Optimal number and allocation of controls among serial production stages

A production system comprised of multiple stages in tandem is considered. Each stage may be in either of two states: desirable or undesirable. Each stage may be placed under control so that it remains in the desirable state and produces the maximum fraction of conforming production units. Stages remaining uncontrolled may change randomly from the desired state to the undesired state. The controls may be mechanical or manual but involves costs which may or may not be dependent on the stage being controlled. It is desirable to find the optimal number of controls and their allocation among the stages which will maximise the net profit of production. The problem is formulated as a nonlinear mathematical program with binary variables. For the identical control cost case (independent of the stage to which control is applied), an 0(n) linear runtime algorithm is provided, wheren is the number of stages. It is shown that a k or nothing (wherek is the total number of controls applied) control policy is optimal and depends on a critical cost computed from the given parameters of the problem. In addition, conditions are provided under which all or nothing control policies are optimal. This is based on the computation of a critical cost and is independent of the number of stages in the system. It is shown that when these conditions are met the profit function is pointwise convex ink. Optimal solution techniques are provided and analysed for special cases in terms of the relationships between control cost and production parameters. Sensitivity analysis is provided for each of the parameters of the problem. The solutions are in general robust, with respect to these parameter variations. Numerical examples are provided throughout the paper to illustrate the relevant theorems. The paper ends with a discussion on the general control cost case and some feasible bounds on the optimal solution are offered.     

Magnetic inspection of the hardness of cast-iron milling rolls

The effects of the chemical composition and parameters of the cast-iron smelting and teeming process on the coercive force have been studied. It is shown that only chromium and carbon appreciably affect the coercive force. For rolls with cylindrical surfaces cast from ТПХН-60 iron, a reliable correlation has been established between the hardness and readings of a coercimeter with an attachable electromagnet. For flanges and blooming passes of sizing rolls made from ТШХН-50 cast iron, equations for the relation between the hardness and readings of a coercimeter have been obtained and analyzed. These equations can be used in nondestructive testing of hardness.     

混合型CIMS中生产作业计划系统的研究与实现

通过分析中国包装进出口天津公司纸箱厂混合生产过程的特点,生产作业计划的特点与存在问题,提出了适合该厂生产作业计划管理的解决方案,我们对引进的MRDII软件进行了二次开发,使其适应混合企业生产过程的特点,设计并开发了纸板排料子系统,并与MRPII系统有机集成,从而实现纸箱厂生产作业计划的编制,最后总结出CIMS环境下混合型企业生产作业计划的特点。     

串行连续生产线的缓冲库存控制与可靠性研究

以可靠性理论为基础,建立了单元化的串行连续生产线模型,为保证连续生产的可靠性,研究了缓冲库存最小安全量的计算,同时研究了缓冲库存的补给,提出了非均匀节拍法,可有效保障安全库存量,具有一定的应用价值。对生产线的整体可靠度进行了研究,得到了其可靠性计算公式,从中可知生产的可靠性与设备故障率、修复率、缓冲库存量、生产节拍和时间相关。在最小成本原则基础上,提出了生产单元可靠度、设备故障率与维修率的设计方法,可供参考。     

国内可锻铸铁连杆的研制开发

可锻铸铁连杆技术国外只有日本、美国等国家能生产应用 ,而国内目前仅处于试制开发阶段。以 Chero-kee发动机可锻铸铁连杆的研制开发为例 ,论述了可锻铸铁连杆技术在国内发动机行业的应用前景     

混合生产中作业计划体系研究

对于兼有离散和连续生产特征的混合生产行业,由于其计划体系的复杂性和多样性,尚未形成成熟的具有通用意义的应用方案。分析了混合生产的特征和混合生产计划体系的特点,提出了研究混合生产计划体系的思路,构建了该作业计划体系框架并描述了功能要求及信息联系,研究了前连续后离散这种混合生产模式的作业计划排程问题的离散制造与连续制造分解逻辑,并以毛纺织行业为背景,进行了连续生产环节计划排程优化算法研究,探讨了毛纺织混合生产计划体系对物料清单、工艺路线等基础数据管理的增强要求。     

Measurement and control technology of the size for large hot forgings

Aiming at the different characteristics and measurement requirements of large hot forgings, a size measurement and control method is proposed. For irregular forgings, a measurement model based on line laser scanning is first constructed and then a solution of the optical center motion trail on the basis of the chessboard reference plane is proposed. The motion trail is solved according to the feature point coordinates on the reference plane in different frames. The overall three-dimensional size is finally achieved by combining the measurement model with the optical center motion trail. In addition, for regular forgings, under the guidance of images obtained by CCD, the two-dimensional size can be achieved according to the displacement of the line laser along the rail. Moreover, the size control of the forgings can be realized by rolling reduction control and the working position location. The measuring method proposed is feasible according to the experimental results.     

事件驱动的流水线建模与质检机器配置优化

数字孪生车间环境下获取生产数据更加便捷,使系统运行过程中收集机器故障、质检报废等扰动事件成为可能.为了科学评估并及时应对扰动事件对系统性能的影响,面向考虑质检报废的流水线,研究流水线性能评估与质检机器配置优化问题.考虑流水线中的质量检测操作,定义了质检报废事件,定量分析了机器故障与质检报废等扰动事件对系统产出的影响,建...     

