Experimental investigation of a process cooling system retrofitted with HFC-404A refrigerant for precise manufacturing application

Precise-manufacturing facilities, which emphasize accurate and stable machining of the working components to be used in semiconductor industry, cannot function properly without appropriate and precise cooling. HCFC (hydro-chloro-floro-carbon) has been commonly used as the coolant for precise manufacturing facilities; but it is facing the pressing schedule to be phased out. Additionally, the dramatic variation of heat load during high-accuracy and high-speed applications need a critical control of coolant (brine or water) temperature. Use of eco-friendly HFC 404A to replace HFC has been suggested as an effective alternative to alleviate the problems. In this study, the performance of a process cooling system retrofitted with HFC-404A refrigerant was evaluated; the energy efficiency ratio and accuracy of temperature control specific to −15°C precise manufacturing application were examined. Effects of using thermostatic expansion valve associated with hot-gas by-pass control scheme under different loading conditions have been investigated extensively. The energy efficiency ratio and accuracy of temperature control for the cooling system were measured and analyzed for comparing and evaluating HCFC-22 and HFC-404A using different throttling devices under specific coolant temperatures. The comprehensive studies on improving the accuracy of temperature control and energy-saving efficiencies through different temperature control strategies are presented in this paper.     

绝热毛细管长度的设计计算

分析了毛细管内制冷剂的流动过程,运用两相流动的均相流模型建立了绝热毛细管的数学模型,开发了毛细管长度的计算程序,该程序对新工质制冷系统毛细管的设计具有一定的参考价值。     

机床的进给驱动(下)

提出了设计高端机床进给驱动的若干原则.分析了滑动和滚动导轨的结构形式及其优缺点.讨论了不同直线进给和圆周进给的结构形式及其发展趋势.最后对保证进给运动精度的测量传感系统作了全面的介绍.     

机床床身导轨的磨损及其对机床精度的影响

介绍机床床身导轨的精度对机床精度有决定性影响，它直接影响被加工零件的尺寸、形状和位置误差值；导轨的磨损是造成机床床身导轨精度下降的根本原因，并以不同的形式对被加工零件的误差产生影响；导轨的磨损包括磨粒磨损、粘着磨损和腐蚀磨损等，在不可避免的情况下，介绍所采取的一些措施。     

并联机床控制事务的矩阵描述

为了简化并联机床各种控制事务间的逻辑关系,分析了并联机床控制事务的各种时序关系,提出采用状态矩阵来描述机床的当前控制状态,采用控制矩阵来描述机床的控制逻辑,并通过比较控制矩阵和状态矩阵,实现并联机床各事务的控制。     

普通机床的数控改造

普通机床加工出来的产品大多存在着质量差、品种少、档次低、成本高、供货期长等问题,在国内国外市场上缺乏竞争力。介绍了普通机床数控化改造的意义和必要性,重点阐述了普通机床的机械结构和数控操作系统的改造,可为相关技术改造提供参考。     

数控机床参考点的设定

本文以数控车床为例介绍参考点设置的方法，供用户及同行参考。     

降低机床噪声的几种途径

对机床噪声进行分析,探讨通常情况下降低机床噪声的几种有效途径,具有良好的可行性。     

滚丝机床的一种定心装置设计

介绍滚丝机床的一种定心装置设计,并给出该装置的结构及设计参数。     

浅谈数控机床的验收

数控机床的验收是一项非常复杂的工作，介绍数控机床验收的必要性，对验收过程和应注意的问题进行详细阐述。     

A machine vision system for tool wear assessment

Automated tool condition monitoring is gaining considerable importance in the manufacturing industry. This can be attributed to the transformation of manufacturing systems from manually operated production machines to highly automated machining centres. Modern image processing techniques and machine vision systems can now enable direct tool wear measurement to be accomplished in-cycle. Such a system, characterized by its measurement flexibility, high spatial resolution and good accuracy, is presented here. The system consists of a fibre-optic light source to illuminate the tool and a CCD camera (used in conjunction with a high resolution video zoom microscope) to capture the reflected pattern. The extent of the flank wear land has been determined using both textural and gradient operators; a texture operator has been implemented in the final system.     

