On the machining of fiber reinforced plastic (FRP) composite laminates

With the increasing use of fiber reinforced plastic (FRP) composites outside the defense, space and aerospace industries, namely, civilian industries, machining of these materials is assuming a significant role. Unit cost rather than solely performance at any cost will be the consideration for the implementation of FRP composites to consumer industries. The current knowledge of machining FRP composites, unfortunately, is inadequate for its optimum utilization in many applications. This paper presents some observations made on the orthogonal machining of unidirectional carbon fiber reinforced plastic (UD-CFRP) laminates with different fiber orientations. Iosipescu shear test was adopted to evaluate the inplane shear strength of varied fiber angle test specimens. A model for predicting the cutting forces and the dependence of cutting direction on machinability requirements is presented.     

Application of genetic algorithms—determination of the optimal machining parameters in the conversion of a cylindrical bar stock into a continuous finished profile

This paper proposes an optimisation technique based on genetic algorithms for the determination of the cutting parameters in multi-pass machining operations by simultaneously considering multi-pass roughing and single-pass finishing operations. The optimum machining parameters are determined by minimising the unit production cost of converting a cylindrical bar stock into a continuous finished profile involving seven machining operations; with each operation subject to many practical constraints. The cutting model developed for each machining operation is a non-linear, constrained problem. Experimental results show that the proposed technique is both effective and efficient.     

Calculation of optimum cutting parameters based on minimum energy footprint

Environmental sustainability in machining requires that the energy and carbon footprint of machined products be optimised. The original contribution in this paper is that a minimum energy criterion recently proposed by the authors is exploited in the development and implementation of a methodology for selection of optimum cutting conditions. The energy saving impact of the new methodology was quantified by comparing to traditional practice. The synergy between minimum cost and minimum energy solutions was also explored. This timely research illustrates how the energy intensity and energy cost of a machined component can be minimised and hence reducing carbon dioxide emissions.     

The optimal cutting-parameter selection of production cost in HSM for SKD61 tool steels

The main purpose of this study was to construct an investigation of optimal cutting parameters for minimizing production cost on the rough machining of high speed milling operation. A machining model is constructed based on a polynomial network. The polynomial network can learn the relationships between cutting parameters (cutting speed, feed per tooth, and axial depth of cut) and tool life through a self-organizing technique. Once the material removal volume for machined parts and various time and cost components of the high speed milling operations are given, an optimization algorithm using a simulated annealing method is then applied to the polynomial network for determining optimal cutting parameters. The optimal cutting parameters are subjected to an objective function of minimum production cost with the feasible range of cutting parameters.     

Machining parameters for an intelligent machining system for composite laminates

Composite laminates exhibit very high in-plane strengths but are plagued by delamination damage when subjected to machining. This is due to their poor transverse strengths and low delamination fracture toughness. In drilling, delamination is initiated when the thrust force exceeds a threshold value, particularly at the critical entry and exit locations of the drill bit. To minimize damage, therefore, it is important to monitor process variables such as the machining forces and the position of the tool relative to the workpiece. The availability of a suitable model coupled with an intelligent control scheme would be a large advancement in the machining of composite laminates. This paper explores the development of such models for machining of composites and for coupling the models to intelligent control strategies. Using a machining center, a series of drilling experiments were conducted on carbon fiber-reinforced composite laminates to determine key process parameters for various cutting conditions. An intelligent machining scheme is proposed as the basis for the design of a new machine tool.     

微磨料水射流加工脆性玻璃的冲蚀机理研究

微磨料水射流加工技术正成为制造微细结构零件重要的经济高效的微细加工技术。作者在玻璃上进行微磨料水射流微细槽加工的实验基础上,对微磨料水射流加工的表面形貌、材料冲蚀去除机理及加工工艺性能进行了研究。结果表明,玻璃加工表面沿着槽道的方向形成了波纹状形貌,呈非对称或对称的波形,波纹表面很光滑,波纹图案沿着射流冲击区的径向方向发展。由于黏性流体的阻滞作用,脆性玻璃在微磨料水射流加工过程中,在黏性流区域没有发现任何裂纹,材料的冲蚀去除主要是以塑性断裂的方式为主,形成了光滑的加工表面。适当地控制加工工艺参数,在低压下,微磨料水射流加工是一种用于脆性材料上微细通道的加工切实可行的方法,并可获得良好的加工表面质量。     

