Integrated Inspection and Machining for Maximum Conformance to Design Tolerances

Designers' intent for the form, fit and function of products is expressed by design tolerances the conformance to which is the main objective of manufacturing processes. A methodology for maximizing the adherence to the specified tolerances using an integrated machining and inspection system is presented. Considering the desired tolerance envelope of the part, an error decomposition technique is developed to model machining errors caused by the systematic and non-systematic errors in the machine tool. The model is used to adaptively plan the final machining cuts, based on inspection feedback, to enhance the geometric accuracy of the final product and is illustrated by an example. This approach reduces scrap and rework and their associated costs.     

The application of tool deflection knowledge in process planning to meet geometric tolerances

Machine tool deflections due to cutting forces can result in dimensional errors on workpieces. The problem is most severe when flexible tools such as end mills are used. When dimensioned features are specified with tolerances, process planning should examine the compromise between achieving high productivity rates and meeting dimensions within the specified tolerances. The use of geometric dimensioning and tolerancing permits interaction between size and position and makes bonus tolerances available. The errors occurring in end milling are first examined and modelled using regression methods. A procedure is proposed for selecting optimal feed rates that ensure that tolerances can be met. The process is demonstrated in machining a slot using the down milling mode. The use of a tolerance analysis chart clarifies the results of the test in relation to the tolerance standards. The need to consider the transient errors at the exit of the cut is demonstrated.     

Concurrent optimization of design and machining tolerances using the genetic algorithms method

The allocation of design and machining tolerances has a significant effect on both manufacturing cost and quality. This paper presents a procedure to concurrently allocate both design and machining tolerances based on optimum total machining cost. The non-linear multi-variable optimization problem formulated is solved using the genetic algorithms method. Two design examples involving concurrent allocation of both design and machining tolerances are presented to demonstrate the effectiveness of the method.     

薄壁曲面零件的锻造成形工艺

某产品上用的一重要零件为薄壁曲面类零件,实际生产中主要采用机械加工制作,工序多,时间长,并浪费原材料.本文采用锻造成形工艺,锻模设计为曲面分模面模具结构,实现了薄壁曲面零件的锻造成形.零件成形后,无需再进行后续机械加工,产品的尺寸和形状均可直接达到使用要求.经过工艺试验和小批量的试生产考核,其尺寸和形状均能满足图纸技术要求,并且产品尺寸和形状的一致性好.与机械加工工艺相比,锻造成形工艺大幅度提高了产品生产效率和材料利用率,极大降低了生产成本.     

Assembled camshafts for automotive engines

Assembled camshafts offer an attractive manufacturing alternative over conventional methods to meet the demand for high performance camshafts at reduced costs. The manufacture of camshafts has traditionally involved the casting, forging, or machining of a rough blank which was further machined to the finished cam geometry. A new method will be discussed in which individual near-net shaped components are precision assembled onto a tube to pregrind tolerances. Completion of this camshaft only requires a finish grinding operation. The individual components are manufactured by casting, precision warm or cold forging, high speed turning, or powder metal consolidation. The process allows for material selection flexibility to optimize materials for all components with respect to performance and cost. In addition to the inherent advantages of the assembled camshaft, the process typically results in cost advantages over conventionally processed camshafts.     

Manufacturing feature-based cost estimation of cast parts

Seventy percent of new product cost is committed in the design phase. Therefore, the cost needs to be minimized. Incorporating accurate cost estimation capabilities into manufacturing processes can help industries to minimize the cost and optimize the design. The casting process has been employed as a key process to manufacture parts having the advantage of low cost and customized products in foundry industry. This paper presents a cost estimation system for the casting process based on the design features, which incorporates the casting information at the design stage of castings. It aims to deliver the best cost-effective choice for casting design features of a product. Two kinds of knowledge, namely economical knowledge(describing the relation between the casting design considerations and the cost) and technical knowledge(involving the material of the casting features) were structured in this research work. On the basis of the minimum product cost, casting material selection can be carried out in detail. The developed system has been validated through an industrial case study.     

