Milling System Research Articles

On Some Equations Modeling the Yang–Mills Equations

The paper considers plane-wave solutions of the Yang–Mills equations, which allow one to write out three systems of equations modeling the Yang–Mills system. An explicit form of all plane-wave solutions of the Yang–Mills equations with the $${\text{SU}}(2)$$ gauge symmetry and zero current in a (pseudo)Euclidean space of arbitrary finite dimension is presented.

Influence of graphene content and nickel decoration on the microstructural and mechanical characteristics of the Cu/Sn–Ag–Cu/Cu soldered joint

In this research article, lead-free nanocomposite soldering is assessed by using the eutectic composition of Sn-3.5Ag-0.7Cu (SAC, wt%) solder alloy as the matrix and graphene nanoplatelets (GNPs) as the reinforcing agent. Powders of these materials are mixed in a mechanical milling system, then compacted, and sintered before application. The effects of GNPs content with different amounts of 0.05, 0.1, and 0.2wt% are examined to prepare nanocomposite solders as compared to the SAC solder alloy. Furthermore, to improve the metallurgical compatibility between the graphene and SAC solder matrix, the surface of GNPs was decorated by nickel particles using electroless plating techniques before incorporation. After that, the solderability of these prepared lead-free nanocomposite solders is investigated on the copper substrate. As the main result, the formation of the intermetallic compound (IMC) layers at the interface between the Cu-substrate and solder material was found very determinative to control the mechanical performance of soldered joints during lap-shear testing. The content of GNPs and Ni-coating modification strongly affected the morphology and growth of IMC layers at the interface. By increasing the amount of GNPs up to ∼0.2wt% and using Ni-coating, the growth of IMC layers was considerably suppressed, leading to a significant improvement of the joint strength up to ∼27%, despite a reduction of ∼50% of the ductility. Furthermore, isothermal aging at 150°C up to 100h resulted in a remarkable increase in the shear strength (∼45%) and elongation to failure (∼19.9%) through controlling the growth of the IMC layers at the interface.

Comparison of Marginal and Internal Fit of Different CAD/CAM Copings

This study compared the internal and marginal gap between CAD/CAM copings to determine the clinical acceptability. Hundred dental stone duplications of a metal major maxillary molar die were fabricated and separated into five. All copings were produced by milling and laser sintering method in the form of twenty groups. At x 180 magnification, marginal and internal gaps of each coping were measured at 75 points, and a total of 7500 measurements were performed for six regions on digital photographs taken with video microscope. Data were analyzed using one-way analysis of variance (ANOVA) and post hoc test (Tukey and Bonferroni). The internal and marginal gaps of the milling group were significantly larger than the laser sintering group (P All copings were presented clinically acceptable marginal and internal accuracy. Milling and laser sintering systems are suitable for manufacturing of copings.

Processing of green tea pastes by micro wet milling system: Influences on physicochemical and functional properties

This study aimed to develop green tea paste using a new micro wet milling (MWM) system. The influence of milling conditions on the particle size, morphology, solubility, and antioxidant properties of Matcha, shaded Yabukita, unshaded Yabukita, and Hojicha pastes were studied. MWM green tea paste retained smaller particles, better color, higher solubility, and antioxidant properties than the dry milled Matcha paste. Storage temperature and time affected the stability of ascorbic acid and visual green color at 20, 4, −18, and −60 °C for four weeks. Kinetic analysis demonstrated that first-order kinetic models could predict the degradation of ascorbic acid and the reduction in visual green color of green tea pastes during storage. Temperature-dependent rate constants of ascorbic acid and color of green tea pastes obeyed the Arrhenius relationship. The total viable count revealed that green tea paste could be stored for 7 days at 20 °C and 21 days at 4 °C within the permissible limit.

