Vibratory Mill Research Articles

Operational Impact Excitation Method for Milling Robot End Frequency Response Function Identification Under Movement State and Pose-Dependent Dynamic Compliance Analysis

Abstract Robot milling has become an important means of machining large structural parts, and the dynamic compliance of the robot end is the key factor affecting machining quality and efficiency. The dynamic characteristics of the milling robot end are different in movement state and static state and have significant pose dependence. In order to effectively evaluate the dynamic compliance of the robot end in the workspace under the movement state, the operational impact excitation method for robot joint relative frequency response function (FRF) identification based on operational modal analysis (OMA) used in machine tool is established, the inertial force generated by the joint acceleration and deceleration movements is used as the excitation force, the robot end relative dynamic compliance index (RERDCI) is proposed to evaluate the dynamic compliance of robot end in different poses, and verified by cutting experiments. Based on RERDCI, the effect of the robot pose on end dynamic compliance is analyzed, and some theoretical guidance for improvement of dynamic performance to resist vibration in milling is given.

Bifurcation and chaos analysis of mold splicing zone vibration under thermal-mechanical coupling

To improve the machining quality of the splicing area of the hardened steel mold, this paper proposes a bifurcation and chaos analysis method for the milling vibration of the splicing area of the mold under the coupled thermal-mechanical effect. First, based on the instantaneous milling force model at the splice, the milling dynamics equations of a two-degree-of-freedom rectangular spliced mold part are established. By applying the Galerkin method, the resulting nonlinear partial differential equation is reduced to a single-degree-of-freedom nonlinear system. Meanwhile, by using the Melnikov function method, the criteria for chaos motion are obtained by the Smale horseshoe mapping. Then, the fourth-order Runge-Kutta algorithm is applied to solve the bifurcation diagram, largest Lyapunov exponent diagram, displacement waveform diagram, and phase plane diagram of the nonlinear dynamic system in the mold splicing area. Subsequently, the influence of spindle speed and cutting depth on the nonlinear vibration system in the mold splice area is quantitatively analyzed. Finally, the effect of spindle speed and cutting depth on the vibration system of the workpiece is investigated through experiments. The obtained results indicate that the milling vibration amplitude in the rectangular splicing mold area can be controlled more easily and effectively by changing the cutting depth than by changing the spindle speed.

Tailoring strength-ductility of titanium matrix composites reinforced with graphene nanoplatelets

In this study, graphene nanoplatelets reinforced titanium matrix (GNPs/CT20) composites with adjustable performance were fabricated via 3D vibration milling and spark plasma sintering. With the progressive increase of GNPs, a quasi-continuous 3D reinforcement (TiC-GNPs-TiC) network was established and a peculiar phenomenon is observed that the ductility of GNPs/CT20 composites trends in hump type while the strength increases monotonically. The first crest of the humping ductility for GNPs/CT20 composites was attributed to the fine-grained CT20 matrix contributed by GNPs and in-situ generated TiC. Subsequently, the increasing TiC with discrete distribution dominated the tensile ductility behaviour which showed as the valley of humping ductility. Further additions of GNPs led to the network distribution of TiC-GNPs-TiC, which contributed to a relatively uniform deformation and the near equiaxed fine-grained microstructure gradually replacing the original Widmanstätten microstructure, thus promoting the second crest of the humping ductility. Finally, lots of TiC-GNPs-TiC further improved strength but inevitably reduced ductility for their serious agglomeration. This study focuses on the strengthening and toughening mechanisms of the quasi-continuous 3D TiC-GNPs-TiC network in titanium matrix reinforced by GNPs (TMCGs) and provides new insights into the design and fabrication of TMCGs with excellent strength-ductility.

Production of bovine hydroxyapatite nanoparticles as a promising biomaterial via mechanochemical and sonochemical methods

This study aimed to evaluate the effectiveness of sonochemical and milling nanoparticulate techniques using HA of bovine origin. The starting powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), and transmission electron microscopy (TEM) (75 μm). Sonication was performed with 40% of the maximum amplitude (750 W) and 20 Hz in an aqueous solution (4 h). The milling technique used a polyethylene jug loaded with 40 vol% milling elements placed in a rotatory mill (104 rpm, 48 h), then in a vibratory mill (72 h). The results revealed that the final average grain size of HA was 40 nm for the milling technique and 60 nm for the sonication (TEM). FTIR analysis showed a broad band at 1300–500 cm−1, and similar peaks without HA bond degradation, regardless of the two forms of HA nanoparticles. XRD analysis showed peaks equivalent to those of synthetic and animal HA. In addition, the equivalence between the method peaks demonstrated non-degradation of structural. The same chemical characteristics between groups were also observed in the EDX samples. We concluded that both methods were able to decrease the size of particles preserving the crystal structure, but the milling method produced smaller particles.

