CNC Grinding Research Articles

Thermal environment optimization and process product design of CNC grinding machine based on improved neural network

In the machining process of CNC grinding machine, the non-uniformity of heat source often leads to the deformation of the workpiece, the intensification of wear and the machining error, so the optimization of thermal energy environment has become an important research direction to improve the machining performance. The aim of this study is to optimize the thermal energy environment of CNC grinding machine by improving the neural network algorithm, so as to achieve the goal of improving the machining precision and surface quality. We hope that by establishing thermal environment model, we can deeply analyze the characteristics of thermal energy distribution and put forward effective optimization measures. The improved neural network model is used to model the heat energy distribution of CNC grinding machine. The accuracy of the model is improved by introducing multi-layer perceptron and convolutional neural network. At the same time, combined with the experimental data, training and testing are carried out to verify the effectiveness of the model. Genetic algorithm and fuzzy control are used to adjust the thermal energy environment and obtain the best process parameters. The experimental results show that the prediction accuracy of the improved neural network model is significantly improved, and the prediction error of the model is significantly reduced compared with the traditional method. After thermal optimization, the surface roughness of the workpiece is reduced, the dimensional accuracy is significantly improved, and the overall processing efficiency is significantly improved. By improving the neural network model, the thermal energy environment of CNC grinding machine is effectively optimized, and the machining precision and surface quality are successfully improved.

The Structure-Dependent Dynamic Performance of a Twin-Ball-Screw Drive Mechanism via a Receptance Coupling Approach

The drive at the center of gravity (DCG) concept-based twin-ball-screw drive mechanism (TBSDM) is vital in automated factories for its robustness and reliability. However, changes in the worktable mass or position result in changes in the center of gravity (CG), significantly affecting the system’s dynamic properties. In this regard, this paper introduces a novel analytical model using improved receptance coupling to analyze vibrations in four modes. A mathematical framework for the twin TBSDM is generated, and the effect of changing the worktable position–mass on each mode is examined. The applicability of the proposed method is verified based on dynamic experiments that were carried out on a TBSDM of a CNC grinding wheel machine tool. After thoroughly analyzing the experimental and theoretical results, it is revealed that changing the worktable position primarily influences the rotational and axial vibrations of the twin ball screw (TBS). Furthermore, changes in the worktable mass significantly affect the coupling vibration among the TBSs and rotors or bearings. Moreover, in terms of performance, the variances between the theoretical and experimental natural frequencies are consistently below 5%. Thus, the proposed method is promising for the improvement of the modeling and analysis of the TBSDM.

88‐3: Fast Selective Laser‐Induced Etching and Asymmetric 3D Hologram Laser Beam for Narrow Bezel Thin Display †

Here we demonstrate fast selective laser‐induced etching (SLE) process with three‐dimensional (3D) hologram optics to reduce display bezel thickness with cost effective methods. To apply fast SLE for display manufacturing, one‐side etching process should be presumed to protect display active area. We developed one‐side selective laser‐induced etching with asymmetric 3D hologram laser beam satisfying with commercial mechanical strength. Faster etch process having etch rate 10 µm/min than common SLE, 1~3 µm/min was developed. Furthermore, we achieve that bezel thickness is 100 µm shorter than wheel scribing and CNC grinding.

Development of a CNC Grinding Process for the Manufacturing of Crystal Glass Products

Traditional manufacturing and finishing operations of crystal products use intensive specialized labour resulting in high cycle times and production costs. It is intended to investigate the applicability of automated finishing technology, namely grinding in a CNC machining centre, with consideration of material’s characteristics and geometric variability to crystal processing. A case study will be presented, involving cutting tools development, cutting parameters optimization, CAM programming of machining strategies and toolpaths, product clamping systems and finally product machining and quality control that is being implemented at Vista Alegre Atlantis company.

Opportunistic maintenance strategy optimization considering imperfect maintenance under hybrid unit-level maintenance strategy

Opportunistic maintenance is a widely adopted strategy for maintaining multi-unit systems, which has garnered significant attention from researchers. However, the current opportunistic maintenance still suffers from certain limitations, such as single preventive maintenance strategy at unit-level and lack of flexibility in optimization model. In this paper, an optimization model for scheduled maintenance (SM) and condition-based maintenance (CBM) at the unit-level is presented, and the associated maintenance costs are analyzed. Subsequently, a preventive opportunistic maintenance strategy optimization model under hybrid unit-level maintenance strategies is established by considering imperfect preventive maintenance. An optimization algorithm based on Monte Carlo simulation is designed to solve the model. Finally, the opportunistic maintenance strategy of CNC gear grinding machine is developed. Comparing the opportunistic maintenance strategy given in this paper with other maintenance strategies, the results show that the maintenance strategy presented in this paper can significantly reduce the maintenance cost of the CNC grinding machine. The opportunistic maintenance strategy optimization method proposed in this paper can provide guidance for relevant enterprises to formulate maintenance strategies.

ГРАФОАНАЛИТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ШЕРОХОВАТОСТИ ПЕРЕДНЕЙ ВИНТОВОЙ ПОВЕРХНОСТИ РЕЖУЩЕГО ИНСТРУМЕНТА

The paper deals with a method for grapho-analytical modeling of micro-roughness (surface roughness) formed on the helical front surface of a cutting tool during its manufacture or resharpening using CNC grinding machines and grinding wheels with a simple shape of the generative surface.
 A simulation model of roughness on the formed front surface is presented, and a calculation scheme for determining its value is made. Based on the statistical results of the formed technological 3D models of helical front surfaces, the resulting equations of complete factorial experiments are presented, taking into account the combined influence of factors.
 Graphs of the normal distribution of the roughness parameter and the parameter of the grinding wheel installation affecting it are given.
 It is shown that an important result of modeling is the definition of the micro-roughness direction, and a recommendation is given to indicate the directions of micro-roughness in the drawings of the cutting tool in order to mearure roughness taking into account the requirements of regulatory and technical documentation.

Accuracy design optimization of a CNC grinding machine towards low-carbon manufacturing

Accuracy design is an important and essential step for CNC machine tools, and traditional methods always focus on the accuracy optimization itself and ignore other objectives, such as low-carbon manufacturing. With the increasing concern about resources and the environment, energy consumption and carbon emissions should be taken into consideration in accuracy design optimization. This paper takes a novel CNC slider grinding machine with dual-head-dual-lead structure as an example to build an accuracy design model considering sustainable development. Specifically, the feed system of the machine tool is examined, which presents significant accuracy design challenges and has a great impact on the machine's positioning accuracy. By using the improved Sobol method, a sensitivity analysis is conducted to extract the critical geometric error terms, and the sensitivity indices of these terms are utilized to guide the optimization process. By considering manufacturing cost, quality loss, and carbon emissions of the grinding process with long period and high energy consumption, a more comprehensive accuracy design model is built and optimized by using the NSGA-II algorithm. Moreover, the Pareto optimal solution for balancing the objectives is selected through combining entropy-weight and technique for ordering preferences by the similarity of the ideal solution (TOPSIS). The optimization results demonstrate that the accuracy level of the machine tool can be ensured while reducing carbon emissions and total cost up to 30.2% and 18.4% respectively, which is important for promoting clean production in machine tool manufacturing. Besides, the proposed accuracy design framework has the potential to apply to other components and manufacturing processes of CNC machine tools to enhance sustainability and reduce carbon emissions.

Innovative process for precise grinding of optical free-form elements

The aim of the presented article is to share experience gained throughout the course of two projects focused on precise grinding of a free-form glass optical element with the objective of achieving a surface shape error of less than approximately 10 μm PV before the subsequent polishing phases. Compared to spheres or aspheres machining, it is considerably more demanding, mainly due to the impossibility of using rotationally symmetric shape corrections. The developed and tested process combines a mechanical engineering approach based on the use of the current Computer Aided Design and Computer Aided Manufacturing software with their respective strengths and weaknesses and an optical engineering approach, for which the employment of CNC machines featuring precise control but low flexibility is typical. Therefore, attention is paid mainly to the description of particular process steps like CAD construction and CNC grinding step programming with regard to the necessary software and data handling, as well as the required parametrisation of the used machine equipment.

