渐开线内齿参数对插齿让刀干涉的影响

渐开线内齿的插齿让刀干涉问题是影响内齿加工精度和效率的重要因素.国内外相关专家、技术人员对插内齿让刀干涉的发生机理和干涉分析计算进行了大量深入的研究,但缺乏内齿设计参数与插齿让刀干涉关系的研究.结合生产过程中出现的插齿让刀干涉问题实例,以插齿让刀干涉理论研究为基础,分析总结试验案例,得出了内齿参数与插齿让刀干涉影响的关...     

车齿虚拟切削仿真技术研究及应用

研究车齿刀设计、车齿过程三维切削仿真有助于对车齿技术深入了解及应用,对车齿刀的齿部和结构进行精确三维建模及搭建车齿机床三维模型,通过使用Vericut软件进行车齿切削过程仿真,可直观地验证车齿加工系统结构干涉、工件齿部成形过程、刀具设计以及车齿加工的齿形误差等。以Pittler公司PV630车齿机为目标机型搭建车齿机三维模型,基于圆锥车齿刀设计方案对车齿刀进行精确三维建模,使用Vericut软件搭建车齿三维仿真平台。     

齿面的重迭干涉和让刀干涉

<正> 齿面的重迭干涉是内齿轮传动中可能发生的四种干涉之一,它一般发生于齿数差(Z_2-Z_1)较少的传动中。在发生重迭干涉的前提下如果将小齿轮换成同样参数的插齿刀,则就要发生让刀干涉。让刀干涉时内齿轮齿顶附近齿面拉伤并挤出毛刺;同时刀具的切削刃磨损严重。因让刀干涉的实质是重迭干涉在插内齿时的再现,因此,说明让刀干涉必须先从重迭干涉的原理说起。1、重迭干涉和不发生重迭干涉的条件:     

螺旋内花键切削仿真研究

研究长轴大螺距螺旋内花键成型工艺。探索拉削速度、刀具参数对工件成型及加工精度的影响。基于有限元DEFORM-3D仿真软件,分别研究刀具前角、后角、拉削速度等参数对应力及加工精度的影响规律;通过改进预制孔和拉削工艺,调整刀具参数,确定拉刀参数及成型工艺流程。结果表明,在拉刀前角为15°、后角为2°、齿升量为0.06mm时,切削应力及切削热比较合理,可以在一定程度上解决深孔内螺旋花键加工时出现的让刀现象,得到的工件表面精度较高。     

内齿轮插齿仿真系统的研发

非标准齿形齿圈插齿让刀干涉一直是困扰内齿设计、加工的难题。通过对插齿加工过程进行仿真可提前获取插齿过程中让刀干涉情况,为齿形优化设计、插齿刀具设计提供依据。研究二维轮廓布尔求减算法及让刀干涉量计算算法,在C++builder中将上述算法予以实现,完成了内齿轮插齿仿真系统的开发,实现了插齿过程的图形仿真及让刀干涉量的计算,并在实际生产得到了应用、验证。     

非圆齿轮插齿加工中的退刀干涉机理及规避方法研究

分析了利用三轴数控插齿机插制非圆齿轮产生退刀干涉的原理，提出了一种使插齿刀的回转中心偏离几何中心以规避退刀干涉并实现连续插齿加工的新方法，并以非圆行星齿轮液压马达内齿圈的插制加工为例，给出了这种方法的实施过程和相关算法。     

精密加工变齿厚内齿轮插齿刀设计

针对标准插齿刀通过斜插法或插削角优化法难以实现变齿厚内齿轮高精度加工的问题,提出了一种精密加工变齿厚内齿轮的专用插齿刀设计方法。该插齿刀齿廓方程同时包含刀具几何参数和插削角工艺参数。基于啮合原理推导了刀具齿廓方程,建立了插齿刀切削刃数学模型,给出了插齿刀切削刃参数优化流程。对比分析了不同加工方法的齿形误差,研究了设计参数变化对齿形误差的影响规律。结果表明,所提出的方法在各种设计参数下均能有效减小齿形误差,设计出的刀具按优化倾角做直线插削即可实现变齿厚内齿轮的精密加工,无需对机床进行改造,易于推广。     

