Stylus Tip Research Articles

Influence of the Traverse Speed of the Stylus Tip on Changes in the Areal Texture Parameters of Machined Surfaces

Measurements of areal (3D) surface texture using optical methods are very popular because of the short measurement time compared to the stylus tip technique. However, they are very sensitive to measurement errors. In some cases, optical measurements are not recommended. The stylus measurement method is well known and can be the reference technique for surface texture measurement. The main disadvantage is the long measuring time. This time can be shortened using higher speeds of measurement. The effect of the speed of the measurement of stylus profilometer on changes in surface texture parameters was studied. Fifty surface topographies were measured using the stylus profilometer at speeds 0.5, 1, 2, 3, 4, and 5 mm/s in the same places. Surfaces after lapping, polishing, grinding, milling, laser texturing, and two-process random surfaces were measured and analyzed. Changes in parameters caused by the increase in the traverse speed depend on the characteristics and parameters of the surfaces. The random surfaces changed more than the deterministic ones. The increase in the traverse speed from 0.5 to 1 mm/s caused small changes in the parameters.

A screening method for cervical myelopathy using machine learning to analyze a drawing behavior

Early detection of cervical myelopathy (CM) is important for a favorable outcome, as its prognosis is poor when left untreated. We developed a screening method for CM using machine learning-based analysis of the drawing behavior of 38 patients with CM and 66 healthy volunteers. Using a stylus pen, the participants traced three different shapes displayed on a tablet device. During the tasks, writing behaviors, such as the coordinates, velocity, and pressure of the stylus tip, along with the drawing time, were recorded. From these data, features related to the drawing pressure, and time to trace each shape and combination of shapes were used as training data for the support vector machine, a machine learning algorithm. To evaluate the accuracy, a receiver operating characteristic curve was generated, and the area under the curve (AUC) was calculated. Models with triangular waveforms tended to be the most accurate. The best triangular wave model identified patients with and without CM with 76% sensitivity and 76% specificity, yielding an AUC of 0.80. Our model was able to classify CM with high accuracy and could be applied to the development of disease screening systems useful outside the hospital setting.

Study of surface texture measurement errors

The textures of the surfaces of machine elements affect their functional properties. It is practically impossible to assess the surface texture using only one parameter. However, the number of parameters should not be excessively high. The selected parameters should be functionally relevant, manufacture related and of small sensitivities to measurement errors. In this paper, a number of errors in various machined surface textures measurements were analyzed. Parameters sensitivities to mechanical filtration by a stylus tip, presences of high-frequency noise and spikes, stitching, change of measurement method, sampling interval increase, change of sampling area, and digital filtration were studied. Robust parameters and those that were susceptible to errors were obtained. The spatial parameters were found to be the most robust, whereas those describing the shape of the height distribution, Ssk and Sku, were highly sensitive to measurement errors.

Development of a High-Function Fiber Stylus for Microstructure Measurement with Water-Repellent and Antistatic Coatings

The precise measurement of microstructures and other micron-sized materials has garnered considerable interest in recent years. We have developed a measurement system that uses an etched small diameter optical fiber as a stylus to measure microstructures with low contact force. However, when the diameter of the stylus tip is less than a few tens of micrometers, the surface forces between the measured surface and the stylus tip become larger than the gravity of the stylus tip, causing the stylus tip to stick to the measured surface. This adhesion leads to an increase in measurement time and a decrease in measurement accuracy. In this study, we fabricated a high-function stylus with water-repellent and antistatic coatings applied to the stylus tip to reduce the adhesion between the stylus tip and measured surface due to surface forces, and conducted performance evaluation tests. As a result, the average separation distance was 13.8 µm when a fluorinated resin coating with a contact angle of 105° was used, confirming that the influence of liquid bridge forces could be reduced by approximately 78%. Additionally, when static elimination experiments were conducted by scanning the charged surface at a pitch of 0.5 µm using an antistatic coating stylus with a gold on the stylus surface, the average adsorption distance was 3.6 µm, confirming that the effect of electrostatic force could be reduced by 71%.

