基于圆弧走刀的尖角加工铣削力建模

为实现尖角加工过程中铣削力的精确预测,给出了工件轮廓与刀具路径的参数化统一表示方法,分析了两种情况下的铣削工艺过程,依据铣削特征化分为五个阶段,推导出每个铣削阶段的实际径向切深算式。基于实际径向切深,给出了切入/切出角的计算方法,建立了尖角加工的瞬时铣削力模型。利用直线铣削完成了切削力系数辨识,对尖角加工的瞬时铣削力进行预测,并进行试验验证,结果表明预测铣削力与实测铣削力具有良好的一致性,证实了铣削力模型的有效性和精确性,从而为工艺参数优化和颤振抑制提供了理论基础。     

BP神经网络在立铣刀结构参数优化中的应用

钛合金薄壁件的铣削加工过程中,刀具磨损速度快,并且工件容易变形,其主要因素是加工过程中切削力大,切削温度高。文章利用有限元仿真软件Advant Edge FEM铣削仿真数据,建立整体式立铣刀结构参数与切削力和切削温度的BP神经网络预测模型,并对切削预测模型进行了切削实验验证。在此基础上,利用BP神经网络模型的预测结果对整体式立铣刀的结构参数进行了优化,切削实验证明,优化后的刀具参数可以有效地降低切削力和切削温度,从而有效地改善过程中刀具的切削性能和工件的加工质量。     

基于斜角切削的铣削力三维数值模拟

采用有限元软件建立反映金属切削过程中高温、大应变、大应变率的模型,模拟了A16061 - T6铣削加工中刀具微元的斜角切削过程,得到了微元切削力的变化曲线.利用不同切削厚度的仿真结果,分析了切削力、切削力系数与厚度的关系,建立了切削力系数与切削厚度的函数关系模型.利用此模型,模拟了瞬时铣削力.通过铣削试验获得了相同铣削条件下的铣削力,与模拟铣削力比较,发现两者具有良好的一致性,证明了模型的正确性.为复杂工况下铣削力的研究、工件变形预测以及铣削工艺参数优化奠定了基础.     

微铣削切削力的解析模型分析

针对传统铣削模型不能较好的反映出微铣削刀具因尺寸效应而易受切削力与切削振动的影响效果的问题,建立了微铣削刀具运动轨迹和动态切削厚度模型和考虑刀具磨损的微铣削犁力模型和剪切力模型,通过Deform-2D切削仿真获得了犁力系数和剪切力系数,建立了考虑刀具磨损的微铣削切削力模型。同时通过切削力测试实验与仿真结果进行比对,检验了切削力模型与测试结果的偏差,结果表明该切削力模型预测结果可以较好的反应实际切削力值,可以利用该模型进行微铣削切削力的近似计算,进而验证了模型的正确性与可信度。     

不锈钢0Cr18Ni9铣削力建模与实验研究

在难加工材料的铣削加工中,铣削力对质量有很大影响。对难加工不锈钢0Cr18Ni9铣削加工中的切削力模型与实验加工技术进行研究。将不锈钢0Cr18Ni9铣削加工中的切削力分解为切向铣削力、径向铣削力和轴向铣削力,由铣削力和切削加工参数之间的关系,建立不锈钢0Cr18Ni9铣削力模型。采用正交试验法设计加工试验获得铣削力数据,通过多元线性回归确定不锈钢0Cr18Ni9铣削力仿真模型中的系数。回归参数的显著性检验结果表明,所建立的铣削力模型能够对铣削力进行预测和控制。     

钛合金高速铣削的切削力实验研究与建模

针对难加工材料Ti6Al4V(TC4)进行高速铣削的铣削力研究,通过多因素正交试验,分析切削参数对切削力的影响,得出对难加工材料宜采用高速小切削的方法加工。将铣削加工中的切削力分解为纵向铣削力、横向铣削力和轴向铣削力,根据铣削力和切削加工参数之间的关系,采用最小二乘法等概率统计方法和回归分析原理,建立了三向铣削力模型。对所建立的铣削力模型进行回归参数显著性检验,分析所构建模型的置信度和残差,结果表明所建立的铣削力模型能很好地符合原始实验数据,可靠性好,能用于铣削力的预测和控制,为高速铣削钛合金的参数优化提供可靠依据。     

