Robotic AutomatedDeburring of

Aerospace GearsiMichael Nanlawalal

~DtroduetioDThis report presents some interim results from

an ongoing project being perfonned by INFAC,the Instrumented Factory for Gears ..The purpos-es of tllisinitial phase of the project were todemonstrate the feasibility of robotic automateddeburriag of aerospace gears, and to develop aresearch. agenda. for future work in that area.

Deburring of machined metal parts, such asgears, isa costly and labor"intensive process withassocia.tedquality, consistency and health risks. Itis a particular problem and a major cost driver forgears that are considered aerospace- or precision-grade (AGMA Class 12 and above).

Wherever possible, gears are deburred byusing simple mechanical equipment that is com-merciaUy available ..However, complex gears thathave specific chamfering requirements, as do pre-cision-grade gears, must currently be deburredmanually (Figure I),

Manual. deburring is not only a labor-intensiveprocess, but it is also. associated with the qualityproblems resulting from inconsistent manualoperation; healtb-, safety- and environmental-related issues; and high indirect costs as 8 resultof 8 high turnover of operators.

Automation of the debwring process can sig-nificaatly reduce cost, improve productivity,andimprove the quality and consistency of deburred'edges. This situation has led roan industry-widedemand to replace manual deburring with 8. moreefficient, reliable, and safer automated deburringsystem. The INFAC Robotic AutomatedDeburring research project. was initiated toaddress that need. It is a joint technical effortbeing conducted by fiT Research Institute, UnitedTechnologies Sikorsky Aircra.ft, and UnitedTechnologies Research Center.

Using the robotic automated debw::riog systemdeveloped under. the project, the INFAC team hassuccessfully deburred 8. number of aerospacegears, ranging in size from 3 inches to 30 inches'in diameteJ:. The system uses commercially avail-able, off-the-shelf hardware, includjng a six-axis

progmmmable robot, a programmable indextable, various types of deburring heads, and sev-eral different types of cutters.

In addition to cost savings that, in some eases,exceeded 90 percent and substantial qualityimprovements, such an automated deburring system

can. eliminate potentially unsafe and relativelyunhealthy working conditions. The system enablescomputer control and automation 10 be applied mthe deburring processes, bringing it at last into thedomain of computer integrated manufacturing.

BackgroundMachinimg processes, such as milling, drilling,

turning, bobbing, or other gear tooth ,cutting oper-ations, create burrs on the edges of metalpwrtswhen the cutting tool pushes material over anedge rnther than. cutting cleanly through the mate~rial. The size. sbape and characteristics of theresulting burrs depend upon a number of processfactors, such as tool material and i.ts har1lness,tool. sharpness, tool. geometry, cutting forces, due-tili.ty of the material being machined,. the speedarid feed of the cutting tool, and the depth of cut.A subsequent deburring operati.on isgenera11yrequired after those machining processes toremove loose burrs from the machined edge andto apply a chamfer to remove the sharp comers.In addition to the removal of loose burrs, thedeburring of the edge produces benefits, such asthe removal of sharp edges, increasing the ease o.fassembly, prevention of edge chipping or break-age, and improvement of air flow over the edge ofrotating parts, Removing sharp edges by debur-ring and chamfering also eliminates the possibili-

Fig. 1 ManllJll ddunin,gis labo~inU1lSi¥t. im;ollS.is·,(wand ,exp,nsi,e ..

MichaeIIIN8o'I'aw,a)ahas IIfO.~ IhQJ! 15years ofexperience ill 1If(lll.ufoc.tur.ing ,c-Ol1!l1!ercio.l-quality(LIla

aero.rPfJce.quality (grormdtooth) gear~ Qf almost alltypes. He has beenwo-'"killgas a senior engineer for lITReseard» Jrutitute/or ,morethanfive years and hasbeen aCriw.lyengagedlnvarious research pmjec.iS toimprove the quality andreduce the cost ofmamifQC~luring gew~, primarily foraerospace app1tcalloru.Nanlawola hlU ,0 degree inmechanical and aerwpaceengineering from IllinoisImlituteofTechnology,Chicago. He is a registeredprofessional engineer (p.E.)in the stale oflllinoi.J. He .ualso a certified manufactur-ing engineer (CMlgE) 'Withthe Society ofManufacturing Engineer1.

