinelli beaker geometry was simulated. Then, the experimental efficiency calibration was carried out using the detector for those 1 L liquid standard sources in Marinelli beaker geometry. The detector dead layer was determined by comparison of the simulation and experimental efficiency curve results. Then, a relation between simulation and experimental measurements, that is, between pulse-height per emitted particle, F8 tally, and estimated amount of spiked radioactive solution into the 1 L distilled water in Marinelli beaker was found. Then, the efficiency calibration of the large volume liquid standard sources was simulated. The estimated amount of spiking radioactive solution into the large volume distilled water (100 L) has been taken into account dividing experimental efficiencies (in Marinelli beaker) by the simulated efficiencies (in 100 L). Finally, by spiking the large volume distilled water with the radioactive solution, efficiency calibration of the potable HPGe detector for 100 L geometry was done.     

Reaffirmation of measurement uncertainty in pressure sensitivity determination of LS2P microphones by reciprocity method

The paper presents the accuracy and precision associated with realization of primary standard of sound using the reciprocity method. An experimental determination of the front cavity volume on Universal Measuring Machine has lead to reaffirmation of measurement uncertainty in pressure sensitivity determination to 0.04–0.15 dB in frequency range 31.5 Hz to 25 kHz. The reduced measurement uncertainty has also been validated from the results of the recent APMP Key comparison and also by comparison to the manufacturer’s value for LS2P microphones. The use of optical method for measuring the front cavity volume has refined the measurement methodology followed with adaptation of a self reliant, traceable and systematic measurement procedure in comparison to the earlier use of nominal values for sensitivity fitting exercise conducted on MP.EXE program. Consequently, the measurement uncertainty associated with the calibration of working standard microphones, multifunction acoustic calibrator and A-weighted sound pressure level measurements is also reduced.     

Three-point-support method based on position determination of supports and wafers to eliminate gravity-induced deflection of wafers

The flatness measurement of large and thin wafers is affected greatly by gravity. Inverting method is often used to cancel the effect. However, it is required that the positions of the supports and wafers are perfectly symmetric about the inversion axis. In this study a three-point-support method based on position determination of supports and wafers was proposed. The supporting balls and the wafer were placed in arbitrary positions and their positions were obtained by measurement and fed into the FEM model which was developed to calculate the gravity-induced deflection (GID). The methods to acquire the positions of the supports and the wafer were proposed. The position measurement accuracy of the supports was improved greatly by circle fitting to the profile of the supporting ball. Wafer edge point was obtained accurately as the intersection point between the wafer surface line and the edge profile. The method to measure the wafer thickness using only one displacement sensor on the same equipment was presented. The simulation results were verified by experimental results. The centering device for the wafer and the positioning accuracy requirements of the supports are not needed any more. The effect of the positions of the supports and the wafer was reduced to be less than 1 μm for a 300 mm diameter and 397 μm thickness wafer with GID over 140 μm. This method could also be used for accurate flatness measurement of other large and thin panels.     

An orifice meter for bidirectional air flow measurements: Influence of gas thermo-hygrometric content on static response and bidirectionality

This paper presents the design and calibration of an ISO non-compliant orifice plate flowmeter whose intended use is for respiratory function measurements in the bidirectional air flow range ±9 L/min.The novelty of the proposed sensor consists of a plate beveled in both upstream and downstream sides: a symmetrical geometry is adopted in order to perform bidirectional measurements of flow rate. A mathematical model is introduced to quantify the influence of temperature on the sensor output. Four different positions of the pressure static taps are evaluated in order to maximize bidirectionality. An index is also introduced in order to quantitatively estimate the anti-symmetry of the sensor's response curve.Trials are carried out to evaluate the influence on sensor output of air temperatures (22 °C, 30 °C and 37 °C) at different values of relative humidity (5%, 55% and 85%). Experimental data show a quite good agreement with the theoretical model (R²>0.98 in each condition).The influence of air temperature on the sensor output is minimized by introducing a correction factor based on the theoretical model leading to measurement repeatability better than 2% in overall range of calibration. The mean sensitivity in the calibration range is about 2 kPa L⁻¹·min allowing to obtain a sensor discrimination threshold lower than 0.2 L/min in both directions. The time constant of the whole measurement system, equal to 2.40±0.03 ms, leads to a bandwidth up to 80 Hz making the sensor suitable for respiratory function measurements.     

