DIAGNOSTICS OF DRUM TYPE WOOD SHREDDER MACHINES

Main enginepower (kW)200 200Main enginerevolutions (rpm)1000 1000Table 1. Shredder machine mainparameters4.2. Cutting process characteristiccalculationsFurther calculations that characterize thecutting process describe parameters andtheir real value compared with thoseannounced by the manufacturer.The difference is expressed in percentageform relating to the initial value, in order toevaluate the significance of discrepancies.• Cutting speedCutting speed depends on the rotordiameter and revolution count. The rotordiameter remains constant while revolutioncount was altered therefore, cutting speed vis:(1)where:D – rotor diametern – rotor revolution count per minuteWe can easily see that increasing the rotorrevolution count leads to a cutting speedincrease of approx. 12%.• Supply speed on the teethSupply speed on the teeth depends onsupply speed in one minute, rotorrevolutions and the number of teeth in therotor.where:Sm – supply speed in one minutez – number of teeth(2)By setting more teeth in rotor, therevolution count has increased by 13%,supply speed has reduced by 12% and feedon the individual teeth has reduced by51%. Accordingly, mean length ofmanufactured wood chip has reduced. Atthe same time, the aforementionedalterations have reduced the overall load onthe shredder.4.3. Shredder vibration forecastThe main cause of vibration in the workingprocess is the floating/variable load, whichoccurs because of the cyclic entrance ofblades into the working area.The oscillation frequency is constant andcan be easily obtained by equation 3. Thevariable value is the oscillation amplitude,depending on the amount of in-comingshredding material at a precise moment andcondition of blades. The amount ofsupplied material is the time variable andhardly prognosable value because theamount depends on working modes ofother related setups. It is not necessary toestimate described oscillationsindividually. But knife wear provokesregular amplitude raise, which include alsooscillations caused by the amount ofcrumble mass alterations.(3)where:z – number of rotor teethn – rotor revolution countAs seen from the calculations, the basicoscillation/ vibration frequency is 27.8 Hz.This specific amplitude will be the mainfactor by which to draw conclusions aboutthe condition of the blade and supportingblade.5. METHOD USED, STATUS ANDRESULTS242