Modern Computer Numerical Control Research Articles

Адаптация системы ЧПУ станка к условиям комбинированной обработки

Introduction. Increasing the efficiency of processing technologies for products made from modern high-strength, difficult-to-process materials with increased physical, mechanical and operational properties consists not only in improving the technology itself, the tools for its implementation, but also in modernizing technological equipment taking into account new achievements in the field of mechanical engineering. Modern computer numerical control (CNC) equipment is now quite advanced in terms of controlling basic cutting movements. Adaptive monitoring and control systems, as a rule, additionally installed on processing equipment, make it possible to further improve the quality of processing parameters. With the development of new hybrid and combined technologies that combine several types of influence on the product being processed, the issue of synchronizing the automatic control of the movements of parts of technological equipment with the control and management of accompanying processes of combined technologies has become acute. One example of such technologies is electrochemical diamond grinding with periodic dressing of the working surface of a diamond wheel using reverse polarity current. The polarity of the current and the duration of its pulses are controlled by special programmable devices. Current switching units are connected to it. It serves to supply alternating currents of direct and reverse polarity to the electrical circuit and is made on the basis of key elements. Installing such programmable devices on CNC machines leads to its’ equipping with an additional autonomous automatic control system. At the same time, it is difficult to coordinate the operation of the machine’s CNC system, which controls the movements of its working parts, and the programmable device used to control the polarity and duration of current pulses during combined processing. The purpose of the work is to synchronize the CNC system of the machine with the control system for the process of periodically changing the polarity of the current. The study was carried out on an experimental stand. Methods. The research methodology involved conducting an experiment consisting of synchronizing the operation of the machine’s CNC system with the operation of the control system for the process of periodically changing the polarity of the current. To evaluate the results, the time of movement of the diamond wheel as a result of the working stroke was compared with the duration of current pulses of different polarities specified in the control program of the developed software. Results and discussions. As a result of the research, it is established that the developed software and hardware complex makes it possible to synchronize in the CNC system of the machine tool the control of the movements of the working parts with automatic control of the periodic change of current polarity during electrochemical diamond grinding, which can significantly expand the technical capabilities of CNC machines.

Metrological characterisation of tool pre-setting optical systems based on 2D imaging

Accurate tool geometry is vital in modern computer numerical control machine tools for ensuring the accuracy of the manufactured parts in machining processes. The tool pre-setting optical systems play an important role by establishing accurate, efficient, and repeatable tool data for cutting tools varying from macro to micro size tools. The tool data is later utilised by the numerical control programs to accomplish precision machining operations with the required accuracy. However, the traceability of tool pre-setting optical systems is not guaranteed due to the lack of specific international standards, and there is a strong need of establishing a traceable measurement process which requires calibrated reference artefacts. In this work, we have established the metrological characteristics of an image-based tool pre-setting optical system based on ISO 15530 part 3. For this purpose, an artefact with sharp cutting edges was manufactured from a calibrated cylindrical gauge pin, measured on a coordinate measuring machine by two different approaches, and the impact of the edge radius is incorporated in the measurement process. The artefact was later employed in the performance verification of the optical system for on-machine tool characterization analogous to the production workshop environment, and the measured outcome of the optical sensor was evaluated with the developed metrological approaches. Experiments have shown the applicability of the measurement procedures and the relevance of the proposed reference artefact for the characterisation of image-based tool pre-setting optical systems.

Online tool wear monitoring by super-resolution based machine vision

The tool condition has been a major concern in modern computer numerical control (CNC) machining due to its direct effects on the quality of final product both in the surface and dimensional integrity. The conventional machine vision-based tool condition monitoring (TCM) approaches cannot meet the high precision requirement in micro machining, as the cutting parameters are in micro scale and the spindle works in high rotation speed which makes online tool wear measurement quite difficult. To meet these challenges, this study develops a single image super-resolution (SISR) approach for direct tool wear estimation in micro-milling. Motivated by the self-similarity of tool wear image morphology, this study proposes a sparse decomposition framework by learning dictionaries from the tool wear image pyramid. Based on their multi-scale invariant properties, the similar image patches of coarse scales can be retrieved from fine scales to reconstruct the high-resolution image fastly and in high quality. The reconstructed high-resolution image then can be conveniently applied to wear monitoring, and overcomes the image acquisition deficiencies of the conventional machine vision-based monitoring approaches. Experimental results validate this approach for the tool wear area estimation as well as its generalization of the wear width with regarding to the conventional manual measurements.