An ultra high-pressure test rig for measurements of small flow rates with different viscosities

Within the framework of a research project regarding investigations on a high-pressure Coriolis mass flow meter (CMF) a portable flow test rig for traceable calibration measurements of the flow rate (mass - and volume flow) in a range of 5 g min⁻¹ to 500 g min⁻¹ and in a pressure range of 0.1 MPa to 85 MPa was developed. The measurement principle of the flow test rig is based on the gravimetrical measuring procedure with flying-start-and-stop operating mode. Particular attention has been paid to the challenges of temperature stability during the measurements since the temperature has a direct influence on the viscosity and flow rate of the test medium. For that reason the pipes on the high-pressure side are double-walled and insulated and the device under test (DUT) has an enclosure with a separate temperature control. From the analysis of the first measurement with tap water at a temperature of 20 °C and a pressure of 82.7 MPa an extensive uncertainty analysis has been carried out. It was found that the diverter (mainly due to its asymmetric behaviour) is the largest influence factor on the total uncertainty budget. After a number of improvements, especially concerning the diverter, the flow test rig has currently an expanded measurement uncertainty of around 1.0% in the lower flow rate range (25 g min⁻¹) and 0.25% in the higher flow rate range (400 g min⁻¹) for the measurement of mass flow. Additional calibration measurements with the new, redesigned flow test rig and highly viscous base oils also indicated a good agreement with the theoretical behaviour of the flow meter according to the manufacturers׳ specifications with water as test medium. Further improvements are envisaged in the future in order to focus also on other areas of interest.     

Quasi-constant rotational stiffness characteristic for cross-spring pivots in high precision measurement of unbalance moment

This paper proposes a design method for cross-spring pivots with quasi-constant rotational stiffness in the field of unbalanced moment measurement. To achieve high precision measurement of unbalance moment, the relationship between instrument sensitivity and the rotational stiffness of the cross-spring pivot is revealed. In order to eliminate the impacts of payload changes on instrument sensitivity, the relationship between geometric parameters and the rotational stiffness of the pivot is studied. Further, cross-spring pivots with quasi-constant rotational stiffness are designed as the rotation unit of a static balancing instrument, while the center shift of pivot takes the minimum value. Certain amount of unbalance moments is measured by the instrument. Experimental studies of the instrument show that the maximum measurement errors of unbalance moments 0.162 g mm, 0.319 g mm and 1.300 g mm are 0.068 g mm, 0.086 g mm and 0.053 g mm, respectively, when the payload ranges from 0 g to 7000 g. The instrument can achieve a relatively high precision measurement and the instrument sensitivity is almost not affected by the changes of payloads. The effectiveness of the method and the stiffness property of the pivot are verified by the experiments. So this kind of pivot has good prospects in unbalance moment measurement.     

Application of blue laser direct-writing equipment for manufacturing of periodic and aperiodic nanostructure patterns

