High-precision Computer Numerical Control Research Articles

A D-band extracted pole waveguide bandpass filter based on TE202 and TE301 resonator

This paper presents a D-band waveguide bandpass filter (BPF) with high selectivity based on extracted pole technology. Unlike a single transmission zero (TZ) in the traditional design, the basic structure of the proposed extracted pole resonator is the novel TE202 and TE301 resonator, which provides two TZs. In which, each TZ position can be independently controlled by adjusting the dimensions of the resonant cavity. As an illustrative example, a pseudo-elliptic waveguide filter with two pairs of TZs generated on both sides of the passband using the extracted pole resonator and two dual-mode cavities. The filter is fabricated using high-precision computer numerical control (CNC) milling technology. The strong agreement between measured and simulated results validates the enhanced selectivity of the filter achieved by this novel extracted pole resonator.

Precision-milled simulated curved root canals in bovine dentine for the assessment of chemo-mechanical root canal preparation.

The aim was to develop a standardized curved root canal model in bovine dentine and to assess whether that natural substrate would behave differently from the resin in standard plastic training blocks when prepared chemo-mechanically. The impact of substrate microhardness on simulated canal transportation was considered. High-precision computer numerical control (CNC) milling was used to recreate a simulated root canal from a resin training block (Endo Training Bloc J-Shape, size 15) in longitudinally sectioned, dis- and re-assembled bovine incisor roots. Optical overlays obtained from 10 resin blocks were used to identify an average canal and program the CNC milling apparatus accordingly. Resin and dentine microhardness were measured. Simulated root canals in resin training blocks and their bovine counterparts were then instrumented at 37°C using Reciproc R25 instruments (VDW) with water or 17% EDTA (n = 10). Open-access image processing software was used to superimpose and analyse pre- and postoperative images obtained with a digital microscope. Centering ratios were averaged to indicate canal transportation. The effects of substrate and irrigant on canal transportation were assessed by two-way anova. Superimposed images showed that resin blocks under investigation varied considerably in terms of simulated canal length and curvature, whilst the milled canals were highly similar. The microhardness of dentine was more than three times higher than that of the resin. Conversely, canal transportation was considerably greater in dentine compared to resin, and in dentine had a tendency to be increased by EDTA. There was a strong effect of substrate on canal transportation (p < .001), no overall effect of irrigant, and a marginally significant interaction between irrigant and substrate (p = .077). CNC milling allows to create standardized simulated curved root canals in bovine dentine. These models may be useful to test and compare materials and concepts of chemo-mechanical root canal instrumentation. Microhardness is a bulk feature that does not predict the response to chemo-mechanical instrumentation of a composite material such as dentine.

A Feedrate Planning Method in CNC System Based on Servo Response Error Model

Reducing servo response error and further making reduction on contour error is crucial for high-precision computer numerical control (CNC) machine tools. For a permanent magnet synchronous motor (PMSM) servo system, there is always a response lag in feedrate tracking, which would introduce response error into the machining trajectory. Therefore, it is necessary to improve the performance of feedrate planning and interpolation for trajectory path. In this paper, a novel contour error compensation strategy is proposed. Compared with the mainstream methods, the proposed method offers a simplified alternative to existing contour error estimation techniques. Through a three-closed-loop control structure of a PMSM servo system, a response error model is founded. Afterwards, an improved S-model feedrate planning method is introduced according to the servo response error compensation. This predicted error is subsequently compensated in each interpolation cycle, resulting in a reduction of contour error. Finally, simulations and experiments are performed to demonstrate that the contour error can be reduced in both the ‘∞’-shaped Non-Uniform Rational B-Spline (NURBS) curve path and the butterfly-shaped NURBS curve path using the proposed method.