碳纤维复合材料铣削与磨削加工对比研究

使用单层钎焊金刚石磨头和金刚石涂层玉米铣刀对T800碳纤维增强环氧树脂复合材料层压板进行切边加工,研究铣削加工和磨削加工工艺对碳纤维增强复合材料(carbon fiber reinforced plastics,CFRP)表面质量的影响。通过对加工表面微观形貌的观察和表面粗糙度的测量对比,讨论2种加工方式下表面质量差异和缺陷形成的原因。结果表明:磨削加工的表面质量优于铣削加工的表面质量,铣削加工后CFRP表面会出现凹坑和树脂涂覆等缺陷,但磨削加工的表面纤维断口清晰可见,无明显缺陷。铣削工艺下的凹坑是纤维集束断裂而形成的,树脂涂覆是由刀具后刀面与工件材料的频繁挤压、摩擦而形成。在表面质量和加工缺陷要求严格的条件下,应优先选用磨削加工工艺。      

螺旋锥齿轮数控铣齿加工过程几何仿真研究

利用面相对象技术和CAD系统的三维建模功能及其ObjectARX技术，根据螺旋锥齿轮的加工原理，提出了CNC铣齿机、齿坯和刀具三维模型的构建方法以及基于全局光照明的加工环境光照计算的具体方法。利用齿坯实体模型和刀具实体模型做布尔减运算，来实现模拟工件材料的去除过程；同时，采用全局光照明模型建立了具有真实感的数控加工虚拟现实环境。实际应用表明，该系统不但实现了螺旋锥齿轮的计算机辅助铣齿，提高了加工效率，降低了加工成本；而且还提供了非常真实的仿真效果。所获仿真结果可为齿面接触分析、有限元应力分析、齿轮的数控加工等提供精确的三维几何模型。     

Design of reconfigurable machining lines: A novel comprehensive optimisation method

We present a novel comprehensive optimization model for designing reconfigurable machining lines. Due to the proposed fine mathematical modelling, it is possible to optimize simultaneously the whole set of machines and machining modules as well as their cutting parameters, their configuration that will be used for processing of each part and part position at each machine. The experimental results show that the proposed optimization approach substantially outperforms the existing heuristic design method and therefore it can be used by the designers in order to reduce the total system cost and improve the efficiency of reconfigurable machining lines.     

活塞环槽激光处理工艺优化

总结了该厂多年激光表面硬化处理经验.认为激光淬火和激光熔凝都能硬化球铁和中碳合金钢材料的活塞环槽表面,但从现有工艺性、质量和成本综合考虑,认为激光淬火适合于中碳合金钢活塞,激光熔凝则更适合于球铁活塞.对于进行这两种激光处理前后的机加工工艺也完成了相应优化.     

椭圆旋摆加工内多边形技术

针对内多边形加工问题,通过深入研究椭圆加工轨迹数学模型,探讨了利用椭圆曲线实现旋摆加工的基本思想。在此基础上构建了内多边形加工工艺系统。实际切削操作表明:工艺系统调整简单,易于控制;大大地提高了加工效率,同时降低了加工成本。     

排列管电极电解切割加工技术研究

采用微细铜管排列组成具有任意待加工形状的电极,可进行高效率、低成本的切割加工。对排列管电极电解加工过程进行了建模仿真,对电解加工过程机理的研究具有一定参考价值。采用排列管电极加工出深度分别为100、200 mm的圆弧形及"V"形切缝,加工过程稳定,无火花短路现象发生。大深度试件的成功切割证明了排列管电极电解切割加工技术的可行性。     

A study of pre-compensation for thermal errors of NC machine tools

Thermally-induced errors are major contributors to the overall accuracy of machine tools. In this paper, an error pre-compensation system is developed to correct the thermal errors of the spindle and lead screws. A simple gauge 1-D ball array is used to accelerate and simplify the error measurement. An auto-regressive model based on spindle rotation speed is then developed to describe the thermal errors. Using the model, the thermal errors can be predicted without measuring the temperature field of the machine tool as soon as the workpiece NC machining program is made. By correcting the program, the errors can be pre-compensated before machining. Thus the process of compensation is greatly simplified and the cost is reduced. The test results on a vertical machining center show that a 70% reduction of thermal errors has been gained after compensation.     

Fabrication of deep micro-holes in reaction-bonded SiC by ultrasonic cavitation assisted micro-EDM

Ultrasonic vibration was applied to dielectric fluid by a probe-type vibrator to assist micro electrical discharge machining of deep micro-holes in ceramic materials. Changes of machined hole depth, hole geometry, surface topography, machining stability and tool material deposition under various machining conditions were investigated. Results show that ultrasonic vibration not only induces stirring effect, but also causes cloud cavitation effect which is helpful for removing debris and preventing tool material deposition on machined surface. The machining characteristics are strongly affected by the vibration amplitude, and the best machining performance is obtained when carbon nanofibers are added into the vibrated dielectric fluid. As test pieces, micro-holes having 10 μm level diameters and high aspect ratios (>20) were successfully fabricated on reaction-bonded silicon carbide in a few minutes. The hybrid EDM process combining ultrasonic cavitation and carbon nanofiber addition is demonstrated to be useful for fabricating microstructures on hard brittle ceramic materials.     

基于遗传模拟退火算法的铣削用量优化

由于传统的切削用量选择方法的局限性,数控机床的功率不能被充分发挥,这使得数控加工这种高费用的加工手段变得更加昂贵。通过考虑机床、工件和刀具的实际约束来建立加工时间和加工成本的铣削用量数学模型,采用遗传模拟退火算法对铣削用量进行优化,实例表明遗传模拟退火算法优化铣削用量比采用遗传算法优化更迅速、更有效。     

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.     

航发压气机叶片的加工仿真分析

航发压气机叶片型面及加工工艺复杂。为降低加工成本、提高加工效率,对某型复杂薄壁航空发动机压气机叶片零件进行加工仿真研究。分析叶片的结构特点,结合加工工艺路线制定原则,制定了叶片加工工艺路线,规划了刀具轨迹;根据五轴机床行程及运动特点,定制了五轴机床专用后处理器,并将刀具轨迹后处理生成了叶片加工的NC程序,同时输出加工总计用时;构建立式五轴数控机床仿真模型,对加工工艺进行仿真验证,取代实际加工试切步骤,节省生产成本和时间。仿真加工结果验证了加工工艺的合理性和后处理的正确性,为加工参数的进一步优化和加工误差分析奠定了基础。     

Modeling economic efficiency of multi-technology platforms

It is believed that for complex workpieces and small lot sizes complete machining with multi-technology platforms reduces cycle times compared to multiple stand-alone machines and is economically more efficient. However, so far in literature no mathematical model has been applied to compare these alternatives with respect to cost and productivity. This paper introduces a mathematical model for part costs and productivity and examines conditions under which multi-technology platforms are economically efficient. It is concluded that depending on the reduction of reconfiguration and processing times efficient production with multi-technology platforms is not solely limited to small lot sizes.     

高速铣削加工工艺优化技术的研究

针对高速加工安全性高、切削效率佳、工艺性好等独特的编程要求,构造出了以切削时间短、加工成本低、表面质量高为优化目标的,并以满足零件尺寸精度要求为约束条件的加工工艺方案评优模型。该模型已应用于自主开发的高速铣削Superman CAMⅡ原型系统中,以指导粗精加工刀轨的生成。实验结果表明：该模型具有合理性和实用性,对工艺人员编制高速加工工艺有一定的参考价值。     

Tolerancing for manufacturing via cost minimization

The purpose of dimensioning and tolerancing for process planning is to determine the dimensions and tolerances that are to be produced at each stage in the manufacture of a component in order that the design dimensions and tolerances specified on the engineering drawing of the component are satisfied. Three proposed objective functions for cost minimization are developed in this paper according to various situations. When cost information is available average cost per acceptable unit produced in minimized, otherwise ratio of number of components to be machined to output is minimized. If residual tolerances exist sum of manufactured tolerances are maximized by assigning weights according to their process capabilities. Combining these objective functions a computerized optimization program has been developed which determines the optimum set of dimensions and tolerances which satisfies the specified design dimensions and tolerances and the permissible machining allowances, with the cost of producing all dimensions to the respective tolerances to be minimal.

This system takes into account machining cost, scrap and where in the production process it occurs, manufactured dimensions and their distributions, allocated tolerances and process capabilities.