Structure Improvement and Optimization of Gantry Milling System for Complex Boring and Milling Machining Center

To enhance the efficiency and machining precision of the TX1600G complex boring and milling machining center,a study was conducted on the structure of its gantry milling system.This study aimed to mitigate the influence of factors such as structural quality,natural frequency,and stiffness.The approach employed for this investigation involved mechanism topology optimization.To initiate this process,a finite element model of the gantry milling system structure was established.Subsequently,an objective function,comprising strain energy and modal eigenvalues,was synthesized.This objective function was optimized through multi-objective topology optimization,taking into account certain mass fraction constraints and considering various factors,including processing technology.The ultimate goal of this optimization was to create a gantry milling structure that exhibited high levels of dynamic and static stiffness,a superior natural frequency,and reduced mass.To validate the effectiveness of these topology optimization results,a comparison was made between the new and previous structures.The findings of this study serve as a valuable reference for optimizing the structure of other components within the machining center.

Use of Discrete Wavelet Features and Support Vector Machine for Fault Diagnosis of Face Milling Tool

This paper presents the fault diagnosis of face milling tool based on machine learning approach.While machining,spindle vibration signals in feed direction under healthy and faulty conditions of the milling tool are acquired.A set of discrete wavelet features is extracted from the vibration signals using discrete wavelet transform(DWT)technique.The decision tree technique is used to select significant features out of all extracted wavelet features.C-support vector classification(C-SVC)andν-support vector classification(ν-SVC)models with different kernel functions of support vector machine(SVM)are used to study and classify the tool condition based on selected features.From the results obtained,C-SVC is the best model thanν-SVC and it can be able to give 94.5%classification accuracy for face milling of special steel alloy 42CrMo4.

DYNAMICS ANALYSIS OF SPECIAL STRUCTURE OF MILLING-HEAD MACHINE TOOL

The milling-head machine tool is a sophisticated and high-quality machine tool of which the spindle system is made up of special multi-element structure. Two special mechanical configurations make the cutting performance of the machine tool decline. One is the milling head spindle supported on two sets of complex bearings. The mechanical dynamic rigidity of milling head structure is researched on designed digital prototype with finite element analysis（FEA） and modal synthesis analysis （ MSA ） for identifying the weak structures. The other is the ram structure hanging on milling head. The structure is researched to get dynamic performance on cutting at different ram extending positions. The analysis results on spindle and ram are used to improve the mechanical configurations and structure in design. The machine tool is built up with modified structure and gets better dynamic rigidity than it was before.

TK 5440 CNC VERTICAL BORING AND MILLING MACHINE

This machine tool produced by theQinchuan Machine Tool Worksincorporates all the commonmachining functions, and is equipped withan advanced CNC system. It can continuouslyfinish multiple working procedures such asdrilling, milling, boring, reaming and tappingwithin one clamping. Not only is it universaland efficient, but also it can machinecomplicated parts which cannot be machinedon general universal machines, such as variouskinds of precision molds, plates, disks,

Experimental Study on Titanium Alloy Cutting Property and Wear Mechanism with Circular-arc Milling Cutters

Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.

基于PowerMILL Vortex旋风铣与MachineDNA系统应用研究

旋风铣Vortex是Delcam最新的高速区域清除加工策略,可用于2轴、3轴、定位五轴以及残留加工。和传统高速加工方法相比,可节省多达60%的加工时间。Machine DNA是Delcam的一项最新专利技术,它可捕捉单个机床的运行特点和数据,并使用捕捉的数据来完善Power MILL产生的刀具路径[1]。旋风铣Vortex与Machine DNA的结合使粗加工效率提升的同时,最大限度地发挥机床潜能,从而可在合理安全的切削条件下实现加工效率最大化。

Development of an In-Situ Laser Machining System Using a Three-Dimensional Galvanometer Scanner

In this study, a three-dimensional (3D) in-situ laser machining system integrating laser measurement and machining was built using a 3D galvanometer scanner equipped with a side-axis industrial camera. A line structured light measurement model based on a galvanometer scanner was proposed to obtain the 3D information of the workpiece. A height calibration method was proposed to further ensure measurement accuracy, so as to achieve accurate laser focusing. In-situ machining software was developed to realize time-saving and labor-saving 3D laser processing. The feasibility and practicability of this in-situ laser machining system were verified using specific cases. In comparison with the conventional line structured light measurement method, the proposed methods do not require light plane calibration, and do not need additional motion axes for 3D reconstruction;thus they provide technical and cost advantages. The insitu laser machining system realizes a simple operation process by integrating measurement and machining,which greatly reduces labor and time costs.