Improved TM Dual-Mode Filters With Reduced Fabrication Complexity

This work presents an alternate and improved approach for the design of dual-mode filters that utilize transverse magnetic (TM) and nonresonating modes. The method that is proposed in this work allows for an improvement of the typical TM dual-mode filter design through the reformation of the coupling irises that connect the TM dual-mode cavity to the source/load waveguide ports, where the new interconnection means takes the form of resonate slot-irises. In this manner, a fourth-order quasi-elliptic response can be achieved within a very limited physical geometry and able to cover more than double the usable fractional bandwidth than previously reported. Furthermore, the selectivity and insertion loss of the filter response is significantly improved when compared to the typical single-cavity TM dual-mode filter response that uses coupling irises, while on the comparison of equal-order structures, a reduction in fabrication complexity and improved insertion loss is achieved. A characterization of the dimensional variations and effects of altering one of the source/load port positions in the proposed filter design is investigated in order to demonstrate notable effects on the rejection characteristics and positions of transmission zeros. A presentation on the design theory is given and formulations of various filter responses are examined. The fabrication of an experimental prototype with approximately 7.3% fractional bandwidth (FBW), centered at 90 GHz is conducted using high-precision computer numerical control (CNC) milling in order to demonstrate that the unique simplicity and overall compaction of this method can be easily applied at millimetre-wave frequencies without the need of tuning means. The results which are presented demonstrate highly accurate measurements throughout the W-band range, while an additional Q-factor analysis is provided in order to compare the improved filter scheme with other known design methodologies.

A D-Band Manifold Triplexer With High Isolation Utilizing Novel Waveguide Dual-Mode Filters

This letter presents our design of a wideband manifold-coupled triplexer with high isolation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> -band. The basic structure of channel filters is the novel TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">120</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> dual-mode cavity, which provide two reflection zeros and one transmission zero. To achieve good computational efficiency and design accuracy, the space-mapping technique, consists of a coarse distribute model and a fine full-wave electromagnetic model, is adopted in the development of the triplexer. The proposed triplexer is fabricated by high-precision computer numerical control milling technology. The measured results are all in good agreement with the simulated ones. The measured lowest in-band insertion loss is 0.54/0.62/0.55 dB for three channels, respectively. The return loss of each channel is better than 14 dB and the isolation between each channel is better than 45 dB.

On-site calibration method of the AACMM based on a high-precision CNC machine tool

An articulated arm coordinate measuring machine (AACMM) is a kind of instrument used to test workpieces in the industrial field, and its measurement uncertainty depends on the on-site environmental factors to a certain extent. If there is a problem with the AACMM during on-site testing, it needs to be re-calibrated to ensure the measurement uncertainty. In this work, a fast on-site calibration method for the AACMM is proposed using a high-precision computer numerical control (CNC) machine tool. The AACMM is fixed on the machine tool table. The calibration artifact is clamped on the machine tool spindle. This calibration artifact can move to any point in the global space of the AACMM along with the operation of the spindle. Then, a virtual calibration artifact with calibration points is achieved using the CNC machine tool. The positions of these points are calculated using the improved Hammersley sequence. The calibration method using a high-precision CNC machine tool is experimentally verified through the single-point articulation performance test of ASME B89.4.22-2004 and the length measurement test of ISO 10360-12. The calibration method proposed in this work only uses an on-site high-precision CNC machine tool, one of the most common machines in many industrial fields, as the calibration instrument for the AACMM calibration. No extra equipment is required, which is convenient and beneficial to calibrate the AACMM. In addition, the CNC machine tool can construct different kinds of virtual structures for the AACMM calibration, such as virtual rods, virtual circles, virtual balls and even non-uniform 3D artifacts with complex curved surfaces. This may give rise to many novel calibration methods and further improve the calibration accuracy.

Thermal error modeling and compensation based on Gaussian process regression for CNC machine tools

Thermal errors are one of the main factors affecting the accuracy of high-precision computer numerical control machine tools. Modeling and compensation are the most common approaches for reducing the influence of thermal error on machine tool accuracy. Accuracy and robustness are the key indicators of machine tool thermal error prediction models, especially under different working conditions. Existing thermal error modeling algorithms provide only point predictions of the thermal error; however, interval predictions of the thermal error are important for understanding the stochastic nature of the thermal error prediction and analysis of reliable risk. To address these challenges, this study proposes a novel thermal error modeling method based on Gaussian process regression (GPR) that provides interval predictions of thermal error and achieves high prediction accuracy and robustness. First, multiple batches of experimental data are used to establish the GPR thermal error model to ensure sufficient modeling information. Second, while existing methods select temperature-sensitive points (TSPs) before modeling, the GPR algorithm can adaptively select TSPs during training of the thermal error GPR prediction model. Third, the proposed model provides interval predictions of thermal errors for evaluating the thermal error prediction reliability. The prediction effects of the GPR model are compared with those of existing thermal error models. The experimental results indicate that the proposed model has the highest prediction accuracy and robustness under different working conditions of the tested compensation models. Furthermore, thermal error compensation experiments are conducted to verify the effectiveness of the proposed model.