Development of a two-step stylus with elastic hinge for microstructure measurement to improve sensitivity and vibration characteristics

In recent years, there has been an increasing demand for measuring a small hole with a diameter of 10 μm or less. Many micro coordinate measuring machines (micro CMMs) have been developed so far. However, as the diameters of these probes decrease below 10 μm, the rigidity of the probe decreases, making it difficult to detect contact between the stylus tip and the measured surface. For the same reason, the stylus with large aspect ratios cannot be used. Therefore, we have been developing a measurement system using an optical fiber as a stylus to measure microstructures with low measurement force. In this research, we proposed the two-step plus hinge stylus with a diameter less than a few μm to improve sensitivity and vibration characteristics. The design parameters of the stylus were simulated by the finite element method, and the results of the actual examination are summarized as follows. The simulation results using the finite element method indicate that the contact sensitivity was improved from 17% for the standard stylus to 37% for the two-step plus hinge stylus. The experimental results indicate that the contact sensitivity was improved from 17% for the standard stylus to 35% for the two-step plus hinge stylus. The results of the stylus stability evaluation experiment showed that the maximum fluctuation of the standard stylus is approximately 1 μm, and that of the two-step plus hinge stylus is approximately 0.05 μm, which confirms that the use of a two-step plus hinge stylus can improve vibration characteristics. The performance of this stylus was evaluated by measuring the micro hole with a diameter of 7 μm. The repeatability of each measurement point was approximately 50 nm.

Inertial-Measurement- Based Biometric Authentication of Handwritten Signature.

With increased reliance of digital storage for personal, financial, medical, and policy information, a greater demand for robust digital authentication and cybersecurity protection measures results. Current security options include alpha-numeric passwords, two factor authentication, and bio-metric options such as fingerprint or facial recognition. However, all of these methods are not without their drawbacks. This projects leverages the fact that the use of physical handwritten signatures is still prevalent in society, and the thoroughly trained process and motions of handwritten signatures is unique for every individual. Thus, a writing stylus that can authenticate its user via inertial signature detection is proposed, which classifies inertial measurement features for user identification. The current prototype consists of two triaxial accelerometers, one mounted at each of the stylus' terminal ends. Features extracted from how the pen is held, stroke styles, and writing speed can affect the stylus tip accelerations which leads to a unique signature detection and to deter forgery attacks. Novel, manual spatiotemporal features relating to such metrics were proposed and a multi-layer perceptron was utilized for binary classification. Results of a preliminary user study are promising with overall accuracy of 95.7%, sensitivity of 100%, and recall rate of 90%.

Development of a Sharp-Tipped L-Shaped Stylus for Measurement of Nanoscale Sidewall Features

This paper presents a system for measuring nanoscale sidewall features using an L-shaped stylus with a sharp tip. By sharpening the tip of the stylus to the nanometer scale, it is possible to measure nanoscale sidewall features. The stylus shaft is deflected when the sharpened stylus tip contacts the measured surface, and this deflection is measured optically. In this study, we develop the fabrication method of an L-shaped sharpened stylus 20 μm in diameter and 4 mm in length by etching, CO2 laser processing, and bonding. Then, the measurement accuracy and repeatability are examined by measuring V-grooves with nanoscale features. The results clarify that the pitch is approximately 0.3 μm, which is almost the same as the value measured using the photographic image, but the depths measured by the styli fabricated by CO2 laser processing and bonding are approximately 0.15 and 0.07 μm, respectively. The depth measured by the stylus fabricated by bonding is smaller than that measured from the image (approximately 0.16 μm), presumably because of the morphological filter. The maximum repeatability errors for 10 measurements using the styli fabricated by CO2 laser processing and bonding are within ±0.056 and ±0.022 μm in scanning mode, respectively. It is also confirmed that the stylus tip exhibits minimal wear even after 500 measurements.

Long-term outcomes following repair of nasal valve collapse with temperature-controlled radiofrequency treatment for patients with nasal obstruction.

Long-term outcomes following repair of nasal valve collapse with temperature-controlled radiofrequency treatment for patients with nasal obstruction.

A new stylus orientation planning strategy for sculpture surface inspection based on touch position graph

On-machine inspection (OMI) is an important technology for precise machining. Accuracy and efficiency improvement is a challenge for sculpture surface inspection. Before the inspection, if the practical touch position on the stylus tip is calibrated accurately, more accurate compensation of the pre-travel error could be applied in the inspection results. Meanwhile, time consumption on the calibration process could be reduced if the number of preset to-be-calibrated positions in the calibration is as small as possible. Thus, for precise compensation, the practical touch position on the stylus tip needs to be assigned during the inspection. In further, to reduce the calibration time, the quantity of practical touch position on the stylus tip requires to be least. A new stylus orientation planning strategy that controls the practical touch positions on the stylus tip is investigated in this paper. In terms of the strategy, a touch position graph (TPG) is proposed for the five-axis machine tool to discover the relationships between the practical touch positions, the angle combinations of rotary axis and the stylus orientations. The practical touch positions on the stylus tip and the rotation direction change of the machine tool’s rotary axes can be reduced as much as possible by optimizing the stylus orientations. In further, the pre-travel error on each to-be-inspected point can be compensated by accurate calibration results and the introduction of the rotation axes error can be decreased to prove the inspection accuracy improvement. At last, an experiment is applied on the impeller to verify the proposed OMI planning strategy.

