Machine Tool Bed Research Articles

Mechanical Properties of Aramid Fiber Reinforced Resin Mineral Composites for Machine Tool Beds

Mechanical Properties of Aramid Fiber Reinforced Resin Mineral Composites for Machine Tool Beds

Topology Optimization and Analysis of the Compound Boring and Milling Machining Center TX1600g Bed Structure

The overall performance of the machine tool bed of the boring and milling center has an important impact on the accuracy of the overall machining, in order to improve the machining accuracy and structural performance of the overall machine tool, the structure optimization design of the machine bed is carried out for the TX1600g composite boring and milling center. The maximum static displacement and mass of the bed were used as the evaluation index to optimize the topology and structure of the bed. An orthogonal test of 5 factors and 5 levels was designed, the maximum displacement generated by different positions in work was analyzed, the frequency under this working condition was explored, and modal analysis was conducted. The Hyperwork selective variable density method is used to optimize the beam structure with multiple objective topologies. By comparing and optimizing the performance parameters of the front and rear beams, the total static displacement is reduced by 9%, which proves the effectiveness of this method to solve the multi-objective optimization problem.

Contact modeling of heterogeneous materials of the machine tool bed–foundation interface based on the gradient of contact stress distribution

Contact modeling of heterogeneous materials of the machine tool bed–foundation interface based on the gradient of contact stress distribution

ЭКСПЕРИМЕНТАЛЬНЫЕ МЕРОПРИЯТИЯ ПО УЛУЧШЕНИЮ ТЕПЛОВЫХ ХАРАКТЕРИСТИК В ДВУСТОРОННИХ ТОРЦЕШЛИФОВАЛЬНЫХ СТАНКАХ

The results of full-scale and computational experiments to improve the thermal characteristics of the machine tool are presented. This can lead to a decrease or achieve symmetry of the resulting thermal deformations. The implementation of four schemes for the redistribution of heat fluxes is considered: the heat flux of the main electric motors, directed under the protective casing of the drive pulley, and the heat flux of the belt drive are removed through special windows in the casing to the environment; jointly with the first scheme of redistribution of heat fluxes, cooling of the ends of the grinding headstocks is provided with the help of an impeller fixed on each drive pulley; jointly with the second scheme, heat flux isolation from the left and right electric motors is provided; heating the ends of the machine tool bed. The first three schemes are implemented at idling of the machine tool; the fourth scheme is implemented when the machine is operating under thermal load. The joint implementation of three schemes makes it possible to reduce the displacement of the right circle at idle by 1.5 times, the left circle practically did not move. The test of the first three circuits during the operation of the machine tool under a thermal load does not reveal significant changes in the thermal characteristics. The implementation of the fourth heat flux redistribution scheme help to compensate for thermal deformations from heating in the central part of the bed and reduce changes in the angular position of the grinding wheels.

Study on the application of a granite composite material in five-axis CNC-VMC machine Tool

A five-axis CNC-VMC machine tool generally has a high-speed spindle spinning at a maximum rotation of 50,000 rpm, under which the machine tool bed will violently vibrate that leads to poor machining precision and surface quality of workpiece. The gray cast iron, as the typical material of a machine tool, exhibits poor dynamic suppression of vibration that its processing yield and quality can no longer satisfy the product demand of current market. Consequently, in this study, we proposed granite composite material (GCM) in place of gray cast iron for the structure of machine tool, which would be mixed with main ingredients of high-strength epoxy resin and cemented carbon fibers and fillers to maximize the structural properties of the machine tool. The sample of granite composite material would first be tested for its mechanical properties. The results showed that the GCM cast with only 1/3 density of gray cast iron could withstand a maximum compressive stress of 125.8 MPa. With this granite composite material used in a digitally controlled machine tool bed, the maximum stress and the maximum strain exerted on the machine tool were reduced by 68.93% and 72.6%, respectively, when compared with the cast iron, while the 1st to the 6th-order natural frequencies of the machine tool of mineral composite was significantly increased by 20% to 30%, giving it more resistance to vibration than the gray cast iron. The stability and precision of the machine tool were shown to have been drastically improved by using the granite composite material.

The Optimization Simulation Analysis of Heavy NC Machine Tool Bed

In order to reduce the high manufacturing cost of heavy numerical control (NC) machine tool bed, the paper first introduced the stiffness and strength calculation method of constant cross-section and constant span beam, and deduced the theoretical optimization model with the minimum cross-section area of the bed as the optimization objective. Using the interior point method completed the optimization analysis of the machine bed. Then, the ISIGHT software was used to realize the integration of design software and analysis software, and the optimization simulation analysis of the machine bed was completed under the same interface. Finally, the calculation accuracy of the theoretical model is verified by comparing the optimization results of the theoretical model and the simulation model. The weight can be reduced by more than 10% on the basis of ensuring the stiffness and strength of the machine bed. The method lays a theoretical foundation for the manufacture of the machine bed.