A 200–225-GHz Manifold-Coupled Multiplexer Utilizing Metal Waveguides

This article presents a 220-GHz four-channel, noncontiguous, and manifold-coupled waveguide multiplexer for future terahertz (THz) multichannel communication application. The multiplexer is composed of four Chebyshev bandpass filters based on metal waveguide technology. Through a unique design in which the tuning dimensional variables are reduced to 14 and a co-design of low-order electromagnetic (EM) distributed models and full-wave EM models, the design optimization is achieved with a good computational efficiency and design accuracy. The proposed multiplexer is fabricated by high-precision computer numerical control (CNC) milling technology, in which the fabrication errors are evaluated to be within <inline-formula> <tex-math notation="LaTeX">$\pm 3~\mu \text{m}$ </tex-math></inline-formula>. The measured results exhibit 1.7 dB of in-band insertion loss and better than 15 dB of average common-port return loss for each of the channel filter. The measured results are all in good agreement with the simulated ones, thereby validating the complete design procedure.

3-D-Printing and High-Precision Milling of W-Band Filter Components With Admittance Inverter Sequences

This work presents the design of an additively manufactured W-band bandpass filter and a subtractively manufactured W-band diplexer to demonstrate the use of admittance inverter sequences for the ease of manufacture at millimeter-wave frequencies. Contrary to typical impedance inverters (E-plane and H-plane irises), the use of admittance inverters (E-plane and H-plane stubs) allows for larger dimensions to be specified and ultimately does not impede the general waveguide path. The proposed bandpass filter is designed with all E-plane stubs, while the diplexer is designed with one branch using both E-plane and H-plane stubs as an arbitrary sequence, and the second branch using all H-plane irises. The additively manufactured bandpass filter is fabricated using the most elementary-level stereolithography (SLA)-based methods, demonstrating that a hobbyist-type SLA printer and metallization method can procure exceptional results for millimeter-wave filter designs. The subtractively manufactured diplexer is fabricated using high-precision computer numerical control (CNC) milling to highlight the use of arbitrary inverter sequences in a more complex and robust design profile, while the dispersive transmission zeros that are caused by over-moding of the inverter stubs are used to demonstrate unique isolation characteristics in the upper W-band region. The design concepts, fabrication profiles, simulations, and measurements which are presented in this work highlight a viable option for overcoming miniaturized dimensions in millimeter and submillimeter-wave applications.

W‐band TE102‐mode filter with doubly loaded E‐plane and H‐plane irises

In this correspondence, high-precision computer numerical control milling is utilised to demonstrate a doubly loaded iris, cross-coupled waveguide bandpass filter for inline operation within the W-band. This sixth-order filter is designed in a stacked H-plane configuration and utilises both E-plane and H-plane doubly loaded irises to maintain the flow of a TE102-mode electromagnetic field. In this configuration, a high rejection level is maintained outside of the passband while a good unloaded quality factor is obtained through the support of larger resonator dimensions. The filter is designed for approximately 2% fractional bandwidth centred at 97.5 GHz and has been fabricated as three brass components. Measurements of the filter agree very well with the simulated results and demonstrate a spurious-free design over the full W-band.

