Swept volume generation for the simulation of machining processes

To enhance the accuracy of five-axis milling processes, a simulation based NC-path optimization provides an efficient approach. The key to a reliable simulation of cutting processes is the accurate geometric modeling of engagement conditions and the resulting workpiece geometry. The article proposes a novel approach to calculate the cutter profile for modeling swept volume with respect to trajectory of the cutter. In terms of envelope theory, a swept volume is created as a NURBS surface representation. The proposed method is robust and the results can be applied to material removal simulations based on Boolean operation, as well as discrete methods.     

Optimal setup for five-axis machining

This paper presents a new optimization model designed to minimize kinematics error introduced by the initial setup of a five-axis milling machine. An initial setup consists of the position and orientation of the workpiece with respect to the mounting table and, optionally, the machine's initial configuration. Given a set of cutter contact points and tool orientations, a least-squares optimization procedure finds the optimal setup parameters. Since the set of optimization parameters depends on the machine's characteristics, three basic types of five-axis kinematics are introduced. The classification into types depends on the sequence of positions of the machine's rotary axes in its kinematics chain. For each type, sets of invariant and dependent variables are identified, a corresponding system of nonlinear equations is constructed, and then the system is solved numerically. The method is not only efficient, but also provides tangible accuracy increases in tests on practical machining problems.     

Penetration–elimination method for five-axis CNC machining of sculptured surfaces

In this paper, a new tool positioning strategy for five-axis machining, called the penetration–elimination method (PEM), is introduced. The PEM gains from two innovative techniques that can considerably improve the computational efficiency during the calculation of the optimal tool orientations.The first technique includes developing a quantitative definition for the gouging concept and using this definition in conjunction with powerful numerical root-finder algorithms to determine the optimized tool orientations. The second technique dynamically detects the ineffective grid points and drops them from calculations and consequently takes a great role in reducing the computational burden. The ability of the PEM in removing various types of gouging has been shown via several examples. The computational efficiency of the PEM has been compared with another recently described method named the arc-intersect method (AIM). This comparison shows that although the two methods reach the same solution for the tool orientation, the PEM is averagely 7.5 times faster than the AIM.     

Bézier polygons for the linearization of dual NURBS curve in five-axis sculptured surface machining

Motivated by the excellent performance of three-axis NURBS interpolation, this paper presents a numerically efficient and accuracy controllable five-axis sculptured surface machining method with dual NURBS curve. Unlike the traditional three-axis NURBS interpolation, a dual NURBS format of the five-axis toolpath is developed to accurately and smoothly describe the tool movement in the part coordinate system. Different from the subdivision methods using the Taylor series expansion or inverse function, a piece-wise Bézier curve method is implemented to fast subdivide the NURBS curve within the user-defined tolerance. A generic rotation tool center point management module is also designed to realize the coordinate transformation and adaptive nonlinear error control for major five-axis machine tools. The overall effectiveness of the proposed five-axis NURBS machining scheme is demonstrated by the five-axis machining of an impeller’s flow channel.     

Quadric method for cutter orientation in five-axis sculptured surface machining

Existing orientation strategies in 5-axis sculptured surface machining mostly limit the cutter to incline in one direction and lack an effective approach to assess the orientation. This paper presents the quadric method (QM) that exploits fully the two orientation angles to maximise the machining efficiency at a cutter contact point. The geometric construction assumes that the local shape of a sculptured surface can be suitably approximated by two quadrics. An upper quadric lying above the surface is used to orient the cutter, and a lower quadric lying below the surface is used to evaluate machined strip width. Then, the cutter orientation is optimised with respect to the width and is guaranteed to give no gouging. Both flat-end cutter and fillet-end cutter are considered. Simulated examples demonstrate the improved machining efficiency of the QM over current published methods.     

The analysis of correlative error in principal axis method for five-axis machining of sculptured surfaces

Correlative error is a kind of error between the cutter locations. This text presents a detailed analysis about correlative error in the principal axis method (PAM) that is a strategy of tool positioning for five-axis machining. It points out all the strategies based on linear projection cannot avoid this interference and cannot be disregarded especially in the strategies with large stepover. Accurate calculating is made individually on linear and curve feed and formulae are developed. The author also gave the available application range of PAM and the algorithm for estimating correlative error.     

Development of a hybrid rapid prototyping system using low-cost fused deposition modeling and five-axis machining

Currently, two major processes are being used to produce prototypes, namely machining and rapid prototyping. Machining is generally more accurate and precise, but it is difficult to produce objects with certain complicated features. In contrast, rapid prototyping can produce objects with complicated features, which allows materials to be used more efficiently. However, due to the uneven shrinkage and residual stresses within rapid prototyping products, their accuracy is usually uncertain. This study attempts to integrate these two manufacturing processes and develop a hybrid rapid prototyping system in order to overcome the disadvantages associated with each process and to develop new applications. Fused deposition modeling (FDM) was used as the rapid prototyping process in this work. A spindle and a low-cost FDM extruder were designed to be placed on each end of a rotary axis in a five-axis machine tool. The proposed design allows the rotation of the axis on the five-axis machine to switch between machining and FDM, thus achieving the advantage of reducing costs for extra actuators without sacrificing working space. The case studies demonstrated that the proposed hybrid system can build FDM objects without using support materials and produce FDM parts with metal embedded to increase the stiffness. The system can also conduct five-axis machining on a completed FDM part or trim the freeform surface fabricated by FDM to achieve more accurate dimensions or better surface finish.     

