Precision Engineering

This paper describes a value of information-based experimental design method that uses Bayesian inference for belief updating. The application is process damping coefficient identification in milling. An analytical process damping algorithm is used to model the prior distribution of the stability boundary (between stable and unstable cutting conditions). The prior distribution is updated using experimental results via Bayesian inference. The updated distribution of the stability boundary is used to determine the posterior process damping coefficient value. A value of information approach for experimental test point selection is then demonstrated which minimizes the number of experiments required to determine the process damping coefficient. Subsequent experimental parameters are selected such that the percent reduction in the standard deviation of the process damping coefficient is maximized. The method is validated by comparing the process damping posterior values to residual sum of squares results using a grid-based experimental design approach. Results show a significant reduction in the number of experiments required for process damping coefficient parameter determination. The advantages of using the value of information approach over the traditional design of experimental methods are discussed.

This paper presents the development and validation of a length verification laboratory in Trinidad and Tobago to establish traceability for length measurements used in trade, in alignment with international metrological standards. The initiative supports the country's legal metrology efforts by ensuring that commonly used instruments such as rigid rulers are accurately verified and traceable to the SI unit of length. The project involved the strategic procurement of precision measurement equipment, its calibration against internationally recognized standards, and the implementation of robust measurement procedures. Intra-laboratory comparisons were conducted using both En values and Z scores to assess measurement agreement and repeatability during the calibration of the instrument standard and the verification of a rigid ruler. Results from these comparisons demonstrated strong internal consistency, with all En values within acceptable limits and Z scores indicating stable and reliable performance. These outcomes confirm the laboratory's technical competence and its readiness to support fair trade practices through traceable length measurements across Trinidad and Tobago.

Quality management decisions require precise and reliable measuring results. In manufacturing and assembling processes, production metrology plays a significant role in generating such results. For this reason, coordinate measuring machines (CMMs) are used more and more often due to their universality and flexibility. The quality of results generated by CMMs is highly dependent on the skills of the CMM operators. In order to minimize technicians' influence, they need to be provided with the necessary knowledge to carry out such tasks. Efforts to introduce training at a national level led to the European project EUKOM, which developed a usercentred training course using new learning methods to meet the demands of CMM operators [1]. This project led to the foundation of the registered association CMTrain. Today, this association offers manufacturer-independent courses in coordinate metrology and it is continually improving learning methods and learning contents.

Limitations imposed by the phase meters used in heterodyne interferometers are evaluated. These instruments measure the phase relationship between electrical signals generated by the heterodyning process, allowing the interferometers to resolve fractions of an optical fringe. Measurements indicate that the phase meters used in currently available heterodyne interferometers probably limit achievable accuracy to a greater extent than barriers imposed by the optics. We show that a new class of time interval counters offers a means of greatly improving accuracy in these instruments.

We present a control scheme for video-rate atomic force microscopy with rosette pattern. The controller structure involves a feedback internal-model-based controller and a feedforward iterative learning controller. The iterative learning controller is designed to improve tracking performance of the feedback-controlled scanner by rejecting the repetitive disturbances arising from the system nonlinearities. We investigate the performance of two inversion techniques for constructing the learning filter. We conduct tracking experiments using a two-degree-of-freedom microelectromechanical system (MEMS) nanopositioner at frame rates ranging from 5 to 20 frames per second. The results reveal that the algorithm converges rapidly and the iterative learning controller significantly reduces both the transient and steady-state tracking errors. We acquire and report a series of high-resolution time-lapsed video-rate AFM images with the rosette pattern.

This paper presents a novel one-degree-of-freedom microelectromechanical systems (MEMS) force sensor. The high-bandwidth device contains on-chip sensing and actuation mechanisms, enabling open-and closed-loop modalities. An active compliance mechanism is incorporated to render the device more conducive to characterization of soft samples. When operated in closed loop, the adjustable stiffness enables the sensor to attain a larger dynamic range and minimize the nonlinearities originating from flexures. Analytical models are employed to design and calibrate the sensor. In open loop, the sensing resolution of 23.3 nN within a bandwidth of 2.35 kHz and a full-scale range of ± 42.6 µ N are experimentally obtained. The resolution is enhanced to 9.3 nN by employing an active compliance mechanism. When operated in closed loop, a resolution of 12.9 nN is achieved within a dynamic range of 71.2 dB and a sensing bandwidth of 3.6 kHz is demonstrated. The sensor performance is tested by obtaining the stiffness of an atomic force microscope probe and measuring the force produced by a self-actuated piezoelectric microcantilever.