C60 intercalating Ti3C2T MXenes assisted by γ-cyclodextrin for electromagnetic interference shielding films with high stability

Ti3C2Tx MXenes with excellent metallic conductivity and flexibility have shown a promising prospect as electromagnetic interference (EMI) shielding materials. Ultrathin, hierarchical hybrid films were fabricated by using C60 intercalating Ti3C2Tx MXenes with the assistance of water-soluble γ-cyclodextrin (CD). The C60/CD complex was obtained by high-speed vibration milling using hydrophilic CD as dispersing agent. After thermal annealing treatment, the obtained hybrid film exhibited excellent EMI shielding (53.52±0.43 dB), hydrophobicity (water contact angle: 93.7°) and mechanical stability (over 0.9 million bending times). Taking advantage of the antioxidant of C60, the chemical durability of Ti3C2Tx MXenes based hybrid films was also improved as expected. These results indicate that the well-designed hierarchical hybrid films with the intercalation of C60 have promising potential for high-performance EMI shielding applications.

Specific features of nickel waste grinding in gaseous media

Machining of metal parts generates metal waste in the amount of up to 30 % of the original product mass requiring proper disposal. The main recycling technology in the market involves briquetting, followed by remelting, which is quite energy intensive and has a number of disadvantages. This paper proposes an alternative metal waste recycling method based on mechanical grinding. The data in various studies suggest that gases may be rated as follows in terms of their effect on disintegration of metal powders: hydrogen > helium > argon > nitrogen > air. In terms of the efficiency of removing sorbed gases from metal powders, the sequence is as follows: nitrogen > hydrogen > helium > argon. The results of the study on their effects on nickel chips disintegration suggest the following order: air – nitrogen – helium – argon (for ball mill grinding) and air – helium – argon – nitrogen (for vibration mill grinding). When grinding in air, the metal is actively covered with an oxide film; this prevents the aggregation of particles, which is otherwise observed in inert media as a result of cold welding. The use of inert media in mechanical grinding helps reducing the oxygen content on the surface of particles and prevents oxidation. These materials are applicable in powder metallurgy, in particular, for additive manufacturing and for making various parts by sintering. In terms of preventing metal oxidation, we recommend using helium for high-intensity grinding and nitrogen for traditional ball grinding. It must, however, be taken into account that helium is a more expensive gas. The authors express their gratitude to the scientific consultant of the work, Doctor of Engineering Sciences V. A. Arsentyev.The study was carried out under the grant issued by the Russian Science Foundation (project No. 20-79-10125).

A semi-active control method for magnetorheological dampers to suppress the milling vibration of thin-walled workpieces

Thin-walled workpieces are widely used in the aerospace field, and milling is the main processing method of such components. However, thin-walled workpieces are prone to vibrate during milling because of their weak stiffness, and the vibrations significantly affect the processing quality. Therefore, it is important to develop a novel milling vibration suppression method for thin-walled parts. The present work focused on the milling vibration control of a thin-walled workpiece using a semi-active magnetorheological (MR) damper. The forward dynamic model and inverse control model of the MR damper were first established, and its actuating position on the workpiece was then determined by modal analysis. The dynamic model of the MR damper at this position was built based on the proposed dynamic parameter acquisition method and used in the following semi-active control algorithm design. The effectiveness of this algorithm was verified by MATLAB/Simulink simulations. Finally, six groups of milling experiments were carried out using the non-damper, the rigid rod, the damper applied with 1-, 2-, and 3-A currents, and the semi-active control damper to validate the practical effect of the proposed algorithm. It was found that the designed semi-active control MR damper outperformed the constant-current control dampers or the rigid rod. In comparison to the non-damper experiment, the root mean square (RMS) values of milling forces in x- and y-directions decreased by 45.12% and 48.58%, respectively, and surface roughness decreased by 40.22%.

