高精进口磨床砂轮主轴轴承维修技巧

目前我国许多企业由于加工要求,需要从国外进口机床,那么进口机床的维修就是摆在国内机床维修人员面前的一项关键工作,由其是一些高精度机床,本文就进口高精度磨床的维修介绍了一种简单的维修技巧。     

对数控机床维修方法教学的思考

数控机床的维修,全面的掌握数控机床的原理进而处理故障对于一般学生来讲是不现实的我认为可以重点放在几个常见故障的处理。随着机床使用时间的延长,数控机床会出现故障,本文就以经济型数控机床的常见故障为例,谈了一些解决的办法及在教学中的体验。     

数控机床的使用与管理

数控机床是一种高精度、高效率的自动化设备,是一种典型的机电一体化产品。本文力求在数控机床的使用要求、提高数控机床的加工效益、数控机床的管理等方面作必要的说明。     

宏程序的开发与应用

运用宏程序开发数控机床的功能可以提高编程的效率,并能扩展数控机床的使用范围。本文通过典型案例阐述了在数控加工中,用户可以根据实际需求,开发设计、应用宏程序功能。由此证明,运用宏程序开发数控机床的功能是充分发挥数控机床性能的最佳途径。     

Maintenance management: Keeping up with production's changing trends and technologies

Current trends in manufacturing have led to reduced levels of work-in-process inventory and increased levels of automation and machine complexity. These changes have two important implications for maintenance management. First, machine breakdowns not only cause a loss of output from the down machine, but also result in lost production on downstream machines. This occurs because of the elimination of buffer stock between workstations. Second, the gap between the technological expertise of the operators and the technological sophistication of their machines has widened. This gap decreases the ability of operators to make adjustments and minor repairs to their own machines.These two factors cause an increase in maintenance costs associated with machine downtime and maintenance labor. Historically, the proportion of preventive and corrective maintenance has attempted to balance these costs. As buffer stock is reduced and more machines are coupled, the costs of downtime will increase, increasing the need for preventive maintenance and decreasing its cost compared to the cost of lost production.Increases in the use of computer-based planning systems have resulted in the development of computerized preventive maintenance systems that have proven to be successful in planning for maintenance labor and materials. Integrating planning methods with corrective maintenance tasks will help reduce breakdowns, make more efficient use of maintenance craft labor, and provide information for inventory control of maintenance, repair, and operating (MRO) materials.This article examines methods of reducing machine downtime costs, maintenance labor costs, and MRO inventory costs in today's changing production environment. Techniques for reducing these costs are explored in the areas of maintenance planning, maintenance methods improvement, and MRO inventory control.     

浅析数控机床的技术特点及发展趋势

本文以分析数控机床为主要研究对象,首先通过与普通机床的对比,讲述了数控机床的技术特点,以及分析了数控机床的组成部分,尤其对数控机床的新技术进行详细描述;接下来对我国数控机床的发展现状和发展趋势做出介绍。科技的快速发展对数控机床的技术特点要求越来越严密,数控机床自动化、智能化、网络化已经成为一个热点话题。     

浅谈机床外观设计

机床作为机械制造的母机，在国民生产中占有举足轻重的地位在一般人眼中，机床的核心价值是其加工能力，外观设计只是机床行业模仿消费品制造行业的作风，在机床设计工作结采以前对设计方案进行的局部修饰．而忽略了其外观的关学设计，现通过对国内外机床产品外观设计进行分析，阐述了机床外观美学设计的意义，从美的和谐本质展开机床外观羡学设计的论述，提出机床外观美学设计的基本内容     