Uncertainty Propagation and Assessment of Five-Axis On-Machine Measurement Error

Abstract As an important technology of adaptive machining, on-machine measurement (OMM) is always used to measure the shape of the to-be-cut surface. Due to the multi-source errors in an OMM system, the confidence of the measurement accuracy becomes particularly important before planning the next cutting procedure. OMM is implemented by multi-components involving machine tools, fixture, and on-machine probe. Each component introduces uncertainty of error into the measurement result. The positioning error, alignment error, and eccentricity error are investigated in terms of the expectation, uncertainty, and probability density function. By the kinematics of the components participated in the measurement, these errors are accumulated to affect the measurement results. Thus, the uncertainty of the final measurement result is determined by the accumulation of uncertainty of error sources. In order to evaluate the uncertainty of measurement error, an uncertainty propagation model involving positioning error of five-axis machine tools, alignment error of workpiece, and eccentricity error of the stylus tip is established in terms of the kinematic chain of OMM. Then, the uncertainty of the measurement result in vector form is obtained. Finally, the simulation and the experiment about the impeller are employed to validate the effectiveness and repeatability of the uncertainty propagation model for five-axis OMM.

Stylus tip radius and wear estimation using the Rsk or the Rp and Rv parameter of a sine wave (Type C1) standard

Determination of the stylus tip radius and its wear or damage is a classical problem in tactile surface topography measurements. The determination of the stylus geometry may be tedious and inconvenient, therefore we looked for an easily applicable method. This study shows that the Rsk parameter and the difference between the Rv and Rp parameter may indicate the stylus tip radius as well as wear when using a sine-wave profile material measure, which is commonly supplied with a roughness tester for calibrating and/or adjusting the vertical amplification coefficient. This effect is derived from theoretical calculations on real and simulated styli and specimens and verified experimentally using two commonly used specimens and stylus tips with radii of nominally 1, 2, 5, and 10 µm. When using a standardized stylus with a nominal 2 µm tip radius and 60° cone angle on a typical C1 reference specimen with nominal parameters Ra = 3 µm and RSm = 100 µm, the Rsk value should be approximately −0.01. Any stylus wear will decrease the measured Rsk value. When the Rsk value decreases to a value of −0.06 or lower it may be time for closer inspection and/or replacement of the stylus.

Bottom-up approach for traceable calibration of tip geometry of stylus profilometer

A novel approach for accurate and traceable calibration of stylus tip geometry is introduced in the paper. The approach consists of several steps. Firstly, the geometry of an AFM tip is calibrated to a kind of line width standard whose geometry is traceably calibrated to the lattice constant of crystal silicon. Then, the stylus tip to be calibrated is measured by the calibrated AFM tip in an AFM, thus its tip geometry can be accurately determined after the contribution of the AFM tip geometry being corrected from the measured AFM image. After being calibrated, the stylus tip can be applied in measurements of vast microstructures and surfaces, where the measurement results can be in turn corrected using the characterized stylus tip geometry. In such a way, the stylus tip geometry and its measurement results can be finally traceable to the lattice constant of silicon, using this bottom-up approach. Detailed experimental examples are illustrated. For a stylus type RFTHB-50 studied in this paper, its tip radius is measured as 1.727 μm with a standard deviation of 0.007 μm. It is significantly smaller than its nominal value of 2 μm, indicating the need of the calibration. The application of calibrated stylus tip in measurements of microspheres is demonstrated. Compared to conventional tip characterization methods based on tip characterizers the proposed method has advantages of (i) no risk of damaging sharp edges of tip characterizers, (ii) capable of directly characterizing the 3D geometry of stylus tip, (iii) high accuracy.

Self-Calibration Method and Pose Domain Determination of a Light-Pen in a 3D Vision Coordinate Measurement System.

