Multiaxis Machining: PKMs and Traditional Machining Centers

Since the first CNC-type hexapod machine tool prototypes were presented at the 1994 International Machine Tool Show (IMTS) in Chicago, much debate has ensued on whether or not these machine tools will ever reach the place where they challenge traditional machining centers. This paper presents a review of research topics in the field of parallel kinematic machining for manufacturing, as well as a parallel view of the state of the art of traditional multiaxis machining. After discussing similarities as well as differences in issues faced by parallel kinematic machines and traditional machining centers, a survey of existing prototypes is provided.     

氢氧化钽对水体中磷酸盐的吸附去除作用

采用氢氧化钽为吸附剂,对水中磷酸盐的吸附性能进行了研究,考察了吸附时间、pH值、磷酸盐的初始浓度、反应温度对吸附量的影响。实验结果表明:pH值越小,氢氧化钽对磷酸盐的吸附量越大,当pH值为2时氢氧化钽对磷酸盐的吸附性能优,并且pH值对磷酸盐的吸附量影响较大;磷酸盐的初始浓度越大,吸附量越大,吸附平衡时间越短;氢氧化钽对磷酸盐的吸附量和吸附速率都随着温度的升高而增加。在25℃、pH=2、初始浓度为200 mg/L、吸附30 min时达到平衡时最大吸附量为76.69 mg/g。吸附后的氢氧化钽红外谱图在1066 cm-1处出现特征峰,该峰恰好是吸附磷酸盐的伸缩振动峰,并且在638 cm-1与670 cm-1之间Ta-O键由于磷酸盐的吸附发生了蓝移。采用6 mol/L的NaOH对吸附了磷酸盐的氢氧化钽进行解吸,当pH=12时解吸率为52.45%。研究结果表明,氢氧化钽能够有效的去除水溶液中磷酸盐的吸附剂。     

Machining assessment of nano-crystalline hydroxyapatite bio-ceramic

Hydroxyapatite (HAP) is a widely used bio-ceramic in the fields of orthopedics and dentistry. This study investigates the machinability of nano-crystalline HAP (nHAP) bio-ceramic in end milling operations, using uncoated carbide tool under dry cutting conditions. Efforts are focused on the effects of various machining conditions on surface integrity. A first order surface roughness model for the end milling of nHAP was developed using response surface methodology (RSM), relating surface roughness to the cutting parameters: cutting speed, feed, and depth of cut. Model analysis showed that all three cutting parameters have significant effect on surface roughness. However, the current model has limited statistical predictive power and a higher order model is desired. Furthermore, tool wear and chip morphology was studied. Machined surface analysis showed that the surface integrity was good, and material removal was caused by brittle fracture without plastic flow.     

机械加T振动公害控制

根据多年从事机械、环保科研设计及工厂的实践,仔细分析了机械加工振动污染源对操作者及周围居民的危害.并提出了对其所造成的公害进行适应控制的基本措施.     

机械加工振动公害控制

根据多年从事机械、环保科研设计及工厂的实践 ,仔细分析了机械加工振动污染源对操作者及周围居民的危害。并提出了对其所造成的公害进行适应控制的基本措施。     

车装焊复合加工装备的服役可靠性评估

目的评估某型航天用车装焊复合加工装备在服役过程中的服役可靠性。方法首先分析装备常见的故障模式,统计装备在使用过程中的故障数据,由于装备故障数据样本量较少,所以提出基于贝叶斯理论的小样本车装焊复合加工装备可靠性评估方法,其中通过马尔科夫链蒙特卡罗(MCMC)法抽样解决贝叶斯理论中后验积分复杂的问题。结果确定了车装焊复合加工装备的寿命威布尔分布模型,并运用贝叶斯方法,计算出该车装焊复合加工装备的平均无故障工作时间(MTBF)。结论评估结果略低于设计要求,原因是目前该装备处于服役初期,服役初期故障数据较多。待进入稳定服役期时,故障率会有一定程度的降低后趋于稳定,MTBF会有一定幅度的增加,所以该车装焊复合加工装备MTBF基本满足设计要求。     

Comparison of Parallel Structure Concepts for Five-Axis Machining

Parallel structures are characterized by closed kinematics chains. Compared with conventional structures, which have serially arranged axes and are thus characterized by open kinematics chains, parallel structures have a variety of advantages. These primarily include lower moved mass, high dynamics, the high number of possible repeating parts, and the advantageous integration of measures in the control system that are relevant to accuracy. The following presentation classifies parallel structures with six degrees of freedom according to the type of drive used. Based on free-form surface machining in die and mold making, kinematics requirements will be explained and various concepts regarding kinematics, structure. loading, and stiffness will also be discussed. Finally, a preferable solution will be provided in the summary.     

加工回转体零件的柔性制造系统

概述了柔性制造系统的组成、各部分功能以及维护等方面的内容 ,为了解认识FMS提供了背景知识 ,旨在推广FMS的应用范围。     

Machining evaluation of a hybrid MQL-CO2 grinding technology

Although there are already successful industrial experiences in other machining industries with the elimination of coolants, this is not so in the grinding industry due to the large amounts of generated heat that must be evacuated from the contact zone. In this work, a new approach to the elimination of fluids in grinding is presented. The technology is based on the use of a hybrid Minimum Quantity of Lubricant (MQL)-low temperature CO₂ system that reduces lubrication consumption. Abrasive grits are protected by the layer of frozen oil, resulting in a significant improvement in grinding wheel life and surface quality of the machined component. Although the cooling action is reduced with respect to the conventional coolant, no thermal damage was observed on the workpiece.     