NOMEX蜂窝芯超声振动插削刀设计研究

针对蜂窝芯材料工件圆弧转角无法机加成形的瓶颈难题,依据超声振动加工原理及蜂窝芯材料特性,设计了一种超声振动插削刀。基于刀具初始结构设计,采用ABAQUS有限元软件对插削刀进行了模态分析,验证了该新型插削刀结构设计的合理性,并为该超声刀具的发展研究提供了结构参数支持。结果表明:第七阶振型为插削刀的理想振型,振幅分布有规律,振动稳定;刀具长度L=27mm,刀具厚度t=2.5 mm,楔角θ=13°为插削刀结构的适宜参数,符合超声切削加工对刀具的要求。     

钻削碳纤维复合材料切削温度的仿真研究

为研究切削参数对钻削碳纤维增强复合材料的切削温度影响规律，基于ABAQUS有限元分析软件建立了T300碳纤维复合材料的钻削仿真模型，对钻削加工中切削温度的分布和特点进行了研究。基于正交试验法在不同切削参数下进行钻削仿真试验得到其切削温度，采用单因素试验法进行钻削加工仿真，得到钻削碳纤维增强复合材料时不同切削参数对钻孔切削温度的影响规律。结果表明：钻头切削刃刀尖处的温度远高于钻头边缘处的温度，钻头后刀面的切削温度高于钻头前刀面的切削温度。对切削温度影响最大的钻削参数为钻头直径，切削速度和进给量的影响次之；切削用量组合为钻头直径4mm、切削速度40m/min和进给量0.08mm/r时，切削温度最低；切削温度与钻头直径和切削速度呈正相关，切削温度与进给量呈负相关。     

斜齿轮数控插削加工的运动分析和仿真

数控插齿机取代螺旋导轨插齿机对于促进国内齿轮制造业的发展具有重要的现实意义.针对国内研发的数控插齿机,对插削机构的往复运动和回转运动进行运动学分析,推导出位移方程;利用ADAMS软件仿真斜齿轮插削运动,得到插齿刀与被加工齿轮的干涉曲线图以及运动曲线图,证明了对插削机构运动学分析的正确性.最后通过比较不同主运动机构的机构形式,指出数控插齿机插削机构今后研发的方向.     

Residual stress fluctuates periodically via the workpiece rotation phase during low frequency vibration cutting

The turning process is a standard machining process employed in diverse sectors. However, it produces long continuous chips that can affect the efficiency of the process, accelerate the tooling's wear, or damage the machined surface. As a solution, low frequency vibration cutting synchronizing with the spindle rotation has recently been developed as a new machining method in turning operation. It applies vibrations in the tool feed direction and can synchronously control the applied vibrations and the spindle rotation. It can also effectively divide the long continuous chips generated by the turning process and has the potential to reduce thermo-mechanical load on the tool by periodically enabling the tool to leave the workpiece due to the vibrations. Low frequency vibration cutting, the cutting characteristics of which differ from those of conventional turning, induces residual stresses in the machined surface; however, the properties of these stresses have not yet been studied. Residual stress can have both beneficial and negative effects on the fatigue life of products. While compressive residual stress increases the fatigue life of the product, tensile residual stress facilitates the growth of fine cracks on the product's surface and reduces fatigue life. Therefore, it is important to understand the characteristics of the residual stress developed on a machined surface. In this study, an annealed 0.45% C steel bar was machined via straight turning of the vibration cutting process synchronizing with the spindle rotation, and the residual stress on the finished surface was measured. Particular focus was placed on analyzing the effects of the spindle phase on the characteristics of the residual stress inside the machined surface, especially the effects of the number of vibrations per spindle rotation, D, which is a unique parameter defining the vibration condition. Our results revealed that the residual stress varied depending on the position of the finished surface owing to the change in feed with the spindle phase during the process. Furthermore, D was observed to heavily influence the distribution of the residual stress on the finished surface. By means of adjusting its value, the residual stress value could either fluctuate periodically according to the phase of the workpiece or not fluctuate.     

