复合型陡峭曲面高速加工刀路的优化

针对现有数控加工中螺旋刀轨对曲面形状适应性差、无法应用于复杂陡峭曲面的问题,提出了一种复合型内侧陡峭面螺旋刀轨。一方面,通过构建圆柱螺旋线的方法获得光顺的螺旋驱动曲线;另一方面,通过抽取实体并将顶部曲面替换为平面的方法构建检查几何体;然后将螺旋驱动曲线和检查几何体导入CAM软件,对进退刀轨迹进行光顺化处理,从而生成连续光顺的螺旋刀轨。刀轨模拟和实际加工结果表明,复合型内陡峭面螺旋刀轨有效解决了高速加工中的切削颤振,显著提高了内侧陡峭面的加工效率和加工精度。     

基于某薄壁螺旋片的高速切削技术研究

高速切削具有切削力小、残余应力少、加工效率高等优点,非常适合薄壁零件的加工。本文设计了典型零件薄壁螺旋片,并运用高速铣削成功加工出了合格零件,对高速切削技术进行了较为系统的研究。     

圆锥面及与平面倒圆角面螺旋插补铣削工艺及宏程序设计

数控铣床加工圆锥面及其与平面倒圆角面时,通常采用CAD/CAM软件自动编程或手工以等高加工方式编程,存在不能满足高速切削和产生接刀痕的问题。螺旋插补铣削工艺设计和宏程序编制实现了刀具连续下刀并平稳运行,提高了此类曲面加工的效率和质量。     

面向高速加工的复合曲线螺旋轨迹生成方法

针对现有螺旋切削方式仅仅适合圆形或类圆形边界曲面的问题,提出了一种复合曲线螺旋切削法,利用直线圆弧构建规则形状的辅助边界以包容不规则的曲面原始边界,以辅助边界构建光顺网格曲面作为螺旋线的投影曲面,然后桥接投影曲线与平面螺旋线作为驱动曲线从而生成复合螺旋刀路,在避免边界尖角影响的同时保留了刀轨连续的优点,适用于各种具有不规则边界的平坦曲面。软件模拟和实际加工结果表明,复合曲线螺旋切削法有效解决了刀轨的连续性和矢量突变问题,特别适合复合曲面的高速加工。     

面向高速加工的复杂曲面螺旋刀路优化

针对现有螺旋切削轨迹对曲面形状适应性较差,无法直接应用于复杂曲面的局限,提出一种基于曲面重构的螺旋曲线切削法。对于复杂曲面根据各自的特点分别采用曲面提取、修补、延伸等方法重构目标曲面,以重构后的曲面作为圆柱螺旋线的投影对象获取驱动曲线,在CAM软件中以曲线驱动方式生成螺旋曲线轨迹并进行优化。VERICUT软件仿真和实际加工的结果表明:复杂曲面采用曲面重构螺旋切削法可以获得满足高速加工要求的光顺切削路径,扩展了先进螺旋切削方式的应用范围。     

高速切削加工工艺的现状与优化趋势

针对高速切削和传统切削加工工艺之间存在较大差别的现象,通过对高速切削加工切削参数、切削路径、切削刀具、冷却方式等进行现状阐述分析,提出高速切削加工工艺的优化趋势。     

复杂曲面微小零件切削加工工艺研究

随着微机电和纳米技术的快速发展,复杂形面微小零件的加工显得越来越重要。本文对复杂形面微小零件的精密切削工艺进行了分析,重点探讨了微细切削加工机理、刀具选择、刀具路径规划以及切削用量的选择。     

基于GCMT2500数控机床的摆线齿锥齿轮齿面切削研究

在摆线齿锥齿轮的小轮切削加工中,设计一种新型的克制刀盘安装在GCMT2500数控螺旋锥齿轮复合机床上。结合机床自身性能,对齿轮切削方法进行研究。对小齿轮切削分别拟定了粗、精加工方案,找到一种合理的切削方法。在精加工中分析了各种加工方式得到的齿面粗糙度,并提出了精加工时采用斜切法对齿面进行切削齿面精度可以满足传动要求。     

大平面高速精铣

大平面高速精铣天津中德现代工业技术培训中心（３００１９１）李林大平面高速精铣是采用红硬性及耐磨性好的硬质合金宽刃刀具,选择较高的切削速度、大走刀、小切深切削参数,在加工零件上获得半网纹刀痕的一种光整加工方法。采用该方法加工的零件,其表面粗糙度可稳定达...     