Some types of manufactured parts like sheet metals and skins often have a significantly different shape in a free-state position compared to their state-of-use position (as defined by their nominal CAD models) due to a combination of gravity and/or the residual effects of stress. Traditionally known as flexible (nonrigid compliant) parts, these dedicated fixtures are used for inspection operations in order to maintain flexible parts from a free-state position to a state-of-use position. This paper introduces a new automatic defect identification method primarily intended for two less-investigated manufacturing defect types: contour profile errors and hole localization. By combining simple techniques such as mesh boundary detection, fast boundary-based correspondence searches and accurate fast marching on triangulated meshes, the semi-geodesic distances from each boundary vertex on the acquired SCAN mesh to all the other boundary vertices is calculated, stored in a table and then compared to the corresponding values on the part's nominal CAD mesh. The comparisons found in the tables result in an estimation of the location and amplitude of the two aforementioned defect types. Compared to other work in this field, the overall approach does not rely on any mesh registration or finite-element analysis with tedious boundary conditions setup. It is also relatively fast. A fast algorithm/app based on this method was named the AFDA (Automatic Free-state Defect Approximation) and was validated against case studies in the aerospace sector. The results reflect the utility and effectiveness of the proposed approach.

Resonant vibration generators, such as vibratory feeders or ultrasonic sonotrodes, are often employed in manufacturing to generate harmonic vibrations with suitable amplitude, spatial shape, and frequency, in order to meet the process requirements. These underactuated systems are usually excited in open loop by few actuators, and therefore, it is not ensured that the desired response is correctly achieved, since the feasible motions should belong to the subset of the allowable motions. To achieve the closest approximation of the desired vibrations, some new solutions are here proposed. The first strategy is the optimal shaping of the harmonic forces exerted by the actuators, by solving an inverse dynamic problem through a coordinate transformation and the projection of the desired response onto the subspace of the allowable motion. By exploiting the formulation of such a subspace, a second approach that involves concurrently both the force shaping and the modification of the inertial and elastic system parameters is proposed. The idea of this approach is to exploit the modification of the elastic and inertial parameters to properly shape the allowable subspace in such a way that it spans the desired response. A solution method is developed, and analytical sensitivity analysis is proposed to choose the design variables. Validation is proposed through a linear vibratory feeder with a long flexible tray, taken from the literature. The results show the effectiveness of the proposed strategies that lead to a very precise approximation of the desired response.

Resonant vibration generators, such as vibratory feeders or ultrasonic sonotrodes, are often employed in manufacturing to generate harmonic vibrations with suitable amplitude, spatial shape, and frequency, in order to meet the process requirements. These underactuated systems are usually excited in open loop by few actuators, and therefore, it is not ensured that the desired response is correctly achieved, since the feasible motions should belong to the subset of the allowable motions. To achieve the closest approximation of the desired vibrations, some new solutions are here proposed. The first strategy is the optimal shaping of the harmonic forces exerted by the actuators, by solving an inverse dynamic problem through a coordinate transformation and the projection of the desired response onto the subspace of the allowable motion. By exploiting the formulation of such a subspace, a second approach that involves concurrently both the force shaping and the modification of the inertia...

The ISO GPS and ASME Y14.5 standards have defined dimensional and geometrical tolerance as a way to express the limits of surface part variations with respect to nominal model surfaces. A quality-control process using a measuring device verifies the conformity of the parts to these tolerances. To convert the control measurement points as captured by a device such as a coordinate measurement machine (CMM) or noncontact scan, it is necessary to select the appropriate algorithm (e.g., least square size and maximum inscribed size) and to include the working hypotheses (e.g., treatment of outliers, noise filtering, and missing data). This means that the operator conducting the analysis must decide on which algorithm to use. Through a literature review of current software programs and algorithms, many inaccuracies were found. A benchmark was therefore developed to compare the algorithm performance of three computer-aided inspection (CAI) software programs. From the same point cloud and on...

