Conception d'une machine d'usinage à bois

Details

Supervisors

Raucent, Benoît ; Herman, Benoît

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien, à finalité spécialisée

Abstract

enThe purpose of this thesis is to study the request of Mr. Christian Fromholz, a trained engineer and inventor of the TOBI woodworking machine. This machine has a special epicycloidal machining process and can be used to machine large wooden beams. Following this project, he wishes to adapt the concept of this machine to a reduced scale in order to machine small wooden elements the size of a toothbrush. The objective of this thesis is to define a specification and to propose a solution for the production of small wooden objects. Among other things, the study allows us to know whether there is a solution, already designed or not, that is more efficient and simpler than an adaptation of the solution implemented for TOBI. Firstly, a precise description of the functioning of the previous TOBI machine is given. This description makes it possible to understand the objectives of the new machine and to establish a functional specification. A study of the existing machining machines showed that the machining of thin objects with a cross-section of about one centimetre and a length of about ten centimetres does not have a commercial solution. A design process was therefore followed to develop different solutions. These solutions were then compared on the basis of criteria such as quality and processing speed. The chosen solution has two notable characteristics. On the one hand, the wood rotates around its axis and translates in a machining area. On the other hand, the translation is carried out by holding the sides of the wood and not the two ends as on a conventional lathe. The wood can thus be held just before the machining zone, which prevents bending or even breaking of the wood for objects with a very thin section. The tool is rotated and its movement allows the machining section to be varied. Different aspects of the solution are then studied: the rotation of thin and long wood, and the machining rate. With regard to the rotation of the wood, a prototype was designed to simulate the machine at high speed. Two results were obtained. Firstly, the rotation of thin wood, held on one side only, is not a problem at speeds of 2500 rpm for sections of at least 8mm diameter, for species such as beech and pine. In addition, the particular holding of the wood in the machine is not a problem. The dynamics of the wood is therefore not a major problem for the proposed solution. This solution is therefore quite feasible. This work also gives an estimate of the minimum machining time on different toothbrush shapes. Two estimates were made taking into account only the dynamics of the tool in translation. It was found that a simple toothbrush could be machined in 1.5 minutes and a more complex toothbrush in 4 minutes.