DIAGNOSTICS OF DRUM TYPE WOOD SHREDDER MACHINES

8th International DAAAM Baltic ConferenceINDUSTRIAL ENGINEERING19-21 April 2012, Tallinn, EstoniaDIAGNOSTICS OF DRUM TYPE WOOD SHREDDER MACHINESZarins, M., Torims, T. & Vilcans, J.Abstract: This paper investigatesdiagnostic methods and proposes modernservice technologies for wood-processingequipment. The aim of this study is toensure systematic, research-based woodprocessingservices and continuous, nofailureoperation of facilities. We describethe working principle of a particularindustrial, drum-type wood shredder anddiscuss the problems that occurred duringoperation, including potential excessengine load or construction imperfections.Cutting regime calculations are provided,along with a description of actualimprovements and a comparison of cuttingregimes before and after improvements.The intended result of this research is amonitoring unit which, with help of a fewmodifications, can be used on any drumtypewood processing equipment.Key words: List 4-5 keywords. (woodprocessingfacilities, drum-type woodshredder).1. INTRODUCTIONThis paper is based on the dissertation andresearch conducted during its preparation.It is the first paper on the subject,describing the problem of the dissertation,the attainable target and a reflection on theresearch process at the present stage.Given the current complex economicsituation, employers are obliged tooptimize their manufacturing processes andreduce the prime cost of an item, in a bid tosurvive and remain profitable. One meansof saving is in manufacturing facilitymaintenance and repair.It is possible to reduce expenditure onspare parts and avoid sudden stoppages bymodelling a modern, thought-out, researchand diagnostics based manufacturingfacility service. A diagnostics model of thejunction condition can be developed byperforming a series of cyclic measurementsand analyzing the results. In this way, theprecise moment can be identified whenexpenditure on complementary partsresources is timely but not destructive.The present research has been conducted incooperation with Latvijas Finieris, Ltd,which is the leading secondary woodprocessing company in Latvia and has avery large number of manufacturingfacilities at its disposal.All of these require constant maintenanceand repair, which usually results in majorfinancial outlays. Added to this, suddenstoppages of manufacturing facilities forunscheduled repairs generate significantlosses.The focus of the current research isinvestigation and analysis of a waste woodshredder machine. At the present researchstage, the setup has been carefully studied,its working principle and analysis havebeen conducted. The main problems andtheir probable causes have been identified.The work accomplished so far provides abasis for further study, for choosingmeasuring instruments and the appropriatemethodology, as well as for developing acommon service system.2. FIELD OF APPLICATIONThe object of the study is a drum-typewood shredding machine designed toprocess large amounts of waste wood intowoodchips. We expect that results will beunified and applicable to any kind of drumtypewood shredder diagnostic system andservice technology elaboration.240

3. PROBLEM STATEMENTSAt this moment we have defined severalproblems related to setup of the operationprocess.Fig. 1. Shredder setup RAUTE TR 1020 –1300 V kinematic schemeFig. 2. Blade sketchMostly these are connected with highdynamic loads, which occur in junctionsduring shredder machine operation.The following problems in particular havebeen identified: (fig. 1., 10) corpus squirm;posterior counter knife deformation (fig. 1.,13); stowage of forward lead-in plate (fig.1., 14) fixation screws and working bladewear (fig. 2).Mainly, the impact initiated by the blade atthe moment when the wood chip ischopped from the whole chipping mass issuch that the load is delivered to the firstsupporting blade. The load is large enoughto squirm the counter knife casing, see fig.3.Fig. 3. Deformation of supporting blade.When regulating the machine, a gap of 0.4-0.7 mm must be set between the blade andthe supporting blade. After the saidsupporting blade casing deformation, itbecomes impossible to restore thenecessary gap. In particular, if the gap isset in the middle, the edges of blade go intothe rotating blades operation zone; but ifthe regulation is performed at the edges,the middle gap becomes too large for thesupposed standard. Engaging the squirmedsupporting blade in the cutting processleads to increased loads in the working areaand the wood chip quality decreases.A load increase is induced not only by theblade-supporting blade gap, but also bynormal blade wear which is inevitable. Atthis moment it is a common practice to usere-sharpened blades after a two-weekworking cycle. This service model isaccepted and implemented without anytheoretical background, there are noexperimental results to affirm or refute thenecessity of the described service cyclemodel.Increasing cyclic loads in the shredderworking area also increases load on themain engine. As a result there have been anumber of cases of main engine overloadand even fires.4. RESEARCH COURSE4.1. Data outputA summary of the working processdescribing parameters was required inorder to undertake any kind of analysis andcalculations. Some of these parametershave been partially changed in order to findprecise values, and direct measurementshave been performed. The main parametersand discrepancies between factory data andreal setup working parameters can be seenin Table 1.ParameterFactorydataActualdataRotor diameter(mm)1020 1020Feed roll diameter(mm)313.6 313.6Rotor revolutions(rpm)493 556Supply speed(m/min)50 44Number of blades 2 3Input hatchdimensions (mm)1310x375 1310x375241

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

Currently measurements are being taken atregular intervals to reflect changes in theblade and supporting blade interactionduring working process. This is achievedby measuring the gap between the bladeand supporting blade at three points, once aday (figure 4, points A, B, C). Thesereadings show both the progress ofsupporting blade deflection and total wearon the blade and supporting blade. As thein-situ experimental process is currently inthe initial stage, the amount of gathereddata is insufficient to give a statisticallyreliable description of wear progress or todevelop a mathematical model thatdescribes this process.Up-to-date results relate to shreddingmachine working principle research andanalysis, defining actual workingcharacteristics and calculations. At thispoint, the main constructive improvementsfor the shredding machine have beendefined, mentioning that further study cannot take place without these improvements.The most problematic and importantjunction points have been defined, whichrequire new service technology consistingof regular junction condition follow-up anda diagnostic-based maintenance system.6. FURTHER RESEARCHThe next stage is to summarize blade andsupporting blade interaction measurementdata and place sensors under the supportingblade (figure 4). By setting up load sensors,it will be possible to follow-up and analyzeover time the effect of increasing loads onthe supporting blade.Following this, we shall define therelationship between the blade andsupporting blade reciprocal wear conditionand load sensor data, which in future willmake it possible to perform indirect bladesupportingblade monitoring, based on loadsensor measurement data. As a result ofresearch, it is planned to develop aprogramme that will automatically signalwhen there is a need for facilitymaintenance or terminate operation of thefacility, if necessary.11. REFERENCES1. Bershadsky A. L., Rezanie drevesini,Vishaia shkola, Мinsk, 19752. Tuherms H., Kokapstrādes instrumenti,Zvaigzne, Riga, 19853. Holmberg, K., Helle, A. & Halme, J.,Prognostics for Industrial MachineryAvailability, presented at the InternationalSeminar on Maintenance, ConditionMonitoring and Diagnostics, Oulu (FI), 28-29th September 20054. Kalpakjian S. and Schmid, S. R.,Manufacturing Engineering andTechnology, Pearson Education Ltd.,London, 20065. Measurement and control tools [WWW],http://www.ge-mcs.com/en/bently-nevadasensors-and-transducers.html.(22.02.2012)7. CORRESPONDENCE ADDRESSMSc.ing. Marcis ZarinsRTU, Faculty of Transport and MechanicalEngineering, Department of MaterialProcessing Technology,Ezermalas 6, LV-1006 Riga, LatviaPhone: +37126113009E-mail: marciszarins@gmail.comFigure 4. Measurement scheme243