高效铣削镍基高温合金GH4169的有限元数值模拟

在DEFORM软件中,根据实际加工情况建立整体硬质合金立铣刀加工镍基高温合金GH4169的三维有限元仿真分析模型。针对镍基高温合金GH4169加工效率低和切削刃磨损严重的问题,采用单因素试验法仿真探讨了切削用量(v、f_z、a_p、a_e)对切削力和切削温度的影响规律。获得了能有效提高镍基高温合金GH4169加工效率的切削用量,为实际加工中实现高效铣削镍基高温合金切削用量的选择提供依据。     

半球形零件的聚氨脂橡胶引伸模设计

探讨了使用聚氨酯橡胶模拉深半球形零件的方法;说明了聚氨脂橡胶的性能和优点;介绍了模具的结构和工艺参数,设计思路.该套模具不需要压边圈,结构简单,加工调试方便,提高了生产效率,并显著改善了零件的成形质量,并且有一定的通用性,通过实践,取得良好效果.     

Prediction and analysis of surface roughness characteristics of a non-ferrous material using ANN in CNC turning

Surface roughness, an indicator of surface quality is one of the most-specified customer requirements in a machining process. For efficient use of machine tools, optimum cutting parameters (speed, feed, and depth of cut) are required. So it is necessary to find a suitable optimization method which can find optimum values of cutting parameters for minimizing surface roughness. The turning process parameter optimization is highly constrained and non-linear. In this work, machining process has been carried out on brass C26000 material in dry cutting condition in a CNC turning machine and surface roughness has been measured using surface roughness tester. To predict the surface roughness, an artificial neural network (ANN) model has been designed through feed-forward back-propagation network using Matlab (2009a) software for the data obtained. Comparison of the experimental data and ANN results show that there is no significant difference and ANN has been used confidently. The results obtained conclude that ANN is reliable and accurate for predicting the values. The actual R _a value has been obtained as 1.1999???m and the corresponding predicted surface roughness value is 1.1859???m, which implies greater accuracy.     

Application of Taguchi and response surface methodologies for surface roughness in machining glass fiber reinforced plastics by PCD tooling

This paper discusses the use of Taguchi and response surface methodologies for minimizing the surface roughness in machining glass fiber reinforced (GFRP) plastics with a polycrystalline diamond (PCD) tool. The experiments have been conducted using Taguchi’s experimental design technique. The cutting parameters used are cutting speed, feed and depth of cut. The effect of cutting parameters on surface roughness is evaluated and the optimum cutting condition for minimizing the surface roughness is determined. A second-order model has been established between the cutting parameters and surface roughness using response surface methodology. The experimental results reveal that the most significant machining parameter for surface roughness is feed followed by cutting speed. The predicted values and measured values are fairly close, which indicates that the developed model can be effectively used to predict the surface roughness in the machining of GFRP composites. The predicted values are confirmed by using validation experiments.     

AN APPRAISAL OF EMPIRICAL MODELING AND PROPRIETARY SOFTWARE DATABASES FOR PERFORMANCE PREDICTION OF MACHINING OPERATIONS

Abstract

In this paper the importance of quantitatively reliable technological machining performance measures and their influence on the economic performance of machining operations has been demonstrated. It has been shown that since F.W. Taylor's time these technological performance measures were required to select cutting conditions which optimise the economic performance of machining operations and that the trend to use ‘recommended’ rather than economic ‘optimal’ cutting conditions can result in significant economic penalties which need to be eliminated. The ‘empirical’ approach and equations developed since Taylor's seminal paper are reviewed as are some computerised technological machining performance databases incorporated in modem proprietary software packages. The various strategies used to minimise the amount of testing required to establish the comprehensive sets of ‘empirical’ equations in manuals and handbooks published in the U.S.A., China and Russia are described and the penalties in the quantitative reliability of the predictions discussed. Two computerised machining performance databases are explored, the ‘short cuts’ identified and the plausibility of the predictions discussed. While the mathematical form of the ‘empirical’ equations in those databases could be considered plausible the values of the exponents and constants in the equations, which greatly affect the quantitative reliability of the performance predictions, can be considered dubious for the drilling databases. It is shown that a ‘large gap’ exists between the development of reliable technological machining performance databases and the selection of cutting conditions which optimize the economic performance of machining operations advocated by Taylor since 1907.     