The current trend in miniaturization of products and components requires appropriate technologies for the manufacture of miniature dies and moulds. The work presented here deals with the process planning of micromilling for the production of miniature mould cavities, required in ultrasonic moulding in order to reach high precision. Several aspects of process planning are addressed, including cutting tool geometry selection, segmentation of cavity geometry, minimum chip thickness, chordal tolerance, and type of interpolation. The case study involves the successful micromilling of a complex aluminium mould cavity for ultrasonic moulding. The proposed process plan is demonstrated through the micromilling of the mould cavity and silicone replicas of the miniature geometrical model. In general terms, good precision is obtained following the proposed methodology. In a randomly located set of geometric features, the dimensional error was below 5% for most features (32 out of a total of 40).

This paper presents Bouc-Wen hysteresis modelling and tracking control of piezoelectric stack APA120S. The actuator is used to control a microgripper. A modified Bouc-Wen non-symmetric model is applied to study the behaviour of the system in static and dynamic state. The good agreement between predicted and measured curve showed that the Bouc-Wen model is an effective mean for modelling the hysteresis of piezoelectric actuator system. Subsequently, the inverse Bouc-Wen model is formulated and applied to cancel the non-linear hysteresis. In perspective of a control design, it is desirable to linearize the non-linear Bouc-Wen model to produce a static system. Finally, in order to increase damping of the actuator system and to improve the control accuracy, a cascaded PID controller is designed with consideration of the dynamics and static behaviour of the actuator. Experiment result shows that error is of only 5% if PID is cascaded with hysteresis compensation. Therefore, hysteresis co...

This paper presents a design of a variable size spatial filter used in the wavefront sensor subsystem of the Gemini Planet Imager instrument. It describes an adjustable mechanism consisting of two slides forming a square aperture which can be varied in size between 1.8 and 6.7 mm. These slides are located on athermalized flexure mounts that move opposite to one another driven by a single precision linear actuator. The device retains long term dimensional stability, resolution, and repeatability on a micron level for all gravity vector orientations and for temperatures between -5°C and + 25°C.

Usage of cutting fluids during machining makes machining process efficient for 'difficult-to-cut' materials (like nickel based Inconel 718 superalloys). However, cost associated with cutting fluid acquisition, usage, dumping of utilized oil, and cleaning of the end product appears nearly four times more than the cost of machining under dry condition. In addition, increased attention towards sustainable manufacturing by imposition of stringent government regulations nowadays enforce industries to restrict environmental degradation as well as to reduce/minimize occupational health hazards; hence, utilization of cutting fluids in manufacturing industries is being restricted, and, therefore, industries are being encouraged towards dry machining. In the context, present work experimentally investigates different tool wear modes for machining of Inconel 718 under dry condition using uncoated tungsten carbide insert. Effects of cutting speed and depth of cut on cutting force, and flank wear progression depth are investigated. It is observed that cutting force and flank wear progression depth increase with increasing cutting speed as well as depth of cut. In all worn out tool inserts, dominant wear mechanism observed is combined adhesion and abrasion. Chip's macro/micro morphology is studied; effects of input variables on chip morphology are discussed as well.

Freeform surfaces have important applications in various industrial fields. However, achieving a high level surface finish on freeform surfaces using polishing is always a challenging task. Hybrid robots are promising alternatives to conventional computer numerical control (CNC) machines and industrial robots for ultraprecision machining. Herein, we present a novel custom-built hybrid robot for freeform polishing. After the laboratory prototype was successfully developed, its automation for a specific freeform surface was a major obstacle preventing its application. This critical issue was addressed by presenting a process to deal with tedious robot programming. Random tool path planning was performed in the task space, and hybrid robot motion planning was conducted in the joint space. By integrating the process flows, a robot programming toolkit was developed to directly output the control program for a specific robot controller. An illustrative example with a freeform surface is provided to verify the functionality of the developed hybrid robot and the proposed control processes, and the corresponding experimental results verify their effectiveness.

This paper proposes a lifting wavelet model for enhancement of accuracy of surface roughness characterisation. In this work, the theory and fast algorithm of the lifting wavelet are briefly introduced and a lifting wavelet model for extraction of roughness of surfaces has been developed. The rough surface recovered has good refinement accuracy in contrast to the least squares polynomial fitting. Applications are conducted by using a series of typical surfaces, planes and curves, measured by contact (stylus) and non-contact (phase-shifting interferometry) instruments, to demonstrate the feasibility and applicability of using the lifting wavelet model in the analysis of these surfaces.

