With a predictive model that can predict failures of a manufacturing machine, many benefits can be obtained. Unnecessary downtime and accidents can be avoided. In this study a wood chipper which has 12 replaceable knives was examined. The specific task was to create a predictive model that can predict if a knife change is needed or not. To create a predictive model, supervised machine learning was used. Decision forest was the algorithm used in this study. Data samples were collected from vibration measurements. Each sample was labeled with help of ocular inspections of the knives. Microsoft Azure learning studio was the workspace used to train all models. The data set acquired consist of 106 samples, were only 9 samples belongs to the minority class. Two strategies of training a model were used, with and without oversampling. The result for the best model without oversampling obtained 87.5% precision and 77.8% recall. The best model with oversampling achieved 79% precision and 86.7% recall. This result indicates that the trained models can be useful. However, the validity of the result has been hurt by a small data set and many uncertainness of acquiring the data set.

L’utilisation des plaquettes bois dans le secteur de l’énergie est en pleine croissance depuis les objectifs fixés par le grenelle de l’environnement. Cette utilisation croissante nécessite de plus en plus de matière première ainsi que des matériels de transformation. Ces machines de type déchiqueteuse / broyeur forestier consomme beaucoup d’énergie et dont la principale source est le pétrole. C’est pourquoi cette recherche propose dans un premier temps de définir un moyen d’évaluer la performance énergétique de ces machines puis dans un deuxième temps d’évaluer l’influence des paramètres de coupe sur la performance énergétique. Ce critère est défini comme le rapport entre la tonne de plaquettes sèches et l’énergie consommée par la déchiqueteuse. Il permettra d’évaluer une déchiqueteuse du marché. L’évaluation de la performance énergétique est réalisée en deux endroits distincts de la déchiqueteuse, proche de la coupe et de manière globale. Les différents résultats de l’influence des paramètres de coupe sont présentés afin de caractériser les plus importants dans le but d’une optimisation de la machine étudiée. Cette optimisation a permis de doubler la performance énergétique de la machine. La thèse a également mis en évidence les limites de l’utilisation de certains organes de sécurité réduisant la performance énergétique de 40%. Les différents travaux de recherche doivent permettre d’aider les concepteurs dans le dimensionnement de la source d’énergie nécessaire pour déchiqueter le bois / Consumption of fuelwood, mainly in the form of wood chips, is growing to achieve the goal fixed by the “Grenelle de l’Environment” Laws. Increasing wood chip production needs more and more raw materials and use of wood chippers or shredders is well established. These machines are very energy-consuming particularly in gasoline. First, this thesis presents original methods for measuring chipper performance and focuses on influence of cutting parameters on energy efficiency. Wood chipper energy performance is defined by the ratio between tonnes of dry wood chips and power consumed by the machine to produce them. Using energy efficiency determination method, all wood chippers will be compared and will help customer to choose the machine that consumes the least energy to produce wood chips. Wood chipper performance is measured at two different locations: one closer to the cutting area and the other at the wood chipper drive. The results show that wood chipper performance factor is properly defined and cutting parameters impacts wood chip performance. Cutting optimization halves the chipper fuel consumption to produce the same wood chips quantity. The results also show the limits of safeguard that reduce by 40% chipper performance. This thesis must help designers for developing more efficient machines to reduce their impact on the environment

This paper aims to derive qualitative model for energy requirements for wood chipping process. There is relationship shown between energy requirements and properties of biomass, which is quite variable material. Relationship between comminution machinery and energy necessary for the process is highlighted. Derivation of the model is focused on chipping but in general it’s possible, to make it available both for different types of biomass (f. ex. agricultural residues) or for different type of comminution machinery (f. ex. hammermills) just by using different material properties adjusted to machinery mechanics. Properties used in derivation are mend to be easy to measure. Model is mend to be used as a base for quantitative model that, thanks to measurements performed on real comminution machinery and using wood with known properties, could give answers for two important questions: Would hypothetical changes in desired size of output material increase total system efficiency, taking into consideration lowest efficiency of combustion process (i. ex. higher amounts of unburned fuel)? How to optimise comminution as an operation in biofuel supply chain, with respect to energy used for the process?

The aim of this master's thesis is to design of wood chipper connected to the tractor ZETOR 3011. In the introduction of this thesis it is described the general use of wood chippers. First part of thesis contains recherche from wood chippers' area. Then it is followed with the description of the own chipper design and with the basic design calculations. Part of the thesis is 3D model of the machine and drawing documentation of selected parts. Next part is given economic evaluation. In the last part of thesis is made analysis of risk.

The goal of this thesis is structural design of the trailer for a LASKI chippers and to create a construction drawings. Important part is information about legislation rules, which this trailer has to fulfill. The aim of this work is to do a dynamic simulation using multi-body system. Results of this simulation are used for a stress analysis witch using a fine element method.