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Fig•.2-The Si"glt·Ax~CompUtulJ IltlUJ (SACH)

from AnD debuTring a. double helkal piaw.n.

life.Aerospace gears are usually precision ground to

AGMA quality 12 to 14. For such gears, in addi-tion to therequired de burring of gear teeth, thereare also, very specific chamfering requiremeors,SUtchasedge waviness and chamfer depth variabil-ity, surface finish, and the absence of under- orlover-tempering of the debum:d edges. Chamferwidth must also be uniform along the entire geartooth profile, as well as the root radius.

As mentioned earlier, wherever feasible, gearsare deburred using relatively simple mechanicalequipment However, those machines Iack thedexrerity and the programmability that are essen-tial to meet the specific cbamfering needs of theusually complex-shaped aerospace gears. III gen-eral" such machines do a satisfactory job debur-ring and chamfering spur gears and helical. gearswith smaller helix angles, p.rovided that the shapeand size of the gear do Dot create an accessibilityproblem. for the cutter, grinding wheel or grindingdisc. In some cases, it is also feasible to deburrand ,chamfer helical gears with higher helixangles and spiral bevel gears using such mechan-ical equipment However, to' meet the specificchamfering requirements, the semi-chamferedgear need to be touched up manually after theautomated operation. further, secondary brushingoperations are sometimes required to meet otherchamfer requirements, such as edge radiusing andsurface roughness, for those reasons, most aero-space gears are currently de burred and chamferedmanlla,lIy.

In a typical manual deburring and chamferingoperation, a. skilled operator removes matenalwith a rotary fileor a rotary grinding wheel ordisc attached to a. hand-held air driven or electri-caUy powered tool.

Manual debarring is tedious, boring, liiiboriaus.very time conswning and thus vel)' expensive,Manual deburring alse produces inconsistent andoften unsatisfactory results. Furthermore, manual

deburring is ergonomically and environmentallyundesirable, causing safety hazards, such as minorcuts, splinters, burns, bruises, and eye injuries. Itmay also cause long-term health. hazerds.sueh asarthritis. carps] tunnel syndrome, and illnessesassociated with dust inhalation. Oilier disadvan-tages of manual deburring include a high rate ofrework or scrap, additional inspection. costs, lowerproductivity" high worker turnover, and ltigllt train-ing cost to train new workers.

In a manual. deburring situation, finishiag oper-ations can represent up to 20 percent of total pro-duction costs. Therefore, automating the deburringprocess can. result in significant. 'cost reduction. [pro-

ductivity impmvement, and quality enhancementof deburred edges.

Robots are emerging as an econemieal solutionto automating many types of processes.Historically. when robots were applied to less pre-cisefinishing operations like brushing, they bavebeen shown to achieve more than a SOl percentreduction in processing times. Still, until. recentimprovemeats were developed, their accuracy hasbeen prohibitively poor for use in the precisiondebuning of contoured edges. Those technologicalimprovements inc/.l.ldethe in1lroduction of precisionrobots having better than ± O.OO4-inch repeatabilityand. the development of deburring heads like theCADET (Chamfering and Debarring End of AnnTool) and other commercially available force-eon-trol:ledheads,

The strategy behind a force-colltrolled head isto Use an industrial robot asa coarse positioningdevice, waichearries and orients the force-con-trolled bead to the appropriate part edge to bedeburred and chamfered ..Fine motion capabilitjesof'the force-controlled head allow thetool to trackedges based on force control, so that edge con-tours can be traversed and precise chamfer depthsmaintained in spite of unknown process variablesincluding the robot's positional inaccuracies,deviations in part geometry (or contour), and fix.-turing errors. Foree contra] has the added benefitwith respect to gears of reducinglhe potential forgrinding bum.

Robot SelectionRobots are available in different types and sizes.