The need to develop a European framework for training in Precision Engineering for Advanced Manufacturing was identified and implemented by the creation of the PREFAM project. Led by euspen, the project is supported with six renowned partners across Europe to increase the availability and recognition of short specialised training courses. This project will support course providers with guidelines and tools that are aligned to the European approaches and instruments for course design and learning assessment, as well as monitoring and improvement processes. The innovation of pedagogical approaches to learning will allow course providers and participants to recognise and promote their skills and competencies thus reflecting their wider knowledge of precision engineering. The systematic approach based on eight key deliverables is intended to support the precision engineering community with added quality assurance. By offering a standardised framework of training courses and guidelines, to monitor learning gaps and create new learning pathways for users and course providers, PREFAM will support the needs and sustain the pan-European market.

In this paper, an operator-based nonlinear vibration control of a flexible arm experimental system using piezoelectric actuator with hysteresis is discussed. The piezoelectric actuator exhibits hysteretic effects in the output displacement responses, which can cause inaccuracy and undesirable oscillations, where Prandtl-Ishlinskii(PI) model is used to describe the hysteresis. In order to compensate the hysteretic effects, using the model, and based on the concept of Lipschiz operators and robust right coprime factorization, nonlinear vibration controllers are proposed to the experimental system. Further, a tracking operator design method is given to ensure the tracking performance of the considered system. Finally, simulation results and experimental results are presented to support the effectiveness of the proposed design method.

Surface characteristics and machining performances of micro-pockets manufactured by μEDM as a function of different process conditions are studied in this paper. The micro-pockets were obtained using different combinations of process parameters on different ultra-high temperature ceramics (UHTCs) with the same base matrix (ZrC) and different volume fraction of the second phase (MoSi 2 ). This work presents an analysis of the process performances with different machining approaches, from pre-roughing down to fine-finishing. Microstructure analysis of the as-sintered and machined materials was conducted to identify materials modification due to the electrical discharges. A removing material mechanism during the μEDM process has been hypothesized, correlating the ED-machined surface structure and the main process performances.

In this paper, an inverse compensator based on the Bouc-Wen model is used to reduce the effect of hysteresis on a piezoelectric micro-actuator. This compensator is used as an open loop controller which partially eliminates the system hysteresis effect. In the last step, in order to increase the reliability of the system and to achieve the desired goals, a H∞ robust controller is proposed in the presence of a compensator, to detect in the presence of modeling error and compensator error. At the end, simulation results are provided by MATLAB to demonstrate the effectiveness of the proposed control scheme. These results indicate that the proposed scheme provides a robust system performance and the tracking error reaches zero with acceptable accuracy.

In this paper, an inverse compensator based on the Bouc-Wen model is used to reduce the effect of hysteresis on a piezoelectric micro-actuator. This compensator is used as an open loop controller which partially eliminates the system hysteresis effect. In the last step, in order to increase the reliability of the system and to achieve the desired goals, a H∞ robust controller is proposed in the presence of a compensator, to detect in the presence of modeling error and compensator error. At the end, simulation results are provided by MATLAB to demonstrate the effectiveness of the proposed control scheme. These results indicate that the proposed scheme provides a robust system performance and the tracking error reaches zero with acceptable accuracy.

Electromagnetically compensated balances (ECB) are reliable and well-established weighing instruments. As completely electromagnetically compensated types they are commercially available with mass ranges from two grams to several kilograms. They also represent a highly stable and linear scale for force. In this publication it will be shown how ECBs can be used for force standard machines (FSM) having a range of a few Newtons and a feed-back stabilized resolution of single micro Newtons. Moreover, such FSMs conform to the future requirements of continuous calibration.