A review on vibration analysis and control of machine tool feed drive systems

With the development of the modern manufacturing industry, especially that of high-speed and high-precision machining, higher performances of computer numerical control (CNC) machine tools are necessary than ever. For high-precision CNC machine tools, vibration in high-speed machining is an important factor to affect the machining accuracy. As a significant part of CNC machine tools, the dynamic characteristics of the feed drive system have a great impact on the machining performance. Ball screw drive systems are widely applied in the majority of CNC machine tools for the time being. In the process of high-speed machining, the vibration of the ball-screw drive system will affect the stability of the control system and the machining accuracy of CNC machine tools. Thus, further investigation of dynamic characteristics and vibration control methods of the ball-screw drive system will be of great importance to improve the machining performance. A comprehensive review is carried out here to research statuses of vibration analysis and control methods for feed drive systems. Related studies on system modeling, parameter identification, and vibration control technologies are classified and summarized. The advantages and disadvantages of different methods are discussed and compared. Moreover, the linear parameter-varying (LPV) modeling method of ball-screw drive systems and corresponding control technologies are introduced in detail. Finally, related research prospects are systematically presented based on the existing studies, and these research directions which are rarely studied will be of great significance to develop vibration control technologies for CNC machine tool feed drive systems.

Research on the Error Averaging Effect in A Rolling Guide Pair

By studying the effects of geometric precision on kinematic accuracy, an error mapping model has been established, based on the hypothesis that a motion pair and its installation surface are rigid. However, when using this assumption, there is a significant error induced in high-precision computer numerical control (CNC) machine tools as compared with reality. One of the most important reasons for this error is failing to consider the error averaging effect of motion pair elements. Therefore, this work examines a high-precision horizontal machining center as its research object, and analyzes the error averaging mechanism of a rolling guide pair under a deformation of the rolling elements. The carriage bearing forces caused by guideway straightness errors are obtained by constructing a geometric error model of a single carriage. The relationship between guideway straightness errors and carriage bearing forces is described by a transfer function in the spatial frequency domain, and its characteristics are analyzed. It quantifies the so-called error averaging effect of the rolling guide system and, on this basis, a static model for four carriages is established to reflect the error averaging effect of the rolling guide pair on the position and orientation errors of the motion pair. In addition, it is found that the wavelengths and phase differences of guideway errors affect this error averaging mechanism, but the amplitude and preload have little influence thereon. The experiment result shows that the kinematic straightness errors in the x- and y-directions were approximately 1/3 to 1/2 of the guideway straightness errors in the corresponding directions. The results can be used to guide the precision design and assembly of machine tools.

WM380 (675–700 GHz) Bandpass Filters in Milled, Split-Block Construction

Filters play an invaluable role in RF analysis and communications hardware, blocking unwanted signals, limiting bandwidth, attenuating harmonic components, etc. In waveguide construction for mm-wave frequencies, where the powers are generally low, the iris-coupled-resonator bandpass filter has proven to be very practical and amenable to easy machining. At Virginia Diodes, much of our technology has been constructed using standard “split-block” techniques, in which high-precision computer numerical control milling machines are used to mill out the features from solid blocks of metal. Typical machining tolerances are on the order of +/−5–10 μ m. Construction of such filters to ∼200 GHz has been routine but pushing the operation into the Terahertz regime requires special considerations. Described here is a WM380 (WR1.5) filter for the 500–750 GHz waveguide band having a passband of 675–700 GHz. The filter is proof of concept for a 640 GHz heterodyne polarimeter, designed as a part of a Small Business Innovative Research (SBIR) Grant to develop technology for NASA's planned Aerosol, Cloud, and Ecosystems mission. From the very beginning, filter design and optimizations were carried out assuming the structure would be milled, hence necessitating that all internal features accommodate the finite radii of available machine tools. Construction of this filter required careful attention to machining tolerances to be able to push the milling machines to their absolute limits of +/−2.5 μ m or better. Measured results of a batch of filters are shown and compared to simulations to illustrate just how well these filters can be made. Furthermore, the filters can be tuned by simple mechanical means and data are presented to illustrate how easily the filters can be adjusted. Additional modifications to the filter topology to simplify machining, and allow other construction techniques to be utilized are also demonstrated. Ultimately it should be possible to push the split block technology to manufacture iris coupled resonator filters for use at frequencies of well over 1 THz.