起重支架的数控铣工艺处理及工装设计

起重架的锡青铜轴瓦毛坯在焊接后产生轴瓦圆度、同轴度偏差,利用数控铣削工艺来改变这种形位公差超差、刀具让刀现象等。通过控制切削过程、合理匹配切削用量、优化走刀路线、设计数控加工程序及选用刀具、设计工装等,优化了工艺,提高了加工效率,节约了成本。     

基于矩阵的工艺尺寸链分析与解算

文章基于尺寸链原理,借助一个机械加工实例,详细分析了工艺尺寸式方程的建立、查找及解算过程;并在此基础上引入基本尺寸矩阵方程和公差矩阵方程,采用Matlab语言编写计算机程序.系统完整地解决了机械加工过程中涉及到的所有尺寸及公差的计算机解算问题,明显地提高了尺寸链的解算速度和质量.     

Determination of optimal cutting conditions using design of experiments and optimization techniques

In process planning or NC part programming, optimal cutting conditions are to be determined using reliable mathematical models representing the machining conditions of a particular work-tool combination. The development of such mathematical models requires detailed planning and proper analysis of experiments. In this paper, the mathematical models for TiN-coated carbide tools and Röchling T4 medium carbon steel were developed based on the design and analysis of machining experiments. The models developed were then used in the formulation of objective and constraint functions for the optimization of a multipass turning operation with such work-tool combinations.     

某雷达关键件的加工工艺分析与夹具设计

分析某雷达关键件——支臂零件的结构特点,制定支臂的加工工艺流程,并进行相应的液压夹具设计。实践证明:采用该专用夹具可使该零件的加工时间缩短50%以上,加工质量和加工精度明显提高,增强了企业竞争力。     

FE approach and experiments for an axisymmetric micro-yoke part forming using grain element and grain boundary element

Until present, an axisymmetric yoke part of electro-magnetic micro-speaker/receiver had manufactured by machining through the material’s removal. However, this machining process have some problems such as long production time, high precision of tool and costs. In this study, a program based on finite element method developed to establish milli-structure forming technology for micro-yoke component, one of the key parts in the multi-functioned micro-speaker/receiver. This developed program is applied for the milli-part forming in order to replace the machining process of micro-yoke. A new numerical approach is proposed to simulate intergranular milli-structure in forming the miniature yoke, in which grain elements and grain boundary elements are introduced. The results of the finite element analysis for micro-yoke part are confirmed by a series of experiments.     

钛薄壁圆盘的无飞边冲压工艺

一般的封头型零件都是冲压成型后再经机加工而成.但对于冲压成型壁厚仅为2 mm的钛圆盘,由于钛塑性好、刚性差,冲压后产生飞边,后续工序困难.为此分析了采用冲压成型制作薄壁钛圆盘而不产生飞边,不须后续精加工的可行性,并制订了多个工艺方案.通过优选建立了无飞边一次冲压成型制作薄壁钛圆盘的工艺,并设计了专用冲压模.采用本工艺及其模具冲压成型的钛圆盘,无飞边、无毛刺、底面平整、盘壁无皱折,且出模容易,变形较小,完全符合图纸设计要求.     

A Manufacturing-Oriented Intelligent CAD-System

This paper discusses the capabilities and implementation of an “intelligent” CAD system (INCAD). The system provides direct feedback from the manufacturing experience to the CAD process by guiding its user to design with a view to manufacturing, to economic manufacturing, and to automated manufacturing. Specific features include checks for consistency of multiple views, appropriateness of tolerances, missing dimensions, adequate bending radii for sheet metal parts, hole spacings, proper utilization of standard parts, etc. Such an intelligent CAD system is currently under development at UCLA utilizing the CADAM system.An INCAD system may operate in an interactive and/or a postprocessing mode. It may provide various types of responses whose severity can be adjusted. INCAD systems can be developed for various types of CAD models and in various application areas. A proposed architecture would allow convenient modular implementation.     

Design and analysis of a prototypical sensory Z-slide for machine tools

Due to the advancements in high speed and high performance cutting, further improvements of machine component design and process monitoring are necessary. For this purpose, new machine components with process monitoring capabilities have to be developed. In this paper, a new spindle carrying Z-slide for a 5-axis machining center with integrated sensing capabilities for process monitoring is presented. First, the overall system design is described. The sensing capabilities to enable process monitoring are realized by application of a micro-strain gauges network on to the structure of the slide. The optimal sensor positions are computed by application of a special sensor placement algorithm. The prototype of the slide has been built up to investigate the system behavior. The electronic system of the prototype to realize the signal amplification and the communication via an industrial bus are presented. Furthermore, the results of the system analysis of the prototype are described. Because the sensor amplitudes, which can be monitored by strain gauges on stiff structures, are generally small, a method to increase these amplitudes by use of the notch effect and new micro-strain sensors is discussed. With this method, the signal amplitudes can be increased significantly, without degrading the stiffness noticeably. At the end of the paper a method to manufacture notches in the prototype by a milling process is presented. The surface roughness of plan notch ground, measured with a laserprofilometer, shows roughness values lower than 3 μm.     

