Three-dimensional modeling of gear skiving kinematics for comprehensive process design in practical applications

Gear skiving is a high-performance gear manufacturing process, whose design typically requires numerical models to calculate the multivariate cutting conditions. Since simulation software for gear skiving is still commercially hardly available, two-dimensional approximations have widely been used by gear manufacturers to calculate the extreme values of cutting conditions. In this work, a three-dimensional model for the calculation of cutting speed, rake angle and uncut chip thickness extreme values is presented and validated by penetration volume simulations. The comparison with the two-dimensional approaches shows a significant benefit in model accuracy over a wide parameter range and its suitability for practical applications.     

A holistic approach for gear skiving design enabling tool load homogenization

Gear skiving is a highly productive manufacturing process for internal gears. Due to its challenging cutting conditions often insufficient tool life is achieved and localized wear occurs. There is a lack of tool parameters in process design that allow for an uniform and comparable characterization of the process kinematics and tool geometry. In this paper, a new method for calculating process kinematics and tool profile based on parameters of profile-shifted conical gears and an approach for tool load homogenization are presented. The high potential of the methods is demonstrated by comparative tool life tests with an improvement of 300%.     

刀具半径补偿使用中出现过切及其解决方法

刀具半径补偿是进行二维数控加工时应用的一种补偿功能，极大地方便了被加工零件程序的编制．但刀具半径补偿功能的使用不当会引起过切，文章结合实例讨论分析了刀具补偿使用中出现过切的原因，提出了有效的解决方法，方便了数控加工程序的编制。     

An implementation of drive key cellular manufacturing

The drive key is one of the most important high-precision components of aircraft braking systems. In this paper, a cost effective drive keys manufacturing process is developed. This proposed manufacturing process makes use of near-net-shape manufacturing, computer numerical control (CNC) machining, and cellular manufacturing methods. To make the proposed process a reality, proper engineering with the proposed parts along with group technology are applied to the product design in conjunction with the proposed manufacturing methods. In addition, a general spreadsheet program is developed for each style of fixture modules to assist in part program coding. Moreover, statistical process control (SPC) is implemented to verify product quality and accept the product at the point of manufacture. It is observed that the implementation of the proposed drive key cellular manufacturing process results in a tremendous improvement in quality, throughput and productivity as well as a drastic reduction in manufacturing operations, workholding fixtures, cutting tools, and inspection media.     

汽车轮毂件冲压成形断裂分析

板料冲压过程是一个非常复杂的塑性成形过程,许多因素都直接或间接影响着成形的结果.以Forge2D软件为平台,采用弹塑性有限元法对某一汽车轮毂零件的成形过程进行数值模拟,揭示零件冲压过程中板料的变形行为,预测冲压过程中可能出现的各种工艺缺陷,例如坯料的局部减薄和破裂,并以模拟结果为依据提出改进工艺参数的办法,优化工艺参数,可以减少调试和修模的次数,以此实现降低模具费用、缩短制模时间、提高产品成品率和材料利用率,最终达到减少产品成本的目的.在此基础上,对3种冲压工艺方案分别进行了数值模拟,对比研究了各方案的成形特点,得出了较好的成形工艺参数方案.     

Design of hob cutters for generating helical cutting tools with multi-cutting angles

This paper studies the design of hob cutters for generating the multi-cutting angles (radial rake angle, relief angle, and clearance angle) of helical cutting tools in one hobbing process. The current manufacturing process can be greatly improved if the cutting edges in the normal section profile, the rack profile, of a hob cutter are designed with several cutting edges with different pressure angles, so that the helical cutting tools with multi-cutting angles can be formed in one generating process. This paper, therefore, designs a rack profile of a hob cutter consisting of three straight cutting edges with different pressure angles and a curved cutting edge. By applying the equations of designed rack profiles of hob cutters, the principle of coordinate transformation, the theory of differential geometry, and the theory of gearing, the mathematical models of the helical cutting tool can be derived. In addition, the formulas for the radial cutting angle, relief angle, and clearance angle can be derived. Meanwhile, solid modelling of the helical cutting tool can be carried out with computer graphics programming. The results of this paper will contribute to the improvement of the design technology of hob cutters, to enhance the manufacturing processes of helical cutting tools, and to assist tool-related industries in upgrading their technology and competitive abilities.     