Development of a New Micro Drilling Tool with H-Shaped Chisel Edge

In order to improve the tool life and micro-hole machining quality, the H-shaped chisel edge micro-drill (HCE-MD) was developed in this paper. The HCE-MD was characterized by the inner edge formed through the chisel edge thinning. In the micro-drilling process, the inner edge can perform positive rake cutting, so the machining area of the workpiece extruded by cutting edge with a negative rake angle is reduced. Based on this, the distribution of rake angle near the chisel edge corner is improved. Then, the HCE-MD was fabricated on the six-axis CNC grinding machine. The grinding process parameters of the micro-drill were optimized based on the orthogonal grinding test and grey relational grade theory. The size and shape accuracy of the micro-drill were controlled by the multi-axis linkage grinding method and the movement-axis micro compensation method. Finally, the 0.25 mm HCE-MD was fabricated with the cutting edge radius of 1.94 μm and the flank surface roughness of 0.25 μm. The drilling performance of HCE-MD was evaluated through comparative drilling experiments. The experimental results show that, compared with common micro drill, the HCE-MD produced lower thrust force and better micro-hole roundness accuracy, and reduced the micro-drill wear on the chisel edge and the flank.

ОСОБЕННОСТИ ПРИМЕНЕНИЯ МНОГОКООРДИНАТНЫХ ШЛИФОВАЛЬНЫХ СТАНКОВ С ЧПУ ДЛЯ ПОВЫШЕНИЯ ПРОИЗВОДИТЕЛЬНОСТИ, КАЧЕСТВА И ТОЧНОСТИ ОБРАБОТКИ ДЕТАЛЕЙ И УЗЛОВ АВИАЦИОННЫХ ГАЗОТУРБИННЫХ ДВИГАТЕЛЕЙ

The paper is aimed at improving the productivity, quality and accuracy of manufacturing gas turbine engine parts and assemblies for the modern growing passenger aviation transport based on the use of technical capabilities of modern multiaxis CNC grinding machining centers. The paper shows the results of successful application of a five-axis CNC grinding machining center MFP-050.65.65 made by Magerle (Switzerland), which allows reducing by five times the number of operations, universal machines, special devices and cutting tools by increasing the number of machined surfaces for one set of nozzle blades of an aviation gas turbine engine. Simultaneously with a significant increase in the productivity of machining various multidirectional surfaces of the nozzle blades due to the use of new highly porous grinding wheels and rational modes of deep grinding, a higher burn-free quality of the ground surfaces is ensured and an important task is solved to increase the accuracy of the flow sections of the turbine nozzle apparatus with the combined use of CNC system and special software for correcting errors of part casting surfaces during their installation, turning and deep grinding of the base surfaces. The developed new technology of nozzle blades machining was introduced for the first time in the Russian Federation at the Aviadvigatel enterprise for manufacturing nozzle blades of modern newly produced gas turbine engines.

Схема формообразования задней поверхности пятигранных твердосплавных пластин на станках с ЧПУ

The methods of grinding the rear surfaces of multifaceted carbide inserts, as well as various schemes for shaping the back surfaces, are considered. The process of shaping the rear surface of a five-sided carbide insert is modeled. An algorithm for the implementation of the kinematic scheme for shaping the rear surface of pentahedral carbide plates using CAD tools has been developed. The processing of a multifaceted carbide inserts on a CNC grinding and grinding machine was carried out using the obtained mathematical dependence.

Investigations on the causes of process vibrations in CNC grinding processes and their effects on achievable surface qualities on fused silica

The presented investigations build on the results already presented at EOSAM 2022 on the in-situ monitoring of grinding processes, in which high correlations between vibrometry, force and topography data of machined fused silica samples could already be proven. With the help of new measurement setups, it was possible to also detect high-frequency vibration components in CNC grinding processes and to check their effects on the resulting surface qualities. The investigations were carried out on a 5-axis CNC machine and monitored with the help of vibrometric and white-light interferometric measurement technology. The aim was to look at the influences of process-side parameters on the process vibrations and the resulting surface qualities.

Integrated mathematical approach for design and manufacturing of power-skiving tool for interference-free involute internal gear cutting

Power-skiving is one of the most effective methods for producing internal gears. However, without the support of corresponding CNC NC code conversion software, it is difficult to manufacture power-skiving tools using traditional tool grinding technology. Accordingly, manufacturing methods for power-skiving tools must be developed from scratch in accordance with basic tool design principles. Due to the particularity of the machining kinematics of power-skiving tools, special attention must be paid to avoiding cutting interference between the flank face of the cutter and the gear tooth surface during the machining process. This consideration greatly increases the time and complexity of the design process. Accordingly, this study presents a systematic mathematical approach for the design and manufacturing of power-skiving tools. A four-step method is first proposed for the design of interference-free power-skiving tools for the machining of involute internal gears. A mathematic approach is then presented for generating the NC code required to grind the clearance surface and rake surface of the designed tool using a five-axis CNC grinding machine. The simulation and experimental results confirm the feasibility of the proposed approach.