Reducing dynamic loads in the mechatronic system of a rolling mill

A correction method for regulating the mechatronic system of a «DUO-300» rolling mill with a direct current electric drive is considered. The results of the study of dynamic processes in the mechatronic system with the proposed correction are presented. Keywords rolling mill, mechatronic system, model, electric drive, engine, regulator, correction. simalafeev@gmail.com

Research on Online Mathematical Models of Tandem Cold Rolling

The tandem cold rolling process control system is an important part of the computer control system of the tandem cold mill coupled pickling line, and it is an important means to ensure the output and quality of cold rolled strip. On-line mathematical models of tandem cold rolling are the premise of formulating rolling rules, setting of rolling mill parameters and calculation of load distribution. They calculate the set values and rolling parameters required by the automation system based on the rolled piece and equipment parameters. Therefore, it is of great practical significance to study the on-line mathematical models of tandem cold rolling and to establish a model of high precision and high value-added products.

Femtosecond laser micro-milling dental glass ceramics: An experimental analysis and COMSOL finite element simulation

Dental glass ceramic materials are widely used in all-ceramic restoration technology. In order to effectively solve the problems existing in the process of traditional diamond cutter milling dental glass ceramic materials, such as severe needle loss, large tool wear and general milling efficiency, a new method of ultrafast laser milling dental glass ceramics is proposed. In this paper, 1030 nm femtosecond laser with pulse width of 600fs was used to micro-mill dental glass ceramics. Confocal laser microscopy was used to measure the milling depth and surface roughness of single-layer milling under selected laser processing parameters. The pre-layered milling software was developed to control the z-axis lifting and to compensate the focal length synchronously. Scanning electron microscope (SEM), Raman spectrometer and Vickers micro-hardness tester were used to characterize the dental glass ceramics after femtosecond laser milling. The results showed that under the specific laser processing parameters, the infrared femtosecond laser milling system can achieve a good processing morphology without changing the surface composition and surface hardness of dental glass ceramics. This new dental glass ceramics processing method based on ultrafast laser technique indicated a new direction for further chair processing of dental all-ceramic restoration technology.

Five-axis flank milling stability prediction by considering the tool-workpiece interactions and speed effect

Chatter is one of the challenging topics in the field of metal cutting. The dynamic characteristics of five-axis milling system are complex and variable. Especially in high-speed milling process, the influence of the tool-workpiece interactions and speed effect on milling stability is more obvious. It is necessary to investigate the influence of various interaction effects on milling stability. In this paper, the dynamical model of spindle system was established, and then the model was applied to investigate the influence of gyroscopic effect and centrifugal force on the dynamical characteristics of the tool tip. In order to solve the chatter problem of five-axis flank milling, the extended dynamical model of five-axis flank milling which considers the tool-workpiece interactions and speed effect was established. Based on the established milling dynamical model, the influence mechanism of the spindle system-tool-workpiece interaction effects on five-axis flank milling stability was investigated. The stability lobe diagrams of five-axis flank milling which contains the tool-workpiece interactions and speed effect can be obtained. Experimental results show that the proposed five-axis flank milling dynamical model can predict the milling state more reliable than the traditional ones. The research results are of great significance in preventing five-axis flank milling chatter.

Dynamics modeling and stability analysis of five-axis ball-end milling system with variable pitch tools

Chatter has become a major obstacle in realizing high efficiency milling under the premise of ensuring structure integrity, as it creates violent vibration to the milling system and in turn results in poor surface finish and accelerated tool wear. Although some promising methods have been applied to the avoidance and suppression of chatter, and among them variable pitch tools play a critically important role, few studies focus on the stability prediction of five-axis ball-end milling with variable pitch tools. In this paper, a comprehensive dynamic model characterized by multiple delays is first built for five-axis ball-end milling system with variable pitch tools, and the milling stability lobe diagrams (SLDs) are predicted with an extended second-order semi-discretization method (2nd SDM) by taking the multiple modes of cutter into account. Then, the effects of tool orientation on the stability prediction of five-axis ball-end milling with variable pitch tools and regular tools are analyzed. The optimal cutter pitch angle can be obtained by comparing the SLDs for the stability improvement. Finally, the effectiveness of the proposed method is verified by experiments with a variable pitch ball-end cutter in five-axis machining center.