Strength-toughness combination in nickel matrix composites reinforced by hybrid graphene nanoplatelets-titanium diboride

Synergistic strengthening has attracted increasing attentions for exploring advanced metal matrix composites with considerable strength-toughness. In present study, nickel (Ni) matrix composites reinforced with hybrid graphene nanoplatelets (GNPs) and titanium diboride (TiB2) particles were fabricated by a two-step 3D vibration milling strategy. Characterization results show that both the GNPs and TiB2 are homogeneously dispersed, and the TiB2 acting as the extra milling media could relieve the stacking of exfoliated GNPs. The further refined matrix grains were achieved by introducing the hybrid GNPs-TiB2, and the obtained composites demonstrated the significantly improved tensile strength of 825 MPa (74.8% higher than that of milled Ni), derived from the synergistic strengthening effects. Meanwhile, the well-maintained fracture elongation of 27.4% was acquired for GNPs-TiB2/Ni composites, exhibiting a better combination in strength and ductility compared to individual GNPs or TiB2 reinforced Ni-based composites. Furthermore, the composites with hybrid GNPs-TiB2 also revealed the high toughness modulus, which can be attributed to the improved strain hardening capacity as well as GNPs-induced bridging and pull-out effects. This work provides an effective route to fabricate and design advanced Ni matrix composites with both superior strength and toughness.

Heterogeneous selective ensemble learning model for mill load parameters forecasting by using multiscale mechanical frequency spectrum

A ball mill is a heavy mechanical device and its safe operation affects the entire grinding process. Mill load is a key index in the optimum operation of the grinding process, but it cannot be measured directly. In industrial practice, operational experts normally estimate its value based on their experiences and the mechanical signals produced by the ball mill. In this paper, we proposed a heterogeneous selective ensemble method by using a multiscale mechanical frequency spectrum. The multicomponent adaptive decomposition algorithm is first used to decompose the original shell vibration and acoustic signals into sub-signals with different timescales. Then, selective ensemble (SEN) kernel projection to latent structure algorithm is used to model the spectral data of these sub-signals. Furthermore, the latent features of multiscale spectra are extracted to construct SEN models based on fuzzy inference. Finally, the two types of heterogeneous SEN models are fused by using information entropy. The main contribution of this study is that the proposed soft-sensing model has a dual-layer ensemble structure that can fuse multi-source information in different mechanical sub-signals with physical meaning. Moreover, the proposed model can simulate the fuzzy cognitive behavior of domain experts in the mineral grinding process. The effectiveness of the method is verified by the shell vibration and acoustical data of a laboratory-scale ball mill.

Microstructure evolution and tensile properties tailoring of graphene nanoplatelets/nickel composites fabricated by two-step 3D vibration milling

Uniformly dispersing graphene nanoplatelets (GNPs) with well-preserved structure into matrix is essential for pursuing high-performance nickel (Ni) based composites reinforced by GNPs. In this study, a two-step 3D vibration milling strategy was proposed to prepare GNPs/Ni composites with evenly-dispersed and slightly damaged GNPs. During step I milling, GNPs were exfoliated by Ni powders from graphite balls and initially distributed on powder surfaces synchronously. Followed by step II milling with zirconia balls, the uniform dispersion and thinner thickness of exfoliated GNPs were promoted, while the increased damage to GNPs was induced at higher vibration frequencies. The improved milling frequency boosted deformation of Ni powders and resulted in fine-grained matrix. The GNPs/Ni composites milled at 15 Hz in step II demonstrated a combination between homogeneously distributed GNPs with less defects and refined grains, thus actualizing the superior tensile strength (592 MPa) and ductility (30.6%). Therefore, it is feasible to tailor the microstructure and achieve exceptional mechanical properties for GNPs reinforced metal matrix composites by adjusting proper frequency in the two-step 3D vibration milling strategy.

