A linear optimization approach to the combined production planning model

Two fundamental processes usually arise in the production planning of many industries. The first one consists of deciding how many final products of each type have to be produced in each period of a planning horizon, the well-known lot sizing problem. The other process consists of cutting raw materials in stock in order to produce smaller parts used in the assembly of final products, the well-studied cutting stock problem. In this paper the decision variables of these two problems are dependent of each other in order to obtain a global optimum solution. Setups that are typically present in lot sizing problems are relaxed together with integer frequencies of cutting patterns in the cutting problem. Therefore, a large scale linear optimizations problem arises, which is exactly solved by a column generated technique. It is worth noting that this new combined problem still takes the trade-off between storage costs (for final products and the parts) and trim losses (in the cutting process). We present some sets of computational tests, analyzed over three different scenarios. These results show that, by combining the problems and using an exact method, it is possible to obtain significant gains when compared to the usual industrial practice, which solve them in sequence. (C) 2010 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.

Rough turning of titanium alloy (6Al-4V)

Metal machining is the complex process due the used cutting parameters. In metal cutting process, materials of workpiece differ widely in their ability to deform plastically, to fracture and to sustain tensile stresses. Moreover, the material involved in the process has a great influence in these operations. The Ti-6Al-4V alloy is very used in the aeronautical industry, mainly in the manufacture of engines, has very important properties such the mechanical and corrosion resistance in high te mperatures. The turning of the Ti-Al-4V alloy is very difficult due the rapid tool wear. Such behavior result of the its low thermal conductivity in addition the high reactivity with the cutting tool. The formed chip is segmented and regions of the large deformation named shear bands plows formed. The machinability of the cutting process can be evaluated by several measures including power consume, machined surface quality, tool wear, tool life, microstructure and morphology of the obtained chip. This paper studies the effect of cutting parameters, speed and feed rates, in the tool wear and chip properties using uncoating cemented carbide tool. Microe-structural characterization of the chip and tool wear was performed using scanning electron microscopy (SEM) and Light Optical Mcroscopy (LOM).

Proposta de uma máquina para processo de abrasão baseado na combinação de algumas características da lapidação e retificação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de produtividade de padrões de corte na indústria de móveis

Pós-graduação em Matemática - IBILCE

Estudo dos mecanismos governantes do efeito de escala na microusinagem

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Utilização de lâminas serrilhadas no corte basal da cana-de- açúcar

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Reciclando o destino: a trajetória do cortador de cana que se tornou catador de recicláveis e autogestor de seu ofício

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos do teor de umidade da madeira no fresamento de Pinus Elliottii

Pós-graduação em Engenharia Mecânica - FEG

Euterpe edulis Seedlings in the Understory of Two Forest Fragments

The palm Euterpe edulis is one of the most exploited due the intense illegal extraction, which is very harmful because this species dies right after the cutting process. This study aimed to assess the palms' development as an enrichment plant in a forest fragment belonging to a Preservation Area and the Biosphere Reserve of the Green Belt of Sao Paulo State, in Embu das Artes city. The seeds were obtained from the Instituto Florestal, which follows all the regulations for seeds, in order to get seedlings with a high genetic variation. The seedlings were planted in two successional stages: secondary forest with low trees (SFLT) and secondary forest with medium trees (SFMT). The seedlings survival and growth were periodically assessed and the results were compared by the variance analysis. Both areas presented high rates of survival, which were superior comparing to other similar studies with Euterpe edulis. Despite the successional difference between the areas, the development of the seedlings did not show significant difference on the analysis of variance regarding leaf number, height growth, stem diameter and survival, except for plant height at 60 days after planting, when seedlings planted in SFLT reached higher height (21.38 cm) than when planted in SFMT (19.31 cm).

Método de Taguchi aplicado a um processo de corte por fusão de um tecido sintético

A company must have full knowledge and control of its operations so as to meet the market requirements and meet their production goals. Thus this paper uses the Taguchi method to extend the operational control of a cutting process by fusion of a synthetic fabric in the longitudinal direction. For process analysis and tracking of possible causes of the problem techniques of Production Engineering as the cause and effect diagram, also known as Ishikawa diagram, and design of experiments were used, the last one was applied to the design techniques of Taguchi. Finally the preparation method of understanding and design of experiment was due to the use of the software MINITAB v15 ®, which showed that the speed of rolling the fabric after cutting is crucial for controlling the entire operation