低刚度零件切削射流支撑技术研究进展

低刚度零件广泛应用于机械、航空航天、军工等行业及人们的生产生活中,由于该类零件的低刚度特性,在切削过程中容易产生加工误差。本文分别对低刚度零件切削和水射流技术国内外研究现状进行了分析,并对低刚度零件提出一种运用水射流辅助支撑的新型加工技术,为今后低刚度零件的加工提供新理论指导。     

CNC Tool-Path Planning for High-Speed High-Resolution Machining Using a New Tool-Path Calculation Algorithm

Reduced machining time and increased accuracy for a sculptured surface are both very important when producing complicated parts, so, the step-size and tool-path interval are essential components in high-speed and high-resolution machining. If they are small, the machining time will increase, whereas if they are large, rough surfaces will result. In particular, the machining time, which is a key factor in high-speed machining, is affected by the tool-path interval more than the step size. The conventional method for calculating the tool-path interval is to select a small parametric increment or small increment based on the curvature of the surface. However, this approach has limitations. The first is that the tool-path interval cannot be calculated precisely. The second is that a separate tool-path interval must be calculated in three separate cases. The third is the requirement of a conversion from the Cartesian domain to the parametric domain or vice versa. Accordingly, for high-speed and high-resolution machining, the current study proposes a new tool-path interval algorithm, that does not involve a curvature or any conversion, plus a variable step-size algorithm for NURBS.     

复杂陡峭曲面分段式螺旋刀路的设计

针对现有螺旋刀轨在实际应用中限制较多、无法直接应用于复杂陡峭曲面加工的局限,提出一种分段式螺旋刀轨。通过对流线驱动刀轨、曲面驱动刀轨和螺旋复合曲线驱动刀轨的有机整合,对复杂陡峭曲面的不同部位采用不同的加工方式,工艺针对性更强。同时,对作为流线的边界曲线采用提取、光顺和替换的方式进行重构,使得流线驱动螺旋刀轨更加光顺。实际加工和VERICUT软件仿真的结果表明,分段式螺旋刀轨能够满足高速加工刀轨连续光顺的要求,在生产中可操作性强。     

A Path Interval Generation Algorithm in Sculptured Object Machining

The features of a sculptured object are represented by a set of section curves. A fast algorithm is presented to calculate cutting depths based on the scallop height using these curves. The calculated cutting depth can be used for tool-path generation. This tool-path generation approach is particularly useful for constant z level contouring and high-speed machining.     

Double spiral tool-path generation and linking method for complex pocket machining

Complex pockets with one or more islands have been widely used in industrial and manufacturing production. In this paper, a new double spiral tool-path generation and linking method are proposed for complex pockets with islands which can be used for high-speed machining (HSM) is used. Taking into account the path interval, step length and other processing parameters, precise milling can be achieved without cutter lifting and retraction motions to guarantee machining accuracy and reduce processing time. The method has been implemented in several simulations and validated successfully through the actual machining of a complicated pocket. The results indicate that this method is superior to other existing machining methods, and it can achieve HSM of complicated shaped pockets based on parametric surface.     