Dynamic Amplitude-Frequency Characteristics of Vertical–Torsional Coupling System with Harmonic Response in Hot Tandem Mill

Vibration is a common and urgent technical issue in the steel industry. The world’s first multi-mode continuous-casting and rolling plant of Shou Gang Jing Tang Iron and Steel Co., Ltd. (Tangshan, China), has a finishing mill, F3, that experiences frequent, strong vibrations during the process of rolling thin-gauge (<1.5 mm) strip steel, which have seriously hindered the production of high-quality thin strip steel products. The changes in the strips’ surface quality are among the factors that induce rolling mill vibrations. In this study, considering the nonlinear surface quality of strip steel, a finite element model of the F3 mill was established, and the harmonic response method was used to obtain a rolling mill vertical system in the ANSYS environment. This study assesses the sensitive amplitude versus frequency characteristics curve of a torsional coupling system, the influence of strip thickness and strip hardness fluctuations on the vibration of the primary drive system, and the dynamic amplitude versus frequency characteristics of the three directions on the top of a torii. Finally, the field experiment verifies the correctness of the analytical results, which provides theoretical guidance for suppressing rolling mill vibrations and has a certain application value.

Vibration monitoring and analysis of strip rolling mill based on the digital twin model

A vibration monitoring method of strip rolling mill based on the digital twin model was proposed which could effectively reduce the structure complexity and test cost of the traditional monitoring system. Firstly, the coupling vibration mechanism model of the dynamic characteristics of roll system and bearings of four-high mill was established. Secondly, the digital twin model of strip rolling mill vibration was built based on the mechanism model. At the same time, the traditional monitoring test of the rolling mill was carried out to verify the accuracy of the digital twin model. Through analyzing the experimental results, it could be found that the roll system is vibrating intensely with the increase of rolling force obvious fluctuation. Finally, based on the above research results, the corresponding measures were put forward to suppress the rolling mill vibration. In conclusion, the rolling mill vibration monitoring theory based on the digital twin model provided the technical support and theoretical basis for improving equipment operation stability and reducing testing costs.

Multiscale mathematical modelling of drug activation by co-grinding

Since the 1980s, drug activation by grinding or co-grinding has evolved considerably, allowing the conversion of microcrystals into nanocrystals or amorphous phases, whose increased solubility brings a significant improvement in drug bioavailability. This has prompted many researchers to investigate and understand the entire grinding/co-grinding process. Therefore, the present work focuses on the multiscale mathematical modelling of these three aspects to establish a rational relationship between the mill setting and the properties of the milled drug. Based on the developed model, it was possible to correctly interpret and describe the experimental data obtained when we ground two poorly water-soluble drugs (nifedipine and nimesulide) with a stabiliser (cross-linked polymer; polyvinylpyrrolidone) in two mills (vibrational and planetary mills). Interestingly, despite the complexity of the whole phenomenon, the implementation of the model only required the use of a Microsoft Excel sheet in which a suitable user-defined function was embedded.

Stability analysis of milling process for multi-hardness splicing die

The tool bears the impact load and the alternating force load caused by the sudden change of hardness in the milling process of automobile panel splicing die, which aggravates the milling vibration and reduces the accuracy of die surface. According to the machining characteristics of automobile panel splicing die, the dynamic equation considering the impact of through-seam is established. The state item, the time-delay item and the periodic coefficient item in the state space form of dynamic equation were discretized by multi-order Lagrangian interpolation, and a fourth-order complete discretization method is proposed. Based on the proposed fourth-order complete discretization method, the multi-period milling stability lobe was obtained, and the milling stability lobe band in the splicing region was obtained by combining the maximum and minimum envelope method. The correctness of the dynamic model was verified by the time-frequency domain method such as Fourier transform and milling vibration and milling force data collected from the machining process. The research results can provide theoretical support for the selection and optimization of milling process parameters of splicing die.

Correction to: Experimental study on a two‑dimensional ultrasonic vibration platform and milling of Ti2AlNb intermetallic alloy

Correction to: Experimental study on a two‑dimensional ultrasonic vibration platform and milling of Ti2AlNb intermetallic alloy

Chatter Detection in Robotic Milling Using Entropy Features

Chatter detection in robotic milling is a difficult issue due to the complex dynamic behavior of robots. In this paper, a novel approach to detecting chatter in the robotic milling process is proposed. The method of improved complete ensemble empirical mode decomposition with adaptive noise is introduced for decomposing the milling vibration signals into a series of intrinsic mode functions (IMFs). The effective IMFs are chosen according to the correlation between the original signals and each IMF. Signal reconstruction is conducted using the selected IMFs. The weighted refined composite multiscale dispersion entropy is extracted from the reconstructed signals in order to characterize the chatter states. Then, a classification model is established for chatter detection. Experimental results prove that the proposed method is feasible for chatter detection in the robotic milling process under different robot configurations and machining parameters.

