Este trabalho apresenta estudos de usinabilidade de chapas MDF (Medium Density Fiberboard), tendo por objetivo principal efetuar uma análise do desempenho de corte em relação à qualidade da superfície usinada e à força específica de corte paralela necessária, a fim de se verificar a influência dos parâmetros estudados para operações de usinagem de acabamento e desbaste, respectivamente. No estudo para operação de acabamento verificou-se a influência da espessura de corte,velocidade de avanço e sentido de corte, em operação de fresamento cilíndrico periférico, sobre a rugosidade superficial da borda das chapas MDF. Uma fresadora vertical foi utilizada para gerar as superfícies, cuja rugosidade superficial foi medida por um perfilômetro de apalpamento. No estudo para operação de desbaste, a força específica de corte paralela foi avaliada em função da variação do ângulo de saída, da espessura de corte e da profundidade de corte, em operação de corte ortogonal. Para tanto, foram empregadas uma plaina limadora e uma célula de carga de extensômetros resistivos, conectada a um programa de aquisição e análise de dados. A partir da análise dos resultados obtidos, foi possível identificar a influência de cada parâmetro de corte empregado. / This work presents a MDF (Medium Density Fiberboard) machinability study aiming to carry out a cutting performance analysis regarding to surface quality and parallel specific cutting force, in order to verify the cutting parameters effect on the finishing and roughing machining operations, respectively. In the finishing study, it was verified the effect of the cutting thickness, cutting speed and direction of cutterhead rotation with relation to feed direction, in peripheral milling, on the MDF edges surface roughness. The surfaces were developed by a moulder, which roughness were measured by a stylus perfilometer. In the roughing study, the parallel specific cutting force was assessed in relation to the variation of the rake angle, cutting thickness and depth of cut, for the orthogonal cut. For this, it was used a planing machine and a resistance dynamometer, coupled in a data acquisition and analysis system. From the analysis of the obtained results, it was possible to identify the influence of each cutting parameter considered.

Currently, the demand for wood-based panels has been growing solidly in European countries. Medium density fibreboard (MDF) manifests the potentialities for outstanding physical and mechanical properties. However, MDF from different fiber sources is normally designed for internal applications due to the poor moisture resistant capability. This study was conducted on acetylated MDF (Medite® MDF Exterior) to evaluate how physical (i.e. density, moisture content, dimensional stability, thickness swelling) and mechanical (i.e. modulus of elasticity, internal bonding strength before and after accelerated aging, bending stiffness and bending strength) properties behave at different relative humidity (i.e. 35 %, 65 % and 85 % RH at constant temperature of 20 ℃) levels. Bending stiffness was measured non-destructively by means of resonance method. The material used for control samples was commercial MDF. The size, quantity, conditioning and test method were followed in accordance with respective standards. The results showed that physical and mechanical properties were less influenced by Medite® MDF Exterior compared to commercial MDF. Medite® MDF Exterior were superior to commercial MDF in moisture resistance. Medite® MDF Exterior had more stable mechanical properties than commercial MDF with the changes of relative humidity.