Sensorless balance method for the spindle system of computer numerical control gear grinding machine

Background: Spindle imbalance vibration of the computer numerical control grinding machine may result in dramatic effects on tool wear, surface finish, and form-holding of the products, which makes the balancing procedure very essential during their manufacturing process. Although the spindle residual vibration in a single direction can be suppressed effectively by the commonly used commercial balance systems, some real-world application results show that most of these balance systems cannot reduce the spindle residual vibration in horizontal, vertical, and axial direction simultaneously. Methods: To overcome this issue, the limitation of commonly used influence coefficient method–based spindle balance method is discussed first. After that, a novel balance method is experimentally proposed for the spindle vibration control using the position fluctuation information between the carriage and guideway of the servo-axis. In this method, the position fluctuation information between the carriage and guideway and the key phase information are practically measured using the built-in linear scale and spindle servomotor encoder, respectively, in which the position fluctuation information between the carriage and guideway can be considered as an integrated representation of the spindle imbalance vibration. Combined with the influence coefficient method, the imbalance vibration presenting in the horizontal, vertical, and axial direction of the spindle can be suppressed simultaneously and effectively. Results and Conclusions: A field balancing experiment is carried out on a high-precision computer numerical control gear grinding machine. Experiment results demonstrate that, compared with the commonly used commercial balancing system, the proposed method can not only reduce the residual vibration amplitude at the objective balancing speed effectively but also reduce the residual vibration amplitude more than 50% simultaneously in each direction during the whole run-down process.

Kinematic error modeling and error compensation of desktop 3D printer

Desktop 3D printers have revolutionized how designers and makers prototype and manufacture certain products. Highly popular fuse deposition modeling (FDM) desktop printers have enabled a shift to low-cost consumer goods markets, through reduced capital equipment investment and consumable material costs. However, with this drive to reduce costs, the computer numerical control (CNC) systems implemented in FDM printers are often compromised by poor accuracy and contouring errors. This condition is most critical as users begin to use 3D-printed components in load-bearing applications or to perform mechanical functions. Improved methods of low-cost 3D printer calibration are needed before their open-design potential can be realized in applications, including 3D-printed orthotics and prosthetics. This paper applies methodologies associated with high-precision CNC machining systems, namely, kinematic error modeling and compensation coupled with standardized test methods from ISO230-4, such as the ballbar for kinematic and dynamic error measurements, to examine the influence and feasibility for use on low-cost CNC/3D printing platforms. Recently, the U.S. Food and Drug Administration’s “Technical considerations for additive manufactured medical devices” highlighted the need to develop standards specific to additive manufacturing in regulated manufacturing environments. This paper shows the benefits of the methods described within ISO230-4 for error assessment, alongside applying kinematic error modeling and compensation to the popular kinematic configuration of an Ultimaker 3D printer. A Renishaw ballbar QC10 is used to quantify the Ultimaker’s errors and thereby populate the error model. This method quantifies machine errors and populates these in a mathematical model of the CNC system. Then, a post-processor can be used to compensate the printing code. Subsequently, the ballbar is used to demonstrate the dramatic impact of the error compensation model on the accuracy and contouring of the Ultimaker printer with 58% reduction in overall circularity error and 90% reduction in squareness error.

Research on High-Precision Form Grinding Technology of Gear Based on Ambient Temperature Adaptability

The thermal error of high-precision computer numerical control (CNC) form grinding machine has become the critical factor affecting its locating precision. Because the thermal error is more complicated to be measured directly, most of the measurement tests are usually aimed at no-load conditions. In this article, a method to evaluate the machine tool thermal error based on the principle of tooth profile error through the gear grinding precision is presented. Based on high-precision CNC form grinding machine need to maintain isoperibol, this paper proposed the ambient temperature as a variable, for different ambient temperature to measure the thermal error of the machine tool. According to the measurement results of the thermal error, the method of partial least squares neural network is used to structure the thermal error prediction model of the machine tool. The experimental data show that the grade of the gear precision can reach four levels at different temperatures. This approach shows a promising prospect in the application of high-precision CNC gear form grinding machine in the future.