基于NX4的轮胎模具基模五轴数控加工

介绍用NX4软件对轮胎模具基模进行数控加工的过程,阐述了基模模型的建立、加工操作模板父节点的设置、加工参数的设置和基模五轴数控加工的具体步骤。可提高模具加工精度和效率,缩短产品开发周期。     

Improving machined surface textures in avoiding five-axis singularities considering tool orientation angle changes

This paper looks into the irregular machined surface textures appearing in the process of avoiding five-axis singularities using the C-space based tool orientation translation method. At first, the mechanism for the appearances of the irregular surface textures is analyzed. A cutting simulation in VERICUT reveals that irregular surface textures are actually caused by lacking control of the tool orientation angles in the orientation modification process. Realizing that, a modified particle swarm optimization (PSO) is intergraded into the previous tool orientation translation method. In the PSO, the particle evolving equations are redefined and a mutation operation is added. The objective of the PSO is to find an optimal translating vector in the C-space so that the changed tool orientation angles can reach minimum values. In this way, the surface textures can be controlled. Three comparative cutting experiments with fillet endmills are carried out to verify the effect of the proposed method. The experimental results show that: (1) with the tool orientation translation method, the five-axis singular problem can be well avoided; and (2) with the optimal translating vector found by the PSO, the machined surface textures can be greatly improved.     

Optimized tool path generation based on dynamic programming for five-axis flank milling of rule surface

This paper presents a computation scheme that generates optimized tool path for five-axis flank milling of ruled surface. Tool path planning is transformed into a matching problem between two point sets in 3D space, sampled from the boundary curves of the machined surface. Each connection in the matching corresponds to a possible tool position. Dynamic programming techniques are applied to obtain the optimal combination of tool positions with the objective function as machining error. The error estimation considers both the deviation induced by the cutter at discrete positions and the one between them. The path planning problem is thus solved in a systematic manner by formulizing it as a mathematical programming task. In addition, the scheme incorporates several optimization parameters that allow generating new patterns of tool motion. Implementation results obtained from simulation and experiment indicate that our method produces better machining quality. This work provides a concise but effective approach for machining error control in five-axis flank milling.     

等螺旋角锥度刀具简易数控加工法

文章提出了一种在经济型数控机床上实现等螺旋角圆锥螺旋线的加工方法,其原理是用等导程螺旋线去逼近此种曲线.这个方法计算简单,结果精确,并可保证整段曲线上误差相等,而且其大小也可控制.     

数控加工中自由曲面干涉区域求解算法的研究

质量和效率是自由曲面零件数控加工所追求的一对相对矛盾的目标,本文就解决这一问题的自由曲面零件分片加工方法中的关键问题－自由曲面的干涉区域求取,提出了利用自由曲面的几何信息通过优化和迭代方法进行干涉区域快速跟踪求取的算法,保证了求取的快速,可靠,并通过具体的计算实例验证了算法的有效性。     

基于SolidWorks的数控加工过程仿真系统的设计

介绍了在SolidWorks平台上，运用Visual Basic编程语言开发数控加工过程仿真系统，重点论述了仿真系统的编程模块和仿真模块。经使用表明，数控加工过程仿真系统完全满足实际生产现场要求，具有高可靠性、低成本、易扩展等优点。     

基于数控加工的工艺处理

文章主要对数控加工中的工艺处理问题进行了探讨,阐述了数控加工中工艺处理的若干原则和方法.     

Validation of volumetric error compensation for a five-axis machine using surface mismatch producing tests and on-machine touch probing

In order to validate volumetric error compensation methods for five-axis machine tools, the machining of test parts has been proposed. For such tests, a coordinate measuring machine (CMM) or other external measurement, outside of the machine tool, is required to measure the accuracy of the machined part. In this paper, a series of machining tests are proposed to validate a compensation strategy and compare the machining accuracy before and after the compensation using only on-machine measurements. The basis of the tests is to machine slots, each completed using two different rotary axes indexations of the CNC machine tool. Using directional derivatives of the volumetric errors, it is possible to verify that a surface mismatch is produced between the two halves of the same slot in the presence of specific machine geometric errors. The mismatch at the both sides of the slot, which materializes the machine volumetric errors is measured using touch probing by the erroneous machine itself and with high accuracy since the measurement of both slot halves can be conducted using a single set of rotary axes indexation and in a volumetric region of a few millimetres. The effect of a compensation strategy is then validated by comparing the surface mismatch value for compensated and uncompensated slots.     

型面联结件的数控加工

文章介绍了在数控机床上加工型面联结体的方法.先把型面曲线按等误差的要求离散成微小直线段,求出节点坐标,按直线插补原理编程就可以加工出这种非圆轮廓曲线.方法与现有文献比较,计算特别简单,而且结果也足够精确.     

五轴加工技术在模具零件加工中的应用

以实际模具零件加工为例,分析了五轴加工技术在模具零件加工中的应用,与三轴加工技术相比较,五轴加工技术提高了零件质量和加工效率,减少了电极数量,缩短了模具生产周期,在模具制造业中有广阔的应用前景。     

A tool-path control scheme for five-axis machine tools

This paper presents a new servo control method for five-axis machining applications. The proposed method conducts a direct elimination of the deviation error, the orientation error, and the tracking-lag error that are the main concerns for five-axis tool-path control. To achieve this purpose, the proposed five-axis control system is based on a real-time transformation between the drive-coordinate basis, in which the five drives are operated, and the workpiece-coordinate basis, in which the deviation error etc., are defined.     

粉末冶金齿轮成形模具数控线切割加工仿真

根据数控线切割加工粉末冶金模具的加工工艺方法,利用Pro／E系统的Pro／NC模块,研究了粉末冶金齿轮成形模具型腔的数控线切割加工仿真,并自动生成了数控加工程序,从而将产品的计算机辅助设计（CAD）与计算机辅助制造（CAM）实现了无缝结合,大大提高了粉末,台金制品的制造精度,实现了加工自动化,缩短了开发周期,降低了制造成本。