SAŽETAK. U uvodu je opisano kako su u posljednjih 30 godina smanjivane dimenzije GPS prijamnika od velikih dimenzija instrumenata do malih dimenzija u mobitelima. Pritom je znatno povećana i točnost GPS prijamnika, ali ipak nisu riješeni svi problemi. Na primjer u slučajevima kada se ne mogu primati GPS-signali koji su odaslani sa satelita, mogu se koristiti inercijski sustavi (žiroskopi i akcelerometri), koji za sada imaju relativno malu točnost. Kako bi se problemi riješili, Britansko ministarstvo obrane odlučilo je poboljšati te sustave financirajući projekte kojima se nastoje konstruirati točniji atomski interferometrijski žiroskopi i atomski akcelerometri, tj. atomski inercijski uređaji. Da bi to ostvarili primjenjuju snižavanje temperature pomoću tri para lasera u međusobno suprotnim smjerovima kao što je predloženo u otkriću za koje je dodijeljena Nobelova nagrada za fiziku 1997. godine. Osim toga, za to koriste Sagnacov i Ramanov efekt.

The authorities of the standards organization International Organization of Standardization (ISO) advocate mastering any uncertainties in all parts of the industrialization process. In the three-dimensional (3D) measurement process, uncertainty is usually obtained at the end of a battery of tests. It is defined as a whole because it includes several types of errors, known systematic components, unknown systematic components and random components. Automated calculations of uncertainty can be made based on statistics. This method is based on statistical concepts, which are in accordance with "The Guide to the expression of the uncertainty in measurement" (GUM). It also enables us to generate uncertainties on the verification of ISO specifications (or specs in the ISO directives). In the course of this article, a usage will be presented that takes the knowledge of uncertainties into account: this usage will help the operator to take a decision on the conformance of a mechanical part in reference to its conformance to geometric tolerance.

In this paper, the vibration of an atomic force microscope (AFM) cantilever in tapping mode with two whole piezoelectric layers submerged in liquid medium is investigated. In the performed modeling, the sample surface has been considered as rough, and to show these surface asperities, two models of Rumpf and Rabinovich have been employed for analyzing the attractive Van der Waals force. This paper has been organized in two sections. The first section deals with the functioning of cantilever over rough surfaces, which accompanies the changes of the attractive Van der Waals force, and the second section involves the changes in the Van der Waals force which lead to a change in the liquid medium. The cantilever is totally submerged in the liquid. To show the effect of liquid on cantilever, first, only the cantilever tip is immersed in the liquid and it is dynamically analyzed. Then, the cantilever is totally submerged and then taken out of the liquid, so that the additional mass and damping of the cantilever could be calculated. In these two manners of cantilever immersion in liquid, the effects of the added mass and damping on the cantilever can be measured. When a cantilever vibrates totally in liquid, since the mass and damping of the liquid that is present on the cantilever cannot be determined, first, the cantilever's natural frequency in liquid is estimated in the laboratory and then by using this frequency and the cantilever stiffness (which is not medium-dependent and is always considered as constant), the additional mass and damping of the cantilever are determined.

This paper presents results of 3-axis CNC machine tool diagnostics performed with XL-80 laser interferometer and XC-80 environmental compensation unit, including pressure, humidity and temperature sensors. Furthermore, the paper includes the methodology and results of conducted measurements of linear positioning errors, which supplied data for further analysis. The conclusion section presents important results of conducted experiments. Measurement results were presented in figures, charts and tables.

This paper presents results of 3-axis CNC machine tool diagnostics performed with XL-80 laser interferometer and XC-80 environmental compensation unit, including pressure, humidity and temperature sensors. Furthermore, the paper includes the methodology and results of conducted measurements of linear positioning errors, which supplied data for further analysis. The conclusion section presents important results of conducted experiments. Measurement results were presented in figures, charts and tables.

Achieving high workpiece accuracy is the long-term goal of machine tool designers. There are many causes for workpiece inaccuracy, with thermal errors being the most common. Indirect compensation (using prediction models for thermal errors) is a promising strategy to reduce thermal errors without increasing machine tool costs. The modelling approach uses transfer functions to deal with this issue; it is an established dynamic method with a physical basis, and its modelling and calculation speed are suitable for real-time applications. This research presents compensation for the main internal and external heat sources affecting the 5-axis machine tool structure including spindle rotation, three linear axes movements, rotary C axis and time-varying environmental temperature influence, save for the cutting process. A mathematical model using transfer functions is implemented directly into the control system of a milling centre to compensate for thermal errors in real time using Python programming language. The inputs of the compensation algorithm are indigenous temperature sensors used primarily for diagnostic purposes in the machine. Therefore, no additional temperature sensors are necessary. This achieved a significant reduction in thermal errors in three machine directions X, Y and Z during verification testing lasting over 60 h. Moreover, a thermal test piece was machined to verify the industrial applicability of the introduced approach. The results of the transfer function model compared with the machine tool's multiple linear regression compensation model are discussed.

