Vibration based preload estimation in machine tool spindles

Prevention of catastrophic bearing failures caused by excessive thermally induced preload is one of the key issues in the design and operation of high speed spindles. Temperature monitoring and shutting the spindle off in hazardous conditions is at present the most common method of avoiding bearing seizure. However, due to a rapid heat built-up and measurement delay, this solution in not reliable. An improved protection can be achieved either by custom systems with springs or hydraulic actuators that maintain a steady preload, or by monitoring the instantaneous preload and appropriate, predictive adjustment of machining conditions. While the former approach increases the cost of spindles and degrades their potential reliability, monitoring and proactive control of the actual preload eliminates these disadvantages. Its feasibility is predicated upon fast, reliable and accurate in-process preload estimation. A suitable estimation algorithm proposed in this paper employs vibrations of the spindle housing measured by means of accelerometer(s) and analyzed in the context of mechanical multi-degree-of-freedom model of the spindle assembly treated as a component of the entire machine tool. Representative experimental results are presented.     

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。     

年产100万t棒材生产线低成本改造模式探讨

目前国内年产量超过100万t的棒材(钢筋)生产线基本上都是采用多线切分工艺实现的,由于钢筋新国标的实施,给采用切分工艺的棒材厂生产成本带来了很大压力。为此,基于如何降低高强钢筋中的合金含量及提高产品尺寸精度两方面提出了双线高速棒材的生产方案以适应现有棒材生产线的改造。项目实施过程中不改变现有生产线主体设备布局,仅在现有的精轧机和冷床之间增加控冷设备、高速精轧机组、高速分段飞剪及冷床上料设备,停工时间短。新增设备可全部国产,投资少,见效快。     

高速精加工集成自适应控制的设计与实现

高速精加工由于速度的大幅度提高，使得数控伺服系统对于随机干扰的敏感性增大。高速切削数控系统的稳定性和精度受到很大影响，产生了很多问题需要解决，本文根据这些问题，设计了以高精度、高效率和稳定性为目标的两轴高速精加工集成自适应控制系统，取得了良好的实际效果。     

串级萃取最低成本优化萃取比方程

以寻求串级萃取最低生产成本的工艺条件为最优化目标,通过将萃取工艺参数与随之会发生变化的生产成本关联,建立了分馏萃取最低成本优化萃取比方程,为简化计算,推导出萃取段,洗涤段最低成本萃取比方程,如果不考虑酸碱消耗的成本变化,推导出的简略方程其优化目标与现有最优萃取比方程相一致,计算值相近,建立的最低成本优化萃取比方程及其优化目标发展了现有最优萃 取比理论。     

A Taguchi and experimental investigation into the optimal processing conditions for the abrasive jet polishing of SKD61 mold steel

This study introduces an abrasive jet polishing (AJP) technique in which the pneumatic air stream carries not only abrasive particles, but also an additive of either pure water or pure water with a specified quantity of machining oil. Taguchi design experiments are performed to identify the optimal AJP parameters when applied to the polishing of electrical discharge machined SKD61 mold steel specimens. A series of experimental trials are then conducted using the optimal AJP parameters to investigate the respective effects of the additive type and the abrasive particle material and diameter in achieving a mirror-like finish of the polished surface. The Taguchi trials indicate that when polishing is performed using pure water as an additive, the optimal processing parameters are as follows: an abrasive material to additive ratio of 1:2, an impact angle of 30°, a gas pressure of 4 kg/cm², a nozzle-to-workpiece height of 10 mm, a platform rotational velocity of 200 rpm, and a platform travel speed of 150 mm/s. Applying these processing parameters, it is found that the optimal polishing effect is attained using #8000SiC abrasive particles and a 1:1 mixture of water-solvent machining oil and pure water. The experimental results show that under these conditions, the average roughness of the electrical discharge machined SKD61 surface is reduced from an original value of R_a=1.03 μm (R_max: 7.74 μm) to a final value of R_a=0.13 μm (R_max: 0.90 μm), corresponding to a surface roughness improvement of approximately 87%.     