O problema de porte de estoque numa indústria moveleira

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A STUDY ON THE FEASIBILITY OF UNIVERSAL CHIP CONTROL IN MACHINING

A novel solution to the long standing issue of chip entanglement and breakage in metal cutting is presented in this dissertation. Through this work, an attempt is made to achieve universal chip control in machining by using chip guidance and subsequent breakage by backward bending (tensile loading of the chip's rough top surface) to effectively control long continuous chips into small segments. One big limitation of using chip breaker geometries in disposable carbide inserts is that the application range is limited to a narrow band depending on cutting conditions. Even within a recommended operating range, chip breakers do not function effectively as designed due to the inherent variations of the cutting process. Moreover, for a particular process, matching the chip breaker geometry with the right cutting conditions to achieve effective chip control is a very iterative process. The existence of a large variety of proprietary chip breaker designs further exacerbates the problem of easily implementing a robust and comprehensive chip control technique. To address the need for a robust and universal chip control technique, a new method is proposed in this work. By using a single tool top form geometry coupled with a tooling system for inducing chip breaking by backward bending, the proposed method achieves comprehensive chip control over a wide range of cutting conditions. A geometry based model is developed to predict a variable edge inclination angle that guides the chip flow to a predetermined target location. Chip kinematics for the new tool geometry is examined via photographic evidence from experimental cutting trials. Both qualitative and quantitative methods are used to characterize the chip kinematics. Results from the chip characterization studies indicate that the chip flow and final form show a remarkable consistency across multiple levels of workpiece and tool configurations as well as cutting conditions. A new tooling system is then designed to comprehensively break the chip by backward bending. Test results with the new tooling system prove that by utilizing the chip guidance and backward bending mechanism, long continuous chips can be more consistently broken into smaller segments that are generally deemed acceptable or good chips. It is found that the proposed tool can be applied effectively over a wider range of cutting conditions than present chip breakers thus taking possibly the first step towards achieving universal chip control in machining.

Estudio experimental del desgaste del flanco y de la rugosidad superficial en el torneado en seco de alta velocidad del acero AISI 316L

La mejora continua de los procesos de fabricación es fundamental para alcanzar niveles óptimos de productividad, calidad y coste en la producción de componentes y productos. Para ello es necesario disponer de modelos que relacionen de forma precisa las variables que intervienen en el proceso de corte. Esta investigación tiene como objetivo determinar la influencia de la velocidad de corte y el avance en el desgaste del flanco de los insertos de carburos recubiertos GC1115 y GC2015 y en la rugosidad superficial de la pieza mecanizada de la pieza en el torneado de alta velocidad en seco del acero AISI 316L. Se utilizaron entre otros los métodos de observación científica, experimental, medición, inteligencia artificial y estadísticos. El inserto GC1115 consigue el mejor resultado de acuerdo al gráfico de medias y de las ecuaciones de regresión múltiple de desgaste del flanco para v= 350 m/min, mientras que para las restantes velocidades el inserto GC2015 consigue el mejor desempeño. El mejor comportamiento en cuanto a la rugosidad superficial de la pieza mecanizada se obtuvo con el inserto GC1115 en las velocidades de 350 m/min y 400 m/min, en la velocidad de 450 m/min el mejor resultado correspondió al inserto GC2015. Se analizaron dos criterios nuevos, el coeficiente de vida útil de la herramienta de corte en relación al volumen de metal cortado y el coeficiente de rugosidad superficial de la pieza mecanizada en relación al volumen de metal cortado. Fueron determinados los modelos de regresión múltiple que permitieron calcular el tiempo de mecanizado de los insertos sin que alcanzaran el límite del criterio de desgaste del flanco. Los modelos desarrollados fueron evaluados por sus capacidades de predicción con los valores medidos experimentalmente. ABSTRACT The continuous improvement of manufacturing processes is critical to achieving optimal levels of productivity, quality and cost in the production of components and products. This is necessary to have models that accurately relate the variables involved in the cutting process. This research aims to determine the influence of the cutting speed and feed on the flank wear of carbide inserts coated by GC1115 and GC2015 and the surface roughness of the workpiece for turning dry high speed steel AISI 316L. Among various scientific methods this study were used of observation, experiment, measurement, statistical and artificial intelligence. The GC1115 insert gets the best result according to the graph of means and multiple regression equations of flank wear for v = 350 m / min, while for the other speeds the GC2015 insert gets the best performance. Two approaches are discussed, the life ratio of the cutting tool relative to the cut volume and surface roughness coefficient in relation to the cut volume. Multiple regression models were determined to calculate the machining time of the inserts without reaching the limit of the criterion flank wear. The developed models were evaluated for their predictive capabilities with the experimentally measured values.

FEM Analysis to Optimally Design End Mill cutters for Milling of Ti-6Al-4V

This paper presents an FEM analysis conducted for optimally designing end mill cutters through verifying the cutting tool forces and stresses for milling Titanium alloy Ti-6Al-4 V. Initially, the theoretical tool forces are calculated by considering the cutting edge on a cutting tool as the curve of an intersection over a spherical/flat surface based on the model developed by Lee & Altinas [1]. Considering the lowest tool forces the cutting tool parameters are taken and optimal design of end mill is decided for different sizes. Then the 3D CAD models of the end mills are developed and used for Finite Element Method to verify the cutting forces for milling Ti-6Al-4 V. The cutting tool forces, stress, strain concentration (s), tool wear, and temperature of the cutting tool with the different geometric shapes are simulated considering Ti-6Al-4 V as work piece material. Finally, the simulated and theoretical values are compared and the optimal design of cutting tool for different sizes are validated. The present approach considers to improve the quality of machining surface and tool life with effects of the various parameters concerning the oblique cutting process namely axial, radial and tangential forces. Various simulated test cases are presented to highlight the approach on optimally designing end mill cutters.