Most robots can be categorized into one of a fewbasic groups such as single-axis, mu1ti,-axis,SCARA (selective compliance assembly robotanns), Cartesian, cylindrical,. etc. A minimum of sixaxes of movement is necessary to arbitrarily posi-tion and orient a. tool and is therefore required todeburr the more complicated geometries of gearssuch as spiral. bevels. The six-axis robot also makes

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it easier to manipulatelhe cutting tool to reach dif-ficult access areas, such as narrow grooves, tilevery limited space between two gear faces or anadjacent shoulder and tile gear face. As far as therobots are concerned, gear tooth deburring is a pre-cision operation, Therefore, a robot selected fordeburring preferably should have better than± 0.003-inch repeatability Furthermore, to mini-mize deflection, the robot ann should be morerigid than is required for most other eperations.Stated another way. the end-of-arm payload capac-ity of the robot should be large enough that,llIlderthe weight ef the end effector, debwring bead, andcutting tool, the ·deflectian of the arm will be min-imal. A robot selected for the purpose of debumngshould have its rated payload capacity preferablyat least 50 percent higher than the maximum antic-ipated load al Ihe end of the ann.

Considering the above factors, an ABB FlexibleAutomation robot, model No, [RB 2400/10, wasselected. for this study. The robot has a new S4 con-troUer w:ilhlhe Rapid™ programming language.This robot's end-of-arm payload capacity is W kg,or approximatery 22 lbs., and the reach of the armis 59 inches.

Deburrtng ·HeBd SelectionWhile the robot itself is responsible far coarse

positioning and orientation of the deburring tools,a specialized deburring head is needed to performthe actualprocessing, The deburring head func-tions milch like ,aw:risl. at the end of the robot rum.The heads have either pneumatic compliance orelectromagnetic force eontrel that allows the cutterto "noat"011 the pan edg c and control the materiallremoval mt. Th c bead is thus able to .adj\1St toprocess variations. including robot positionalerrors, part errors, tixturingerrors and burr size toperform uniform material removaland minimizecutter loading, cutter wear and part burning.

Many deburri.ng heads are available, and a largenumber were investigated Three in particularyielded interesting results and will be discussedhere. They includedl.hc Navy-developed CADETbead. a single-axiscompliant head (SA:CH) tramABBflexible Automation, and a two-axis compli-ant head (TACH) from ABH. The SACH system iscapable of being fittedwilh two different types ofcylinders, one low-speed option (15,000 rpm to40,000 rpm) and one high-speed option (45,000rpm to 85,000 rpm). The low-speed option wasused for deburnng pillions, while the high-speedoption was applied to gears. Another option con-sidered early in the pn>ject. was a high-speed, axi-ally ccmpliant device from ATI IadustrialAutomati.on. However, it was eliminated in pre.

liminary assessments based on unacceptable Sill-

face finish and tool life.The CADET head is not commercially avail-

able, and only a few prototypes exist, It hasclosed loop force control, making it easier to pro-gram since the trajectory points do not need to beas exactly specified. It also offers the best controlover the material removal process because itoperates in. a closed forQ:-:feedback loop. Theother two heads investigated are commerciallyavailable, otf~the-shelf equipment and thereforeless expensive to acquire, operate and maintain.The commercial heads also provide more optionsin cutter selection and allew operation at higherspeeds than the CADET.

The CADET is a dual-axis force control headthat uses a 5,000 rpm to 6,000 rpm electric spindlemounted w.ithim a force transducer assembly. Theforce transducer assembly is mounted within atwo-axis gimbalthat penn:its movement ohlle cut-ter tip in a direction perpendicular to the spindleaxis over a 5-sq\la.re centimeter work area. Thegimbal ISinstrumented with position traasdueers intwo axes, which enable measurement of cutter tipposition. A unique dual-axis direct dri.ve aeuiator,mounted above the transducer assembly and linkedto the cutting process through the two-axis gimbal,provides the power for the cutting force control.The entire design is balancedgmvitationally anddynamically in any orientation to minimize sensi-tivity to forces other than the cutting forces.

The CADET is controlled using a high-band-width, high-accuracy force servo loop. Finemotion capabilities of the eADET allow the cuttertonack edges and control the material removalprecess based on force feedback. 0 that edge con-tours can be traversed and precise chamfer depthsmaintained in spite of process variations.