Este trabalho apresenta estudos de usinabilidade de chapas MDF (Medium Density Fiberboard), tendo por objetivo principal efetuar uma análise do desempenho de corte em relação à qualidade da superfície usinada e à força específica de corte paralela necessária, a fim de se verificar a influência dos parâmetros estudados para operações de usinagem de acabamento e desbaste, respectivamente. No estudo para operação de acabamento verificou-se a influência da espessura de corte,velocidade de avanço e sentido de corte, em operação de fresamento cilíndrico periférico, sobre a rugosidade superficial da borda das chapas MDF. Uma fresadora vertical foi utilizada para gerar as superfícies, cuja rugosidade superficial foi medida por um perfilômetro de apalpamento. No estudo para operação de desbaste, a força específica de corte paralela foi avaliada em função da variação do ângulo de saída, da espessura de corte e da profundidade de corte, em operação de corte ortogonal. Para tanto, foram empregadas uma plaina limadora e uma célula de carga de extensômetros resistivos, conectada a um programa de aquisição e análise de dados. A partir da análise dos resultados obtidos, foi possível identificar a influência de cada parâmetro de corte empregado. / This work presents a MDF (Medium Density Fiberboard) machinability study aiming to carry out a cutting performance analysis regarding to surface quality and parallel specific cutting force, in order to verify the cutting parameters effect on the finishing and roughing machining operations, respectively. In the finishing study, it was verified the effect of the cutting thickness, cutting speed and direction of cutterhead rotation with relation to feed direction, in peripheral milling, on the MDF edges surface roughness. The surfaces were developed by a moulder, which roughness were measured by a stylus perfilometer. In the roughing study, the parallel specific cutting force was assessed in relation to the variation of the rake angle, cutting thickness and depth of cut, for the orthogonal cut. For this, it was used a planing machine and a resistance dynamometer, coupled in a data acquisition and analysis system. From the analysis of the obtained results, it was possible to identify the influence of each cutting parameter considered.

Dissertação apresentada para obtenção do grau de Doutor, na Faculdade de Engenharia da Universidade do Porto, sob a orientação dos Profs. Carlos Albino Veiga da Costa, Mário Rui N. da Costa e Luisa Maria Hora de Carvalho

Thesis (doctoral)--Universität, Göttingen, 1999.

Underlying all my work is a tension between the painter and the builder. I love to paint. I love the lie inherent in paint: that it can make a picture plane masquerade as light, space, or recognizable place with recognizable figuration. I love how paint—particularly oil paint—can rest in gloppy piles, how it can drip, splatter, spread, or how it can squeeze out of paint tubes in long, stringy beads. I love how paint changes how we see an interior space or a three-dimensional form. Yet I also love building things—usually out of wood—measuring and cutting, fastening things together—all to serve a function or solve a problem. In every studio I have had, there has always been an arms race between my fine art supplies and my tools. My work during my three years at the Department of Art and Art History at the University of Texas at Austin has undergone some dramatic changes. In large part this paper will elaborate and evaluate the trajectory of these changes. Yet, in spite of these changes, the competing impulses to paint and to build have remained constant. This report will leave unanswered the question whether these two impulses can or should be reconciled, kept separate, or whether one should be sacrificed in favor of the other. The artist writing this report does not know at this point in time, and cannot hope to answer this question without making more work in a new context. This report instead will reveal how I arrived at the work I am making at the time of writing this report, and why I regard this new body of work as being about the “paint gap.” I define the “paint gap” as the distinction—mild or strong—between paint itself and the object or surface upon which paint is applied. / text