柱状曲面切削力建模与仿真

以柱状曲面所受切削力为研究对象,采用离散化的方法,建立了直线进给时的切削力模型,针对柱状曲面铣削加工的特点,利用坐标变换的方法,建立了该类曲面铣削加工的切削力模型。通过仿真分析得出,加工过程中,切削力的大小和方向是不断变化的,它不仅受切削用量的影响,还与曲面的形状密切相关。切削力是铣削加工过程中引起振动的激振力,通过切削力模型的仿真,实现了对柱状曲面切削力大小和变化规律的预测,为加工误差的预测与控制奠定基础。     

汽轮机叶片曲面加工铣削力预测模型研究

文章针对汽轮机叶片曲面的加工特点,建立了铣削力模型,并从瞬时切削厚度的角度分析了数控工艺参数对铣削力模型的影响。在金属切削有限元模拟的基础上,运用Matlab和Abaqus软件结合四因素四水平正交模拟试验法验证了铣削力模型。并运用汽轮机叶片铣削加工实验进一步验证了铣削力模型和金属切削有限元模拟模型的有效性。     

型腔拐角铣削加工参数优化与研究

在铣削模具型腔拐角时,拐角处铣削力突变是影响加工质量的重要原因。通过分析刀刃切削轨迹,提出了一种基于单刃等面积切削模型的铣削力参数优化方法。首先根据实际工况下刀刃轨迹路线,计算和分析了拐角处接触角瞬时变化情况,得到单刃等切削面积参数数学模型;然后运用有限元分析软件DEFORM对工件进行动态加工模拟,仿真结果表明:切削力能随着铣削路径实时变化,较传统参数方法该模型设置能够有效的降低拐角处50.20%与36.52%的切削力。并且在VERICUT中进行验证,结果显示优化模型使拐角更加光滑,达到了平稳过渡,为型腔拐角铣削加工工艺参数优化及仿真分析等方面的研究提供了理论依据。     

基于BP神经网络的轮胎模具微铣削能耗预测

针对子午线轮胎模具微铣削加工过程中能耗计算问题,以主轴转速、每齿进给量、切削深度3个重要铣削参数作为变量,设计轮胎模具微铣削加工能耗实验.根据实验数据构建基于BP神经网络的微铣削能耗预测模型.通过改进预测模型的激活函数,提高模型的预测精度.结果表明:所提的预测模型有效,可以实现不同铣削参数组合下的能耗预测.     

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.     

飞机蒙皮镜像加工变形迭代预测方法

飞机蒙皮尺寸大、壁厚小,易发生加工变形,并且切削力与加工变形之间存在着复杂的耦合关系,普通的无迭代加工变形预测方法难以实现较好的预测效果。针对飞机蒙皮镜像加工变形现象,在建立镜像铣定制刀具切削力模型的基础上,提出一种加工变形迭代预测方法,该方法较好地解决了切削力与加工变形之间的复杂耦合关系问题,并通过仿真和试验证明了该方法的有效性。相对普通无迭代预测方法,该方法预测加工变形量的变化趋势和变化幅值更符合实际蒙皮镜像加工,加工变形仿真预测值与实际加工变形的差值更稳定,预测误差更小,可以更准确有效地预测出蒙皮镜像加工变形量。     

Prediction of cutting forces in milling of circular corner profiles

This paper proposes an approach to predict the cutting forces in peripheral milling of circular corner profiles in which varying radial depth of cut is encountered. The geometric relationship between an end mill and the corner profile is investigated and a mathematical model is presented to describe the different phases of the cutter/workpiece contact. The milling process for circular corner is discretized into a series of steady-state cutting processes, each with different radial depth of cut determined by the instantaneous position of the end mill relative to the workpiece. A time domain analytical model of cutting forces for the steady-state machining conditions is introduced to each segmented process for the cutting force prediction. The predicted cutting forces can be calculated in terms of tool/workpiece geometry, cutting parameters and workpirece material property, as well as the relative position of the tool to workpiece. Experiments are conducted and the measured forces are compared to the predictions for the verification of the proposed method.     

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.     

On cutting parameters selection for plunge milling of heat-resistant-super-alloys based on precise cutting geometry

In plunge milling operation the tool is fed in the direction of the spindle axis which has the highest structural rigidity, leading to the excess high cutting efficiency. Plunge milling operation is one of the most effective methods and widely used for mass material removal in rough/semi-rough process while machining high strength steel and heat-resistant-super-alloys. Cutting parameters selection plays great role in plunge milling process since the cutting force as well as the milling stability lobe is sensitive to the machining parameters. However, the intensive studies of this issue are insufficient by researchers and engineers. In this paper a new cutting model is developed to predict the plunge milling force based on the more precise plunge milling geometry. In this model, the step of cut as well as radial cutting width is taken into account for chip thickness calculation. Frequency domain method is employed to estimate the stability of the machining process. Based on the prediction of the cutting force and milling stability, we present a strategy to optimize the cutting parameters of plunge milling process. Cutting tests of heat-resistant-super-alloys with double inserts are conducted to validate the developed cutting force and cutting parameters optimization models.     