Theoretical modeling of cutting temperature in high-speed end milling process for die/mold machining

A parametric model of cutting temperature generated in end milling process is developed according to the thermal mechanism of end milling as an intermittent operation, which periodically repeats the cycle of heating under cutting and cooling under non-cutting. It shows that cutting speed and the tool-workpiece engagement condition are determinative for tool temperature in the operation. The suggested model was investigated by tests of AlTiN coated endmill machining hardened die steel JIS SKD61, where cutting temperature on the flank face of tool was measured with an optical fiber type radiation thermometer. Experimental results show that the tendency of cutting temperature to increase with cutting speed and engagement angle is intensified with the progressing tool wear.

Ensemble Model for Spindle Thermal Displacement Prediction of Machine Tools

Numerous factors affect the increased temperature of a machine tool, including prolonged and high-intensity usage,tool-workpiece interaction, mechanical friction, and elevated ambient temperatures, among others. Consequently,spindle thermal displacement occurs, and machining precision suffers. To prevent the errors caused by thetemperature rise of the Spindle fromaffecting the accuracy during themachining process, typically, the factory willwarm up themachine before themanufacturing process.However, if there is noway to understand the tool spindle’sthermal deformation, the machining quality will be greatly affected. In order to solve the above problem, thisstudy aims to predict the thermal displacement of the machine tool by using intelligent algorithms. In the practicalapplication, only a few temperature sensors are used to input the information into the prediction model for realtimethermal displacement prediction. This approach has greatly improved the quality of tool processing.However,each algorithm has different performances in different environments. In this study, an ensemble model is used tointegrate Long Short-TermMemory (LSTM) with Support VectorMachine (SVM). The experimental results showthat the prediction performance of LSTM-SVM is higher than that of other machine learning algorithms.

EQUIVALENT NORMAL CURVATURE APPROACH MILLING MODEL OF MACHINING FREEFORM SURFACES

A new milling methodology with the equivalent normal curvature milling model machining freeform surfaces is proposed based on the normal curvature theorems on differential geometry. Moreover, a specialized whirlwind milling tool and a 5-axis CNC horizontal milling machine are introduced. This new milling model can efficiently enlarge the material removal volume at the tip of the whirlwind milling tool and improve the producing capacity. The machining strategy of this model is to regulate the orientation of the whirlwind milling tool relatively to the principal directions of the workpiece surface at the point of contact, so as to create a full match with collision avoidance between the workpiece surface and the symmetric rotational surface of the milling tool. The practical results show that this new milling model is an effective method in machining complex three- dimensional surfaces. This model has a good improvement on finishing machining time and scallop height in machining the freeform surfaces over other milling processes. Some actual examples for manufacturing the freeform surfaces with this new model are given.

Theoretical and Experimental Investigation of Laser Milling Assisted with Jet Electrochemical Machining

In laser milling assisted with jet electrochemical machining(LMAJECM),the source of energy is a pulsed laser beam aligned coaxially with a jet of electrolyte,which focuses optical energy on the surface of workpiece.The impact of jet of electrolyte develops a state-of-art work to perform operations such as electrolytic etching,effective cooling,and transportation of debris.Therefore,a special jet cell is designed to obtain stable jet as to be a kind of noncontact tool,i.e.,electrode.According to the theoretical model of on-off pulse time process,laser machining and electrolytic anodization are simulated by finite element analysis(FEA)method.Grooves on a 0.5mm thick 321 stainless steel sheet produced by LMAJECM is performed with pulsed Nd:YAG laser at the second harmonic wavelength.Compared with laser milling under ambient atmosphere conditions,the recast layer and burrs are effectively diminished.And the accuracy of depth is dedicated to laser milling,whilst that of width is dominated by jet electrochemical machining.It is demonstrated that LMAJECM can be a highly potential approach for fabricating 3-D micro components.