There are four big medium density fibreboard (MDF) plants in New Zealand with a total production capacity of close to one million cubic meters per year. A significant quantity of boards (nearly 3% or about 30,000 cubic meters per year) is rejected due to defects such as weak core, low modulus of rupture and elasticity, low internal bonding and delamination. The main cause of these defects, is lack of complete understanding of the inter relationship during the hot-pressing stage between the initial inputs such as temperature, moisture content, platen pressure and its impact on the properties of boards. The best solution is to develop a mathematical model to assist in understanding these relationships and to solve the equations in the model by using advanced software. This will reduce the number of expensive experiments and will enable us to see some of the parameters, which are otherwise difficult to visualise. Several earlier researchers have tried to model hot pressing of wood composites, mostly either for particle board or oriented strand board (OSB), and only a few are for MDF. The type of numerical methods used to solve the model equations and various assumptions, changes from one investigator to the other. The non-availability of source code to convert the mathematical equations into programme, is one of the reasons for this model development. To improve the productivity of MDF plants in New Zealand, there was a need to develop a computer programme which can include all the latest findings and can remove the defects which are present in earlier models. This model attempts a more complete integration than in the previous models of all the components such as heat transfer, moisture movement and vertical density profile formation in a one-dimensional model of hot pressing of MDF. One of the important features added in the heat and mass transfer part of the model is that the equilibrium moisture content (EMC) equation given for solid wood was modified to be applicable for the MDF fibres. In addition, this EMC equation can cover the complete range of hot pressing temperature from 160ºC to 200ºC. The changes in fibre moisture content due to bound water diffusion, which was were earlier neglected, was considered. The resin curing reactions for phenol formaldehyde and urea formaldehyde resins are also incorporated into the model, with the energy and water released during the curing reaction being included in the energy and mass balances. The validation of the heat and mass transfer model was done by comparing the values of core temperature and core pressure from the model and the experiments. The experimental value of core pressure and core temperature is obtained by putting a thermocouple and pressure transducer in the middle of the mat. The experimental core temperature results show qualitative agreement with the predicted results. In the beginning, the core temperatures from both experiment and model overlap each other. In the middle of the press cycle, the experimental core temperature is higher by 10ºC and by the end the difference decreases to 5ºC. The vertical density profile (VDP) is a critical determining factor for the strength and quality of MDF panels. The earlier concept of ratio of modulus of elasticity of the layer to the sum of modulus of elasticity of all the layers in the previous time step, given by Suo and Bowyer (1994), is refined with the latest published findings. The equation given by Carvalho et al. (2001) is used to calculate the MOE of different layers of the mat. The differential equation of a Maxwell element given by Zombori (2001) is used to measure stress, nonlinear strain function and relaxation of fibres. The model gives good agreement of peak and core density at lower platen temperature at 160ºC but with the increase of platen temperature to 198ºC, the rise in peak density is comparatively higher. There is a distinct increase in predicted peak density by 150 kg/m³ in comparison to the experimental result, where the increase is only by 10 kg/m³. There is a large decline (50 kg/m³) in core density in the experimental results in comparison to only a slight decline (13 kg/m³) in the predicted results. The use of Matlab provides a very convenient platform for producing graphical results. The time of computation at present is nearly 20 hrs in a personal computer with Pentium four processor and one GB RAM. The model can predict properties of a pressed board for the standard manufacturing conditions and also the new hot pressing technologies such as the use of steam injection or a cooling zone in the continuous press. A comparative study has been done to show the advantages of using new hot pressing technology. The present model will become an important tool in the hands of wood technologist, process engineers and MDF manufacturing personnel, to better understand the internal processes and to improve production and quality of MDF boards. This theoretical model helped in developing better understanding of internal processes. By using it, we can analyse the impact of platen temperature, moisture content on the core temperature, core pressure and density profile. It gives better insight into the relationship between core pressure and delamination of the board. The model is also able to predict the internal changes in the new hot pressing technologies such as the steam injection pressing and the use of a cooling zone in a continuous press. Using the simulation results, the exact time needed for the complete curing of resin can be calculated and then these results can be applied in the commercial plants. If the pressing time is reduced, then the over all production of both batch press and continuous press will increase. The second part of the project is the development of an empirical model to correlate the physical properties from the MDF board to the mean density. The empirical model is simple and straightforward, and thus can be applied in commercial operation for control and optimization. The empirical model can predict peak density, core density, and modulus of rupture, elasticity and internal bonding within the limits in which those relationships are derived. The model gives good results for thickness ranging from 10 to 13.5 mm and density ranging from 485 kg/m³ to 718 kg/m³.

No description available.

The master thesis is focused on measuring of cutting forces and milling on the CNC machine SCM Tech 99 L when MDF (Medium Density Fibreboard) is used as the machined material. The dynamometer Kistler 9257 B and DynoWare software is used for the measurement of forces and data analysis. The theoretical part of the thesis relates to the characteristics of the CNC machine, tools, tool angles and the methods of cutting resistance. The experimental part provides the description of the experiment itself as well as the changes of cutting conditions during the experimental process when using certain tools. Moreover, it explains the procedure of data processing and shows its final results. The conclusion of the thesis evaluates the data of cutting forces and cutting resistance. These data are further compared based on the technology and the parameters.

Subject of presented master thesis are two 7-meter objects of crystalline structure located in production hall in Brno former factory Zbrojovka