Thermal distortion of the major elements of a cylindrical grinding machine

Calculations of the thermal deformations of complex structures such as machine tool frames are insufficiently reliable due to the large differences in the heat transfer coefficients. Therefore, the underlying theme presented in this work is a thorough experimental investigation of the thermal deformations of a cylindrical grinding machine in an effort to present simple equations that will provide the engineer with a few simple rules and ideas in order to minimise the problem. The cylindrical grinding machine chosen and the characteristics of the experimental procedure adopted have been related to the present industrial scene. The amount of heat generated is a function of operating conditions of the machine and therefore investigations have been carried out for the complete speed ranges both for the stable and unstable operating conditions. The machine has been thermally segmented and as a result not only has the relative grinding wheel/work axis movement been determined but the influence on this caused by either the grinding wheel movement or the work axis movement has been shown. In addition, the effect of the major machine elements on either the work or wheel axis movement has also been established. [Continues.

Annual Report of the National Advisory Committee for Aeronautics (1st). [Administrative Report Including Technical Reports Nos. 1 to 7]

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, expenditures, problems, recommendations, and a compilation of technical reports produced

Volume 15 - Issue 2 - November, 1905

https://scholar.rose-hulman.edu/technic/1487/thumbnail.jp

Job shop scheduling under dynamic and stochastic manufacturing environment

Ankara : Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent Univ., 1995.Thesis (Master's) -- Bilkent University, 1995.Includes bibliographical references.In practice, manufacturing systems operate under dynamic and stochastic environment where unexpected events (or interruptions) occur continuously in the shop. Most of the scheduling literature deals with the schedule generation problem which is only one aspect of the scheduling decisions. The reactive scheduling and control aspect has scarcely been addressed. This study investigates the effects of the stochastic events on the s\'stem performance and develops alternative reactive scheduling methods. In this thesis, we also study the single-pass and multi-pass scheduling heuristics in dynamic and stochastic job shop scheduling environment. We propose a simulation-based scheduling system for the multi-pass heuristics. Finally, we analyze the interactions among the operational strategies (i.e, lookahead window, scheduling period, method used for scheduling), the system conditions, and the unexpected events such as machine breakdowns and processing time variations.Kutanoğlu, ErhanM.S

The diesel-electric locomotive and the railway employees

Thesis (Ph.D.) Massachusetts Institute of Technology, Dept. of Economics and Engineering, 1953.Bibliography: leaves [176-180].by Robert James Agnew.Ph.D

Aproximações heurísticas para um problema de escalonamento do tipo flexible job-shop

Mestrado em Engenharia e Gestão IndustrialEste trabalho aborda um novo tipo de problema de escalonamento que pode ser encontrado em várias aplicações do mundo-real, principalmente na indústria transformadora. Em relação à configuração do shop floor, o problema pode ser classificado como flexible job-shop, onde os trabalhos podem ter diferentes rotas ao longo dos recursos e as suas operações têm um conjunto de recursos onde podem ser realizadas. Outras características de processamento abordadas são: datas possíveis de início, restrições de precedência (entre operações de um mesmo trabalho ou entre diferentes trabalhos), capacidade dos recursos (incluindo paragens, alterações na capacidade e capacidade infinita) e tempos de setup (que podem ser dependentes ou independentes da sequência). O objetivo é minimizar o número total de trabalhos atrasados. Para resolver o novo problema de escalonamento proposto um modelo de programação linear inteira mista é apresentado e novas abordagens heurísticas são propostas. Duas heurísticas construtivas, cinco heurísticas de melhoramento e duas metaheurísticas são propostas. As heurísticas construtivas são baseadas em regras de ordenação simples, onde as principais diferenças entre elas dizem respeito às regras de ordenação utilizadas e à forma de atribuir os recursos às operações. Os métodos são designados de job-by-job (JBJ), operation-by-operation (OBO) e resource-by-resource (RBR). Dentro das heurísticas de melhoramento, a reassign e a external exchange visam alterar a atribuição dos recursos, a internal exchange e a swap pretendem alterar a sequência de operações e a reinsert-reassign é focada em mudar, simultaneamente, ambas as partes. Algumas das heurísticas propostas são usadas em metaheurísticas, nomeadamente a greedy randomized adaptive search procedure (GRASP) e a iterated local search (ILS). Para avaliar estas abordagens, é proposto um novo conjunto de instâncias adaptadas de problemas de escalonamento gerais do tipo flexible job-shop. De todos os métodos, o que apresenta os melhores resultados é o ILS-OBO obtendo melhores valores médios de gaps em tempos médios inferiores a 3 minutos.This work addresses a new type of scheduling problem which can be found in several real-world applications, mostly in manufacturing. Regarding shop floor configuration, the problem can be classified as flexible job-shop, where jobs can have different routes passing through resources and their operations have a set of eligible resources in which they can be performed. The processing characteristics addressed are release dates, precedence constraints (either between operations of the same job or between different jobs), resources capacity (including downtimes, changes in capacity, and infinite capacity), and setup times, which can be sequence-dependent or sequence-independent. The objective is to minimise the total number of tardy jobs. To tackle the newly proposed flexible job-shop scheduling problem (FJSP), a mixed integer linear programming model (MILP) is presented and new heuristic approaches are put forward. Three constructive heuristics, five improvement heuristics, and two metaheuristics are proposed. The constructive heuristics are based on simple dispatching rules, where the main differences among them concern the used dispatching rules and the way resources are assigned. The methods are named job-by-job (JBJ), operation-by-operation (OBO) and resource-by-resource (RBR). Within improvement heuristics, reassign and external exchange aim to change the resources assignment, internal exchange and swap intend changing the operations sequence, and reinsert-reassign is focused in simultaneously changing both parts. Some of the proposed heuristics are used within metaheuristic frameworks, namely greedy randomized adaptive search procedure (GRASP) and iterative local search (ILS). In order to evaluate these approaches, a new set of benchmark instances adapted from the general FJSP is proposed. Out of all methods, the one which shows the best average results is ILS-OBO obtaining the best average gap values in average times lower than 3 minutes