Optimal maintenance center inventories for fault-tolerant repairable systems

In many military and commercial contexts, complex equipment which is expected to perform very reliably is often designed to be fault-tolerant, that is, able to function although some of the parts have failed. A popular fault-tolerant design is the m-out-of-n system, where there are n identical parts, at least m of which must be functional for machine operation. Complex equipment of this type often undergoes scheduled maintenance overhauls at regular intervals during which all failed components are replaced. Failure to have replacements on hand for failed parts requires emergency measures at premium cost. When repairable parts are highly reliable and expensive, both holding and shortage costs are high. A reasonable objective is to choose initial spares inventory to minimize the sum of holding costs and expected shortage costs.We first develop a model to determine the optimal repairable parts inventory for a maintenance center servicing machines containing a single m-out-of-n system. The model is then extended to handle a related problem, finding optimal maintenance center inventories for machines containing several m-out-of-n systems of different parts, minimizing total expected costs subject to a constraint on total inventory investment.We assume that there is a fleet of machines, which experience identical workloads. There is a cycle time of T days between overhauls for an individual machine. A machine arrives at the maintenance center for overhaul each day. At the overhaul, all failed parts are removed and sent to a repair shop, from which they eventually return to the maintenance center to be used again as spares. The total number of spares undergoing repair and on hand is a constant. There are no backorders; if the number on-hand spares is insufficient to meet demand at an overhaul, a shortage penalty is assessed which depends on the number and type of spares required.While computing holding costs is straightforward, computing expected shortage costs is more complex. Expected shortage costs are dependent upon several factors, including component failure rates, the values of m and n, part repair rates, and the initial number of spares on hand. We assume that the system of interest is well specified, so that the parameters of the model are known except for the number of initial spares of each type, which are the decision variables. We model the on-hand inventory of each type of part as a Markov chain with the number of spares on hand at the end of each day as the states, under the assumptions that failure rates are constant and repair times follow independent exponential distributions. We then calculate the steady-state probabilities of stockout of various numbers of spares, as a function of the initial spares inventory. The expected shortage costs for a given type of spare may then be calculated by finding the product of the penalty cost for lacking p spares and the probability of lacking p spares and summing over all possible p values.Solutions to the problem of finding optimal initial inventory level for a machine containing a single m-out-of-n system may be found easily by enumeration. Solutions to the constrained problem where the machine contains several independent m-out-of-n systems, may be found by dynamic programming. Sensitivity analysis of costs to changes in the inventory investment constraint is clear, and computational effort is reasonable. A simple example is included to illustrate the solution method for both problems.     

浅析数控车削加工工艺

数控机床是一种高效率的自动化设备,它的效率是普通机床的2～3倍,所以要想充分发挥数控机床的高效率特点,必须在编程之前对工件进行工艺分析,根据具体条件,选择经济、合理的工艺方案。我们在本文中结合生产实践,探讨和总结一些数控车削的工艺问题。     

国产数控机床存在的问题与技术分析

本文主要阐述了国产数控机床存在的问题,分析了现代数控机床的高速高精加工技术、复合加工技术、可靠性技术和现代数控机床的智能化、开放式、网络化趋势。     

Option hedging theory under transaction costs

The problem of option hedging in the presence of proportional transaction costs can be formulated as a singular stochastic control problem. Hodges and Neuberger [1989. Optimal replication of contingent claims under transactions costs. Review of Futures Markets 8, 222–239] introduced an approach that is based on maximization of the expected utility of terminal wealth. We develop a new algorithm to solve the corresponding singular stochastic control problem and introduce a new approach to option hedging which is closer in spirit to the pathwise replication of Black and Scholes [1973. The pricing of options and corporate liabilities. Journal of Political Economy 81, 637–654]. This new approach is based on minimization of a Black–Scholes-type measure of pathwise risk, defined in terms of a market delta, subject to an upper bound on the hedging cost. We provide an efficient backward induction algorithm for the problem of cost-constrained risk minimization, whose associated singular stochastic control problem is shown to be equivalent to an optimal stopping problem. This algorithm is then modified to solve the singular stochastic control problem associated with utility maximization, which cannot be reduced to an optimal stopping problem. We propose to choose an optimal parameter (risk-aversion coefficient or Lagrange multiplier) in either approach by minimizing the mean squared hedging error and demonstrate that with this “best” choice of the parameter, both approaches have similar performance. We also discuss the different notions of risk in both approaches and propose a volatility adjustment for the risk-minimization approach, which is analogous to that introduced by Zakamouline [2006. European option pricing and hedging with both fixed and proportional transaction costs. Journal of Economic Dynamics and Control 30, 1–25] for the utility maximization approach, thereby providing a unified treatment of both approaches.     