This study presents the novel development of low cost, highly efficient blue laser direct-writing equipment for using mask-less laser lithography to manufacture periodic and aperiodic nanostructure patterns. The system includes a long-stroke linear motor precision stage (X, Y), a piezoelectric nano-precision stage (Y, θz), a 3-DOF (degrees of freedom) laser interferometer measurement system, and a blue laser direct-writing optical system. The 3-DOF laser interferometer measurement system gives the control system feedback for displacement (X, Y, θz) of the equipment. The laser processing equipment consists of a blue laser direct-writing optical head, a field-programmable gate array (FPGA) alignment interface, and an optical head servo controller. The optical head operates at a wavelength of 405 nm. Processing the nanostructures on thermo-reaction inorganic resists with precise control of the laser intensity, taking advantage of the threshold effect to exceed the limitations of optical diffraction, and reduces the nanostructure hole size. The equipment can be used to fabricate various periodic nanostructure patterns, aperiodic nanostructure patterns, and two-dimensional patterns. The equipment positioning accuracy is within 50 nm at a speed of 50 mm/s, and the minimum critical dimension can be achieved about 100 nm or so.     

A force-matching method for quantitative hardness measurements by atomic force microscopy with diamond-tipped sapphire cantilevers

We present a new method to improve the accuracy of force application and hardness measurements in hard surfaces by using low-force (<50 μN) nanoindentation technique with a cube-corner diamond tip mounted on an atomic force microscopy (AFM) sapphire cantilever. A force calibration procedure based on the force-matching method, which explicitly includes the tip geometry and the tip-substrate deformation during calibration, is proposed. A computer algorithm to automate this calibration procedure is also made available. The proposed methodology is verified experimentally by conducting AFM nanoindentations on fused quartz, Si(1 0 0) and a 100-nm-thick film of gold deposited on Si(1 0 0). Comparison of experimental results with finite element simulations and literature data yields excellent agreement. In particular, hardness measurements using AFM nanoindentation in fused quartz show a systematic error less than 2% when applying the force-matching method, as opposed to 37% with the standard protocol. Furthermore, the residual impressions left in the different substrates are examined in detail using non-contact AFM imaging with the same diamond probe. The uncertainty of method to measure the projected area of contact at maximum force due to elastic recovery effects is also discussed.     

The design and optimization of micro polycrystalline diamond ball end mill for repairing micro-defects on the surface of KDP crystal

Micro-milling is a promising approach to repair the micro-defects on the surface of KH₂PO₄ (KDP) crystal. The geometrical parameters of micro ball end mill will greatly influence the repairing process as a result of the soft brittle properties of KDP crystal. Two types of double-edged micro ball end mills were designed and a three-dimensional finite element (FE) model was established to simulate the micro milling process of KDP crystal, which was validated by the milling experiments. The rake angle of −45°, the relief angle of 45° and the cutting edge radius of 1.5–2 μm were suggested to be the optimal geometrical parameters, whereas the rake angle of −25° and the relief angle of 9° were optimal just for micro ball end mill of Type I, the configuration with the rake angles ranging from 0° to 35°, by fully considering the cutting force, and the stress–strain distribution over the entire tool and the cutting zone in the simulation. Moreover, the micro polycrystalline diamond (PCD) ball end mills adopting the obtained optimal parameters were fabricated by wire electro-discharge machining (WEDM) and grinding techniques, with the average surface roughness Ra of tool rake face and tool flank face ∼0.10 μm, and the cutting edge radius of the tool ∼1.6 μm. The influence of tool's geometrical parameters on the finished surface quality was verified by the cutting experiments, and the tool with symmetric structure was found to have a better cutting performance. The repairing outlines with Ra of 31.3 nm were processed by the self-fabricated tool, which could successfully hold the growth of unstable damage sites on KDP crystal.     

Measurement of the viscosity of biodiesel by using an optical viscometer

In this paper, we report the characterization of the viscosity of biodiesel produced from jatropha curcas. The viscosity measurement has been carried out by using a modified falling ball viscometer as well as optical technology. The viscosity was measured from 28 to 70 °C, which is the interest for determining the quality of biodiesel. We found that the falling ball optical viscometer offers a resolution of a viscosity measurement of ±0.039 mPa s with a relative error of 1.47933%. The measurement process was compared with a commercial viscometer, and it has been demonstrated that the biodiesel produced in Chiapas has good quality.