Light pens for 3D vision coordinate measurement systems are increasingly widely used due to their advantages, such as their small size, convenience of being carried, and widespread applicability. The posture of the light pen is an important factor that affects accuracy. The pose domain of the pen needs to be given so that the measurement system has a suitable measurement range to obtain more qualified parameters. The advantage of the self-calibration method is that the entire self-calibration process can be completed at the measurement site with no auxiliary equipment. After the system camera calibration was completed, we took several pictures of the same measurement point with different poses to obtain the conversion matrix of the picture and subsequently used spherical fitting, the generalized inverse method of least squares, and the principle of position invariance in the pose domain range. The combined stylus tip center self-calibration method calculates the actual position of the light pen probe. The experimental results verify the effectiveness of the method; the measurement accuracy of the system can satisfy basic industrial measurement requirements.

Observation of ground surface roughness values obtained by stylus profilometer and white light interferometer for common metal materials

To find some practical understandings and to derive some rules for roughness calibration for common metal materials, this paper counts surface roughness on 50 ground workpieces of five different materials obtained by a stylus profilometer (here‐in‐after, ‘SP’) and a white light interferometer (here‐in‐after, ‘WLI’). The materials include iron, stainless steel, 45 steel, copper and aluminium on which hardness values are widely ranged. The results show that SP measurement result is generally smaller than WLI measurement result for its stylus tip size and scratches on surface. The SP method has obvious scratches on soft materials (Al and Cu), which leads to the reduction of low spatial frequency information on the measured profile. WLI measurement result is more accurate when measured surface is smooth while SP is more suitable for rough and hard surface roughness measurement.

The Accuracy of a Screening System for Carpal Tunnel Syndrome Using Hand Drawing.

When carpal tunnel syndrome (CTS), an entrapment neuropathy, becomes severe, thumb motion is reduced, which affects manual dexterity, such as causing difficulties in writing; therefore, early detection of CTS by screening is desirable. To develop a screening method for CTS, we developed a tablet app to measure the stylus trajectory and pressure of the stylus tip when drawing a spiral on a tablet screen using a stylus and, subsequently, used these data as training data to predict the classification of participants as non-CTS or CTS patients using a support vector machine. We recruited 33 patients with CTS and 31 healthy volunteers for this study. From our results, non-CTS and CTS were classified by our screening method with 82% sensitivity and 71% specificity. Our CTS screening method can facilitate the screening for potential patients with CTS and provide a quantitative assessment of CTS.

On-machine non-contact roughness verification system based on Conoscopic holography

The surface quality verification of mechanical components is an essential activity in many applications where surface performance plays an important role in the functional behaviour of the part. Although many of the verification techniques commonly employed are based on the use of contact roughness profilometers, there are some limitations related to the morphological filtering effect associated to the stylus tip radius, as well as the difficulty in using these type of styli to carry out on-machine surface verification. The use of non-contact digitizing techniques helps to overcome some of these drawbacks, although the verification of surface quality using these non-contact systems still requires the development of scanning and data processing procedures similar to those described in the international standards for contact probing techniques. This work analyses the use of a non-contact sensor, based on Conoscopic Holography and integrated in a 3-axis machining centre, applied to the verification of the surface roughness of parts machined by face and cylindrical milling processes. After the calibration of the integrated system, a high-frequency noise filtering procedure specifically designed for roughness verification is proposed. The results demonstrate the feasibility of the system for verifying surface roughness grades from N5 to N12 in the two milling processes. Finally, specific filtering recommendations for each roughness grade of both milling processes as well as a surface verification procedure are provided.

Efficient microspark erosion-assisted machining of a monocrystalline microdiamond stylus using a heat-avoidance path

Monocrystalline diamond possesses covalent bonding making diamond extremely hard and difficult to machine. In this study, a microdiamond stylus typically used in measuring surface roughness is machined to exemplify the proposed ‘microspark erosion-assisted machining with heat-avoidance path’ technique. Based on the high thermal conductivity and weak electrical conductivity of boron-doped monocrystalline diamond, high-frequency pulsed discharge plasma is employed to efficiently perform microspark erosion machining on an extremely hard monocrystalline diamond blank. It was found that the pulse-on time and servo voltage respectively affect erosion plasma length and the erosion gap during diamond machining. Also, the safety distance and safety height of the erosion path dominate heat transfer to filler metal. These factors all affect the firmness of the brazed diamond blank on the substrate. Three mechanisms for removing carbon atoms from the diamond blank surface were observed. They are vaporization, melting, and graphitization of carbon atoms. This graphitized carbon atoms have weak electrical conductivity, which is conducive to inducing the wire-electrode to generate a greater electric field and secondary discharging, facilitating removal of additional carbon atoms. Experimental results indicate that a microdiamond stylus prototype with a tip of 10 μm can be safely formed using a ‘microspark erosion-assisted machining with heat-avoidance path’ technique, creating 93.7% repeatability of the minimum residual stylus diameter. The tangential micro-grinding facilitates the stylus tip to receive grinding from the grinding wheel's maximum tangential speed and create the precision microdiamond stylus with 1 μm in tip-radius. The applied microspark erosion-assisted machining had a diamond material removal rate that was 54% more efficient than conventional grinding of a commercial microdiamond stylus. The formed microdiamond stylus was inspected by Raman spectroscopy and verified by the surface roughness standard gauge to be up to industry standards.

