金刚石绳锯切割混凝土的锯切力实验研究

对烧结金刚石串珠绳锯在锯切混凝土过程中锯切力的变化进行了跟踪检测实验,研究了锯切力随锯切参数及锯切长度的变化规律.实验结果表明:锯切过程中,工件上所承受的锯切力(水平力Fh和垂直力Fv)随着线速度vs的提高而减低,随着进给速度vf的提高而增加.锯切力随着锯切中工件长度L的增加而增加.垂直力与水平力之间存在着良好的对应关...     

焊接吊耳锯切质量评定指标及影响因素

焊接吊耳是钢结构制造过程中用于吊装的重要零件。结合传统的锯切原理,从结构上分析焊接吊耳的锯切,为减小留根量,在利用带锯条锯切焊接吊耳时需要采用水平锯切方式,同时不能使用传统的带锯条扭转装置,而应该增大张紧力保证锯切质量。并将切口表面粗糙度Ra和留根斜度的正切值ρ作为锯切焊接吊耳质量的评定指标。采用正交实验法研究张紧力、锯切速度以及进给速度对焊接吊耳锯切质量的影响。研究表明:张紧力和进给速度对Ra和ρ的影响最大,锯切速度对粗糙度影响较小;张紧力越大,进给速度越小,则锯切质量越好。     

Improved modelling of cutting force coefficients in peripheral milling

Titanium is one of the most widely used metals in the aircraft and turbine manufacturing industries. Accurate prediction of cutting forces is important in controlling the dimensional accuracy of thin walled aerospace components. In this paper, a general three-dimensional mechanistic model for peripheral milling processes is presented. The effects of chip thickness, rake angle and cutting geometry on chip flow, rake face friction and pressure, and cutting forces are analyzed. A set of closed form expressions with experimentally estimated cutting force factors are presented for the prediction of cutting forces. The model is verified experimentally in the peripheral milling of a titanium alloy. For a given set of cutting conditions and tool geometry, the model predicts the cutting forces accurately for the chip thickness and rake angle ranges tested.     

硬脆材料的电镀金刚石线锯超声切割锯切力研究

基于冲量理论和振动加工理论,采用叠加原理建立了电镀金刚石线锯超声切割锯切力数学模型.从理论上分析了电镀金刚石线锯施加超声振动后锯切力与普通锯切力的区别,并进行了超声振动与普通锯切力对比试验研究.结果表明:锯切力的大小随线锯往复频率的提高而降低,随侧向压力的增加而增大.通过比较发现,超声振动锯切力比普通锯切力减小20%～30%.同时,对超声振动锯切过程中单颗金刚石磨粒切削运动轨迹进行了仿真分析,进一步解释了施加超声振动后锯切力减小的原因.     

Mechanistic model for prediction of cutting forces in micro end-milling and experimental comparison

Micro end milling is an important process in the manufacture of micro and meso scale products and has an advantage of creating more complex geometry in a wider variety of materials in comparison with other micro-machining methods. In this paper, a new methodology for predicting the cutting coefficients considering the edge radius and material strengthening effects is presented. Further a mechanistic model is developed to predict the cutting forces in micro end milling operation taking into account overlapping tooth engagements. The mechanistic model, derived from basics considering material property and principles of metal cutting, is valid for a wider range of cutting parameters. The model is validated with the results from micro slot end-milling of mild steel carried out on the basis of full factorial design. On comparing the amplitudes of cutting forces, it is seen that mechanistic model predicts the transverse force with an average absolute error of 12.29%, while a higher prediction error of 19.49% is obtained for feed force. Additionally the mechanistic model is able to predict the variations in the cutting forces with rotation of the cutter and average absolute deviations of 13% and 11% are obtained for feed and transverse forces, respectively.     