Online tool-wear measurement of small-diameter end mills based on machine vision

The objective of this study was to develop an online tool-wear-measurement scheme for small diameter end-mills based on machine vision to increase tool life and the production efficiency. The geometrical features of wear zone of each end mill were analyzed, and three tool wear criterions of small-diameter end mills were defined. With the uEye camera, macro lens and 3-axis micro milling machine, it was proved the feasibility of measuring flank wear with the milling tests on a 45# steel workpiece. The design of experiment （DOE） showed that Vc was the most remarkable effect factor for the flank wear of small-diameter end mill. The wear curve of the experiments of milling was very similar to the Taylor curve.

Machining Parameters Optimization of Multi-Pass Face Milling Using a Chaotic Imperialist Competitive Algorithm with an Efficient Constraint-Handling Mechanism

The selection of machining parameters directly affects the production time,quality,cost,and other process performance measures for multi-pass milling.Optimization of machining parameters is of great significance.However,it is a nonlinear constrained optimization problem,which is very difficult to obtain satisfactory solutions by traditional optimization methods.A new optimization technique combined chaotic operator and imperialist competitive algorithm(ICA)is proposed to solve this problem.The ICA simulates the competition between the empires.It is a population-based meta-heuristic algorithm for unconstrained optimization problems.Imperialist development operator based on chaotic sequence is introduced to improve the local search of ICA,while constraints handling mechanism is introduced and an imperialist-colony transformation policy is established.The improved ICA is called chaotic imperialist competitive algorithm(CICA).A case study of optimizing machining parameters for multi-pass face milling operations is presented to verify the effectiveness of the proposed method.The case is to optimize parameters such as speed,feed,and depth of cut in each pass have yielded a minimum total product ion cost.The depth of cut of optimal strategy obtained by CICA are 4 mm,3 mm,1 mm for rough cutting pass 1,rough cutting pass 1 and finish cutting pass,respectively.The cost for each pass are$0.5366 US,$0.4473 US and$0.3738 US.The optimal solution of CICA for various strategies with at=8 mm is$1.3576 US.The results obtained with the proposed schemes are better than those of previous work.This shows the superior performance of CICA in solving such problems.Finally,optimization of cutting strategy when the width of workpiece no smaller than the diameter of cutter is discussed.Conclusion can be drawn that larger tool diameter and row spacing should be chosen to increase cutting efficiency.

Milling Machinability of TiC Particle and TiB Whisker Hybrid Reinforced Titanium Matrix Composites

The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination.Polycrystalline diamond(PCD)tools with different grain sizes and geometries,and carbide tools with and without coatings were used in the experiments.Milling forces,milling temperatures,tool lifetimes,tool wear,and machined surface integrities were investigated.The PCD tool required a primary cutting force 15%smaller than that of the carbide tool,while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiAlN-coated tool.A cutting force of 300 Nper millimeter of the cutting edge(300N/mm)was measured.This caused excessive tool chipping.The cutting temperature of the PCD tool was 20%—30%lower than that of the carbide tool,while that of the TiAlN-coated tool was 12%lower than that of the uncoated carbide tool.The cutting temperatures produced when using water-based cooling and minimal quantity lubrication(MQL)were reduced by 100°C and 200°C,compared with those recorded with dry cutting,respectively.In general,the PCD tool lifetimes were 2—3 times longer than the carbide tool lifetimes.The roughness Raof the machined surface was less than 0.6μm,and the depth of the machined surface hardened layer was in the range of 0.15—0.25 mm for all of the PCD tools before a flank wear land of 0.2mm was reached.The PCD tool with a 0.8mm tool nose radius,0°rake angle,10°flank angle,and grain size of(30+2)μm exhibited the best cutting performance.For this specific tool,a lifetime of 16 min can be expected.

Heat regulating strategy in numerical control end milling for hard metal machining

The trend in die/mold manufacturing at present is towards the hard machining at high speed to replace the electron dis- charge machining. Failure forms of the AlTiN-coated micro-grain carbide endmill when used for the machining of JIS SKD61 (HRC 53), a widely used material in die/mold manufacturing, are investigated. The endmill shows a characteristic that tool life decreases greatly due to the chipping when overload occurs or the rapid increase of wear when over-heat accumulation in cutting edges. As a consequence of the investigation, a strategy to regulate heat generation in the end milling process is proposed. This is accomplished by controlling the cutting arc length, i.e. the length of each flute engaging workpiece in a cutting cycle. Case studies on the slot end milling and comer rounding are conducted. The results show that the proposed strategy suggests the optimal tool path as well as the optimal pitch between successive tool paths under the cutting time criterion.