Determination of particle abrasion through milling with five different salt grinders – a preliminary study by micro-Raman spectroscopy with efforts towards improved quality control of the analytical methods

ABSTRACT Latest findings suggest that packaging and processing of food may be a contamination source of microplastics. In this study particle abrasion from five different salt mills with grinding burrs made of plastic and ceramic were investigated using micro-Raman (µ-Raman) spectroscopy. The mills were filled with a reference salt and an amount of 0.1 g was milled into a beaker, dissolved, filtered and the residues analysed via µ-Raman spectroscopy in different size classes, beginning with ≥ 1 µm. In the unground reference salt itself 423 ± 161 microplastic particles per 0.1 g were found, mainly consisting of polyethylene terephthalate (PET). These contents were not subtracted from the samples. One of the ceramic grinders also exclusively released PET-particles (527 ± 265 per 0.1 g).The other had compartments of polystyrene (PS) in the milling system and PS particles were found in the ground salt (201 ± 37 PET; 727 ± 226 PS/). Two of the plastic grinders had burrs made of polyoxymethylene (POM) and one with burrs of poly(methyl methacrylate) (PMMA). There were large amounts of 7628 ± 2655 and 5048 + 594 POM particles in 0.1 g salt in the two POM grinders as well as 265 ± 182 and 1546 ± 884 PET particles, respectively; salt from the PMMA grinder had 240 ± 41 PMMA particles/0.1 g and 1643 ± 1174 PET particles. The majority of the PET particles were smaller than 5 µm, whereas the POM, PS and PMMA particles had average sizes greater than 10 µm. In addition to possible microplastic contamination from salt itself, salt mills with grinding burrs made of plastic can emit microplastic particles in large amounts, especially if the burrs are made of POM. Other particles may, however, also be emitted from the grinders, e.g. ceramic particles in a similar size class, leading to the question whether and which kind of particles may be of toxicological concern for humans.

The Stability of Magnetic Levitation Milling System Based on Modal Decoupling Control

Milling stability not only reduces the surface quality of the workpiece but also seriously restricts the high-speed development of CNC machine tools. The electric spindle rotor system with the active magnetic bearing has a strong gyro coupling effect, and with the increasing rotor speed, it will become a major unfavorable factor for the stability of the system during high-speed milling. The strong gyro coupling effect makes the stability region narrow at the time of high-speed milling. So, a modal decoupling control method that can reduce the effects of the gyro effect on the magnetic levitation milling system under high-speed milling is proposed. The effects of the gyro coupling of the magnetic bearing rotor on the milling stability region before and after the decoupling control are studied, which show that the modal decoupling control technology can reduce the effects of the gyro effect on the magnetic levitation milling system.

Smoothness-oriented path optimization for robotic milling processes

Industrial robots are increasingly used for five-axis machining operations, where the rotation of the end effector along the tool-axis direction is functionally redundant. This functional redundancy should be carefully resolved when planning the robot path according to the tool path generated by a computer-aided manufacturing (CAM) system. Improper planning of the redundancy may cause drastic variations of the joint motions, which could significantly decrease the machining efficiency as well as the machining accuracy. To tackle this problem, this paper presents a new optimization-based methodology to globally resolve the functional redundancy for the robotic milling process. Firstly, a global performance index concerning the smoothness of the robot path at the joint acceleration level is proposed. By minimizing the smoothness performance index while considering the avoidance of joint limits and the singularity and the constraint of the stiffness performance, the resolution of the redundancy is formulated as a constrained optimization problem. To efficiently solve the problem, the sequential linearization programming method is employed to improve the initial solution provided by the conventional graph-based method. Then, simulations for a given tool path are presented. Compared with the graph-based method, the proposed method can generate a smoother robot path in which a significant reduction of the magnitude of the maximum joint acceleration is obtained, resulting in a smoother tool-tip feedrate profile. Finally, the experiment on the robotic milling system is also presented. The results show that the optimized robot path of the proposed method obtains better surface quality and higher machining efficiency, which verifies the effectiveness of the proposed method.