数控机床超程故障维修

介绍了数控机床两种超行程保护的工作机理。当机床的某一轴同时触发两个方向的超程警报时,可借助系统诊断功能查询机床PLC的当前状态,结合对机床电气回路的测量,查找并分析故障原因;通过调整行程开关位置并修改相关系统参数,最终排除数控机床的超程故障。     

一种磨削薄壁陶瓷管专用工装

根据薄壁陶瓷管的特殊性,研制和生产了一种专用工装,在M1332外圆磨床上实现该陶瓷管的磨削,介绍了该专用工装的结构及特点。     

CKA6163变频数控车床床头箱的改进

详细分析CKA6163变频数控车床主轴箱刹车时间长、机械液压刹车与电机能耗制动不同步及换档时间长的原因,提出对刹车、换档结构的改进方案、措施,解决在实际生产过程中通过零件加工、部装、总装、调试以及用户使用过程中存在的问题,降低了生产成本,提高了加工效率。     

数控技术全面支持高速复合机床精度的提升

文章概括了保证数控机床精度的三个层面的问题：支撑刚度,导向精度和定位精度与刚度。从上述三个方面,重点介绍了数控技术链的各技术环节对实现大连科德数控有限公司KDL1550FH立式车铣复合加工中心和KDW4200FH卧式铣车复合加工中心高速高精度控制的作用。     

一种新型机床冷却系统的研究

介绍了一种基于脉冲管制冷技术的机床冷却系统。该系统以脉冲管制冷机为冷源 ,将制冷的脉冲管置于切削刀具内 ,通过脉冲管的冷端将切削区的热量带走 ,达到降低刀具的切削温度、提高刀具耐用度的目的     

数控机床的回零及应用

回零是数控机床的重要功能.阐述了NUM系统用于车铣加工中心各个轴的回零方式,介绍了回零在C轴与主轴切换后重新定位中的应用.     

The laser ball bar: a new instrument for machine tool metrology

Current techniques for mapping the volumetric positioning errors of machine tools are time and labor intensive. To address these shortcomings, a linear displacement measuring device is introduced to rapidly and easily determine tool positions via trilateration. The laser ball bar (LBB) consists of a laser interferometer aligned within a telescoping ball bar. The design of the device is discussed and an error budget is developed to estimate its predicted accuracy. Results of repeatability and linear accuracy test of the assembled prototype LBB are given. The LBB is used to map the volumetric errors of a two-axis turning center. Comparison of the LBB error map and the error map obtained through parametric error measurements shows the LBB can accurately map the machine errors in a timely manner.     

Rapid dynamics prediction of tool point for bi-rotary head five-axis machine tool

Receptance Coupling Substructure Analysis (RCSA), an effective approach to rapidly predict the tool point frequency response function (FRF), generally requires the response of spindle-machine assembly by experiments. This method is feasible for three-axis machine tool because the spindle and its posture are normally unchangeable. But in terms of five-axis milling, the spindle-machine assembly changes continuously. The purpose of this study is to propose new techniques to solve the constantly-changing assembly response in order that RCSA can be used for bi-rotary head five-axis machine tools. Based on receptance matrix determination in coupling direction and single degree of freedom coupling simplification, the swivel model for holder tip receptances is established for swivel motion. According to the concept of oriented frequency response function, the rotational model is derived to calculate the holder tip receptances with rotary motion. By combining the swivel model and the rotational model, the holder tip receptance of arbitrary posture can be calculated by three orthogonal postures. A five-axis machine tool with bi-rotary head is used to conduct FRF tests on different postures. Experimental results show that the models proposed can accurately predict tool point frequency response of any posture and large difference in FRFs among those postures of bi-rotary head is detected.     

一种新型串并联机床的工作空间分析

介绍了一种新型串并联机床的结构.同纯并联机床相比,该型机床具有更大的工作空间和更好的刚度性能.文中构建了其运动学逆解模型,分析其工作空间的约束条件,给出了工作空间的求解流程图.实例表明,该型机床的工作空间较大,具有很好的应用前景.