1、91 FTM5Machine Tool Condition Monitoringby: L. E. Stockline, Promess, Inc.American Gear Manufacturers AssociationITECHNICAL PAPERMachine Tool Condition MonitoringL. E. Stockline, Promess, Inc.TheStatements andopinionscontainedherein are thoseoftheauthor and shouldnotbe conslruedas anofficial action
2、oropinion of the American Gear Manufacturers Association.ABSTRACT:Actual production applicationsof computerassisted Tool Condition Monitoring Systemswill be reviewed from casestudies over the last several years. New applications are being encouraged by the aircraft and automotive industrieswhich hav
3、e allowed untended manufacturing due to the development of new sensors and newly developedmicroprocessor strategy. There is a major impact on quality control, maintenance and machine uptime when tool wear,tool breakage and missing tool or forces can be accurately measured.Copyright 1991American Gear
4、 Manufacturers Association1500 King Street, Suite 201Alexandria, Virginia, 22314October, 1991ISBN: 1-55589-573-5MACHINE TOOL CONDITIONMONITORINGLarry E. Stockline, PresidentPage 1MACHINE TOOL CONDITION Tool sensing in the gear makingprocess is very challengingrelated to the variety in whichMONITORIN
5、Ggears are made. We will addressgear cutting, grinding and gearrolling in this study but inmany cases, the applicationtechnology is overlapping.In gear making, the conditionof the tool and health of themachine are paramount to making SENSORSconsistent quality with themaximum available uptime. In gea
6、r cutting (cutting toolsare either single row or multi-A new technology has been row (fig. 1 gear bobbing),developed to allow the builder forces from the contact of theand enduser to “feel“ the gear cutting edge to the workpiecemaking process during the actual are quite high and aremetal forming or
7、metal removal measurable. The complexity ofprocess. We are able to feel the information coming from thethe force of the process via sensor (as an example, sensingspindle bearing sensors or in gear bobbing) is not onlys t at ic s e n s o rs t h a t dependent upon force, but alsoautomatically compensa
8、te for position of the tooth and angle.sensor drift, and allows for To solve these multi-processingthe sensors to be used in an conditions, requires multi-aggressive manufacturing sensors and microprocessorsenvironment, which then focuses on specificsections of the hob (sharp toworn) and starts the
9、processanew when a move to a newsection of the hob is completed.We will also give an indicationwhen no force is “felt“ whichis an indication that a part is qnot present (Example: Automaticloader jam_ed) and you areI cutting air only. To be ableto get precise information fromthe sensor, the sensor mu
10、st be! self calibrating (hot machine,_J cold machine), take away sensordrift, and even moreimportantly, it must be able tomeasure the target differential(sharp tool to a dull tool)A sensing technique that hasbeen highly successful in themanufacturing environment, isa self-calibrating bearingsensor a
11、nd/or a static sensorstrategically mounted to measure_=._ force differential.F_.1 _ H,_b_-g,_c m_e OPERATING PRINCIPLEThere ate three basic componentsto the technique and eachfulfills a specific task thatmust, again, be sustainable inthe non-lab, manufacturingenvironment.They are: - sensors -signal
12、conditioner I- microprocessor “_g. 2Page 2When a rolling bearing isloaded, load proportionalstrains occur in rollingelements in the outer and innerraces of the bearing. Thebearing load is transmitted inthe Herz area. That is in theball bearing in an approximatelypunctual contact zone, in theroller b
13、earing it is “of a lineshape. Within this contactzone, funnel-shaped strain F_.4zones occur under strain.Photoelastic analysis (fig. 2)makes these strains in theroller bearing visible. The In addition to the patented_ represented bearing is loaded rolling bearing sensors, we haveby force F, the magn
14、itude of now applied four additionalwhich influences the magnitude sensing technologies in theof the strains, development of sensing in gearmanufacturing; strain gage,acoustics, linear, and PizeoElectric., SG What this now means is that wehave been able to locate within.= v the machine, an exact loc
15、ation_| r which takes up (by design) allof the major interaction forces_I / _ (we use term passive force)/ _ between the cutting or grindingtime edge and the workpiece. Inaddition to this technology_ 3 breakthrough, we have been ableto focus on the targetdifferential (sharp tool to adull tool) in a
16、very exactingWhen the bearing is revolving, and repetitious way .and are nowthe strain zone circulates in able to tell an operator whenthe outer race. With aid of othe tool is dull or loaded, andstrain gauges, these strains can call for a tool change and/orbe measured. When one of the wheel dress. I
17、n multi-bladerolling elements passes over a applications such as gear hobs,sensor, a strain is registered, we calculate force inAs the rollers above move on, conjunction to position to tellthis strain, again, drops to a the operator when it is time tominimum (fig. 3). The shift to a sharper set of b
18、ladesresistance variation of the on the same cutter.strain gauge is transformed intoa change in voltage byelectronical amplifiers.workpieceFig. 4 illustrates the ou%putof the amplifiers. Each of the _,0bvoltage peaks results from arolling element that passes the- _H0strain gauge. ConsequentlY,this o
19、utput appears on the AC _signal. Furthermore, as the _load vares, so also will thedeformation, resulting in anamplitude modulation. It isthese changes in amplitude thatare used to measure the forces.- Fig.5Page 3In grinding wheel applications, 2_- _ -_wecanseetou_point,grinding _ i /. I iiiforce, an
