Picosecond laser trimming of ceramic cores with porous multi-scale particle microstructure

The ceramic core, produced by hot injection molding, is one of the critical components for manufacturing high-performance aircraft engine turbine blades. However, the injection molding process will cause defects such as burrs and flashes in the fine structure of the formed ceramic core. Manual trimming is necessary, but the trimming quality is poor, and the yield is low. In this paper, the online trimming method of ceramic cores is studied. Based on the orthogonal experiment method, the optimal laser parameters for processing the ceramic core's porous multi-scale particle structure material were obtained. Further, the problems of the match head and tail phenomenon and dimensional accuracy improvement in trimming ceramic cores have been studied. A path optimisation method is proposed to improve the quality and accuracy of the trimming profile effectively. Finally, the overall process flow of ceramic core trimming is elaborated, and experimental verification is given. The results show that the ceramic core online trimming method proposed in this paper has advantages of high precision and high yield compared with the manual method, which will have substantial potential application value in the aviation field.     

An effective method of bulk materials moisture measurement using capacitive sensors

When we speak about capacitance moisture meters for bulk materials we have to face with different values of dielectric permittivity for different bulk materials in dehydrated state, what causes a method error that can be named ‘type uncertainty’. Besides, different varieties of the same material have different values of dielectric permittivity, which depend from geographical origin, processing conditions etc. It can be hardly predicted automatically and type uncertainty can be compensated only in separate situations with the help of preliminary calibration. Main tasks of the research are to develop new comparison principle of moisture measurement with better accuracy due to effective compensation of physical, chemical and granulometric composition influence on the result of moisture measurement, develop new primary and secondary instrument transducers. Moisture sensor consists of four measuring capacitors. Two of them should be filled with a sample, which moisture content should be determined, and other pair of measuring capacitors should be filled with a same substance, but previously dehydrated. Mathematical models, developed to take into account granulometric composition of a bulk material were used to carry out a comparison analysis for three types of instrument measuring transducers. Obtained results proved that suggested principle of moisture measurement provides effective compensation of granulometric composition influence. Developed measuring principle had been experimentally tested what helped to confirm that it provides two times better compensation of different physical and chemical composition for different materials in comparison with the direct comparison method.     

加工切割精度对研磨的影响

本文主要介绍了在加工基板边部时,需将控制边部质量放在首。对于边部质量控制的重要环节是切割工序,切割的精度将直接影响到研磨边部的质量,从而影响边部良品率。因此,切割精度是作为控制边部质量的第一要素。     

Thermal error compensation of a 5-axis machine tool using indigenous temperature sensors and CNC integrated Python code validated with a machined test piece

Achieving high workpiece accuracy is the long-term goal of machine tool designers. There are many causes for workpiece inaccuracy, with thermal errors being the most common. Indirect compensation (using prediction models for thermal errors) is a promising strategy to reduce thermal errors without increasing machine tool costs. The modelling approach uses transfer functions to deal with this issue; it is an established dynamic method with a physical basis, and its modelling and calculation speed are suitable for real-time applications. This research presents compensation for the main internal and external heat sources affecting the 5-axis machine tool structure including spindle rotation, three linear axes movements, rotary C axis and time-varying environmental temperature influence, save for the cutting process. A mathematical model using transfer functions is implemented directly into the control system of a milling centre to compensate for thermal errors in real time using Python programming language. The inputs of the compensation algorithm are indigenous temperature sensors used primarily for diagnostic purposes in the machine. Therefore, no additional temperature sensors are necessary. This achieved a significant reduction in thermal errors in three machine directions X, Y and Z during verification testing lasting over 60 h. Moreover, a thermal test piece was machined to verify the industrial applicability of the introduced approach. The results of the transfer function model compared with the machine tool's multiple linear regression compensation model are discussed.     

提高水质检测准确性与稳定性的方法分析

水质检测质量是水资源管理的重要组成部分,很容易受到人为、系统、随机等多方面因素影响。分析了影响水质检测准确性与稳定性的因素及应对方法,并展开探讨,希望能够为相关业内人士带来一定启发。     

地质痕量金石墨炉原子吸收法检测研究

着重研究了地质痕量金石墨炉检测痕量金的实验过程中吸液量的确定。文中以部分数据的对比分析了吸样量对其灵敏度的影响。对比结果表明:使用适量的吸样量进行实验,可在一定程度上提高样品检验的精确度,灵敏度。     

Virtual prediction and constraint of contour errors induced by cutting force disturbances on multi-axis CNC machine tools

This paper presents a strategy to virtually predict and constrain the contouring errors contributed by cutting force disturbances on feed drives. The tracking errors on each feed drive are predicted as a linear function of tangential feed by evaluating the product of estimated power spectrum of cutting forces and disturbance frequency response function along the tool path in virtual CAM environment. The corresponding tool tip contouring and tool axis orientation errors are estimated and constrained by scaling the feed along the tool path. The algorithm is experimentally illustrated to improve the machining accuracy on a 5 Axis CNC machine tool.     

基于误差预测的机床精度分析与设计

数字化精度分析是当前确保机床设计精度的重要手段。精度建模与精度分析等重要手段主要针对机床几何精度、运动精度及工件表面成形运动精度。对于复杂成形运动机床,目前精度设计标准与工件加工精度之间尚无准确对应关系。为此,提出了基于误差预测的机床精度设计方案,该方案分为两阶段数字化精度分析。第一阶段通过技术系统实现工件到工艺系统各部件精度分配与检测,在规定的精度下达到机床输出精度。第二阶段通过机床系统完成机床输出到机床各组成部件精度分配与检查。文中以YK3610滚齿机为例,详细分析了两系统误差模型及应用方法,并通过试验验证机床的实际切割精度可达5-4-4等级,因此该方法为复杂成形运动机床精度的设计提供了依据。     

阿尔伯托·坎波·巴埃萨的三座建筑

文章通过对建筑师阿尔伯托·坎波·巴埃萨的三个作品的描述,讨论了他的建筑作品中光与空间的精确剖面关系,以及散普尔所说的“切割”和“搭建”这两个概念如何在实践性操作中运用。     

Improving the thickness accuracy of cold rolled narrow strip by piezoelectric roll gap control at high rolling speed

Particularly in fast rolling mills, conventional actuators reach their dynamic limits, when longitudinal thickness variations of the incoming strip shall be reduced with high accuracy by model-predictive roll gap control. Accordingly, the applicability of highly dynamic piezoelectric actuators in combination with electromechanical spindles and a high frequency precision measurement of the thickness in front of the roll gap was examined. Rolling tests in a cold rolling mill for narrow slit strips show that this novel concept is suitable to provide the required dynamic actuation especially at high rolling speed.