Image-based measurement of the dimensions and of the axis straightness of hot forgings

Non-contact measurement of shapes and dimensions is currently quite a common issue. A lot of systems with different speeds and accuracies are in the market. Measurement of high temperature objects is, however, a very special task which ensures a specific solution. This paper presents a measurement system composed of two high resolution single-lens reflex cameras and a software application, which is designed for the fast measurement of shapes and dimensions of rotationally symmetric forgings. The software computes the length, diameter, and straightness of the axis, based on a 3D model constructed from four boundary curves of the forging captured in two images. Experimental measurements have shown an error of up to 2% for the length measurement and 1% for the diameter measurement. Results are available in a few seconds. The proposed measurement approach based on boundary curves shows a great potential for practical use in forging plants.     

基于模糊控制与遗传算法的串行生产控制系统最优设计

为实现系统的最优设计,在建立基于模糊控制的生产存储控制仿真模型和详细描述控制器设计细节的基础上,建立以极小化在制品量和投放波动水平为目标、以满足顾客满意率要求为约束的多目标规划,并提出一种改进遗传算法与过程仿真相结合的求解方法.在该求解方法中,多目标规划通过加权平均转化为单目标规划.为考察模糊控制系统的性能,在实例分析中通过仿真与定量在制品法、看板及全面拉式几种系统进行了比较.结果表明,模糊控制系统不仪能够保持较低的在制品水平,而且能够保持较低的投放波动水平.     

造船工业发展及船用锻件生产

介绍了国内外造船工业发展现状和国内锻件生产水平     

大型饼类锻件预镦粗工序的数值模拟研究

为了解决镦粗变形缺陷,将饼类锻件的预镦粗工序分为锥台砧镦粗和平砧端面整平两个阶段,利用DEFORM-3D计算平台建立锻造过程的有限元模型并进行仿真分析;分别从锻件内部的应力场和应变场等方面研究了锥台砧锥角和压下率对镦粗过程的影响,平砧旋转锻造方式和下砧砧形对端面整平过程的影响,以获得合理的预镦粗锻造工艺参数,指导实际生产过程.     

Improving the wear resistance of high-strength cast-iron gears by applying a thermodiffusional vanadium coating

The application of a thermodiffusional vanadium coating to high-strength cast iron is considered. The rational vanadium content in the powder batch is determined. The wear resistance of vanadium-coated cast-iron gears is tested.     

Investigation of the structure,composition, and properties of the carboplasic contact surface in tribotests

The processes evolving on carboplastic surfaces during contact interaction with a steel counterbody are discussed. The structure, composition, and tribological properties of the film of secondary structures appearing during friction are investigated. The dependences of the friction coefficient and wear on pressure and sliding velocity are established. The results of comparative tests allow us to identify FUT B83 as the carboplastic with the lowest friction coefficient and UGET as the carboplastic with the greatest wear resistance.     

Relationship between the tribological properties of experimental aluminum alloys and their chemical composition

New complex alloying has been designed for aluminum antifriction alloys. Their tribological behavior has been determined, including the running-in ability, scoring resistance, and wear resistance. The interconnection of the tribological properties of experimental alloys with a doping level by different elements has been analyzed. Recommendations on the optimum content of alloying elements for the antifrictionality of the aluminum based alloys have been given.     

飞机起落架锻件高效粗加工的探索与实践

飞机起落架部件主要为高强度钢且结构复杂,制造效率低。如何能够提高起落架制造效率为行业内的研究热点。其中由于起落架精度高,形位公差要求严格,精加工效率提升空间有限,因此粗加工为效率提升的关键。从工程角度出发,对起落架高效粗加工的装夹定位、刀具方案、切削参数等进行了分析与介绍,并提出了一个可行的方案。     

A Markovian approach to determining optimum process means with inspection sampling plan in serial production systems

This paper develops Markovian-based models for determining the optimum process means with the consideration of an acceptance sampling plan in a serial production system. This paper studies a production system where products are produced continuously with specified lower and upper specification limits for each stage in the production system for quality assurance purposes. Considering the inherent variability in production processes, the quality characteristic(s) of a product might fall below the lower specification limit, resulting in scrap cost, or above the upper specification limit, resulting in rework costs. To study the dynamics of this problem, this paper first develops a Markovian-based model for the optimum process target level for a single quality characteristic assuming a single sampling inspection plan for both a single- and a two-stage production system. Then, the proposed model is extended for dual quality characteristics that are dependent for single- and two-stage production systems. Numerical examples and sensitivity analysis are performed to investigate the effect of different system parameters on the expected profit and optimum process means. The results showed that both single- and two-stage production systems have convex function for the expected profit. In addition, the results showed that the optimum process means are slightly larger than the average of the specification limits. Finally, the correlation between the quality characteristics affects the expected profit significantly.     

Modeling relations between physical properties and chemical composition of steels in quenched state

Linear statistical models with multiple parameters have been developed for predicting the magnitudes of the coercive force, saturation magnetization, electric conductivity, and hardness of highcarbon and alloyed steels of various chemical compositions quenched in the normal regimes.