The SACH and TACH that were evaluated areproduced by ABB flexible Automation of NewBerlin, Wisconsin. The range of motion for theSACH is ± 3 ..6". Pneumatic grinders of the user'spreference can be mounted in the head, includingreciprocating tiling tools or spindles of variousspeeds and configurations. In the present study,the SACH was fitted with various speed pneu-matic spindles ([5,000 rpm to 85,000 rpm) andused in conjunction with carbide cutlers or grind-ing discs. It is shown in Figure 2. TIle TACH has± 4mm of two-ax Is radial pneumatic comphaaceand incorporates a 40,000 rpm or 85,000 rpmpneumatic grinder.

Cutting Too~Sel.ec:tlonThe flllal component in the automated debur-

ring system, after the robot and the deburringwww.powe ••r.nsmluIOfl.com.· ..... w.gu rt echnology.com • GEAR TECHNOLOGY' JAN,UARY/F·EBRUARY 2001 .21

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head. is the actual cutting too] that physicallyremoves the brun fr-omthe gears and applies thechamfers. A variety of cutting tools, were investi-gated, including:• 2-inch RexCuil'M disc cutter,• I-inch RexCut™ disc cutter,.' l-inch CBN (cubic boronrtitride) disc cutter,•.31[6·i.nch cylindrical caibide cutter, and• 90" conical cutter (carbide and CBN).

Various combinations of debturing heads andcutters were tested on several different gears, and anumber of output parameters were observed. Theyincluded smface finish. chamfer uniformity, blend-ing, cutter tife, and overall. quality of the process,The results and observations for those tests are sum-marized in Table I, In it, each row represents one oftb.especific gears that were investigated. Each col-wnn represents one of the ,cutting tools used. WithinIfle body oflfle table, for each gear/cutter combina.-tion, an. assessment is listed as to whetaer that toolcould be used! withlhat gear or not, and if so"whichhead was utilized and what results were achieved.Successful combinations, demonstrating feasibilityof the automated debuning process, are indicated inthe table via shading.

As can. be seen in Table I, not all gear/cuttercombinations proved to be successful. The cuttermustaocess tIiIe gear tootlt profile without bittingadjacent features. It mlilSt also 'have tIiIe required

material removal capabilities and wear properties,and it must produce an acceptable surface finish. Alubricant, Aculube TM, was used in most of the cut-ting trials. It was found to improve surface finishand ex.tend the ~ife of the cutter. The eonelusionfrom. this set of tests is that. the cutters. more thantlte comptiant heads that carry th.em, determine thesuocess or failure of tIiIeprocessing procedures,

Excellent results have thus f.ar been achievedwith O.040-inch thick grinding discs of theRexCut™ product, The cutters are the same asthosecurrentiyused in the industry for gear fin-ishing using non-robotic equipment. They areaggressive and :lit wen into small root radii. Theyproduce very good! surface finish and uniformdlllmfers. The larger diameter RexCut™ products:{2-incbdiameter or greater) have sufficient life andfit within the features of many oftlile more complexparts. Using th_ cutters wi.th a compliant head andiii robotic positioning device greatly enhanced theirusefulness, Unilike most machines being used CW'-

rently for gear deburring,the robot pennits optimalorientation and positioning of the cutters for eachfeature being processed ..The oomplJialll heads pro-vide force control ,toprotect the gears from grindingbum, to extend. cutter life and to adapt to inherentpositional errors of 3. dexterous robot

Parts like the double helical bull gear do notpenm"t the use of those discs due to interference

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with adjacent features. Luckily, carbidec:utterswere shown to be successful for the gears,

The CBN (cubic boron nitride) discs underinvestigatlon, while not suffering from the clltterlife problems of die lItexC-lIu™ discs •.do produce a.rougher (yet most likely acceptable) surface 6n~ish. and some cutter loading and chatter wereobserved. Future work should develop the processparameters for improving the deburring processwith the CBN cutters ..

Path Prog,ramminglnadditiOD to oomponent. selection, the program-

ming of motiollSis an essential step intbe develop-mem of an etIectiv·e automated deburring system.Since the INFAC .system is robot-based. a. robotic~ of path programming algorithm was used.