Development of a virtual machining system, part 1: approximation of the size effect for cutting force prediction

In this three-part paper, components of a virtual machining system for evaluating and optimizing cutting performance in -axis NC machining are presented. Part 1 describes a new method of calculating cutting-condition-independent coefficient and its application to the prediction of cutting forces over a wide range of cutting conditions. The prediction of the surface form error and transient cutting simulations, described in Parts 2 and 3, respectively, can be effectively performed based on the cutting force model with the improved size effect model that is presented in Part 1.

The relationship between the instantaneous uncut chip thickness and the cutting coefficients is calculated by following the movement of the center position of the cutter, which varies with nominal feed, cutter deflection and runout. The salient feature of the presented method is that it determines the cutting-condition-independent coefficients using experimental data processed for one cutting condition. The direct application of instantaneous cutting coefficient with size effects provides more accurate predictions of the cutting forces. A systematic comparison of the predicted and measured cutting forces over a wide range of cutting conditions confirms the validity of the proposed mechanistic cutting force and size effect models.     

Development of a virtual machining system, part 3: cutting process simulation in transient cuts

In Parts 1 and 2 of this three-part paper, a mechanistic cutting force model was developed and machined surface errors for steady cuts under fixed cutting conditions were predicted. The virtual machining system aims to simulate and analyze the machining and the machined states in a general flat end-milling process. This frequently involves transient as well as steady cuts. Therefore, a method for simulating the cutting process of transient cuts needs to be developed to realize the virtual machining system concept. For this purpose, this paper presents a moving edge-node (ME) Z-map model for the cutting configuration calculation. The simulation results of four representative transient cuts in two-dimensional pocket milling and an application of off-line feed-rate scheduling are also given.

In transient cuts, the cutting configurations that are used to predict the cutting force vary during the machining operation. The cutting force model (Part 1) and surface error prediction method (Part 2) were developed for steady cuts; these are extended to transient situations using the ME Z-map model to calculate the varying cutting configurations efficiently. The cutting force and surface errors are then predicted. To validate the feasibility of the proposed scheme, the measured and predicted cutting forces for transient test cuts were compared. The predicted surface error maps for transient cuts were constructed using a computer simulation. Also, off-line feed-rate scheduling is shown to be more accurately performed by applying the instantaneous cutting coefficients that were defined in Part I.     

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.     

An examination of the fundamental mechanics of cutting force coefficients

In metal cutting, the cutting force is the key factor affecting the machined surface, and is also important in determining reasonable cutting parameters. The research and construction of cutting force prediction models therefore has a great practical value. The accuracy of cutting force prediction largely depends on the cutting force coefficients of the material. In the average cutting force model, cutting force coefficients are considered to be constant. This study makes use of experiments to investigate the cutting force coefficients in the average cutting force model, with a view to accurately identifying cutting force coefficients and verifying that they are related only to the tool–workpiece material couple and the tool geometrical parameters, and are not affected by milling parameters. To this end, the paper first examines the theory behind identifying cutting force coefficients in the average cutting force model. Based on this theory, a series of slot-milling experiments are performed to measure the milling forces, fixing spindle speeds and radial/axial depths of cutting, and linearly varying the feed per tooth. The tangential milling force coefficient and the radial milling force coefficient are then calculated by linearly fitting the experimental data. The obtained results show that altering the milling parameters does not change the milling force coefficients for the selected tool/workpiece material combination.     

Prediction of cutting force distribution and its influence on dimensional accuracy in peripheral milling

Cutting force has a significant influence on the dimensional accuracy due to tool and workpiece deflection in peripheral milling. In this paper, the authors present an improved theoretical dynamic cutting force model for peripheral milling, which includes the size effect of undeformed chip thickness, the influence of the effective rake angle and the chip flow angle. The cutting force coefficients in the model were calibrated with the cutting forces measured by Yucesan [18] in tests on a titanium alloy, and the model was proved to be more accurate than the previous models. Based on the model, a few case studies are presented to investigate the cutting force distribution in cutting tests of the titanium alloy. The simulation results indicate that the cutting force distribution in the cut-in process has a significant influence on the dimensional accuracy of the finished part. Suggestions about how to select the cutter and the cutting parameters were given to get an ideal cutting force distribution, so as to reduce the machining error, meanwhile keeping a high productivity.