Wear of TiAlN and DLC coated microtools in micromilling of Ti-6Al-4V alloy

The trend toward the miniaturizing of commercial and engineering products is inevitable. Micromilling is the most versatile process to shape microcomponents subtractively. One of the main areas that benefit from micromilling is medical, with titanium and titanium alloy being its most frequently used materials. The popular Ti-6Al-4V alloy has excellent combination of strength and toughness, combined with a great resistance to corrosion and oxidation. This particular alloy dominates other Ti alloys and is used in 50% of all titanium applications. Taking into consideration that this alloy is considered a difficult to cut material, this study investigates the machinability of Ti-6Al-4V in micromilling operations. The wear of micro tools (152.4 μm diameter) coated with TiAlN and diamond-like carbon coating (DLC) are investigated and compared against uncoated tools. The tests are performed on a four-axis CNC milling system with a 60,000 min−1 maximum spindle speed. The tools are tested under dry conditions and wet conditions using the minimum quantity of lubrication. It is used cutting speed of 9.6 m/min, feed rate of 0.1 μm/tooth and axial depth of cut of 10 μm. The test consisted of machining slots 4.2 mm long until the end of the tool life. The results show that edge radius rounding and flank wear are the main wear types. The wear is predominant on the secondary clearance face of the microtool when applying cutting fluid. The lowest tool wear is obtained with the DLC coated microtools under dry conditions, presenting a wear reduction of 640% and 267% when compared to TiAlN coated and the uncoated microtool, respectively.

Hopf bifurcation control for the main drive delay system of rolling mill

In this work, the Hopf bifurcation of the main drive delay system of rolling mill is controlled and analyzed by designing a nonlinear controller. The time-delay is selected as a bifurcation parameter, and the following conclusions are obtained through analysis: (1) in the absence of state feedback control, the system will generate the Hopf bifurcation at the expense of its stability when the bifurcation parameter exceeds the threshold value; (2) in the state under feedback control, the occurrence of Hopf bifurcation is effectively delayed and the stable region of the system is also well extended. More importantly, we can change the properties of bifurcation periodic solutions by selecting the appropriate gain parameters. Some numerical simulations reveal that under the nonlinear feedback control, the vibration amplitude of the system can be effectively reduced.

Advanced Mechanochemistry Device for Sustainable Synthetic Processes.

Mechanochemistry is an alternative for sustainable solvent-free processes that has taken the big step to become, in the near future, a useful synthetic method for academia and the fine chemical industry. The apparatus available, based on ball milling systems possessing several optimizable variables, requires too many control and optimization experiments to ensure reproducibility, which has limited its widespread utilization so far. Herein, we describe the development of an automatic mechanochemical single-screw device consisting of an electrical motor, a drill, and a drill chamber. The applicability and versatility of the new device are demonstrated by the implementation of di- and multicomponent chemical reactions with high reproducibility, using mechanical action exclusively. As examples, chalcones, dihydropyrimidinones, dihydropyrimidinethiones, pyrazoline, and porphyrins, were synthesized with high yields. The unprecedented sustainability is demonstrated by comparison of EcoScale and E-factor values of these processes with those previously described in the literature.

Comparison of the full-discretization methods for milling stability analysis by using different high-order polynomials to interpolate both state term and delayed term

This paper compares different full-discretization methods for milling stability analysis by using different high-order polynomials to interpolate both state term and delayed term (HFDMs) from the aspects of accuracy and efficiency. The dynamic model of milling process with consideration of regeneration effect is described by time periodic delay-differential equation (DDE) in the state-space. Different high-order interpolation polynomials are used to approximate the state term and delayed term. The state transition matrix is obtained on the basis of direct integration scheme. The rates of convergence of different HFDMs are compared with those of the benchmark methods using different process parameter points, the results indicate that it is difficult to evaluate the accuracy of different HFDMs through the convergence rate analysis of limited process parameter points. Then, mean differences and variances between the referenced and predicted critical depths of cut are employed for accuracy analysis. The 3rd-2nd HFDM is, on the whole, proved to be more accurate than the other methods. The efficiencies of different HFDMs are also verified through time-consuming study for both single degree of freedom (1-DOF) and two degree of freedom (2-DOF) milling system. The 3rd-2nd HFDM is proved to be an efficient method by comparing with the other methods. Besides, the HFDMs are available for predicting the stability lobe diagrams under both large immersion condition and low immersion condition.