Stability analysis for the crankshaft grinding machine subjected to a variable-position worktable

This paper serves to evaluate the dynamic performance and the cutting stability of the crankshaft grinding machine. The governing equations for the 7 degrees of freedom (DOF) lumped-mass model are formulated by the Lagrange energy method. The absolute value of the maximum negative real part of the overall dynamic compliance (MNRPODC) and the limiting chip width are the main performance indicators used to explore the structure's dynamic characteristics and the cutting stability of the grinding machine in various worktable positions. The effect on system performance of the distance between the mass center of the workpiece and the worktable module in the z direction is also analyzed. Based on the stability theory for regenerative chatter model, a computer program has been developed that utilizes the three-dimensional stability lobe diagrams of the multi-DOF system to automatically identify the stable and chatter zones. Time domain simulation of the cutting conditions is used to verify the stability lobe diagrams. Finally, an optimization analysis utilizing the particle swarm optimization method is carried out to obtain the optimal design variables. The results, in terms of |MNRPODC| or the limiting critical chip width, show improvements by a factor of 6.5 and are superior to that of the prototype machine.     

典型轴类零件车削加工专家系统的研究

针对典型轴类零件在实际生产中人工编制工艺效率低下、切削参数选择不合理等问题,依据金属切削加工理论,通过分析典型轴类零件车削加工的专家经验,提出了基于Visual和Sql Server建立典型轴类零件车削加工专家系统。系统先通过对零件三维模型的识别,提取出能够用于制定工艺的零件信息,进而采用基于规则推理的技术,实现典型轴类零件的工艺方案自动制定、刀具和切削参数自动选择优化等。     

EFFECTS OF ROTATIONAL SPEED,FEED RATE AND TOOL TYPE ON TEMPERATURES AND CUTTING FORCES WHEN DRILLING BOVINE CORTICAL BONE

Surgical procedures that affect the human body's bone structure, often entail cutting, drilling or screwing operations of bone. The post-operative success of these procedures is largely dependent on the degree of damage introduced by the process. In this article, the influence of the rotational velocity, feed per tooth and two drill bit type on workpiece temperatures and cutting forces when drilling bovine cortical bone has been studied. The purpose is to find the optimum cutting conditions that will generate the lower temperatures and cutting forces. The measurement of temperatures has been carried out with an infrared thermography camera, and a piezoelectric dynamometer has been employed to obtain forces. A model has been developed from which heat flow into the drilled bone can be estimated from specific cutting force and the fraction of total heat generated that flows into the bone. This fraction has been shown to depend on the Peclet number for the process, proportional to the drill rotation speed, the feed per cutting edge and the diameter of the drill. By means of the model, some contradictions in the literature as to the effect on bone heating of increasing rotation speeds and feeds per cutting edge have been resolved.     

Finite element modeling of ultrasonic-assisted turning: cutting force and heat generation

Abstract

Adding ultrasonic vibrations to conventional turning can improve the process in terms of cutting force, surface finish and so on. One of the most important factors in machining is the heat generation during the cutting process. In ultrasonic-assisted turning (UAT) the tool tip also vibrates at very high frequency and this sinusoidal motion causes complexity in heat modeling of the cutting system. Modeling and simulation of cutting processes can help to understand the nature of process and provides information to select optimum conditions and machining parameters. In this article, a finite element model has been developed for predicting tool tip temperature in UAT. The effect of machining parameters including cutting speed, feed rate and amplitude of vibration on the tool tip temperature has been investigated. In order to simplify the machining process, the cutting experiment has been carried out in dry condition. The results showed that by applying ultrasonic vibration to the cutting tool, the tool tip flash temperature increases but in some condition its average value could be less than the conventional machining.