An Effective Dimensional Inspection Method Based on Zone Fitting. (December 2004) Nachiket Vishwas Pendse, B. Eng., Government College of Engineering, Pune, India Co-Chairs of Advisory Committee: Dr. Richard Alexander Dr. Jyhwen Wang Coordinate measuring machines are widely used to generate data points from an actual surface. The generated measurement data must be analyzed to yield critical geometric deviations of the measured part according to the requirements specified by the designer. However, ANSI standards do not specify the methods that should be used to evaluate the tolerances. The coordinate measuring machines employ different verification algorithms which may yield different results. Functional requirements or assembly conditions on a manufactured part are normally translated into geometric constraints to which the part must conform. Minimum zone evaluation technique is used when the measured data is regarded as an exact copy of the actual surface and the tolerance zone is ...

The market for freeform and high quality microdies and moulds made of steel is predicted to experience a phenomenal growth in line with the demand for microsystems. However, micromachining of hardened steel is a challenge due to unpredictable tool life and likely differences in process mechanism compared to macro-scale machining. This paper presents an investigation of the size effect in micromilling of H13 hardened tool steel. In this case, the size effect in micromilling hardened tool steel was observed by studying the effect of the ratio of undeformed chip thickness to the cutting edge radius on process performance. The paper explores how this ratio drives the specific cutting force, surface finish and burr formation in micro-scale machining. In addition, the effect of different microend mill geometry on product quality was explored. The paper provides a valuable insight into optimum micro-scale machining conditions for obtaining the best surface finish and minimizing burr size.

Micro-and nano-CT scanners are increasingly used in precision engineering. Proper selection of the key components of these devices allows elimination of most artifacts already during data acquisition. Typical nano-CT scanners contain an air bearing rotary stage for object manipulation due to their rotational accuracy compared with conventional bearings. In this work, the radial error motion of such an air bearing rotary stage is reduced to 3 nm by optimising the feeding system, leading to a new state of the art record for passive aerostatic bearings to our knowledge.

Micro-and nano-CT scanners are increasingly used in precision engineering. Proper selection of the key components of these devices allows elimination of most artifacts already during data acquisition. Typical nano-CT scanners contain an air bearing rotary stage for object manipulation due to their rotational accuracy compared with conventional bearings. In this work, the radial error motion of such an air bearing rotary stage is reduced to 3 nm by optimising the feeding system, leading to a new state of the art record for passive aerostatic bearings to our knowledge.

The endosurgical grasper is a tool used for tissue manipulation in an endoscopic surgery. By adding a controller into the device, a surgeon can control both the grasping and the input forces. However, it will increase the number of components in the device. This objective of this design is to use the virtue of a compliant material to minimise the number of device components and at the same time keeping the output performance as same as the datum. The mechanism design is analysed using pseudo-rigid-body method. The results have shown that, by decreasing the length of the spring to at least 78% will save about 86.6% of its maximum size. Therefore, the surgeons will feel more comfortable when handling the device as a few of its components, size and weights have been reduced.

A hydraulic hose repair system is presented that was developed for use at the Deepwater Horizon accident site. The system can be deployed with a single ROV with two controllable arms. One arm holds the device and the other arm pushes a severed hose into the device. Hydraulic pressure is applied from the ROV to the device and a hydraulic coupling within the device is crimped into one end of the hose. The second hose end to be spliced to the first is pushed into the other side of the device and the second half of the coupling is crimped onto the second hose end. The device itself is left in place as part of the splice. The design, on-shore testing, and fabrication of multiple devices ready to deploy at the accident site took on the order of a week to complete. They stand ready to be deployed in the case of another deepwater accident.