A Power Drive System for Pipe Rotation and Delivery Mechanisms of a KhPT-250 Cold Rolling Mill

This article is devoted to development of synthesis of power drive system of KhPT-250 cold rolling mill. Selection procedures for process variables of the reducer, electric machine, and power circuits have been developed. It has been noted that the configuration of power circuits can decrease failures by about 30%. It has been demonstrated that, in the power drives of the KhPT-250 mill, it is required to take pipe deformability into account and the control object should be considered as a multicircuit double-mass system. It is proposed to select the gear reduction rate on the basis of the criterion of minimum oscillation. With this aim in mind, the methods of frequency synthesis have been applied to construct asymptotic frequency characteristics used for determination of the reducing gear factor in the case of a restricted amplitude of the resonance maximum. Using the finite element method, the geometrical parameters of the stator and rotor of a synchronous reluctance machine have been selected, and its weight and dimensions have been improved by about 35%. Predictions demonstrate that the best ratio of the flow longitudinal constituent to the transversal constituent is obtained for a axially laminated rotor. Implementation of a power drive system with a field regulated synchronous reluctance motor on a KhPT-250 cold rolling mill made it possible to increase the mill output by 10–15%, with the quality of rolled products improving by 20–25%. According to preliminary estimations, the annual efficiency of the power drive system will be from 2 to 5 million rubles.

Vibration characteristics of multi-parametric excitations and multi-frequency external excitations of rolling mill under entry thickness fluctuation of strip

A dynamic rolling force model with multi-parametric excitations and multi-frequency external excitations caused by entry thickness fluctuation of strip was established. Based on the dynamic rolling force, a nonlinear vertical vibration model with multi-parametric excitations and multi-frequency external excitations was established. The method of multiple scales was used to solve the amplitude-frequency characteristic equation of primary resonance of the nonlinear vibration system of a rolling mill. The transition set and the topology structure of systematic global bifurcation were obtained by using the singularity theory. Finally, primary resonance characteristics of the system under entry thickness fluctuation of strip were analyzed by using actual parameters of the rolling mill. The global bifurcation curves with the change of amplitude and frequency of entry thickness fluctuation of strip were obtained by using numerical simulation, and many dynamic behaviors were found such as single-cycle motion, multi-cycle motion and chaotic motion, which can provide a theoretical reference for further restraining the vibration of a rolling mill.

Research on fault diagnosis of coal mill system based on the simulated typical fault samples

Abstract The operation state of coal mill is related to the security and stability operation of coal-fired power plant. In this paper, a fault diagnosis method of coal mill system based on the simulated typical fault samples is proposed. By analyzing the fault mechanism, fault features are simulated based on the model of coal mill, and massive fault samples are obtained. Then, according to the time series difference of different types of fault, the stacked automatic encoder is established to reduce the dimension of fault data. Furthermore, by learning and classifying the features of fault data after dimensionality reduction, the fault identification of coal mill system can be realized. Simulation results show that the model-based fault simulation can effectively solve the problem of fault samples acquisition, the proposed fault diagnosis method has highly accuracy and can effectively monitor the running status of the coal mill system.

Baseline Flight Potential of Euschistus servus (Hemiptera: Pentatomidae) and Its Implications on Local Dispersal.

The brown stink bug, Euschistus servus (Say), is a damaging pest of multiple crops in the southeastern United States. In addition to crops, both the weedy field borders and wooded areas of a typical farmscape in this region harbor E. servus host plants, many of which are temporally and spatially limiting in availability or nutritional suitability. Therefore, local dispersal is required so that individuals efficiently track and utilize host resources. This research sought to establish the baseline flight capacity of adult E. servus across the season in relation to body weight, sex, and plant host use with a flight mill system. Across this 2-yr study, among the individuals with a flight response in the flight mill, 90.1% of individuals flew in a range of >0-1 km, with an individual maximum flight distance of 15.9 km. In 2017, mean total distance flown varied across the season. Except for the individuals collected from corn in 2019, during both 2017 and 2019, the highest numerical mean flight potential occurred soon after overwintering emergence and a relatively low flight potential occurred during the cropping season. Individuals collected from wheat, corn, and early season weeds lost a higher proportion of body weight after flight than did individuals from soybean and late season weeds. The baseline dispersal potential information generated from this study can be extrapolated to the farmscape level aiming to develop, plan, and implement E. servus management programs.