端面齿形的切削加工与冷锻成形

对端面齿齿形的各种加工原理作了详细的介绍,分析了切削加工及冷锻成形工艺对端面齿齿形的影响.     

Ruled Surface Machining on Five-Axis CNC Machine Tools

To achieve high precision and high productivity in machining sculptured surfaces, a new architecture for a five-axis CNC interpolator for machining ruled surfaces was developed and demonstrated on a milling machine. The objective of the five-axis interpolator is to continuously maintain the milling cutter axis in parallel with the straight lines of the ruled surface. The cutter position and orientation are calculated at each sampling period of the interpolator, and corresponding axial position commands are generated by an inverse kinematics algorithm. This real-time approach produces precise surfaces and requires substantially less machining time compared to the conventional off-line approach. Two new g-codes are also given in this paper for the new interpolator to produce part surfaces in CNC milling machines.     

Estimation of Maximum Allowable Step Length for Five-Axis Cylindrical Machining

Five-axis cylindrical machining is the only way to machine some complicated sculptured surfaces, such as the wheel surfaces of turbo compressors. Current computer-aided manufacturing (CAM) algorithms for five-axis cylindrical machining only consider the surfaces’ geometric information when generating cutter contact points (CC points). Hence, the step length, which is the distance between two CC points, is determined only by the surface parameters for these CAM algorithms. Because of tool-axis rotation, the actual cut trajectory within each step is no longer a straight line passing through two consecutive CC points for five-axis machining. Thus the cut error and the maximum allowable step length should depend on the structural parameters of NC machines as well as the surface's geometry. This paper develops a new algorithm to estimate the maximum allowable step length based on the cut error of five-axis cylindrical machining, and shows that this algorithm provides better estimation than traditional algorithms.     

浅谈锌合金冲裁模制造工艺

介绍了应用锌合金技术制造冲裁模具的工艺方法和注意事项及在生产实际中所达到的效果     

Cryogenic trapping of reduced sulfur compounds using a nafion drier and cotton wadding as an oxidant scavenger

A commercially available Nafion drier (Perma-Pure) was tested under laboratory and field conditions and shown to be suitable for measurements of reduced sulfur compounds such as H₂S, COS, CH₃SH, CH₃SCH₃ (DMS) and CS₂ in dry and humid air in the pptv-range. For the scavenging of oxidants we combined the Nafion drier technique with a cotton oxidant scrubber. Results obtained under laboratory conditions with humidified samples and in the course of a small field experiment confirm the oxidant scrubber qualities of cotton and indicate that the cotton oxidant scrubber in combination with a Nafion drier is suitable for measurements of nearly all reduced sulfur compounds except CH₃SH.     

20 MW水泥窑纯低温余热发电工程设计介绍

利用生产过程中产生的废气余热发电,是水泥生产企业发展循环经济的一种选择模式.介绍了江苏恒来建材股份有限公司水泥窑配套20 MW纯低温余热发电工程的设计方案、工艺流程和设备选型.该工程正常运行后的效益分析表明纯低温余热发电装置目前在我国水泥企业具有广阔的推广应用前景.     

曝气生物滤池工艺处理废旧物加工小区废水

曝气生物滤池(BAF)是近年来国外发展起来的一项废水好氧生物处理的新工艺.根据该工程废水水质,采用曝气生物滤池工艺处理丰城废旧物收购加工区的废水,经过一段时间的运行,取得了良好的效果,系统出水达到<污水综合排放标准>(GB8978-1 996)一级排放标准,整个废水处理工程具有处理能力强、处理效果好、启动快、受气温影响小、耐冲击负荷、不需二沉池、工艺流程简单和菌群简单等优点,说明该工艺在我国具有广阔的应用前景.     

硅钢片冲孔模具的镶块修补技术

电机硅钢片冲孔模具在制造及使用中常因各种原因使某个槽孔损坏而需要修补.此文介绍了该类模具的修补技术.实践证明:该技术可延长硅钢片冲孔模具的使用寿命.     

Crater Wear Evolution in Multilayer Coated Carbides During Machining Using Confocal Microscopy

Steady-state turning experiments were carried out with multilayer coated inserts consisting of TiN/Al₂O₃/TiCN deposited on a carbide substrate. Confocal microscopy was used for the first time to observe the topography of crater wear evolution in multilayer coated inserts. A hump made of TiN coating next to a growing crater of Al₂O₃, traces of attached steel, and the maximum depth regions have been identified. Scoring marks were also detected in the TiN layer, indicating the presence of abrasion wear. Interestingly, the crater depth was stagnant once it reached the Al₂O₃ layer, and the wear progresses by broadening the area of exposed Al₂O₃. It was concluded that the effectiveness of multilayer coated tools comes from the dissolution resistance of the Al₂O₃ layer, which delays depth growth and develops the wear front into a wider area. Confocal microsocopy was found to be a valuable tool to obtain wear topography for multilayer coated tools.     

混凝气浮-过滤工艺处理机械加工废水的生产性试验研究

采用混凝气浮-过滤为主体工艺，对哈轴集团一厂区的生产废水进行了生产性试验研究。试验结果表明：在进水COD和油类分别为400mg／L和200mg／L的情况下，出水水质分别达到了60mg／L和10mg／L，去除率高达85％和95％。经济分析表明：废水的运行成本为1．4元／t，具有显著的经济效益。