Optimization and execution of multiple holes-drilling operations based on STEP-NC

Modern computer numerical control (CNC) is intended to be more flexible, interoperable, adaptable, open, and intelligent. An open CNC control system was developed by added optimization feature in order to create high flexibility, affordable, and fast for STEP-NC drilling applications. Optimization of tool path operation can lead to a significant reduction in non-productive machining time. The newly developed system combines between open CNC control system and ant colony optimization (ACO) algorithm by using LabVIEW software. A developed system is based on STEP-NC interpretation, optimization, 3D simulation, and automatic document generation modules that have been used to verify and validate the system in extract and optimize STEP-NC drilling codes. The percentage of tool path improvement was 16.96%. This experimental study will fulfill the design of an open architecture CNC control system, optimize the CNC movement, and simulate and generate a document of the result.

A Silicon Chip-Based Waveguide Directional Coupler for Terahertz Applications

We propose a waveguide directional coupler design with weak coupling using silicon-based suspended coupling microstrip probes and the split-block type of construction common in integrated millimeter wave components. WR4.0 coupler prototypes with standard UG-387 flanges were fabricated and measured. The simulation and measurement results show that this design achieves a coupling of around -18dB, with atypical ±2-dB variation across the band from 210 to 270 GHz, while the isolation is better than 30 dB. Tolerance studies confirm that this design could be scaled up to terahertz frequency with modern computer numerical control (CNC) machining and silicon chip fabrication technology.

A Compact Machinable 90° Waveguide Twist for Broadband Applications

We present a novel machinable 90° waveguide twist design suitable for broadband applications from microwave to terahertz frequency. The design achieves compactness and ease of fabrication by utilizing a series of quarter-wave transformer steps machined in split blocks. Three WR3.4 (220-330 GHz) prototypes with standard UG-387 flanges were fabricated and measured. The prototypes outperform two commercial waveguide twists in both return loss and insertion loss. The simulation and measurement results show that this design achieves a performance of -25 dB return loss for full waveguide bandwidth. Tolerance studies confirm that this design could be scaled up to terahertz frequency with modern computer numerical control (CNC) fabrication technology. In integrated waveguide systems, the waveguide twist design presented in this article can reduce losses at millimeter wave frequencies and achieve valuable weight savings in aerospace and other applications.

An affordable and miniature ice coring drill for rapid acquisition of small iceberg samples.

Icebergs account for approximately half of the freshwater flux from the Greenland Ice Sheet and they can impact marine ecosystems by releasing nutrients and sediments into the ocean as they drift and melt. Parameterizing iceberg fluxes of nutrients and sediments to fjord and ocean waters remains a difficult task due to the complexity of ice-ocean interactions and is complicated by a lack of observations. Acquiring iceberg samples can be difficult and dangerous, as icebergs can break apart and roll without warning. Here we present open source design files for a small, lightweight ice coring drill that can be reproduced using modern computer numerical control (CNC) machining and 3D printing technology. This ice core drill can rapidly acquire small ice samples from icebergs and bergy bits using a standard commercial, off-the-shelf battery-operated hand drill. Design files and a recent field expedition to Northwest Greenland are described. Ice core collection required only 30s, thereby minimizing risks to scientists.

Electrical discharge machining of ceramic nanocomposites: sublimation phenomena and adaptive control