Temperature-dependent abrasivity of Bukit Timah granite and implications for drill bit wear in thermo-mechanical drilling

Thermo-mechanical drilling combines the advantages of flame thermal treatment and rotary head drilling to achieve a high penetration rate in granitic rocks and a low wear rate of drill bits. This drilling strategy has been recognized as a potential technique to develop deep geothermal energy, but further improvement is still needed to optimize the drilling efficiency, such as the reduction in drill bit wear in thermally treated rocks. We use the Cerchar abrasivity test to investigate the abrasivity characteristics of Bukit Timah granite after the thermal treatment at different high temperatures. The Cerchar abrasivity index (CAI) decreases from 3.5 at 25 °C to 3.0 at 400 °C, remains constant between 400 and 600 °C and subsequently increases to 4.1 at 800 °C. Based on the meso-scale and micro-scale observations using polarizing microscope, 3D scanner and scanning electron microscope, the reduction in CAI value at lower temperatures is due to the abrasive wear of stylus tip, while the mechanical interaction between the stylus cone and abrasive minerals causes the increase in CAI value at higher temperatures. The Cerchar abrasivity test results indicate that overheating rocks may result in the exposure of drill bits to more abrasive minerals and enhance drill bit wear.

A Novel Ultrasound Probe Spatial Calibration Method Using a Combined Phantom and Stylus

Intra-operative ultrasound (US) is a popular imaging modality for its non-radiative and real-time advantages. However, it is still challenging to perform an interventional procedure under two-dimensional (2-D) US image guidance. Accordingly, the trend has been to perform three-dimensional (3-D) US image guidance by equipping the US probe with a spatial position tracking device, which requires accurate probe calibration for determining the spatial position between the B-scan image and the tracked probe. In this report, we propose a novel probe spatial calibration method by developing a calibration phantom combined with the tracking stylus. The calibration phantom is custom-designed to simplify the alignment between the stylus tip and the B-scan image plane. The spatial position of the stylus tip is tracked in real time, and its 2-D image pixel location is extracted and collected simultaneously. Gaussian distribution is used to model the spatial position of the stylus tip and the iterative closest point-based optimization algorithm is used to estimate the spatial transformation that matches these two point sets. Once the probe is calibrated, its trajectory and the B-scan image are collected and used for the volume reconstruction in our freehand 3-D US imaging system. Experimental results demonstrate that the probe calibration approach results in less than 1-mm mean point reconstruction accuracy. It requires less than 5 min for an inexperienced user to complete the probe calibration procedure with minimal training. The mockup test shows that the 3-D images are geometrically correct with 0.28°-angle accuracy and 0.40-mm distance accuracy.

Investigation of Factors Affecting Sensitivity Enhancement of an Optical Fiber Probe for Microstructure Measurement Using Oblique Incident Light

Recently, the demand for accuracy measurement of microstructures has been remarkable. We have been developing a measurement system for microstructures using a stylus made of an optical fiber and prisms. In this measurement system, the oblique irradiation of the laser beam was employed to detect the displacement of the stylus shaft generated by contact between the stylus tip and the measured surface, and to expand the measurable area and depth. After these evaluations, we discovered that the sensitivity was enhanced with the increase in the incident angle of the laser beam on the stylus shaft. Therefore, in this study, we focus on the effect of the incident angle of light on the measurement sensitivity. First, the enhancement sensitivity is confirmed by using the basic experimental apparatus. Next, the relationship between the incident angle of the laser beam and the sensitivity is theoretically examined using the 3D ray-tracing method. Finally, the factor of the sensitivity enhancement is analyzed using the same method. As a result, it was confirmed that the sensitivity was enhanced with the increase in the incident angle of the laser beam on the stylus shaft.