Effect of shape formation on the accuracy of grinding ends while compensating for machine tool errors

There are several general methods for correcting errors related to positioning the machine tool structural units. The task to achieve optimal manufacturing accuracy can be resolved by using a compatible solution to vector equations, a variation of the shape formation function, or applying a matrix of transfer coefficients. However, there is no mutual relationship between various calculation methods for the case of grinding flat surfaces. The methods should be simplified and tested for the elongated shape formation function while considering the links’ dimensions. This paper reports a study into the accuracy of grinding flat surfaces, determining and reducing the share of manufacturing errors. The content of variation matrices and transfer coefficients has been substantiated. The comparison of the orientation angles of the grinding machine headstock relative to the machine tool bed has demonstrated close results from all methods. These angles were taken as machine tool errors. The calculation error does not exceed 1.5 %. The experiments are consistent with the calculations. Different signs of the transfer coefficients in the orientation angles of grinding machine headstocks in the matrix make it possible to mutually compensate for the overall impact. The calculations have shown that the accuracy of the side-end machining is largely affected by a change in the orientation angle in the vertical plane. The effect exerted on the accuracy of individual mated parts by the machine tool structural units has been estimated. The calculations show that the error of positioning a part in the drum window acquires the highest absolute values and is random in nature, which requires a more accurate base positioning. The findings from both theoretical and experimental studies have been applied. The mathematical model makes it possible to determine the degree of scattering the end surface around the base plane via its variance. The measured trajectory provides diagnostic information about the sources of error in the machine tool assembly. A task to calculate the accuracy of the end-grinding machine tool can be solved for other models of machine tools in the same way

Life cycle carbon emission assessments and comparisons of cast iron and resin mineral composite machine tool bed in China

Machine tool is the core of manufacturing, and one of its indispensable parts is the machine tool bed, which is mainly composed of cast iron and exhibits high material consumption. Owing to the high carbon emissions of steel industries and the limitation of steel reserves, resin mineral composite machine tool beds have been developed. But the carbon emissions of the resin mineral composite machine tool bed are not assessed. A life cycle assessment (LCA) was conducted to investigate the carbon emissions across the life cycle phases of cast iron machine tool bed and resin mineral composite machine tool bed. The uses of cast iron and resin mineral composite for machine tool bed were compared. LCA was employed to establish a carbon emission assessment model for the raw material acquisition phase, manufacturing phase, recycling phase, and disposal phase. Carbon emission assessments were conducted based on reliable survey data. The cast iron machine tool bed has a total carbon emission of 5673.60 kgCO2eq, and the resin mineral composite bed has a total carbon emission of 1259.37 kgCO2eq. Compared with the cast iron machine tool bed, the resin mineral composite machine tool bed reduces carbon emissions by 77.80%. It was found that the carbon emission of the cast iron machine tool bed was greater than that of the resin mineral composite tool bed. It lays a foundation for the research on the potentiality of the resin mineral composite machine tool bed to replace the cast iron machine tool bed form the point of environmental aspects.

Cleaning of Graphite Particles Embedded in the Surface of Ductile Iron by Using a Novel Method

Ductile iron has unique mechanical property and has been widely used in many industrial applications, e.g., engine cylinder covers, crank axles, and machine tool beds and cams. The welding performance of ductile iron is normally influenced by graphite particles in the surface of ductile iron, which needs to be removed before welding. In this article, laser cleaning technique was developed to remove graphite particles implanted in the surface of ductile iron. Laser cleaning parameters and the damage threshold value of the substrate were investigated by using a pulsed Nd: YAG laser. The optimized laser cleaning parameters were obtained to achieve high-quality cleaning effect and avoid the formation of the oxide layer. Surface morphologies and elemental compositions of specimens before and after laser cleaning were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Results indicated that graphite particles implanted in the surface of ductile iron were removed completely and efficiently by using the pulsed laser without the protection of inert gas atmosphere, and surface oxidation was not observed during the laser cleaning process.

Design and Investigation of Machine Tool Bed Based on Polymer Concrete Mixture

Design and Investigation of Machine Tool Bed Based on Polymer Concrete Mixture

Influence of fly ash on the curing characteristics of an epoxy resin

With excellent damping capacity, growing interest has been focused on polymer concrete (PC) as a novel machine tool bed material in the field of ultraprecision machining. It is widely acknowledged that the fly ash (FA) is an essential component material in reducing the curing shrinkage of PC, which can significantly affect the curing characteristic of PC. However, the effect of FA on the curing characteristic of epoxy resin is not studied in detail. In this article, the effect of FA on the curing characteristic of epoxy resin was examined by differential scanning calorimetry. Experimental results show that the peak temperature and curing rates of epoxy resin/curing agent and epoxy resin/curing agent/FA increase with the increasing heating rates, and the peak temperature and curing rates of epoxy resin/curing agent are greater than that of the epoxy resin/curing agent/FA with the same heating rates. In addition, the difference between the maximum curing rates of epoxy resin/curing agent and epoxy resin/curing agent/FA decreased with the increasing heating rates. This article can provide technical reference for curing process of PC for machine tool beds and further improve the machining accuracy.