Analysis and correction of the machining errors of small plastic helical gears by ball-end milling

Many small-size precise plastic helical involutes gears are used in electrical appliances to transmit rotary movements con- tinuously and smoothly. Ball-end milling is an effective method for trial manufacture or small batch production of this type of gear, but the precision of the gear is usually low. In this research, the main sources of the errors of the gear, machining errors of the tooth profile and trace of the gear obtained were analyzed. The correction amounts for these errors are then determined by using a CNC gear tester. They are used to generate a new 3D-CAD model for gear machining with better nrecision.

MATHEMATICAL MODEL OF NC MACHINING NONCONVENTIONAL MILLING CUTTERS-FORMING METHOD OF RAKE FACES

How to generate rake faces of nonconventional milling cutters (NCMC) with constant spiral angled and normal rake angled edges on NC machine tools is presented by use of a blunt cup grinder or a cup milling cutter. Motion functions of the NC machining system are mathematically deduced and exam- ed by a experiment. The research will provide theoretical and practical guidance for machining noncon- ventional tools on NC machine tools.

Electrical discharge and arc milling with automatic tracking of optimal flushing direction:A novel high-efficiency compound machining method

The arc milling method has the advantages of high machining efficiency and low cost and is independent of the strength and hardness of machined materials.However,frequent electrode back-offs and the risk of workpiece burning may occur if erosion products are not removed promptly.In this study,it was found that the flushing method of the working medium had a significant impact on the machining performance of arc milling.Based on this,a novel highefficiency compound machining method of electrical discharge and arc milling with automatic tracking of the optimal flushing direction was proposed.An automatic tracking optimizer for external working medium injection was designed to determine the optimal external flushing direction according to the feed direction.The influence of flushing methods,working mediums,and machining parameters on the machining efficiency,tool electrode wear rate,machining error,and surface integrity of titanium alloys were investigated.The results indicated that better machining performance and environmental friendliness were achieved using the compound flushing method of outer compressed air and inner deionized water.Additionally,the automatic tracking flushing method in the opposite direction of the feed direction showed superior results compared to other directions.The material removal rate with the opposite direction injection could be increased up to 1.62 times that of the same direction,and the relative electrode wear rate could be reduced by 14.76%.This novel method has broad application prospects for machining parts with difficult-to-cut materials in aerospace and military industries.

Modeling and Analytical Solution of Chatter Stability for T-slot Milling

T-slot milling is one of the most common milling processes in industry. Despite recent advances in machining technology, productivity of T-slot milling is usually limited due to the process limitations such as high cutting forces and stability. If cutting conditions are not selected properly the process may result in the poor surface finish of the workpiece and the potential damage to the machine tool. Currently, the predication of chatter stability and determination of optimal cutting conditions based on the modeling of T-slot milling process is an effective way to improve the material removal rate（MRR） of a T-slot milling operation. Based on the geometrical model of the T-slot cutter, the dynamic cutting force model was presented in which the average directional cutting force coefficients were obtained by means of numerical approach, and leads to an analytical determination of stability lobes diagram（SLD） on the axial depth of cut. A new kind of SLD on the radial depth of cut was also created to satisfy the special requirement of T-slot milling. Thereafter, a dynamic simulation model of T-slot milling was implemented using Matlab software. In order to verify the effectiveness of the approach, the transfer functions of a typical cutting system in a vertical CNC machining center were measured in both feed and normal directions by an instrumented hammer and accelerators. Dynamic simulations were conducted to obtain the predicated SLD under specified cutting conditions with both the proposed model and CutPro~. Meanwhile, a set of cutting trials were conducted to reveal whether the cutting process under specified cutting conditions is stable or not. Both the simulation comparison and experimental verification demonstrated that the satisfactory coincidence between the simulated, the predicted and the experimental results. The chatter-free T-slot milling with higher MRR can be achieved under the cutting conditions determined according to the SLD simulation.

Design Theory of Full Face Rock Tunnel Boring Machine Transition Cutter Edge Angle and Its Application

At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased.