Simulation of multi-axis grinding considering runout based on envelope theory

As one of the most important methods for machining process with high accuracy, ultra-precision grinding is widely used in fields such as aerospace, automotive and mold, etc. Simultaneously, it is common that wheel and spindle axis do not coincide with each other due to wheel settings, machining errors and so on. This could result in the generation of wheel runout, which may reduce the machining surface’s quality. In this paper, combining this phenomenon, an analytic algorithm method for the multi-axis grinding process is introduced according to the envelope theory. After that, the accuracy of this method is verified. Two experiments are carried out on a 5-axis machining center. The artificial runout is set up and calculated utilizing the least square method. Finally, using the presented method, two examples with and without runout are introduced to illustrate the validation of the proposed model. The error due to the runout effect is also analyzed.     

An approach for machining distortion measurements and evaluation of thin-walled blades with small datum

Inspection techniques for aero-engine blades are a hot topic in industry. Since these blades have a sculptured surface and a small datum, measurement results may deviate from an actual position. There are few proper approaches compensating for non-uniform distribution errors that are within specified tolerance ranges. This study aimed to develop a meshing structure measur-ing approach for the distortion of blades via non-contact optical 3D scanning. A rough measure-ment and a registration procedure are initially adopted to rectify the coordinate system of a blade, which avoids the initial coordinate system errors caused by the small datum. A measurement path with meshing structure is then unfolded on the blade surface. For non-uniform distribution errors, the meshing structure measurement is more visual and clear than the traditional constant height curves method. All measuring points take only 7 min to complete, and the distribution of error is directly and accurately presented by the meshing structure. This study provides a basis for future research on distortion control and error compensation.     

Evaluation of tool wear and cutting performance considering effects of dynamic nodes movement based on FEM simulation

An accurate estimation of tool wear morphology can provide the opportunity to investigate the influence of tool wear on cutting performance as well as reduce the overall production cost. However, tool wear prediction is still a very challenging research issue. In this paper, a novel method for simulating the actual chip formation and wear evolution thorough the 3D finite element model has been carried out. In order to improve the accuracy of simulation results, the influence of worn tool, stress and temperature distribution on wear rate are considered. Then cutting experiment has been conducted by turning AISI1045 with uncoated carbide tools to validate the accuracy of the proposed model. The comparison between experimental and simulation results show good agreement which proves the ability of the proposed model in forecasting the tool wear. The validated finite element model has been further utilized studying how the worn tool affects the cutting performance including actual cutting rake, stress distribution, cutting force and temperature. The results of this paper not only provide a clear understanding of wear evolution between tool rake face and chip, but also are meaningful to optimize tool design and cutting parameters.     

铣削加工透波性Si3N4陶瓷表面质量研究

为了探索透波性Si3N4陶瓷铣削中加工表面创成机理及加工工艺参数对其影响规律,对加工表面形貌和边缘破损特征,以及加工参数与切削力、表面粗糙度、边缘破损的映射关系等开展了试验研究。首先对加工表面形貌进行了分析,由于存在陶瓷粉末去除和破碎性颗粒去除两种形式,造成加工表面形貌结构一种体现为变化平缓,而另一种包含微裂纹、层状结构体等,且存在凹坑、沟槽等缺陷。其次研究了边缘破损形式及产生机理,当刀具运动到出口棱边处,刀尖应力集中处将产生微裂纹,并向工件侧面扩展,从而在加工表面和加工侧面诱导形成边缘破损。最后基于均匀设计试验,分析了工艺条件对加工性能的影响。结果表明:随着切削深度从0. 2增加到0. 5 mm和切削宽度从1增加到4 mm时,x轴切削力呈耦合增长,y轴切削力呈二次方增长;当切削深度和切削宽度分别为0. 2 mm和1 mm、进给速度为500 mm/min时,加工表面粗糙度值最小;转速为2 000 r/min、切削深度和切削宽度最小时,边缘破损幅值最小。此结果可为提高透波性Si3N4陶瓷铣削加工质量提供技术支撑。     

基于MBD的数控工艺设计及快速编程方法研究

面向基于模型定义技术在工艺设计中的应用,从提高工艺设计自动化及编程质量和效率出发,提出了一种基于MBD的数控工艺设计及快速编程方法,该方法根据基于MBD的特征信息描述,采用特征实例化方法,从易于制造及加工应用的角度对产品特征信息进行提取与构造.通过加工特征将几何信息与工艺信息相结合,分析三维关联的数控工艺信息模型内容.最后,利用工艺约束与制造数据库支持进行数控工艺设计,基于工艺结果以加工操作为基本单位驱动与数控加工系统的智能参数化映射,完成数控程序信息的自动生成.采用该方法进行工艺设计可以缩短编程周期,改善和提高加工编程质量和效率.     

UMAC伺服同步控制技术在轨迹制孔上的实现

根据轨迹制孔设备的结构特点和工艺需求,设计研制了一套基于UMAC多轴运动控制器的轨迹制孔控制系统.阐述了UMAC多轴运动控制器的硬件调试系统搭建、软件的应用和设计方法,同时重点介绍了虚轴同步技术在轨迹制孔控制系统中的应用,通过运动控制并给出了测试记录和制孔试验,验证了基于UMAC的伺服同步控制技术在多轴运动控制器在轨迹制孔设备中的实际应用效果的有效性.     

液体火箭发动机增材制造技术研究进展

针对增材制造技术在国内外液体火箭发动机领域的应用成果和研究现状,分别综述了增材制造在发动机的制造技术和流程、制造工艺标准以及在发动机推力室、涡轮泵、阀门、总装及其他组件和整机中的应用研究,并展望了增材制造技术在液体发动机中的发展方向,指出在液体发动机领域,增材制造应该在应用广度和深度、结合增材制造特点的发动机结构设计方...     

Efficiently constructing collision-free regions of tool orientations for holder in five-axis machining of blisk

Blisks with the integral structure are key parts used in new jet engines to promote the performance of aircrafts, which also increases the complexity of tool orientation planning in the five-axis machining. It is an essential task to find the collision-free tool orientation when the tool holder is pushed deep into the channel of blisk to increase rigidity and reduce vibration. Since the radius of the holder varies with the height, the line-visibility is no longer applicable when constructing collision-free regions of tool orientation. In this paper, a method of constructing collision-free regions without interference checking is proposed. The work of finding collision-free regions resorts to solving the local contact curves on the checking surfaces of blisk. And it further transforms into searching the locally tangent points (named critical points) between the holder and surface. Then a tracking-based algorithm is proposed to search the sample critical points on these local contact curves. And the corresponding critical vectors are also calculated synchronously. Besides, the safety allowance, discrete precision and acceptable deviation are introduced in the algorithm to ensure accuracy by controlling the angle between two adjacent critical vectors properly. After that, the searched critical vectors are mapped orderly to two-dimensional space and the collision-free regions are constructed. This method is finally verified and compared with a referenced method. The results show that the proposed method can efficiently construct collision-free regions for holder under the given accuracy.     

Machining deformation of single-sided component based on finishing allowance optimization

Owing to reliability and high strength-to-weight ratio, large thin-walled components are widely used in the aviation and aerospace industry. Due to the complex features and sequence involved in the machining process of large thin-walled components, machining deformation of component is easy to exceed the specification. In order to address the problem, it is important to retain the appropriate finishing allowance. To find the overall machining deformation, finishing allowance-induced deformation (web finishing allowance, sidewall finishing allowance) and initial residual stress-induced deformation were considered as major factors. Meanwhile, machined surface residual stress-induced deformation, clamping stress-induced deformation, thermal deformation, gravity-induced deformation and inertial force-induced deformation were neglected in the optimization model. Six-peak Gaussian function was introduced to fit the initial residual stress. Based upon the obtained function of initial residual stress, a deformation prediction model between initial residual stress and finishing allowance was established to attain the finishing allowance-induced deformation. In addition, linear programming optimization model based on the simplex algorithm was developed to optimize the overall machining deformation. Results have concluded that the overall machining deformation reached the minimum value when sidewall finishing allowance and web finishing allowance varied between 1 and 2 mm. Additionally, web finishing allowance-induced deformation and sidewall finishing allowance-induced deformation were 1.05 mm and 0.7 mm. Furthermore, the machining deformation decreased to 0.3–0.38 mm with the application of optimized finishing allowance allocation strategy, which made 39–56% reduction of the overall machining deformation compared to that in conventional method.