金刚石框架锯锯切研究（2）一锯切破碎机理

在对金刚石框架锯锯切加工动力学研究的基础上，通过单颗粒划痕和单个金刚石结块切削大理石试验，模拟金刚石框架锯锯切过程中，金刚石颗粒和结块在不同加工条件下的切削过程；测量分析了切削力、表面沟槽轮廊和有效切削磨粒数；观察并分析了加工表面形貌；运用岩石脆性断裂力学理论，分析了单颗粒金刚石切削机理。通过金刚石框架锯发加工大理石的切屑粒度分布分析，指出了实际加工切削条件对锯切破碎机理的影响。研究结果证实了金刚石框架锯锯工加工动力学研究的一些基本结论，最后提出了金刚石框架锯锯切大理石破碎机理模型。     

Estimation and experimental validation of cutting forces in ball-end milling of sculptured surfaces

Chip thickness calculation has a key important effect on the prediction accuracy of accompanied cutting forces in milling process. This paper presents a mechanistic method for estimating cutting force in ball-end milling of sculptured surfaces for any cases of toolpaths and varying feedrate by incorporation into a new chip thickness model. Based on the given cutter location path and feedrate scheduling strategy, the trace modeling of the cutting edge used to determine the undeformed chip area is resulted from the relative part-tool motion in milling. Issues, such as the selection of the tooth tip and the computation of the preceding cutting path for the tooth tip, are also discussed in detail to ensure the accuracy of chip thickness calculation. Under different chip thicknesses cutting coefficients are regressed with good agreements to calibrated values. Validation tests are carried out on a sculptured surface with curved toolpaths under practical cutting conditions. Comparisons of simulated and experimental results show the effectiveness of the proposed method.     

Milling force prediction using a dynamic shear length model

Modelling of cutting forces in milling is often needed in machining automation. In this paper, a new method for the determination of the cutting forces in face milling is presented, which applies a predictive machining theory originally developed for orthogonal cutting to milling operations, with a dynamic shear length model developed and incorporated. The proposed dynamic shear length model is developed based on the analysis for the true tooth trajectories of a milling cutter, taking into account of the characteristic wavy surface effects in milling. The prediction for the cutting forces is carried out at each step of the angular increment of cutter rotation from input data of fundamental workpiece material properties, tool geometry and cutting conditions. Cutting forces at a cutter tooth can be predicted once the shear angle, shear length, shear plane area, and the shear flow stress along the shear length have been determined. The milling force prediction using the dynamic shear length model is verified through milling experimental tests. The sensitivity of the difference between the static and dynamic shear length models with respect to the feed per tooth and the cutter diameter is discussed.     

金刚石绳锯加工弧区锯切力分布的研究

本文针对金刚石绳锯的柔性加工以及长锯切弧区的加工特点,采用弧区内分段的实验方法,在弧区七个位置选取了50 mm的微段,对每个微段进行锯切力的测量,进而总结出锯切加工弧区内锯切力的分布情况.研究结果表明:当线速度和进给速度较小时,整个弧区的锯切力的波动较小,随着线速度和进给速度的增大,弧区锯切力在整个弧区的波动随之变大;...     

Mechanistic modeling of five-axis machining with a general end mill considering cutter runout

The accurate and fast prediction of cutting forces in five-axis milling of free-form surfaces remains a challenge due to difficulties in determining the varying cutter-workpiece engagement (CWE) boundaries and the instantaneous uncut chip thickness (IUCT) along the tool path. This paper proposes an approach to predict the cutting forces in five-axis milling process with a general end mill considering the cutter runout effect that is inevitable in the practical machining operations. Based on the analytical model of cutting edge combined with runout parameters, the expression of the rotary surface formed by each cutting edge undergoing general spatial motion is firstly derived. Then by extracting the feasible contact arc along the tool axis, a new arc-surface intersection method is developed to determine the CWE boundaries fast and precisely. Next, the circular tooth trajectory (CTT) model is developed for the calculation of the IUCT with a slight sacrifice of accuracy. In comparison with the true IUCT calculated by the trochoidal tooth trajectory model, the approximation error introduced by the circular assumption is negligible while the computational efficiency improves a lot. Finally, combining with the calibrated cutting coefficients and runout parameters, comprehensive formulation of the cutting force system is set up. Simulations and experimental validations of a five-axis flank milling process show that the novel CTT model possesses obvious advantages in computing efficiency and accuracy over the existing approaches. Rough machining of a turbo impeller is further carried out to test the practicability and effectiveness of the proposed mechanistic model.     