Geometry of chip formation in circular end milling

Machining along continuous circular tool-path trajectories avoids tool stoppage and even feed rate variation. This helps particularly in high-speed milling by reducing the effect of the machine tool mechanical structure and cutting process dynamics. With the increase in popularity of this machining concept, the need for detailed study of a valid chip formation in circular end milling is becoming necessary for accurate kinematic and dynamic modeling of the cutting process. In this paper, chip formation during circular end milling is studied with a major focus on feed per tooth and undeformed chip thickness along with their analytical derivations and numerical solutions. At first, the difference in the feed per tooth formulation for end milling along linear and circular tool-path trajectories is presented. In the next step, valid formulation of the undeformed chip thickness in circular end milling is derived by considering an epitrochoidal tooth trajectory with a wide range of the tool-path radius. The complex transcendental equations encountered in the derivation are dealt with, by a case-based approach to obtain closed-form analytical solutions. The analytical solutions of undeformed chip thickness are validated with results of numerical simulations of tool and tooth trajectories for circular end milling and also compared to the linear end milling. The close resemblance between analytical and numerical calculations of the undeformed chip thickness in circular end milling suggests validity of the proposed analytical formulations. As a case study, the cutting forces in circular end milling are calculated based on the derived chip thickness formulations and an existing mechanistic model. The calculation results reiterate the need of taking into account adjusted feed per tooth and valid chip thickness formulations in circular end milling, especially for small tool-path radii, for more realistic process modeling.     

特种回转面刀具螺旋槽的通用几何模型

针对数控磨削螺旋槽的特点 ,提出了基于一般特种回转面刀具刀刃曲线和刀面截形的螺旋槽通用几何模型。该模型采用统一的形式表示螺旋槽 ,为特种回转面刀具的设计和数控加工提供了理论基础。该模型也适用于其它类型的回转刀具     

Tool-path planning for rough machining of a cavity by layer-shape analysis

In the manufacture of parts with sculptured cavities from prismatic stock, rough machining usually constitutes most of the machining time owing to the significant difference between the stock and the part shape. When using 2 1/2-D milling or a contour-map approach to do the rough machining, the appropriate selection of tool-path pattern for each cutting layer can significantly reduce rough machining time and hence increase productivity. In this paper, the commonly used toolpath patterns are summarised. A knowledge-based parametric approach for optimising the toolpath pattern of a given cutting layer is proposed. Then, a novel methodology is developed to calculate an arbitrary polygon area and locate the concave cavities in the polygon. Procedures for cutting-layer-shape analysis and the optimal comprehensive tool-path pattern generation are also built and proposed in this paper. These procedures can not only be applied to sculptured cavity parts with simple islands, but also to parts with arbitrarily-shaped islands. Finally, an example is given to illustrate the reasoning process.     

Optimal selection of machining direction for three-axis milling of sculptured parts

In the field of free form surface machining, CAM software allows management of various modes of tool-path generation (zig-zag, spiral, z-level, parallel plan, iso-planar, etc.) leaning on the geometry of the surface to be machined. Various machining strategies can be used for the same shape. Nevertheless the choice of a machining strategy remains an expert field. Indeed there are no precise rules to facilitate the necessary parameter choice for tool-path computation from analysis of the numerical model of a part and the quality requirements. The objective of this paper is to provide a method to assist in the choice of the machining direction for parallel plane milling of sculptured parts. The influence of the tool-path on final quality according to the intrinsic geometrical characteristics of the latter (curves, orientation) was studied. Directional beams are introduced and defined from the local surface parameter. Finally, a methodology to optimize machining time while guaranteeing a high level of quality was developed and applied to examples.     

Engagement Angle Modeling for Multiple-circle Continuous Machining and Its Application in the Pocket Machining

The progressive cutting based on auxiliary paths is an effective machining method for the material accumulating region inside the mould pocket. But the method is commonly based on the radial depth of cut as the control parameter, further more there is no more appropriate adjustment and control approach. The end-users often fail to set the parameter correctly, which leads to excessive tool load in the process of actual machining. In order to make more reasonable control of the machining load and tool-path, an engagement angle modeling method for multiple-circle continuous machining is presented. The distribution mode of multiple circles, dynamic changing process of engagement angle, extreme and average value of engagement angle are carefully considered. Based on the engagement angle model, numerous application techniques for mould pocket machining are presented, involving the calculation of the milling force in multiple-circle continuous machining, and rough and finish machining path planning and load control for the material accumulating region inside the pocket, and other aspects. Simulation and actual machining experiments show that the engagement angle modeling method for multiple-circle continuous machining is correct and reliable, and the related numerous application techniques for pocket machining are feasible and effective. The proposed research contributes to the analysis and control tool load effectively and tool-path planning reasonably for the material accumulating region inside the mould pocket.