Entangled structures, such as steel wool, can be used as inexpensive, high cycle, low stiffness, thin profile compressive springs where uniform pressure on a surface is required particularly in elevated temperature and/or harsh environments. Mechanical compression tests were performed on a variety of steel wool samples to determine the stress-strain curve behavior over high cycles. After initial conditioning cycles, good repeatability can be obtained with hysteresis dependent on strain. The results show a nonlinear behavior over large strains (>10%) and reasonable linear behavior for strains less than 10%. The properties of an entangled structure spring can be selected to achieve the desired stiffness for a particular application.

A design for a low profile hydrostatic rotary bearing is presented that utilizes a new type of self-compensation that allows a large number of bearing pockets to be present with only a few precision round parts, thus allowing high hydrostatic averaging with relatively low design complexity. A key feature of this design is that it does not use capillaries or orifices or a complex network of passageways to route fluid. The design consists of five easily assembled round parts which can be manufactured by cylindrical grinding. A seal is incorporated which prevents fluid leakage and creates a closed system. The theory of operation is discussed along with manufacturing considerations. Tests show that the rotary bearing has high stiffness, and achieves a high degree of averaging, resulting in a radial error motion of 0.05 m from components ground to an accuracy of only 2.5 m.

In the field of industrial robotics, many different calibration methods exist to reduce error in the robot system. Locating the manipulator home position is a common calibration technique, which can be divided into three main categories — relative, optimal and leveling based ...

Externally pressurized gas lubricated bearings with small clearance have some practical disadvantages such as difficulties in manufacturing process, price, assembly etc. and so, they don't become widespread. These disadvantages can be solved with use of higher values of clearance in the bearing. But bearings with high clearance have low load carrying capacity in the contrary. The load carrying capacity can be increased by using high value of orifice diameter or more orifice, in other words with higher mass flow rate. In the literature general accepted value for clearance is lower than 50 µm and there is a limited number of study the dynamics of externally pressurized air bearing especially with high values of clearance. In this study the flow between shaft and rotor was modelled using Reynold's Equation which is fluid equation of motion and this model is solved by Alternating Direction Implicit (ADI) numerical solution method, in order to investigate the dynamic of an externally pressurized gas lubricated bearing with increased clearance.

The performance of electrical connectors is critically influenced by the choice of base material and its surface coating. This study investigates the relationship between the chemical composition of the base material, the characteristics of the coating layer, and their combined impact on mating force and contact resistance. By analyzing the trade-offs between these parameters, we aim to provide guidelines for optimizing material selection in high-performance applications. The results highlight the importance of balancing mechanical and electrical properties to achieve both reliability and efficiency.

It is a well known fact that the EDM process results in the formation of a hard, brittle recast layer on the component's surface. Several investigations have been carried out in order to assess the nature of the recast layer in terms of its phase structure, the microhardness, presence and the density of cracks, and other surface features. Some researchers [Barash, Delpretti] have reported mathematical relationships between the thickness of the white layer and 2D amplitude surface roughness parameters (such as R a and R t ). But so far no investigation has been reported which correlates the thickness of the white layer with 3D surface roughness parameters, especially those related to spatial parameters. This paper presents an experimental investigation of the effect of the EDM process factors (current and pulse on-time) on the thickness of the white layer. Empirical equations relating the thickness of the white layer with 3D surface texture amplitude, spatial and volume parameters are presented and their physical basis is discussed. The results of this study show that a better correlation can be obtained between the average thickness of the white layer (AWLT) and the spatial parameter, S ds as compared to other 3D surface texture parameters. This is believed to be mainly due to the similar effect of the current and pulse on-time on both AWLT and S ds . The possible effect of surface tension between the solid and liquid phases on the thickness of the white layer during erosion is also discussed.

A Bose-Einstein condensate (BEC) is a topic of significant interest within the scientific community. It is well understood that Rb-87 and Yb2Si2O7 have been utilized in experiments to explore this phenomenon. These studies have demonstrated that these materials can achieve the BEC phase, a state that has been experimentally validated. In this paper, we further establish, from the perspective of theoretical physics, that silicon is also capable of exhibiting BEC properties. Our approach differs from prior studies in that it uses innovatively certain boundary conditions. Specifically, we employed Yb-70 as a gamma-ray radiation source and a 1 nm linewidth (as the half-width of a 2 nm line). Additionally, we utilized the concept of half-value thickness from nuclear physics absorption models to optimize the semiconductor process. This method effectively removes ytterbium (Yb) during the process, leaving only silicon, silicon-based materials, or silicon topological superconductors on the wafer. This technical procedure results in the creation of "BEC silicon" at absolute zero temperature (0 K), introducing a novel material for BEC realization.

The performance of linear axes is often tested on the basis of one set-up per one or two types of deviations from a NC path. With the applica- tion of multi-axes machining the contouring per- formance in more than two degrees of freedom is of interest. The paper describes a measuring instrument to check the contouring performance of a machine tool in the six degrees of freedom. The three translations and the three rotations of the relative movement between tool side and workpiece side are measured simultaneously. Results of first measurements are presented and discussed.

Diffusion bonding cycle times can be a large factor in the production cost of metal microchannel devices. The challenge is to significantly minimize bonding cycle times through rapid heating and cooling within the bonding process. A novel method is described which takes advantage of the internal flow passages within microchannel devices for convective heat transfer during the bonding process. The internal convective heating (ICH) technique makes use of heated inert gas to provide the microchannel assembly with rapid and uniform heat input. Results demonstrate that the ICH technique is feasible, capable of producing microchannels with higher dimensional integrity and shorter bonding cycle times than traditional vacuum hot press methods. Results suggest that this may be due to smaller thermal gradients within microchannel devices during the ICH bonding cycle.

This paper presents an approach to achieving isotropic compression, which can be used for the compression of irregularly shaped samples. The proposed system integrates six pistons around the sample at right angles to each other and at equal distances to the sample. Mounted on each piston there are high-precision lasers. These lasers dynamically trim the piston faces to match the shape and size of the piston face and that of the sample, this ensures uniform compression. This technique overcomes limitations in current compression methods, such as uneven pressure distribution. This can also be applicable in high-pressure physics and material science.

Micromachining is a key technology in contemporary society, due to the new requirements of the modern industry. The need of higher accuracy and precision, even for details on the finished product (which may also have very small dimensions), can be fulfilled only with micromechanical machining. Among this family of technologies, micromilling is one of the most important and widespread: the potential of this process is due to the great precision level that can be obtained, when machining high strength materials too. One of the main challenges launched by micromilling concerns the understanding of the processes that generate breakages and deterioration of the tool, and the study of their causes, that are usually different from those observed in conventional milling processes, for which the definition and the prediction of the tool-life are regulated by the ISO-8688 standard (part 1 and 2). This standard is not referred to micromilling and a dedicated regulation has not been compiled yet. In this article the results of an experimental campaign, made to investigate the tool wear in micromilling process, are presented. The aim of the work is to provide fundamental knowledge for the development of a future standard that can fill the normative gap. In particular, results describe that the flank wear evolution follows the typical trend characterized by the decreasing, constant and increasing tool wear slope regions. Cutting force, roughness and tool corner radius evolution are related with tool wear. In particular, a statistical analysis based on the Pearson correlation coefficient is presented in order to quantify the correlation between the flank wear and the considered parameters. Details about the influence of feed rate and mill type in flank wear evolution are also provided. Furthermore, results show that flank wear could actually be used for a tool-life criterion in micromilling processes.

The macro-structure of chemical-vapor-deposited (CVD) zinc sulfide (ZnS) substrates is characterized by cone-like structures that start growing at the early stages of deposition. As deposition progresses, these cones grow larger and reach centimeter size in height and millimeter size in width. It is challenging to polish out these features from the top layer, particularly for the magnetorheological finishing (MRF) process. A conventional MR fluid tends to leave submillimeter surface artifacts on the finished surface, which is a direct result of the cone-like structure. Here we describe the MRF process of polishing four CVD ZnS substrates, manufactured by four different vendors, with conventional MR fluid at pH 10 and zirconia-coated-CI (carbonyl iron) MR fluids at pH 4, 5, and 6. We report on the surface-texture evolution of the substrates as they were MRF polished with the different fluids. We show that performances of the zirconia-coatedCI MR fluid at pH 4 are significantly higher than that of the same fluid at

In the article, the form deviation (roundness) measurement with the Coordinate Measuring Machine has been discussed. The influence of the measuring points number and the type of the roundness deviation on the result (since different fitting elements are used) has been presented. The obtained investigation results prove that a minimal number of points is not enough for measurement, while too large of a number does not improve the measurement, as well. A recommendation on the measuring points number has been given.