烧结金刚石串珠绳锯切花岗石的锯切力研究

本文对烧结金刚石串珠绳在锯切花岗石过程中,锯切力及锯切后工件表面的轮廓进行了跟踪检测,研究了锯切过程中,锯切力随锯切参数的变化,以及锯切力与工件表面轮廓的相互关系。实验结果表明：锯切过程中,工件上所承受的锯切力Fh和Fv随着线速度Vs的提高而减低,随着进给速度吩的提高而增加。垂直力与水平力之间存在着良好的对应关系,垂直力与水平力比约为4．18。加工后工件轮廓偏差量随着工件所承受的垂直力的增加而增加,两者之间呈指数关系。     

Virtual cutting and optimization of three-axis milling processes

This paper presents generalized process simulation and optimization strategies to predict and improve the performance of three-axis milling operations. Cutter-part engagement conditions are extracted from a solid modeling system, which can handle free form part surfaces found in dies and molds. The cutting force distribution along the engaged cutting edge-part surface is evaluated based on the laws of mechanics of milling. By integrating the distributed force along the cutting edge, total forces, torque and power are either predicted analytically using closed-form solutions, or numerically if the cutting tool shape is discontinuous. Simulation results are then used in a constraint-based optimization scheme to maximize the material removal rate (MRR) by calculating acceptable feedrate levels. The proposed virtual milling system is demonstrated experimentally in milling a stamping die with free form surfaces.     

Experimental studies of cutting force variation in face milling

The purpose of this paper is to present a developed cutting force model for multi-toothed cutting processes, including a complete set of parameters influencing the cutting force variation that has been shown to occur in face milling, and to analyse to what extent these parameters influence the total cutting force variation for a selected tool geometry. The scope is to model and analyse the cutting forces for each individual tooth on the tool, to be able to draw conclusions about how the cutting action for an individual tooth is affected by its neighbours.A previously developed cutting force model for multi-toothed cutting processes is supplemented with three new parameters; eccentricity of the spindle, continuous cutting edge deterioration and load inflicted tool deflection influencing the cutting force variation. A previously developed milling force sensor is used to experimentally analyse the cutting force variation, and to give input to the cutting force simulation performed with the developed cutting force model.The experimental results from the case studied in this paper show that there are mainly three factors influencing the cutting force variation for a tool with new inserts. Radial and axial cutting edge position causes approximately 50% of the force variation for the case studied in this paper. Approximately 40% arises from eccentricity and the remaining 10% is the result of spindle deflection during machining. The experimental results presented in this paper show a new type of cutting force diagrams where the force variation for each individual tooth when two cutting edges are engaged in the workpiece at the same time. The wear studies performed shows a redistribution of the individual main cutting forces dependent on the wear propagation for each tooth.     

Precise prediction of forces in milling circular corners

Pocket corner is the most typical characters of aerospace structure components. To achieve high-quality product and stable machining operation, manufacturer constantly seek to control the cutting forces in pocket corner milling process. This paper presents the cutting force in corner milling considering the precision instantaneous achievements of tool engagement angle and undeformed chip thickness. To achieve the actual milling tool engagement angle in corner milling process, the details of tool–corner engagement relationship are analyzed considering the elements of tool trajectory, tool radius, and corner radius. The actual undeformed chip thicknesses in up and down milling operations are approached on account of the trochoid paths of adjacent teeth by a presented iteration algorithm. Error analysis shows that the presented models of tool engagement angle and undeformed chip thickness have higher precision comparing with the traditional models. Combined with the cutting force coefficients fitted by a series of slot milling tests, the predicted cutting force in milling titanium pocket with different corner structure and milling parameters are achieved, and the prediction accuracy of the model was validated experimentally and the obtained predict and the experiment results were found in good agreement.     

Real-time determination of cutting force coefficients without cutting geometry restriction

The determination of the cutting force coefficients is a critical point in the case of using the mechanistic cutting force model for predicting the forces during milling processes. The main reason is that the computations require a series of experiments with special geometrical conditions, and the validity of the results is limited. In this paper a cutting force predicting method, based on the mechanistic cutting force model will be introduced, together with an algorithm for determining the cutting force coefficients in the course of a single experiment without restrictions in regard to the cutting geometry. Besides the fact that the proposed method lifts the geometrical restrictions of the previously published solutions, it makes it possible to calculate the coefficients just when they are needed for force prediction right at the machining process, to avoid the problem of the limited validity of the coefficients. In this case the real-time measuring of the cutting forces is needed, while the forthcoming forces can be predicted with an appropriate look-forward algorithm, which is also presented.     