镍基高温合金表面完整性研究现状分析

表面完整性是评价零件表面加工质量的重要标准之一。在切削镍基高温合金GH4169的过程中,加工硬化、变质层的形成等是重要的加工难题,因此研究GH4169零件的表面完整性对其高速切削加工过程有重要的意义。从表面粗糙度、表面加工硬化、白层以及表面残余应力等方面对切削镍基高温合金的表面完整性研究进展进行总结,从切削用量、工艺参数和刀具的选用等方面为提升加工零件表面质量提供了重要依据。     

人工神经网络在模具型腔加工走刀方式选择中的应用

建立基于人工神经网络的模具型腔粗加工走刀方式的选择模型,设计了学习样本.采用3层反向传播BP网络模拟模具型腔几何参数与数控加工走刀方式的非线性关系,应用训练好的BP网络为模具型腔选择合理的走刀方式.切削加工表明,应用人工神经网络选择走刀方式可以提高模具型腔的加工效率.     

Oxidation post-treatment of hard AlTiN coating for machining of hardened steels

In this study, cemented carbide ball nose end mills with nano-crystalline Al_0.67Ti_0.33N hard PVD coatings deposited by cathodic arc evaporation were annealed at 700 °C during 2 h in a controlled atmosphere environment (argon + oxygen mixture) and in vacuum. The changes of structure and properties of the treated coating surfaces have been analyzed using both cross-sectional scanning electron microscopy (SEM) and x-ray absorption spectroscopy (XAS) of the N-K and O-K edges. Cutting tools have been run through ball nose end milling of hardened H13 steel (HRC 50) where temperature or stress dominating phenomena control tool life. The data obtained indicate that an AlTiN coated cutting tool can be modified upon annealing at low temperature conditions and should be considered as a composite surface engineered material. It is shown that increased tool life could be achieved if annealing of AlTiN is performed in an oxygen-containing atmosphere. A variety of different characteristics should be optimized to achieve better wear resistance of the cutting tools with annealed Al_0.67Ti_0.33N coating under high temperature and stress cutting conditions.     

高速铣削与电火花加工在轮胎模具制造中的应用

针对子午线轮胎模具的花纹特点,分析了高速铣削和电火花加工工艺的特点及其在轮胎模具制造中的优势和局限性,指出了选择轮胎模具加工工艺的基本原则,并针对不同类型的轮胎模具给出了具体的加工工艺选择方案,可为轮胎模制造企业在制定轮胎模具加工工艺时提供参考。     

直线电机在机床工业中的最新应用及技术分析

直线电机在机床进给驱动上的应用日益广泛,比起传统的进给驱动方式,它能提供非常高的速度、加速度和位置精度,大大提高了生产率和加工件表面质量。文章介绍了直线电机在机床上的最新应用情况,并就应用中的关键技术问题进行了分析。     

Optimized tool path generation based on dynamic programming for five-axis flank milling of rule surface

This paper presents a computation scheme that generates optimized tool path for five-axis flank milling of ruled surface. Tool path planning is transformed into a matching problem between two point sets in 3D space, sampled from the boundary curves of the machined surface. Each connection in the matching corresponds to a possible tool position. Dynamic programming techniques are applied to obtain the optimal combination of tool positions with the objective function as machining error. The error estimation considers both the deviation induced by the cutter at discrete positions and the one between them. The path planning problem is thus solved in a systematic manner by formulizing it as a mathematical programming task. In addition, the scheme incorporates several optimization parameters that allow generating new patterns of tool motion. Implementation results obtained from simulation and experiment indicate that our method produces better machining quality. This work provides a concise but effective approach for machining error control in five-axis flank milling.     