Investigation of high temperature wear performance on laser processed nodular iron using optimization technique

Nodular cast iron (NCI) are used in nuclear energy and transportation industries. Also, NCI are used in gear boxes, camshaft, crank shaft, rolling mill rolls and machine tool beds. The reliability of the NCI under heavy loading condition is affected through several tribological aspects. In the present study, NCI surface has been melted by using an Ytterbium-doped fiber laser. The wear resistances of the substrate and melted surface have been analyzed by using a tribometer. Sliding speed, load and working temperatures have been considered as input parameters to tribometer. From the optimization trials, the applied load was identified as the most significant parameter followed by sliding speed and ambience temperature. The responses of the optimized tribological parameters attained by GRA was confirmed through experimental and agreed closely to the predicted value. Further, the surface of the substrate and laser melted samples were analyzed. The melted surfaces were free from surface deformities and exhibited a noticeable improvement in the wear resistance compared to the substrate.

Effective resin content and its effect on the overall performance of polymer concrete for precision machine tools

Polymer concrete (PC) is associated with an enormous potential in fabricating the machine tool bed due to its superior damping properties. However, its inferior mechanical property is one of the major drawbacks limiting its application in precision machine tools. Admittedly, the resin content has remarkably affected the mechanical properties of PC, and its heavy use will notably increase the manufacturing cost of PC. Typically, the effective resin content is mainly dependent on the porosity accumulated by the total aggregate. In this study, the effects of fractal dimension on the mechanical properties, damping ratio and porosity of PC were systematically investigated. Our experimental results demonstrated that the porosity, flexural strength and damping ratio of PC were first decreased and then increased with the increase in fractal dimension, whereas the compressive strength had exhibited the opposite trend. Additionally, our experimental results also indicated that the air void was increased on the whole with the increase in fractal dimension. Finally, the relationships between the overall performance of PC (namely, compressive strength, flexural strength, and damping ratio) and the effective resin content were examined, which showed that the overall performance of PC was closely correlated with its effective resin content. Moreover, this study was also of great significance to reduce the manufacturing cost of PC and improve its application in precision machine tool bed.

Vibration Transmission and Isolation in the Cutting Process of Machine Tools

Background: Machining is an important method for manufacturing parts. It is characterized by high cutting speed with a considerable influence of high-frequency vibration. Various relevant papers and patents have studied vibration transmission and isolation in the machining process. Objective: To investigate vibration transmission and isolation in the machining process, and simplify the cutting process of a machine tool. Methods: Firstly single-layer and double-layer vibration isolation models are established, the substructure matrix analysis method is adopted and the vibration power flow transmission characteristics of double-layer vibration isolation system under complex excitation are analyzed. Secondly, the optimal control strategy based on the minimum power flow inputted into the base is proposed. Then the control effect of the active actuator under different installation modes is analysed and compared. Results: It has been proved that low-frequency coupling is characterized by the rigid mode of the workpiece or the grinding wheel when cutting, whereas high-frequency coupling exhibits the dynamic characteristics of the machine tool bed. A good vibration isolation effect can be achieved for three types of installation modes in a double-layer vibration isolation system, and only the actuators installed between the vibration source and the middle mass exhibit the best control effect. Conclusion: The vibration isolation model has been established and the optimal installation mode of the actuator in the double-layer vibration isolation system has been found. And the paper provides a reference for the study of vibration transmission, control of machine tools and the elimination of grinding chatter.

Optimal layout of internal stiffeners for three-dimensional box structures based on natural branching phenomena

ABSTRACTThin-wall box structures combine an outer wall and internal stiffeners. These stiffeners can improve the stiffness of box structures. The adaptive growth method based on natural branching phenomena is applied to solve this layout optimization problem, in which techniques of ground structure construction, stiffener growth direction control, ‘seeding-line’ selection and sensitivity filtering are studied. First, the ground structure with solid and shell elements is established. Then, an iteration formula based on Karush–Kuhn–Tucker optimum conditions is derived. Stiffeners start at the seeding line and grow gradually according to the design sensitivities. Finally, an optimum stiffener layout is obtained. Draft manufacturing constraints are also included in the design procedure. The validity of the method is verified by several design examples. An actual machine tool bed is redesigned, and the performance comparison between the original and optimized beds shows the superiority of the suggested method.