A closed form mechanistic cutting force model for helical peripheral milling of ductile metallic alloys

A closed form mechanistic model is developed for cutting forces in helical peripheral milling (endmilling) of ductile metallic alloys. This paper presents an alternative derivation, using the frontal chip area, to describe two series of cutting force expressions—one using a Heaviside unit step function and the other using a Fourier series expansion. A specific advantage of the present work is highlighted by deriving analytical expressions for sensitivity coefficients required to analytically propagate the uncertainty in the cutting-force model parameters. Another advantage is that even very small radial immersions can be used to derive cutting coefficients reliably, along with their variances. The aforementioned analytical investigations are applied to a series of experimental cutting tests to estimate the force-model cutting coefficients. Experimental investigations include the study of a tool having radial runout. Finally, confidence intervals are placed on predicted forces which experimentally verify the validity of the proposed force model.     

The prediction of cutting force in ball-end milling

Due to the development of CNC machining centers and automatic programming software, the ball-end milling have become the most widely used machining process for sculptured surfaces. In this study, the ball-end milling process has been analysed, and its cutting force model has been developed to predict the instantaneous cutting force on given machining conditions. The development of the model is based on the analysis of cutting geometry of the ball-end mill with plane rake faces. A cutting edge of the ball-end mill was considered as a series of infinitesimal elements, and the geometry of a cutting edge element was analysed to calculate the necessary parameters for its oblique cutting process assuming that each cutting edge was straight. The oblique cutting process in the small cutting edge element has been analysed as an orthogonal cutting process in the plane containing the cutting velocity and chip flow vectors. And with the orthogonal cutting data obtained from end turning tests on thin-walled tubes over wide range of cutting and tooling conditions, the cutting forces of ball-end milling could be predicted using the model. The predicted cutting forces have shown a fairly good agreement with test results in various machining modes.     

金刚石框架锯锯切研究(Ⅵ)--在实验机上模拟框架锯锯切过程

测定金刚石框架锯锯切切削力，金刚石结块磨损和锯条变形等是十分重要也是非常困难的。在前面对锯切运动，锯切机理，锯切切削力和金刚石结块磨损研究的基础上，介绍了一种在实验室里用小型框架锯切实验机模拟框架锯锯切过程的实验方法，比较了用单锯条三节块和单锯条单结块锯切石材的实验结果，优选了结块分布间距，与金刚石框架锯锯切加工实验结果的比较表明，在实验机上用单锯条三节块锯切石材时，测量得到的处于中间的金刚石结块的切削性能，可以较好地反映实际加工中金刚石结块的切削状态，利用这一结果，可快速地通过简单的实验，评价金刚石锯条在实际加工中的切削力和金刚石结块磨损特性，其误差在20%以内。     

金刚石线切割单晶碳化硅锯切力的实验研究

从锯切力的角度对金刚石线锯锯切单晶SiC材料的加工过程进行了研究。得出了线速度、进给速度、线锯张紧力对锯切力的影响规律。从单位长度线锯材料去除量、锯切比能的角度讨论了锯切工艺对锯切力的影响机理。在金刚石线锯锯切单晶SiC过程中,锯切力随着线速度的增大而减小,随着进给速度的增大而增大,线速度与进给速度对锯切力的综合影响表现为:单位长度线锯材料去除量的增加会增大锯切力。单位长度线锯材料去除量对于金刚石线锯锯切单晶SiC材料的锯切比能具有显著的影响。     

Cutting force estimation in sculptured surface milling

Cutting force milling models developed up to now are mostly used for planar milling using end-mills. Only a reduced number of models applying ball-end mills have been developed. Furthermore these models usually only consider horizontal surface machining, even though the main application of ball-end mills is sculptured surface machining. This article proposes a model that is able to estimate the cutting forces in inclined surfaces machined both up-milling and down-milling. For this purpose a semi-mechanistic model has been developed that calculates the cutting forces based on a set of coefficients which depend on the material, the tool, the cutting conditions, the machining direction and the slope of the surface.A coordinate transformation has been included in order to consider the slope milling case with different cutting directions.The model has been tested on two materials, an aluminum alloy Al7075-T6 and a 52 HRC tool steel AISI H13. Validation tests have been carried out on inclined planes using different slopes and different machining directions.The results provide errors below 10% in most of the cases and both the value and shape of the predicted forces adjust the measured cutting force.