A mixed-integer linear programming model for part mix, tool allocation, and process plan selection in CNC machining centres

A mixed-integer linear programming model is developed for the simultaneous determination of part mix, tool allocation and process plan selection in CNC machining centres. Illustration of the use of the model in a hypothetical example and its application to a real problem arising in deep seabed operations demonstrate the utility of the model as one more step towards the integration of computer-aided process planning (CAPP) tasks in CNC machining enviroments.     

Effect of MQL on the tool life of small twist drills in deep-hole drilling

Drilling of deep and small boreholes using twist drills has to be considered as one of the most difficult metal cutting operations. There are many reasons for this, one of them being that the cutting fluid has to be supplied externally. This research work investigates in how far the manner of supplying and the type of minimum quantity lubricant have an effect on the tool life of coated and uncoated high-speed steel twist drills of 1.5 mm diameter. Deep-hole drilling is performed as the holes, drilled into plain carbon steel, had a depth of 10 times the diameter. The feasibility of dry machining as an appropriate alternative to MQL in deep-hole drilling has also been investigated. This work shows that, compared to a continuous supply of the minimum quantity lubricant, a discontinuous supply brings about a significant reduction in tool life, especially in the case of heat-sensitive drills. With respect to the type of minimum quantity lubricant, a low-viscous type with a high cooling-capability gave rise to a notably prolonged tool life. It is also shown that dry drilling is associated with strongly accelerated tool wear for most of the twist drills tested, resulting in a significant reduction in tool life.     

Critical cutting speed for onset of serrated chip flow in high speed machining

The transition of continuously smooth chip flow to periodically serrated chip flow as the cutting speed increasing is one of the most fundamental and challenging problems in high speed machining. Here, an explicit expression of the critical cutting speed for the onset of serrated chip flow, which is given in terms of material properties, uncut chip thickness and tool rake angle, is achieved based on dimensional analysis and numerical simulations. It could give reasonable predictions of the critical cutting speeds at which chips change from continuous to serrated for various metallic materials over wide ranges of uncut chip thickness and tool rake angle. More interestingly, it is found that, as the turbulent flow is controlled by the Reynolds number, the transition of the serrated chip flow mode is dominated by a Reynolds thermal number. Furthermore, the influences of material properties on the emergence of serrated chip flow are systematically investigated, the trends of which show good agreement with Recht’s classical model.     

应用有限元方法对高速电主轴的优化设计

介绍了高速电主轴的结构特点，应用有限元分析软件ANSYS以刚度为目标对高速电主轴进行了优化设计，并对优化后的结构进行了热态校核。     

Fineblanking of high strength steels: Control of material properties for tool life

In order to assess the possibility of fineblanking high strength steels while preserving acceptable tool lifetimes, materials with a wide range of ultimate tensile strengths (200-1500 MPa) were fineblanked experimentally and simulated with finite element modeling. Good agreement was achieved and a refined relationship between cutting force and material strength was discovered. The strain at which the cutting force is maximized was shown to be several times greater than the uniform tensile strain, suggesting the concept of manipulating material strain hardening properties to increase material strengths markedly while maintaining acceptable tool stress levels and thus lifetimes. The concept was shown viable using finite element simulations. The results show the need for steels optimized for fineblanking applications. They will have almost opposite properties of advanced high strength steels, which are optimized for sheet formability by increasing their strain hardening at large strains.     

高速切削机床的关键技术

分析了高速切削的速度范围,研究了高速切削机床的结构特点、刀具系统和数控系统,指出高速切削可提高切削加工水平。     

Development of a cost model and its application in determining optimal size of a diesel engine remanufacturing facility

Remanufacturing represents a business opportunity and a means to promote environmental sustainability. In planning remanufacturing operations for a specific product in a particular market, determining the facility size is a critical decision. A large centralized facility offers economies of scale advantages, but has greater transportation costs relative to a set of smaller distributed facilities. A remanufacturing facility cost model is developed and applied for diesel engine remanufacturing that includes product, operation, inventory, and transportation-related costs. The effects of product yield, remanufacturing efficiency, transportation cost rate, and product mass on remanufactured product unit cost and remanufacturing facility size are examined.