车刀安装和工作运动对车刀角度的影响

刀具是金属切削机床的基本组成部分,它在机械制造业中占着极为重要的地位。在车削过程中,由于车刀受安装位置和工作运动等各种因素的影响,真正起作用的车刀角度已不再是静止的刃磨角度,而是车刀的工作角度。要使车刀的工作角度处于最佳合理值,就必须了解影响车刀工作角度的因素,据此换算出车刀的静止角度,以便于制造和刃磨车刀,使车出的工件符合图样要求。     

精密数控机床联动夹具设计的研究

精密数控机床夹具是机械产品制造不可缺少的工具,它对加工质量、生产效率和产品成本都有直接影响,文章结合精密机床常用夹具应用所产生的问题,提出联动夹具设计与制造研究思路。     

The development of a destructive sampling method designed for high quality production processes (DSM-HQ)

Customers are requiring producers to conduct destructive testing using traditional sampling techniques as monitoring tools. These techniques are not well suited for situations where the quality is high and tests are destructive since a high number of units need to be tested (and in turn destroyed) in order to guarantee good quality. Furthermore, traditional sampling methods are not specifically designed to monitor a high-quality production process where destructive tests are required and therefore make costly and inefficient monitoring tools. A sampling method is developed to monitor quality in high-quality processes where destructive testing is required. This method is based on a cost function, which balances the costs of sampling versus the costs of finding a defect on the field. It assumes a Poisson process defect pattern and uses an empirical Bayes updating scheme.     

数控机床的维护与故障管理

我国的数控机床发展很快,数控机床的产量越来越大。数控机床的发展一方面要提高其质量和数量,另一方面还要充分认识到数控机床应用和维修的重要性,认识到正确的使用和良好的维护、维修措施,是机床长期可靠运行的重要保障。     

移动式法兰盘端面铣床的设计

本文介绍了移动式法兰盘端面铣床的特点,重点对该机床机架的总体设计方案进行了描述,详细介绍了机架设计方案的设计过程,并对支撑装置的设计进行了描述,可为机床的设计提供理论参考。     

Design and cost optimization for hierarchical data

In this paper, we consider balanced hierarchical data designs for both one‐sample and two‐sample (two‐treatment) location problems. The variances of the relevant estimates and the powers of the tests strongly depend on the data structure through the variance components at each hierarchical level. Also, the costs of a design may depend on the number of units at different hierarchy levels, and these costs may be different for the two treatments. Finally, the number of units at different levels may be restricted by several constraints. Knowledge of the variance components, the costs at each level, and the constraints allow us to find the optimal design. Solving such problems often requires advanced optimization tools and techniques, which we briefly explain in the paper. We develop new analytical tools for sample size calculations and cost optimization and apply our method to a data set on Baltic herring.     

Secretary problems with inspection costs as a game

A secretary problem without recall, with given rewards and inspection costs is considered as a game of an opponent against a statistician. Probability distributions on the set of arrangements of the arrivals and randomized stopping rules are the strategies for the two players. We give a condition under which minimax strategies may be obtained in a systematic way.     

在机床结构有限元法建模中的动态力学的研究与应用

本文对机床结合面特性进行了简单分析,重点对机床结构有限元动态分析的基本理论和有限动力学软件和模型进行了分析研究。     

Organizational design with a budget constraint

In this paper we point out that the presence of the budget constraint substantially affects the relative performance of organizational decision rules. For instance, if there are only two types of projects to decide upon, the hierarchy always performs better than the polyarchy. The same result holds for any distribution of the quality of projects. We also illustrate that optimal mechanisms for variable evaluation costs involve stopping rules which look hierarchical, but avoid costly duplication as in hierarchies or polyarchies. Received: 5 November 1995 / Accepted: 18 September 1997