20、d are now applying I ,_ ! I I .constant force monitoring which _= %_iis a new technique which only _ / _! _i,.allows a certain force (example ._20 200 ibs. +/-5 Lbs. ) to be _ i )applied which allows for a very _ _ / consistent product both in ) .-/ ) ) I )I)I%,surface finish and in surface 0quality
21、. 0 6 _ -_ 2_ _ _ _ _ s57,me TGenerally, during the grinding mt_ _ _d_ no_ f_operation, the most significant am-gh_ b _ag cfm_bmgfactor is the grinding force F, dstar.rig-outFig. 6). In internalcylindrical grinding operations,deflection of the grinding arbor , I I I , . rand the degree of workpiece
22、_ _i t I _ iprecision. The effect, because _ , _._i I i 1of wearofthegrindingwheel ! 1 Tin external cylindrical = i . .tangential force Ft. The normalgrinding force is recorded by 2,. ,0 _,6 ,.2 ,., ss7 .,.the measuring bearing. The feedadjustment of the grinding wheel no_ _g fo-=_ _u_t _ _now follo
23、ws in rapid approach, a_u_ b_ c_ ds_g_utuntil the allowed grinding F_.7force has been reached, and thisforce is kept steady for the SIGNAL CONDTTIONINC,duration of the .rough grinding qwork. With the assurance of a goodstable signal coming from the:;i_i2ii:“/_“_._:_._i._:il“_:2i!ii: a distance requi
24、res signal!“:!_-_ :“_i:t!“_ S: sensor, sending this signal overenhancement, and signa 1“. !:;i!i!ii/i:;:“_i shielding from electrical and“.:i/. :.: .!i)i frequency noise that cancontaminate, change or destroythe information from a goodsensor. When this occurs, false-I_ _ :ti;_i_ signals will confuse
25、 the operator and, very quickly, he:“ _:_. will lose confidence in theinformation gatheringtechniques._.6A new technology ofpreamplification has now beenBy regulating the normal completed that takes on thisgrinding force, the rough very specific task. The signalgrinding time can be shortened, is dra
26、wn through a very refined,and now, a more precise “rough monitored, electronic elementgrind“ can be maintained that which increases by i00,000 timesallows a more consistent product the size of the sensor signalto be presented to the final and, at the same time, a shieldfinish grind, is put around th
27、e signal toprotect it from any outsidecontamination as it speedsthrough the sensor to themicroprocessor within i0milliseconds. This developmentwas one of the last hurdleswhich allows this technology toreach and be applied on the shopfloor.page 4HX_OPROC_SSOR _PATYERN RECOGNITION“Sensor stability, fa
28、st, clean MONITORING CONCEPTconditioned signals (singularor multiple) are now processedthrough the microprocessor which The function of this monitoringsystem is not governed by fixedhas multi-limit, settingcapabilities. The limit values, but by limitvalues which have to be adaptedmicroprocessor is a
29、lso designedfor multi tasks such as: Tool to a self-repeating pattern ofwear, tool breakage, machine measured values.overload and missing tool. Inthe gear making process, thereare several software strategiesthat are used and two of thoseare reviewed, i m_su_d value r_-IFixed limit , IlimitvaJuett/2_
30、Ir /I- Pattern or signatureanalysis i- /.It ,. . r“ ,J_ II l I i/ / J-/ value ,/ I_ | IiAn analog measured value is _g. 9compared to fixed, preset limitvalues. For example, therepetitive cycle function of a The EPR offers the following solution=bobbing tool teach in storage of the measurementsignals
31、 as a function of time, startlng of the storage and teach inprocedures by an external signal,A measured value editing of data by means of:Iim_ valueI11 - sum formationj . - geometrical or numerical additionllmitvalueII of several measured valuest automatic choice of the optimalmeasuring range, range
32、s 1:5 the carrying of three limit values,_uas - _ of which the distance from theurecF L measuring signal has been definedin the course of the TEACH IN processlimit _alue IF,g.8 SYSTEM/SOLUTION: illuminated strip-display indicationof the measured values,e free selection of 3 li_it values, setting the
33、 limit values by meansof code switch, Normally, in a gear making_e logging of limit transgressions process,many tools (such aswith potential-freechangers, hobbing, grinding, rolling) are storageof fault-report, used to form the gear. Each of internal or external reset, externally adjustable monitori
34、ng these tools may execute multipleStop and Start (window function), forming profiles. Since the automaticzero-balancing of the forces differ with each tool andmeasured value, automatic switch over of measur- cut, it is desirable toing range, establish the individual limite LED display of active mea
35、suring values for each cut. This canrange, be achieved in the operatingmode “Teach In“, without havingto preset the limit values. Thelimit values are assigned to theproduction sequence by means ofthe tool cutting nnmbers.Page 5110W_t_pow_Fig. I0The PROMESS monitoring systemsfor gear cutting consists
36、 of thefollowing three, principalass_mhlies:i. The transducer2. The preamplifier3. The microprocessorwith softwareSUMMARYThe results of sensing on lineand in real time, has createda new awareness andunderstanding of themanufacturing process.Conventional techniques such aspower monitoring lack insens
37、itivity and reaction time,it will tell you after the factthat a wreck has occurred buthas no ability to tell you thatthe process is changing (toolsdull, part out of position)which will lead to a wreck.Systems in production must bedisciplined to only react totargeted changesinthe process.Machine uptimes are nowapproaching 90% due to ourability to sense a processchange and react to the changebefore it causes machinedowntime.9page 6