The productivity of electrical discharge machining (EDM) is relatively low owing to the natural laws of electrical erosion. Precise EDM demands uninterrupted control of the discharge gap and adjustment of process parameters. It is particularly critical for processing large workpieces with complex linear surfaces and for materials with threshold conductivities such as the new advanced ceramic nanocomposites Al2O3+TiC and Al2O3+SiCw+TiC(30–40%). In these cases, adequate flushing of erosion products is hampered by the geometry of the working space or by the small value of the required discharge gap, which does not exceed 2.2–2.5 μm. The methods of adaptive control in modern computer numerical control systems of EDM equipment based on measuring the electrical parameters in the working zone have been shown to be ineffective in the cases described above. This study aims to investigate the natural phenomena of material sublimation under discharge pulses for conductive ceramics and nanocomposites. The measured conductivities of the samples are higher than the percolation threshold. However, the question of machinability remains open owing to detected processing interruptions and poor quality of machined surfaces. New knowledge on EDM of conductive ceramics and nanocomposites can improve the final quality of the machined surfaces and productivity of the method by the introduction of advanced monitoring and control methods based on acoustic emissions. The manuscript presents an up-to-date overview and current state of the research on the subject area. The obtained morphology of the samples and discussion of the findings complete the experimental part of the study. The scientific basis for a new type of adaptive control system is provided. This can improve the effectiveness of parameter control for machining conductive ceramics and nanocomposites and contribute to an increase in the EDM performance for the most critical cases.

Determination of Waste Industrial Dust Safety Characteristics

This article deals with the assessment of the hazards of dust waste generated by modern CNC (computer numerical control) technologies from the processing of resin-containing plastic composites. The change of the original material into dusty waste predicts the emergence of new hazardous characteristics such as flammability, explosiveness and adverse effects on employee health. The aim of this article is to determine the experimental measurement of dust particle size, its thermal degradation and safety characteristics. Sieve analysis showed that the representative sample contained a 93.8% weight of particles with a size of less than 0.4 mm. Three degrees of thermal degradation of industrial dust samples and heat production (exo reaction ∑ΔH = 9172.9 J/g) were determined by TG (thermogravimetry), DTA (differential thermal analysis) and DSC (differential scanning calorimetr) methods. The measurement safety characteristics such as the lower explosion limit, the maximum explosion pressure, the maximum pressure rise rate, and the calculated cubic constant confirmed that the dust is an explosive, and is determined as explosion class St1 (determined by Cubic constant).

Reducing the Risks during the Purchase of Five-Axis CNC Machining Centers Using AHP Method and Fuzzy Systems

Nowadays, companies are in the process of renewing their manufacturing lines by equipping them with modern five-axis CNC (computer numerical control) machining centers. The decision to select between different five-axis CNC machining centers, with similar technological capabilities is a difficult process, so the main goal of this work was to develop a method for assisting it. The proposed approach relies on seven technical criteria, four quantitative ones (traverse speed, thrust, spindle power, and spindle speed) which can be expressed by crisp numerical values, while the other three (flexibility, operation easiness, and setup time) are qualitative ones. The analytic hierarchy process (AHP) was used for ordering four variants of five-axis CNC milling machining centers. The qualitative criteria were processed using fuzzy systems to be expressed by crisp numerical values, suitable for AHP. Finally, the four variants of five-axis CNC milling machining centers were hierarchized and the best one was chosen. A sensitivity analysis was also unfolded to certify the robustness of the AHP.

On the new Algorithm for Solving Continuous Cutting Problem

The problem of tool path optimization for CNC (Computer Numerical Control) thermal cutting machines as well as its classification are considered. A new approach to solving Continuous Cutting Problem is proposed based on local optimization using Fermat principle and Variable Neighborhood Search approach, which automatically takes Precedence Constraint into account, that is crucial for generating correct CNC programs due to technological features of modern CNC cutting equipment.

A universal velocity limit curve generator considering abnormal tool path geometry for CNC machine tools

Non-linear parametric curves, such as B-spline curves, are becoming increasingly available in modern CNC (Computer Numerical Control) systems. The smoothness of parametric curves offers higher order of continuity and thus invokes less vibration in machines as compared to short line segments. Nevertheless, the computations for velocity limit curves, velocity profiles and interpolation points are quite complicated and time-consuming and therefore approximation methods are applied. Unnecessary accelerations and decelerations, which cost additional time of motion, can be caused by inaccurate computations of the velocity limits around tiny corners. To overcome the problem, the unit arc length increment scanning method (UALISM) is proposed to reduce the time of movement and to improve the efficiency. The scanning interval is fixed at 1 BLU (basic length unit) which is irrelevant to the type, size and shape of the tool path curve. The constraints of chord height errors and axis accelerations are considered and the velocity limit for the specified scanning point is computed using the coordinates of multiple scanning points near the specified scanning point. Simulation results show that the unnecessary accelerations and decelerations can be avoided and thus the total motion time can be reduced by UALISM.