Allocation of assembly tolerances to minimize costs

The cost and quality of an assembly depend on the processes used to manufacture its components. The specific processes and process settings are often dictated by the tolerances on the components. One long-standing challenge is allocating the assembly tolerance to components. Many methods have been proposed, most of which endeavor to minimize cost. We propose a tolerance allocation method that minimizes cost by jointly considering process variation and tolerance specifications. A cost model including processing cost, scrap cost, and quality loss is employed. The cost is minimized by a heuristic strategy. An overrunning clutch assembly case study is used to evaluate the method.     

数控车床高速车削滚珠丝杠的工艺方法

滚珠丝杠属典型的细长轴类零件,由于其长径比比较大,加工后很难获得满意的表面粗糙度和几何精度.传统的滚珠丝杠加工方法是“车-淬-粗磨-精磨”,采用磨削工序能提高滚珠丝杠的加工质量,但磨削设备造价较高,磨削工序耗时较长,能源消耗大.探讨滚珠丝杠加工的工艺方法,设计制造一种新型的丝杠加工专用数控车床,并采用“车-淬-精车-磨”的新工艺,提高了生产效率,降低了生产成本,解决了滚珠丝杠的加工难题.     

整体叶盘叶栅通道径向进给电解加工成形规律研究与阴极设计

整体叶盘叶栅通道的加工是在叶片型面精加工满足设计要求之前不可缺少的工艺步骤。工具电极径向进给加工叶栅通道的模式,可有效解决整体叶盘叶栅通道轮毂型面加工困难的问题。分析了径向进给加工时的侧面的成形规律,利用不同角度的楔形阴极工具开展试验研究,掌握侧面成形规律及二次腐蚀对成形的影响;根据侧面成形规律计算出工具电极截面数据,并拟合成工具电极型面。选择合理加工参数,利用设计出的工具电极在自行研制的电解加工机床上开展试验研究。结果表明,采用该方法设计出的阴极可加工出余量更均匀的叶栅通道。     

Modeling of material removal and surface roughness in abrasive flow machining process

Abrasive flow machining process provides a high level of surface finish and close tolerances with an economically acceptable rate of surface generation for a wide range of industrial components. This paper deals with the theoretical investigations into the mechanism of abrasive flow machining (AFM) process. A finite element model is developed for the flow of media during AFM and the same is used to evaluate the stresses and forces developed during the process. Theoretical analysis to estimate the material removal and surface roughness obtained during AFM is also proposed. The theoretical results are compared with the experimental data available in the literature, and they are found to agree well.     

利用普通轧辊机床加工高硼钢轧辊

通过提高普通轧辊机床系统刚度、选择硬质合金刀具、优化刀具几何参数、正确装夹刀具、选择合理车削用量,实现了普通轧辊机床加工高硼钢轧辊。在正常加工效率下,轧辊尺寸精度、孔型及位置精度、表面质量均达到了设计要求。     

Spin Extrusion - A New Partial Forming Technology based on 7 NC-Axes Machining

Hollow shape component approaches, applied to shafts and similar workpieces, represent a major potential for ground-breaking innovations in lightweight engineering and safety designs. Among suitable forming technologies, spin extrusion is a pioneering and particularly flexible hollow-shaping technique. All outside form elements, straight or stepped cylinders, cones or spherical rotation elements emerge just from the kinematics of tools. The inside hollow shapes, as e.g. circular cross-sections, shaft to collar connections such as spherical triangles, polygons, splines or dovetail forms are manufactured with a shaping mandrel. Spin extrusion can be applied first and foremost at dimensions that are unattainable with other techniques. The application includes hollow shafts, thick-walled cups and semi-finished tubular products that are not to be found in off-the-shelf cross-sections. In these cases the possibility for using of massive bars is connected with very high price advantages. Furthermore material-saving machining is attracting special attention for high-grade materials.The paper characterizes substantial steps of process analysis and the appliance of a new, derived from the bound method, numerical simulation method for spin extrusion process. Holistic process analysis is the prime factor for process capability. The specific application of the developed special methods of simulation, the accumulation of process data and the integrating into the Computer numerical control of spin extrusion machine is a precondition guaranteeing high-quality assurance.