Topological model for machining of parts with complex shapes

Complex shapes are widely used to design products in several industries such as aeronautics, automotive and domestic appliances. Several variations of their curvatures and orientations generate difficulties during their manufacturing or the machining of dies used in moulding, injection and forging. Analysis of several parts highlights two levels of difficulties between three types of shapes: prismatic parts with simple geometrical shapes, aeronautic structure parts composed of several shallow pockets and forging dies composed of several deep cavities which often contain protrusions. This paper mainly concerns High Speed Machining (HSM) of these dies which represent the highest complexity level because of the shapes' geometry and their topology. Five axes HSM is generally required for such complex shaped parts but 3 axes machining can be sufficient for dies. Evolutions in HSM CAM software and machine tools lead to an important increase in time for machining preparation. Analysis stages of the CAD model particularly induce this time increase which is required for a wise choice of cutting tools and machining strategies. Assistance modules for prismatic parts machining features identification in CAD models are widely implemented in CAM software. In spite of the last CAM evolutions, these kinds of CAM modules are undeveloped for aeronautical structure parts and forging dies. Development of new CAM modules for the extraction of relevant machining areas as well as the definition of the topological relations between these areas must make it possible for the machining assistant to reduce the machining preparation time. In this paper, a model developed for the description of complex shape parts topology is presented. It is based on machining areas extracted for the construction of geometrical features starting from CAD models of the parts. As topology is described in order to assist machining assistant during machining process generation, the difficulties associated with tasks he carried out are analyzed at first. The topological model presented after is based on the basic geometrical features extracted. Topological relations which represent the framework of the model are defined between the basic geometrical features which are gathered afterwards in macro-features. Approach used for the identification of these macro-features is also presented in this paper. Detailed application on the construction of the topological model of forging dies is presented in the last part of the paper

Machining of complex-shaped parts with guidance curves

Nowadays, high-speed machining is usually used for production of hardened material parts with complex shapes such as dies and molds. In such parts, tool paths generated for bottom machining feature with the conventional parallel plane strategy induced many feed rate reductions, especially when boundaries of the feature have a lot of curvatures and are not parallel. Several machining experiments on hardened material lead to the conclusion that a tool path implying stable cutting conditions might guarantee a better part surface integrity. To ensure this stability, the shape machined must be decomposed when conventional strategies are not suitable. In this paper, an experimental approach based on high-speed performance simulation is conducted on a master bottom machining feature in order to highlight the influence of the curvatures towards a suitable decomposition of machining area. The decomposition is achieved through the construction of intermediate curves between the closed boundaries of the feature. These intermediate curves are used as guidance curve for the tool paths generation with an alternative machining strategy called "guidance curve strategy". For the construction of intermediate curves, key parameters reflecting the influence of their proximity with each closed boundary and the influence of the curvatures of this latter are introduced. Based on the results, a method for defining guidance curves in four steps is proposed

Diversité des plantes d’intérêt apicole dans la région des plateaux du Togo

Description du sujet. Les plantes d’intérêt apicole regroupent toutes les plantes qui intéressent les abeilles par la fourniture des nutriments indispensables à leur survie, notamment le nectar, le pollen, la résine, la propolis, l’eau. Objectif. Le présent travail a consisté à caractériser les plantes à intérêt apicole rencontrées dans la Région des Plateaux du Togo. Méthodes. Cette caractérisation s’est basée sur le couplage de l’observation directe sur le terrain dans un rayon de 1km autour des ruchers à l’analyse pollinique des miels récoltés dans cette zone d’étude. L’observation directe a consisté de relever sur le site d’étude les différentes espèces végétales visitées par les abeilles butineuses en fonction des nutriments récoltés, alors que l’analyse pollinique a permis d’identifier par observations microscopiques les plantes dont les pollens ont été prélevés par les abeilles et ajoutés au miel. Résultats. La présente étude a permis de recenser 117 espèces à intérêt apicole qui appartiennent à 113 genres répartis dans 45 familles. De façon générale, Les Fabaceae suivies des Asteraceae sont les familles les plus dominantes. Il ressort que les nectarifères (60%) sont les plus abondants suivis des plantes nectaro-pollinifères (21,33%) et des plantes pollinifères (18,67%). Conclusion. La connaissance de ces plantes impliquera leur meilleure valorisation pour une professionnalisation et un développement durable de la filière apicole.   Description of the subject. Plants of beekeeping interest include all plants that are of interest to bees by providing nutrients essential to their survival, in particular nectar, pollen, resin, propolis, and water. Objective. This work consisted of characterizing the plants of beekeeping interest encountered in the Plateau Region of Togo. Methods. This characterization was based on the coupling of direct observation in the field within a 1km radius around the apiaries with pollen analysis of honey collected in this study area. Direct observation consisted of noting on the study site the different plant species visited by foraging bees based on the nutrients collected, while pollen analysis made it possible to identify, through microscopic observations, the plants whose pollen was collected. taken by bees and added to honey. Results. The present study made it possible to identify 117 species of beekeeping interest which belong to 113 genera distributed in 45 families. Generally speaking, Fabaceae followed by Asteraceae are the most dominant families. It appears that nectar plants (60%) are the most abundant, followed by nectaro-polliniferous plants (21.33%) and polliniferous plants (18.67%). Conclusion. Knowledge of these plants will imply their better valorization for professionalization and sustainable development of the beekeeping sector