Model-based predictive force control in milling: determination of reference trajectory

Today, powerful process simulation tools allow an offline process planning and optimization of metal cutting processes. The quality of the optimization strongly depends on the model and its parameters. Real cutting processes are influenced by uncertainties such as tool wear status or material properties, which are both unknown. To overcome this limitation, sensors and process control systems are used. Model-based Predictive Control (MPC) was developed in the 1970s for the chemical process industry. This control method was found to be very suitable to control complex manufacturing processes such as milling processes. Using MPC in metal cutting processes allows considering technological boundary conditions explicitly. Adapting the feed velocity and thus the process force increases the productivity and process stability in milling. A core element of the MPC is the use of a reference trajectory representing the time-dependent set point value in the optimization procedure. The tool path information, however, is given position-based. Thus, calculating the reference trajectory is not trivial and strongly influences the control quality. This paper presents two methods for determining the reference trajectory. The first method is based on an adaptive signal filter. For the second method the MPC is extended to a two-layer MPC: the first layer calculates an optimal reference trajectory; the second layer controls the machine tool.     

A virtual machine concept for real-time simulation of machine tool dynamics

When designing CNC machine tools it is important to consider the dynamics of the control, the electrical components and the mechanical structure of the machine simultaneously. This paper describes the structure and implementation of a concept for real-time simulation of such machine tools using a water jet cutting machine as an application. The concept includes a real control system, simulation models of the dynamics of the machine and a virtual reality model for visualisation. The real-time capability of the concept, including the simulation of electrical and rather detailed mechanical component models is proofed. The validation process indicates good agreement between simulation and measurement, but suggests further studies on servo motor, connection and flexibility modelling. However, already from the initial simulation results presented in this paper it can be concluded that the influence of structural flexibility on manufacturing accuracy is of importance at desired feeding rates and accelerations. The fully automated implementation developed in this work is a promising base for dealing with this trade-off between productivity and accuracy of the manufacturing process through multidisciplinary optimisation.     

航空叶片精锻模具设计与数控加工

叶片是航空发动机的重要组成零件,由于其叶面形状多为复杂的空间曲面,要求它具备良好的力学性能,并且有较高的表面质量和尺寸精度。为了解决叶片难以制造加工的问题,以某航空发动机叶片为例,对其锻件进行工艺分析,采用无余量精密锻造工艺加工叶片。利用UG软件完成叶片三维模型设计;利用Mold Wizard模块完成叶片模具设计;利用UG_CAM模块完成叶片模具的数控加工。对加工工艺参数及走刀轨迹进行优化后,经UG软件仿真及后处理生成合理的刀路轨迹,制作出合格的叶片模具。生产实践证明:用该模具锻造的叶片质量良好、生产效率较高,适合大批量生产。     

基于MASTERCAM的油底壳凹模数控编程与仿真加工

以某型号长城汽车的油底壳拉深模中的凹模为例,设计其加工工艺方案,选择合适的加工刀具和切削参数,进行数控加工编程和仿真加工。该方法提高了模具制造的效率,验证了MASTERCAM在拉深模具高效加工中的有效性。     

面向加工程序优化的铣削过程模拟技术

针对CAD/CAM系统不能自动生成加工参数的问题,国内外许多学者提出了利用加工过程模拟技术加工程序的思想,随着对切削机理认识的不断加深和计算机仿真技术的发展,铣削加工模拟优化系统得到了大量的研究和开发。对铣削过程模拟中的两个关键技术-几何模拟技术和物理模拟技术进行了归纳和分析。     

基于Minitab/TURN5DOE的试验设计在质量管理的应用

对于国内制造型企业而言,提高产品生产制程能力是形成企业核心竞争力的重要方法。在仿真试验平台TURN5DOE内,结合试验设计方法与Minitab软件,以TURN5DOE模拟制造青铜衬套的单点车床车削操作进行数据采样试验;以直径与表面粗糙度作为试验指标,以切削液、机台、刀鼻半径、进料率、切削速度作为影响因素,设计正交试验方案。通过仿真试验得出参数最佳组合,以提高企业生产控制系统的稳定性和生产能力。     

基于MATLAB的切削表面质量预测软件开发

LMBP神经网络具有性能稳定、收敛快的特点,可应用于切削加工表面质量的预测。在MATLAB中设计用户界面,实现对工艺试验数据的读取和对神经网络输入输出的设置;设计了基于LMBP算法神经网络程序,完成软件的编译和验证。将软件应用在切削表面质量预测,预测结果与试验结果误差较小,具有较高精度;软件操作简单,适合现场工作人员使用。     