Development of a feature-based open soft-CNC system

Modern computer numerical control (CNC) is intended to be more flexible, interoperable, adoptable, open, and intelligent. In realisation of such a CNC system, an ISO standard known as STEP for numeric control (STEP-NC) or ISO 14649 was developed in 2004 to alleviate a number of challenges associated with the widely used CNC standard (ISO 6983). Implementation of STEP-NC was initially carried out on some commercial CNC systems via an indirect STEP-NC programming approach. However, this approach failed to meet all the requirements of a modern CNC system, due to the translation of data from the high level to low level, which is vendor-specific and machine tool dependent, thus detrimental to the basic resource independent philosophy of STEP-NC. This paper presents a new generation of CNC systems, based on the Open Architecture Control (OAC) technology supported by STEP-NC data model to fundamentally solve these challenges. The developed system employs a new set of techniques for STEP-NC data interpretation, graphical verification, execution, monitoring, and report generation that supersede the exiting techniques in scope and capability. Using these techniques, the proposed system provides a flexible, intelligent, and adaptable manufacturing platform that can provide unprecedented levels of scalability and resource allocation agility in modern manufacturing enterprises. A prototype implementation of the proposed model is based on STEP-NC interpretation, 3D simulation, machine motion control, and live video monitoring with automatic document generation modules has been used to verify and validate the system in conjunction with industrially inspired test components.

Real time parameter based contour error estimation algorithms for free form contour following

The contour following task of a multi-axis servo system is one of the most important applications of modern Computer Numerical Control (CNC) machine tools, and is widely seen in many types of CNC machining. Hence, the reduction of contour error occurring in the contour following process is paramount and deserves more comprehensive investigation. In general, the calculation of precise contour error in real time is very challenging if not impossible, in free-form curve following tasks. To deal with such a problem, this paper proposes six real-time contour error estimation methods for free-form parametric curves. The feasibility of these methods is verified with several NURBS parametric curve contour following experiments. In addition, experimental results reveal that the proposed methods can provide more accurate contour error estimation for various free-form curves than the other estimation algorithms tested in the experiments. With the proposed contour error estimation approach, advanced motion control schemes can be designed to efficiently reduce contour errors of contour following tasks.

The community FabLab platform: applications and implications in biomedical engineering.

Skill development in science, technology, engineering and math (STEM) education present one of the most formidable challenges of modern society. The Community FabLab platform presents a viable solution. Each FabLab contains a suite of modern computer numerical control (CNC) equipment, electronics and computing hardware and design, programming, computer aided design (CAD) and computer aided machining (CAM) software. FabLabs are community and educational resources and open to the public. Development of STEM based workforce skills such as digital fabrication and advanced manufacturing can be enhanced using this platform. Particularly notable is the potential of the FabLab platform in STEM education. The active learning environment engages and supports a diversity of learners, while the iterative learning that is supported by the FabLab rapid prototyping platform facilitates depth of understanding, creativity, innovation and mastery. The product and project based learning that occurs in FabLabs develops in the student a personal sense of accomplishment, self-awareness, command of the material and technology. This helps build the interest and confidence necessary to excel in STEM and throughout life. Finally the introduction and use of relevant technologies at every stage of the education process ensures technical familiarity and a broad knowledge base needed for work in STEM based fields. Biomedical engineering education strives to cultivate broad technical adeptness, creativity, interdisciplinary thought, and an ability to form deep conceptual understanding of complex systems. The FabLab platform is well designed to enhance biomedical engineering education.

Dynamic Parameters Identification for the Feeding System of Commercial Numerical Control Machine

The precision of high-speed CNC (Computer Numerical Control) machine are greatly influenced by the dy- namic characteristics of servo system. To establish the servo system model accurately, the internal signals of NC, e.g. mo- tor current and rotate speed were adopt as the input or output signal for the system. The ARMA linear identification model was also established to identify the dynamic parameters of the mechanical parts in the servo system, including equivalent inertia, equivalent damping and so on. The friction Stribeck curve was obtained by necessary experiments. The nonlinear friction model was linearized by using higher-order Taylor expansion, and the five parameters of the Stribeck friction model were identified. To verify the effectiveness of the closed-loop identification, experiments are carried out on the feeding system of a commercial NC machine. Signals of servo motor current and rotating rate which are offered in many modern CNC machine tools are needed for the identification and experiments results show that the proposed method per- forms well with rapid convergence and accurate results and parameters of Stribeck model can be obtained accurately by identification. The method is suited for industrial condition and has its practicality.