Agronomic potential value of household urban solid wastes by composting and composts quality assessment

Using composting technology, the biodegradable fraction of solid wastes collected from Agbalepedogan district in Lomé (Togo) was transformed into composts with no phytotoxicity suitable for use in agriculture. The household urban solid wastes were mixed with poultry manure and Mucuna pruriens leaves in appropriate percentages and transformed into composts. The composting process was monitored by temperature, pH and C/N ratio controlling. The composts quality was appreciated by phytotoxicity test, particle size distribution, contents of nitrogen, phosphorus, potassium, organic matter and trace elements. The results showed that composts particle size distribution presented four fractions (>10 mm, 5-10 mm, 2-5 mm and ≤2 mm) whose average percentages are respectively 9.04±0.2%; 10.71±0.2%; 12.68±0.4% and 67.53±0.6%, respectively. Composts produced contained 1.02±0.1% - 2.72±0.2% of nitrogen, 1.35±0.3% - 2.70±0.4% of phosphorus, 1.31±0.2% - 1.72±0.3% of potassium and 23.50±0.4% - 37.75±0.5% of organic matter. The pH in final composts were between 8.50±0.2 and 9.00±0.3 while C/N ratio varying from 8.06±0.2 to 13.13±0.2. The concentrations of some heavy metals in final products were 79.8±1.7 - 140.2±1.6 mg/kg.dm of zinc, 27.1±1.01 - 76.6±1.03 mg/kg.dm of copper, 2.07±0.33 - 9.19±0.22 mg/kg.dm of lead, 4.13±0.16 - 11.05±0.36 mg/kg.dm of nickel and 0.79±0.02 - 2.15±0.03 mg/kg.dm of cadmium. These concentrations were lower than the limited value for heavy metals prescribed by French and US EPA regulation for organic and organic-mineral fertilizers. Int. J. Agril. Res. Innov. Tech. 9(2): 1-8, December 201

Bilan environnemental de l'utilisation de pesticides organochlorés dans les cultures de coton, café et cacao au Togo et recherche d'alternatives par l'évaluation du pouvoir insecticide d'extraits de plantes locales contre le scolyte du café (Hypothenemus hampei Ferrari).

Le bilan environnemental de l'utilisation des insecticides organochlorés dans la culture de coton, café et cacao au Togo par CPG/SM révèle la présence de DDT, aldrine, dieldrine, endrine, heptachlore, lindane et endosulfan dans les sols, les sédiments, le maïs, le niébé, le café et le cacao à des concentrations de 0,18 à 160 µg.kg-1 et dans l'eau de rivières et de puits à des teneurs de 0,02 à 0,40 µg.L-1 excédant les limites maximales tolérables recommandées par la FAO, l'OMS et l'Union Européenne. Des tests biologiques en laboratoire indiquent que les huiles essentielles de cinq plantes aromatiques locales et l'huile de graine de neem ont une activité insecticide sur le scolyte des fruits du caféier (Hypothenemus hampei F.) comparable à celle de l'endosulfan, l'insecticide chimique. La sensibilité du scolyte à ces extraits végétaux dépasse de loin celle du parasitoïde Cephalonomia stephanoderis Betrem exprimant ainsi leur sélectivité. L'huile de graine de neem s'est révélée la plus intéressante. Ces résultats sont prometteurs pour que la recherche entamée dans ce domaine se poursuive. ABSTRACT : Environmental assessment of organochlorinated insecticides used in cotton, coffee and cocoa culture growing in Togo by GC/MS analyses revealed the presence of organochlorinated pesticides such as DDT, aldrin, dieldrin, endrin, heptachlor, lindane and endosulfan in soils, sediments, maize, cowpea, coffee and cocoa (0.18 - 160 µg.kg-1) and in water of rivers and well used as drinking water (0.02 - 0.40 µg.L-1) exceeding the maximum residue set by limit of FAO, WHO and the European Union. Bioassays in laboratory indicated insecticidal activities of five local aromatic plant essential oils and neem seed oil against coffee berry borer (Hypothenemus hampei F.) comparable to that of endosulfan, a commercial chemical insecticide. The sensibility of H. hampei towards plant extracts was higher than that of the parasitoïde Cephalonomia stephanoderis Betrem indicating their selectivity. Neem seed oil was the most interesting. These results on the effectiveness of local plants extracts to fight coffee berry borer were promising and the research started in this field should be continued

Nitrogen Moderate Rates’ Effects on the Performance of Cocoa Seedlings (Theobroma Cocoa Linn.) in the Forest Zone of Togo (West Africa)

The cocoa trees nutrient requirements coverage, especially in nitrogen (N), remains essential for a better growth of the seedlings. The objective of this study was to determine the effects of the moderate nitrogen doses on the agronomic performance of the nursery cocoa seedlings in Togo’s forest zone. Trials were conducted in a complete randomized plot design with four replicates to identify the optimal complementary nitrogen dose helpful for better growth and nutrition of cocoa seedlings. The doses tested were 0; 0.5; 1 and 1.5 g.plant-1 of urea (46% N). The results showed that the doses of 0.5 and 1 g.plant-1 were the most likely to provide the best agronomic performance of nursery cocoa seedlings in the forest zone of Togo. However, the dose of 1 g.plant-1 was optimal for good growth and balanced nutrition of cocoa seedlings and would therefore be recommended for the management of cocoa nurseries in the area