Ternary and Quaternary Nanocrystalline Cu-Based Sulfides as Perspective Antibacterial Materials Mechanochemically Synthesized in a Scalable Fashion.

Twelve Cu-based ternary (Cu–Me1–S, Me1 = Fe, Sn, or Sb) and quaternary (Cu–Me2–Sn–S, Me2 = Fe, Zn, or V) nanocrystalline sulfides are shown as perspective antibacterial materials here. They were prepared from elemental precursors by a one-step solvent-free mechanochemical synthesis in a 100 g batch using scalable eccentric vibratory ball milling. Most of the products have shown strong antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria. For instance, stannite Cu2FeSnS4 and mohite Cu2SnS3 were the most active against E. coli, whereas kesterite Cu2ZnSnS4 and rhodostannite Cu2FeSn3S8 exhibited the highest antibacterial activity against S. aureus. In general, stannite has shown the best antibacterial properties out of all the studied samples. Five out of twelve products have been prepared using mechanochemical synthesis for the first time in a scalable fashion here. The presented synthetic approach is a promising alternative to traditional syntheses of nanomaterials suitable for biological applications and shows ternary and quaternary sulfides as potential candidates for the next-generation antibacterial agents.

Solvent-Free Synthesis of Core-Functionalised Naphthalene Diimides by Using a Vibratory Ball Mill: Suzuki, Sonogashira and Buchwald-Hartwig Reactions.

Solvent‐free synthesis by using a vibratory ball mill (VBM) offers the chance to access new chemical reactivity, whilst reducing solvent waste and minimising reaction times. Herein, we report the core functionalisation of N,N’‐bis(2‐ethylhexyl)‐2,6‐dibromo‐1,4,5,8‐naphthalenetetracarboxylic acid (Br2‐NDI) by using Suzuki, Sonogashira and Buchwald–Hartwig coupling reactions. The products of these reactions are important building blocks in many areas of organic electronics including organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs) and organic photovoltaic cells (OPVCs). The reactions proceed in as little as 1 h, use commercially available palladium sources (frequently Pd(OAc)2) and are tolerant to air and atmospheric moisture. Furthermore, the real‐world potential of this green VBM protocol is demonstrated by the double Suzuki coupling of a monobromo(NDI) residue to a bis(thiophene) pinacol ester. The resulting dimeric NDI species has been demonstrated to behave as an electron acceptor in functioning OPVCs.

Vibration mill-assisted complex enzyme hydrolysis for flavoring of freeze-dried sea cucumber powder.

This study aims to analyze the flavor differences of freeze-dried sea cucumber powder, processed for different time intervals, under vibration mill-assisted complex enzyme hydrolysis using electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS). The results of principal component analysis by E-nose showed distinction among the four groups of freeze-dried sea cucumber powder (papain-neutral protease (PN) and flavorzyme-neutral protease (FN), processed for 60 and 80 min). The GC-IMS revealed 35 volatile compounds. Subsequently, based on the fingerprint and heat map results, the flavor differences among the samples were clearly distinguished. When compared to the other three groups, the 60-FN group exhibited a greater variety and quantity of volatile compounds such as octanal, heptanal, hexanal, (E, Z)-2,6-nonadienal, and nonanal. The 80-PN group exhibited high amounts of 2-propanone, ethylbenzene, ethyl acetate, and 2,5-dimethylpyrazine. In addition, the vibration mill technique was considered to be a mild enzyme-assisted method. PRACTICAL APPLICATIONS: This study found that different enzyme types and physical technology operation time can affect the different volatile flavor compounds of freeze-dried sea cucumber powder, which can be quickly and effectively be identified by E-nose and GC-IMS technology to improve the flavor and quality of the product, while facilitating the rapid adjustment and development of the industry. Meanwhile, the results of the study could provide a reference for the deep processing and flavor improvement of the sea cucumber industry and make an important contribution to the related literature. In addition, this could also promote the development and application of non-thermal processing technologies such as vibratory mill in the freeze-dried sea cucumber powder industry.

Experimental study on a two-dimensional ultrasonic vibration platform and milling of Ti2AlNb intermetallic alloy

Experimental study on a two-dimensional ultrasonic vibration platform and milling of Ti2AlNb intermetallic alloy