Static calculation of the “Spindle unit” elastic system by using transfer matrices method

Methodology, that allows to use the transfer matrices method for the static calculation of spindle unit as elastic system, which consists of a few associate subsystems, has been developed. Restrictions of the dynamic compliances method use for static calculations of «spindle unit» system decomposing has been stated. For such calculations it is suggested to conduct the decoupling of the system with the use of mixed method of indefinable beam systems static calculation. The elastically-deformation model of the «Spindle unit» system, that consist of subsystems: tool, spindle, spindle housing elastically mounted on the machine-tool bed, is being presented. The scheme of decoupling of this system for static calculations has been developed. The analytical solution of task of the elastic displacements calculation in the characteristic points of subsystems has been obtained. The algorithm of static calculation of the «Spindle unit» elastic system has been developed. Offered approach allows applying an identical methodological base for the static and dynamic characteristics simulation of the «Spindle unit» elastic system.

Performance evaluation of cryogenically treated and tempered tungsten carbide insert on face milling of grey cast iron

The objective of this study is to evaluate the wear progression of cryogenically treated (treated and tempered) and untreated tungsten carbide inserts during the face milling of grey cast iron which is a commonly used material in machine tool beds and automotive components due to low cost, high vibration damping capability, and easiness of manufacturing. Commercially available uncoated tungsten carbide inserts with around 6% Cobalt (Co) content were selected for the study. Flank wear and nose wear were taken as the performance evaluation criteria. The results showed that the cryogenically treated and tempered samples have better tool life than the untreated inserts which is ascribed to the martensitic phase transformation of Co from α-Co (FCC) to e-Co (HCP) and the formation of compressive residual stress in the treated insert samples. This was confirmed with the help of metallographic analysis by studying the magnetic saturation and coercivity of the untreated and treated samples. This work focuses on the effect of cryogenic treatment on the magnetic properties of tungsten carbide insert which results in higher wear resistance of about 12% to 20%.

Teoretyczna i eksperymentalna analiza modalna hybrydowego łoża obrabiarki

Teoretyczna i eksperymentalna analiza modalna hybrydowego łoża obrabiarki

2D Meso-Scale Finite Element Modeling and Simulation of Polymer-Mineral Composite Material

Polymer-mineral composite material is prepared by using modified epoxy resin as binder and mineral particles as aggregates. Its excellent damping characteristic and low thermal expansion make it ideal in manufacturing machine tool beds. However, the properties of this material depend on its formula and structure, so it is very important to develop an efficient method to numerically model the materials and then to optimize their properties. In this paper, 2D meso-scale finite element modeling is presented for numerical analysis of the mechanical properties of polymer-mineral composite material. The material was treated as a 2-phase composite composed of aggregates and binder which was epoxy resin mixed with fillers. Based on grading curve, the weights of aggregates were converted into the corresponding area, the aggregate particles were randomly generated and assembled with binder to produce the model. And then 2D numerical simulations were conducted under different gradations. The results show that: (1) the 2D FE model is very close to the real polymer-mineral composite material in the aspect of density and aggregate shapes and sizes, which validate the fidelity of the generated finite element model and numerical analysis method; (2) by comparing the materials’ properties under four different gradations, it can be found that the materials with SAC gradation have the best mechanical property.

Experimental investigation on air void and compressive strength optimization of resin mineral composite for precision machine tool

Resin mineral composite (RMC) consists of epoxy resin, granite aggregate and fly ash, and which can be used to produce precision machine tool beds due to its superior vibration alleviating properties. However, applications of RMC are restricted due to its limited mechanical strength. In this paper, the effects of the air void on the compressive strength of RMC were firstly introduced. Then the effects of vibration time, initial temperature of resin, mass of compression mould, vacuum degree, number of layers and mass content of defoamer on the air void and compressive strength of RMC were thoroughly investigated. Experimental results show that the air void (compressive strength) of RMC first decreases (increases) and then stabilizes as the vibration time and number of layers increases. Results also show that the air void (compressive strength) of RMC first decreases (increases) and then increases (decreases) as the initial temperature of resin, mass of compression mould, vacuum degree and mass content of defoamer increases. In order to further reduce the air void of RMC and increase the compressive strength of RMC, five different compound technologies (i.e., CTA, CTB, CTC, CTD, CTE) at different temperature (10°C and 40°C) were investigated. The optimum air void (compressive strength) of RMC was achieved by the CTE at 10°C, in which the air void (compressive strength) decreased (increased) by 44.4% (19.7%) compared to the RMC poured by CTA (standard pouring technologies) at 10°C. Afterwards, the relationship between air void and compressive strength of RMC was studied systematically. POLYM. COMPOS., 39:457–466, 2018. © 2016 Society of Plastics Engineers