Chip geometry and cutting forces in gear power skiving

This paper describes a new virtual model for predicting the uncut chip geometry and cutting forces in power skiving, which is a high-speed, versatile gear cutting process. The developed kinematic model is applied in a dexel-based solid modeling engine to extract three-dimensional uncut chip geometry, from which the two-dimensional cross section is obtained via Delaunay triangulation. Cutting velocities along discretized cutter edges are calculated and used to determine the effective rake and oblique angles. Then, force predictions are made using the oblique cutting model and validated using measurements from power skiving trials performed on a DMG MORI NT5400DCG mill-turn machine.     

数值模拟技术在大型锻件生产中的应用

数值模拟技术在保证工件质量、减少材料消耗、提高生产效率、缩短试制周期等方面显示出无可比拟的优越性。在钢锭凝固方面,有限元模拟程序MIPS可以分析凝固过程中温度场的分布,确定不同时刻凝固前沿的位置,而且能预测缩孔和疏松的位置及尺寸。使用该程序对220吨钢锭的生产工艺进行优化,成功地解决了疏松进入锭身的问题。在锻造方面,已开发出了基于ANSYS的三维大变形弹塑性、弹粘塑性程序,可以分析复杂的三维金属塑性成形问题。热处理专用软件NSHT不仅可以分析加热、淬火及回火过程中温度场分布,而且可以给出应力的分布及相态的变化过程,并已在实际生产中取得了成功。     

Abrasive points for drill grinding of carbon fibre reinforced thermoset

In this study, an approach for using diamond grinding tools to machine holes in epoxy carbon laminates is described. The development of a suitable tool design and the influence of the cutting parameters are presented. With these tools, large total drilling lengths can be achieved without significant grain wear. Analysis of the results shows that the coolant supply can be reduced without exceeding the resin's glass transition temperature. In addition to the experimental results, a process simulation is applied to improve the tool layout and hence to avoid material clogging at the grinding layer.     

Simulation and verification of parametric numerical control programs using a virtual machine tool

A parametric computer numerical control (CNC) program was developed to make a test complex surface on a vertical milling machine equipped with an external fourth rotational axis. Parametric programming was used in order to get higher flexibility of the manufacturing process. The ball-end milling process was simulated and verified in a virtual model of the machine tool developed with the module integrated simulation and verification of the product lifecycle management software of Siemens NX7^®. After that, the real process was carried out on the shop floor to machine the test surface. This demonstrates that the virtual machine tools are an effective resource to simulate and verify the performance of machining processes controlled by CNC parametric programs. The possibility of accurately simulating the parametric CNC program reduces the risk of its implementation and enables a more frequent use of this efficient feature of contemporary CNC machine tools.     

硬质合金刀具干式切削力的仿真

切削力是刀具切削性能评价的重要指标之一 ,本文提出了一种建立在MATL AB系统上的切削力预报系统 ,它可以十分方便的预报硬质合金刀具切削普通碳素钢的切削力变化规律 ,切削力预报精度较高 ,可以应用于新刀具的开发、生产和设计中     

利用大进给量铣削提升模具制造生产率的研究

大进给量铣削(High Feed Cutting/HFC)工艺是一种以整个铣刀直径用全切削(ae=D)的方式,同时采用较小的切削深度(即背吃刀量ap)和很高的进给速度进行切削的高效切削工艺,有很高的材料切除率.其目的是显著缩短粗加工或半精加工的时间,因此,原则上大进给量铣削(HFC)是属于高效铣削(HPC)工艺的范围....     

基于VERICUT二次开发的数控加工切削力仿真研究

为解决传统有限元仿真软件在数控加工切削力仿真应用中效率低下的问题,论文介绍了一种基于VERICUT二次开发的数控加工过程切削力仿真的快速实现方法.在VC平台下,利用VERICUT软件提供的二次开发工具Optipath API(optimize path - application programming interface),在数控加工几何仿真完成后即时提取加工过程的切削参数.根据切削力经验模型,通过MFC(microsoftfoundation class)编程开发切削力仿真结果输出界面,得到数控加工过程中切削力数值的变化曲线,实现数控加工过程切削力仿真效率的显著提高.