Active vibration control for a CNC milling machine

There is a requirement for improved three-dimensional surface characterisation and reduced tool wear when modern computer numerical control (CNC) machine tools are operating at high cutting velocities, spindle speeds and feed rates. For large depths of cut and large material removal rates, there is a tendency for machines to chatter caused by self-excited vibration in the machine tools leading to precision errors, poor surface finish quality, tool wear and possible machine damage. This study illustrates a method for improving machine tool performance by understanding and adaptively controlling the machine structural vibration. The first step taken is to measure and interpret machine tool vibration and produce a structural model. As a consequence, appropriate sensors need to be selected and/or designed and then integrated to measure all self-excited vibrations. The vibrations of the machine under investigation need to be clearly understood by analysis of sensor signals and surface finish measurement. The active vibration control system has been implemented on a CNC machine tool and validated under controlled conditions by compensating for machine tool vibrations on time-varying multi-point cutting operations for a vertical milling machine. The design of the adaptive control system using modelling, filtering, active vibration platform and sensor feedback techniques has been demonstrated to be successful.

Manufacture of face-hobbed straight bevel gears using a six-axis CNC bevel gear cutting machine

Face hobbing is a continuous indexing and double-flank cutting process whose high productivity and precision has made it one of the leading methods for fabricating spiral bevel and hypoid gears. The current method is inappropriate, however, for cutting straight bevel gears (SBGs) because it generates extended epicycloidal flanks. Nonetheless, a mathematical model of a face-hobbed SBG was successfully established in earlier research that enables straight cutting paths to cut straight tooth spaces based on a hypocycloidal straight-line mechanism in which the rolling circle radius equals half the base circle radius. This mathematical model, however, is based on a virtual universal cradle-type bevel gear cutting machine that has not yet been developed. This paper therefore proposes another mathematical model of face-hobbed SBG based on a modern six-axis computer numerical control (CNC) bevel gear cutting machine. The six-axis nonlinear machine settings are derived through conversion from the cradle-type machine settings. Meanwhile, the usage of electric gearbox (EGB) for bevel gear cutting is not revealed because of commercial consideration. Therefore, we also provide a solution to use EGB of Fanuc 16i CNC controller. A cutting experiment validates the proposed mathematical models using our developed six-axis CNC bevel gear cutting machine to cut the face-hobbed SBGs. Finally, a flank topographic correction is made that, according to postcorrection simulated topographic errors, can effectively reduce manufacturing errors. This paper successfully implements a face-hobbing process for manufacturing SBGs on a modern six-axis CNC bevel gear cutting machine.

Research on Non-Linear Parameters Identification for Servo System of CNC Machine Tools

As phenomena of friction in computer numerical control(CNC) machine tools is inevitable, accurately modeling of friction is need for precise position control and performance evaluation of CNC machine tools. This paper proposed an identification method that non-linear friction model described as Stribeck are linearized by using high order Taylor series expansion and parameters of the model are obtained by least square method (LSM). Signals of servo motor current and rotating rate which are offered in many modern CNC machine tools are needed for the identification and experiments results show that parameters of Stribeck model can be obtained accurately by identification. The method is suited for industrial condition and has its practicality.

Real-time NURBS curve interpolator based on section

Parameter interpolation is more capable of modern computer numerical control (CNC) than traditional linear/circular interpolation with higher speed and higher precision. Most of non-uniform rational B-spline (NURBS) interpolation algorithms were developed based on the chord error and machines capability, where interpolation points are calculated beforehand to overcome acceleration/deceleration (acc/dec) and jerk problem, which needs large memory. In this paper, a NURBS interpolator based on feedrate section is proposed. Instead of a single interpolation point, this interpolator aims to feedrate section, which makes it possible to run on a digital signal processor or field programmable gate array (FPGA) whose memory is limited. Experiment on FPGA showed the performance of interpolation. A mould experiment verifies the feasibility of application.