Design features of end mills with a combination of cutting and deforming teeth for machining tough-plastic alloys

The article shows the design features and possibility of manufacturing workable milling cutters for processing ductile alloys using multi-coordinate grinding machines with numerical control. A mathematical apparatus is given to describe the design features of the cutting part of such cutters consisting in the use of cutting and deforming teeth, which makes it possible to influence the chip shear angle within a single tool. The layouts of cutting and deforming teeth are described, the obtained technological 3D models of the designed samples are shown, and the calculated values of cutting forces and deformation forces of various teeth (cutting and deforming) when processing a viscoplastic material are given. To confirm the operability of the designed tool, using the technological capabilities of multi-axis CNC grinding machines, tool samples were obtained. Testing of the obtained samples showed a decrease in cutting force up to 8% compared to a tool with a classic (constant) geometry of the cutting teeth.

Повышение энергоэффективности шлифовальных станков с числовым программным управлением

Повышение энергоэффективности шлифовальных станков с числовым программным управлением

Optimization of grinding processes on fused silica components using in-process vibrometry and dynamometer measurements

The presented investigations deal with real-time evaluation and recording of vibrations and forces during a CNC grinding process, as well as the analysis and control of process influences on the surface quality of optical components. The experiments were carried out on a 5-axis CNC machine. Rapid subsequent analysis of the topography resulting from grinding is achieved with the aid of white light interferometry. The aim of the investigations is to reduce the surface deviations (roughness, mid-spatials, waviness) influenced by process factors. It is shown that the vibration data measured during the grinding process correlate to a high degree with the recorded topography data.

Razvoj nove CNC brusilice za 3+2 osno brušenje profilnih koturatih glodala

Due to the great expansion of woodworking, profile tools manufacturing has become current and in demand. In wood industry there are two large groups of tools: rotary and spindle milling cutters that can be profile or flat. The technology of making profile rotary milling cutters requires, apart from cutting, turning, milling, 5-axis grinding operation that is performed on a 5-axis CNC grinding machine with the A'OXYZC configuration.It is a machine of a very complex kinematics and high cost-price. The paper presents a new machine that has been built for 3+2-axis grinding - Profilator 100,used for industrial manufacturing of rotary and spindle profile milling cutters. The accuracy of measures and shapes of the profile cutters built on Profilator 100 is of a high level and in industrial exploitation the difference is not observed between the profile cutters built on 5-axis CNC grinding machines. Regarding technoeconomic cost-effectiveness, production costs of Profilator 100 are lower even by ten times compared to the cost-price of 5-axis CNC grinding machines of renowned world manufacturers such as Schneeberger and Volmer.

Tehnologija izrade profilnih koturastih glodala 3+2 osnim brušenjem na horizontalnom obradnom centru

The paper presents the technology of making brazed shaper milling cutters and with special reference to 5-axis grinding process (making of profile blades) on CNC grinding machine tool. Based on the analysis of the kinematics of the 5-axis grinding process, a new concept of profile milling tool production by a 3+2 axis grinding process on horizontal milling center was established. By Applying new concept, one tooth of profile tool was machined by grinding process. By obtained results, new approach for manufacturing of profile milling tools was verified.

Reliability analysis of spindle system of CNC grinder based on fault data

Reliability analysis of spindle system of CNC grinder based on fault data

Thermal error compensation method for CNC machine tools based on deep convolution neural network

To avoid the resetting of temperature-sensitive points caused by seasonal and weather changes and the influence on the accuracy of the thermal error model, a thermal error prediction and compensation method for CNC machine tools without preselected temperature-sensitive points was proposed based on deep learning method. The original temperature data of the CNC machine tool were converted into thermal images and directly serve as the input of the deep learning network. To improve the prediction accuracy of the thermal error model, a thermal error model of CNC machine tool with 10 hidden layers was constructed by using the powerful image feature learning ability of deep convolution network. The nonlinear mapping relationship between temperature image and thermal error without pre-selection of temperature key points was established, and more relationships between thermal error and temperature feature of a machine tool were retained. STM32F4 microprocessor was used as thermal error compensation controller to develop software and hardware system. The application experiment of the thermal error compensation system is carried out on the CNC grinder, and the effectiveness of the thermal error compensation system is verified.