Experimental Demonstration of a 0.34-THz Backward-Wave Oscillator With a Sinusoidally Corrugated Slow-Wave Structure

The design and experimental demonstration of a 0.34-THz backward-wave oscillator (BWO) with a sinusoidally corrugated circular waveguide is presented. The dimensions of the sinusoidally corrugated structure are at the submillimeter scale. Particle-in-cell simulations have predicted that this miniature slow-wave structure (SWS) should be capable of 0.34-THz radiation. The miniature SWS was successfully fabricated using high precision computer numerical control machining and electric discharge machining. In experimental tests, the resulting BWO produced pulse radiation with a peak RF power of ~600 kW and a pulsewidth of 1.66 ns when driven by a 100-kV, 900-A weakly relativistic electron beam. The measured frequency was in the range of 0.32–0.36 THz and the device achieved stable operation at a pulse repetition rate of 10 Hz. We describe the experimental measurement methods of pulsewidth, frequency, and power for the high-power nanosecond terahertz signal. The work is a proof-of-principle demonstration of BWO frequency extension to above 300 GHz through structure miniaturization and precision machining.

Evaluating the accuracy of three-dimensional reconstruction of the intercuspal position for dentition casts aided by a mechanical appliance

To develop a aided mechanical appliance for rapid reconstruction of three-dimensional(3D)relationship of dentition model after scanning and evaluation of its accuracy. The appliance was designed by forward engineering software and fabricated by a high precision computer numerical control(CNC)system. It contained upper and lower body, magnetic pedestal and three pillars. Nine 3 mm diameter hemispheres were distributed equally on the axial surface of each pedestal. Faro Edge 1.8m was used to directly obtain center of each hemisphere(contact method), defined as known center. A pair of die-stone standard dentition model were fixed in intercuspal position and then fixed on the magnetic pedestals with low expansion ratio plaster. Activity 880 dental scanner was used to scan casts after the plaster was completely set. In Geomagic 2012, the centers of each hemisphere were fitted and defined as scanning centers. Scanning centers were aligned to known centers by reference point system to finish the 3D reconstruction of the intercuspal occlusion for the dentition casts. An observation coordinate system was interactively established. The straight-line distances in the X(coronal), Y(saggital), and Z(vertical)between the remaining 6 pairs of center points derived from contact method and fitting method were measured respectively and analyzed using a paired t-test. The differences of the straight-line distances of the remaining 6 pairs of center points between the two methods were X:(-0.05±0.10)mm, Y:(0.02±0.06)mm, and Z:(0.01 ± 0.05)mm. The results of paired t-test showed no significant differences(P>0.05). The mechanical appliance can help to reconstruct 3D jaw relation by scanning single upper and lower dentition model with usual commercial available dental cast scanning system.

Temperature Field Analysis and Thermal Error Testing for CNC Machine Tool's Headstock

The dynamic and thermal characteristics of spindle assembly will affect the final machining performance of a machine tool seriously. It is of great significance to study the dynamic and thermal characteristics of the spindle assembly for improving the level of machine tool's design and manufacturing. The paper takes a high precision computer numerical control lathe as the research object. First the thermal characteristics were obtained by using finite element method. Then the laser triangle measuring instrument and the infrared thermal imager were used to measure the temperature field and thermal deformation of the spindle assembly. Finally in order to get the thermal equilibrium time and the thermal deformation data of spindle system, the wavelet toolbox was used to deal with thermal testing data. The paper's work laid a foundation for the further research on the thermal characteristics analysis and thermal error's compensation of machine tools.

Realization of a 5-axis NURBS Interpolation with Controlled Angular Velocity

5-axis machine tool plays an important role in high-speed and high-precision computer numerical control (CNC) machining of workpieces with complex shapes. A non-uniform rational B-spline (NURBS) interpolation format for 5-axis machining is proposed to adapt to the high speed machining (HSM). With this interpolation format, angles between orientation vectors are chosen as parameters of orientation B-spline constructed by an open controller to achieve reasonable orientation vectors in real-time interpolation process. Coordinated motion between linear axes and rotary axes is achieved by building a polynomial spline which relates interpolation arc lengths of position spline to angles of orientation spline. Algorithm routine of this interpolation format and its realization methods in the supported controller are discussed in detail. Finally, performance of the proposed NURBS interpolation format is demonstrated by a practical example.