Автор: Zhivko Gochev
- INVESTIGATION OF THE INFLUENCE OF THE WEARING AND THE BELT DRIVE PARAMETERS’ CHANGES OVER THE FORCED TORSIONAL VIBRATIONS IN THE SAW UNIT OF A WOOD SHAPER
The proposed study presents an investigation of the influence of the wearing and the belt drive parameters’ changes over the forced torsional vibrations in the saw unit of a wood shaper. These changes affect the elastic and damping coefficients of the machines’ elements. The research is done on the base of a concrete mechanic-mathematical model for numerical investigations of the torsional vibrations of a wood shaper’s saw developed by the authors. The main features in the construction of the wood shapers are rendered an account in this model. Work’s conditions in the practice are modeled with the variable moments on the drive electric motor and the wood shaper’s saw. The conclusions based on the numerical investigations are confirmed by the real conditions.
The results of the whole investigation are applicable to the direct well-founded recommendations concerning the operation of these machines. These recommendations are important for the increase of the accuracy and quality wood shapers’ production. At the same time the results of this research are useful for technical diagnostics of the wood shapers.
Ключови думи: wood shapers, modeling, torsional vibrations
- SAWING OF DOUGLAS FIR LOGS WITH NARROW BAND SAW BLADES IN WINTER CONDITIONS
The report presents some experimental studies carried out by sawing of logs with narrow band saw blades in winter conditions. The experiments were carried out in manufacturing conditions in February. For the purpose a horizontal band saw "Wirex CZ-1/ZM" was used.
Operating conditions were established and the quality of sawn lumber from semi frozen logs of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was tested. The quality preparation of the band saw blade with the used horizontal band saw provides good parameters of the sawn lumber: surface roughness R̅m = 190 μm; variation in the accuracy of the size and shape of 1.5 mm and 1.8 mm at a feed speed of U = 11.5 m.min-1.
Ключови думи: logs, Douglas fir, sawing, narrow band saw blades, winter conditions
- COMPUTATION OF THE HEAT FLUX NEEDED FOR UNILATERAL WARMING UP OF FLAT SPRUCE DETAILS BEFORE THEIR BENDING
An approach for the computation of the heat flux, which is needed for warming up of flat wood details during unilateral heating aimed at their plasticizing in the production of curved outside parts for corpses of stringed music instruments, has been suggested. The approach is based on the numerical integration and differentiation of the solutions of a linear model for the calculation of the non-stationary 1D temperature distribution along the thickness of subjected to unilateral heating flat wood details. The paper presents solutions of the model concerning the non-stationary change in the specific heat flux needed for warming up of flat spruce details with thicknesses of 6, 8 and 10 mm during their unilateral heating at temperatures of the electrically heated metal band equal to 100, 120, and 140 oC.
Ключови думи: unilateral heating, flat wood details, heat flux, plasticizing, bending
- TRANSFORMATION OF TWO MUTUALLY CONNECTED MODELS FOR CONVECTIVE HEATING OF WOOD DETAILS BEFORE THEIR LACQUERING IN A FORM, SUITABLE FOR PROGRAMMING
Using the explicit form of the finite-difference method, two suggested by the authors mutually connected mathematical models have been transformed in a form, suitable for programming. For the numerical solution of the transformed models, a software program has been prepared in the calculation environment of Visual Fortran Professional. With the help of the program, the 1D distribution of the temperature along the thicknesses of flat oak details and of their carrying transport rubber band with hw = 16 mm, lw = 0.6 m, u = 0.08 kg.kg-1, hB = 4 mm,
bB = 0.8 m, and t0 = 20 oC, during unilateral convective heating for a period of 10 min at tha = 100 oC, vha = 2 m·s-1, 5 m·s-1, 8 m·s-1, and tnha = 20 ºC in order to ensure suitable thermal conditions for the subsequent details’ lacquering has been calculated, visualized and analyzed.
Ключови думи: oak details, unilateral convective heating, lacquering, carrying rubber band
- STUDY ON THE POWER – ENERGETIC INDICATORS OF A UNIVERSAL MILLING MACHINE
Experimental studies during milling of solid wood were carried out. The current study was performed at the Laboratory of Woodworking Machinery, University of Forestry, Sofia. The measurements were carried out using universal milling machine FD – 3 (ZDM – Plovdiv). The correlations between fundamental factors influencing the milling process and target functions, such as cutting force and power, specific cutting work, specific power consumption have been investigated. On the basis of the analysis of the obtained results, practical recommendations have been proposed.
Ключови думи: universal milling machine, cutting power, cutting force, specific cutting work, wood milling
- COMPUTATION OF THE ENERGY CONSUMPTION FOR WARMING UP OF FLAT OAK DETAILS BEFORE THEIR BENDING
A software program has been prepared in the calculation environment of Visual Fortran for solving of own 1D non-linear model of the one sided heating process of flat wood details. With the help of the program, the 1D non-stationary temperature field in flat oak details with initial temperature of 20 oC, moisture content of 0.15 kg.kg-1, thickness of 12 mm, 16 mm, and 20 mm during their 30 min one sided heating at temperature of 80 oC of the heating metal body has been calculated. After integration of the temperature field, the energy consumption for warming up of the details before their bending in the production of curved back parts of chairs has been calculated. The obtained results are graphically presented and analyzed.
Ключови думи: oak details, one sided heating, bending, energy consumption
- MODELING OF THE FREE SPATIAL VIBRATIONS OF WOOD SHAPER AND ITS SPINDLE
The proposed study deals with the modeling of the free spatial vibrations of a woodworking shaper and its spindle. An original mechanical - mathematical model of woodworking shaper and its spindle, developed by the authors, is presented in this work. The model provides the opportunity to explore the free undamped space vibrations of this type of machinery. In this model the woodworking shaper and its spindle are regarded as rigid bodies, which are connected by elastic elements with each other and with the motionless floor. A system of matrix differential equations is compiled and analytical solutions are presented. The natural frequencies and mode shapes for a specific machine can be obtained with their help. The model is supplemented in order to investigate the free damped space vibrations of the considerate system. The new model takes into account the damping properties of machine's elements. A new system of matrix differential equations is developed and the relevant analytical solutions are presented. They allow various numerical solutions for specific machines. The models take into account the characteristics in the construction of woodworking shapers. They include all necessary geometric parameters of this system. Numerical solutions and graphs can be obtained with the help of the developed models. These solutions and graphs are necessary for analyzing the free undamped and the free damped space vibrations of a particular considerate machine.
Ключови думи: wood shapers, free vibrations, modeling