There is currently a global increase in Eucalyptus pulpwood plantations. Harvesting systems traditionally utilised in the northern hemisphere are being used in Eucalyptus pulpwood plantations worldwide. However, the small tree size and complexity of debarking Eucalyptus have provided harvesting with productivity and cost challenges not previously experienced in northern-hemisphere conditions. Much research has been invested in these two harvesting methods in northern-hemisphere species and conditions. There is little research available on mechanised processing-machine productivity and costs in Eucalyptus. This investigation aimed to quantify the effect that tree and bundle size has on the productivity of different processing machines in Eucalyptus plantation pulpwood. This was done through regression analysis, whereby productivity models that included tree size and bundle size were constructed. The research also aimed to determine whether or not the multi-stem systems were more cost-effective in smaller tree sizes. The research investigated five mechanised harvesting options that forestry managers could use in Eucalyptus pulpwood plantations. These systems consisted of one CTL system, one full-tree system with single-stem processing and three full-tree systems with multi-stem processing. The CTL system used a harvester to process the trees into logs and to extract them. The full-tree system with single-stem processing used a dangle-head processor (DHP) to process trees into logs. The first full-tree system with multi-stem processing used a chain-flail debrancher debarker (CFDD) to produce debarked and debranched tree lengths, which were slashed into logs. The remaining full-tree, multi-stem systems both produced chips. The first used a chain-flail debrancher debarker chipper (CFDDC) and the second, a CFDD feeding into a stand-alone disc chipper (CFDD&C). The productivity data, measured as m3 per productive machine hour (PMH), was then statistically analysed using regression techniques. Productivity equations were formulated, considering tree size and bundle size, as well as the quadratic functions of these two variables and the interaction between them. Bundle size was only applicable to the multi-stem processing machines. The productivity equations successfully predicted processing-machine productivity, using tree size and bundle size as input variables. Apart from the 0.075 m3 tree size class, the CFDD had the highest overall productivity. The costs of the five systems were then calculated for different tree sizes. No single system was more cost-effective than the others across all tree sizes. In 0.075 m3 trees, the CFDDC system proved the most cost-effective. All systems evidenced high costs in the 0.075 m3 trees, ranging between $19.43 per m3 for the CFDDC system to $28.84 for the harvester system. In 0.40 m3 trees, the cost differences between systems were lower, ranging from $6.91 per m3 for the DHP system to $11.84 per m3 for the CFDD&C. This study confirms that the CTL system was very expensive to operate in the small tree sizes (0.075 m3). There is a cross-over point at 0.25 m3 per tree, where the CTL system costs become lower than those of the full-tree system. At the 0.40 m3 tree size, the full-tree system is slightly more expensive than the CTL system. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Plant Production and Soil Science / unrestricted

In both the chemical and mechanical pulping process, the logs are cut into wood chips by a disc chipper before fibre separation. To make the wood chipping process more efficient, one have to investigate in detail the coupling between process parameters and the quality of the chips. One objective of this thesis was to obtain an understanding of the fundamental mechanisms behind the creation of wood chips. Another objective with the thesis was to investigate whether it was possible to, in a way tailor the chipping process so as to reduce the energy consumption in a following mechanical refining process. Both experimental and analytical/numerical approaches have been taken in this work. The first part of the experimental investigations, were performed with an in-house developed chipping device and a digital speckle photography equipment. The results from the experimental investigation showed that the friction between the log and chipping tool is probably one crucial factor for the chip formation. Further more it was found that the indentation process is approximately self-similar, and that the stress field over the entire crack-plane is critical for chip creation. The developed analytical model predicts the normal and shear strain distribution and to be more specific, the model can predict the compressive stresses parallel to the fibre direction for an assumed linear elastic and orthotropic material. The analytical distributions were found to be in reasonable agreement with the corresponding distributions obtained from a finite element analysis. To be able to study the chipping process under realistic conditions, which for example means to use chipping rates representative for a real wood chipper, a laboratory chipper was developed. Details regarding the chipper and how to evaluate the force measurements are given together with an example of how the force on the cutting tool (the knife) varies with time during cutting. To investigate the influence of a certain chipping process parameter, the chips were after production in the laboratory chipper, refined in a pilot refiner during conditions optimized for TMP (thermomechanical pulp) and CTMP (chemithermomechanical pulp) processes. It was concluded that the details concerning the chip process had a large impact on e.g. the energy consumption in both first stage and second stage refining. Results showing this are given in this thesis. / För både kemisk och mekanisk pappersmassa så tillverkas flis av trädstockar med hjälp av en skivhugg innan fibrerna separeras. För att göra flisningsprocessen mer effektiv, måste kopplingen mellan processparametrar och fliskvalitet studeras. Ett mål med denna avhandling är att ge fundamental kunskap om mekanismerna bakom bildandet av träflis. Både experimentella och analytiska/numeriska metoder har använts i detta arbete. De experimentella undersökningarna har gjorts med hjälp av egen utvecklad utrustning. Resultaten från den experimentella undersökningen visar att friktionen mellan stammen och flisningsverktyget har betydelse vid flisning. Vidare observerades det att inträngnings processen är approximativt självlik (self similar) och att det är spänningsfältet över hela sprickplanet som är kritiskt för bildandet av en flis. Den utvecklade analytiska modellen förutsäger normal- och skjuvspänningsfördelningen över sprickplanet och kan mer specifikt förutsäga den kompressiva belastning som verkar parallellt fiberriktningen i ett linjärt elastiskt och ortotropt material (trä). De analytiskt bestämda fördelningarna stämmer relativt väl överens med motsvarande fördelningar beräknad med finit element analys. För att kunna studera flisningsprocessen under realistiska förhållanden, vilket bl.a. betyder att skärhastigheter som är representativa för en verklig process skall användas, så utvecklades inom ramen för avhandlingsarbetet, en laboratoriesflishugg. Detaljer rörande flishuggen samt hur uppmätta lastsignaler skall utvärderas ges tillsammans med ett exmpel på hur kraften på skärverktyget (kniven) varierar under ett skärförlopp. Inverkan av en viss flisningsprocessparameter undersöktes genom att flis tillverkades i laboratorieflishuggen varefter de raffinerades i en pilotraffinör under förhållanden som var optimerade för TMP (termomekanisk massa) och CTMP (kemitermomekanisk massa) processerna. Det konstaterades att detaljer i flisningsprocessen hade stor inverkan på t.ex. energiåtgången i både första stegs – och andrastegsraffinering. Resultat som verifierar detta ges i avhandlingen. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Submitted. Paper 5: Submitted.</p>

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