Figure 3 illustrates the typical nomenclatureused in pr·ogrammi.ng most of the gear paths forthis study. Each tooth. edge--that is,theobtuseedge and the acute edgc---w.as programmed usingone or two points at the root (either a single pRMor both pRMO and pRMA)!, a point lI.earthe rootbut Oil the tooth profile (pEAPO and pEAPA),apoint. at the midpoint. of the profile (pMAPO andpMAPA),. a point at the outer end of the pJlOfile(pSAPO and pSAIPA) and one or two points at thenose of the gear (either a single pNOS or both apNOSO and pNOSA).

Those points were programmed using the: teachpendant. by first finding an orientation for thehead/clItter that is accessible to all. points anatooth side (acute or ebtuse). Next, each point isjogged to and taught. If deburring is being per-formed wi.th a ,carbide clItter, then 'cutter abrasionis not an. issue and each point is programmed int.othe edge (depressing the compliance) by 1 mm to2 mm, Thus •. when the program. is executed. thecompliance of the bead sbou:ld be depressed. to iii

depth of 1 mm to 2 mmthriOughout the cut. In thecase of an abradable cutter liike the RexCut™wheels, the cutting depth bias is addressed IJsingthe robot programming language's RelTool func-tion. whicb is used to permit program offsets inthe direction. of wear. In this case, the points aretaught by jogging the robot t.o a position. justtoucbing the edge. The compliance depth pro-grammed wing the RelToolfunction then drtvesthe disc into the edge (against the compliance ) inthe compliance dllection of the tool (bead) coer-dinatesystem.

The cutter orientation was chosen to be rough-ly peqx:n:diclliar to the bisector of the edge at themidpoint of the tooth profile, i.e. the edge normal.However, for a helical. 01' spiral bevelgear tooth,that means tile acute profilegeneratly requires a

different cutter orientation than. does the obtuseprofile. That is wby cmrently available non-robot-ic debarring machines with fixed euner orienta-tion cannot produce a un:iform chamfer on bothsides of such gear teeth. It would be preferable to

reorient the cutter in the root so tha:tthe acute sideand the obtuse side bath have their owaoptimumorientations and there is one continuous cut.Unfort\lnately, early trials showed that theincrease in robot dynamics associated wi.th reori-enting me robot produoed divots in the gear teethedge. The ,efforts of this study have, therefore,focused on programming timjectories tDat roain~taineda constant bead/clltter ori.ellta:tiOIllthrough.~out the cut. per side. A natural 'consequence of notcbanging the orientation during the cut is thatthen:: wiU be a region of each tooth edge where ablend from one 'cut to the next must take place(usually in the root).

It. may be possible to develop 8. means 'of reori-enting with minimal dynamics. Approaches, mightinclude adjusting the maxi.mum permissible reori-entation speed or playing w:iththe zone data (bothposition. and orientation). Also, one must use caretha:t the tool center point (TCP) is .accuratelydefined when making reorientations while cutting.

It is important in. programming with a rcbottoallow for both static and dynamic robot error infixtwing, cutter, part, and other process 'errors.Thus,. the programmer is always thinking aboutthe worst case positional errors and aUotting clear-ance for such errors. For example, in progm.m~ming a start point between two teeth, one shollld[~ve suffici.ent room. between th ~cutter and adja-cent features to a.cc01.lDtFor possible processerrors. With modem robots. thiSlypicaHy requiresa. minimum clearance of 0.03 inches.

One should also take advantage of inherentdegrees of freedom inthe system to allow roomfor error. For example, in programming for flankmilling cutting with. a. cyliodri.ca:J c-utter•.the three

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of approximately three-quarters of W1 inch.Processing parameters that were found to work:effectively are summarized in Table 2. In that I1Ihle,the compliance pressure is measured dose to, thedecurring head. The Jr, yand z Euler angles give theorientation of the tool coordinate system willi respectto the robot base 'coordinates.

After a manual debarring operation" the bullgear had an :incomsistent :flnish and many divots.After processing with the automated deburring sys-tem,lheedges were smooth and uniformly cham-fered. Time li.pe1It to deburr this gear manuaUy wasapproximately 12 hours, Time to deburr using theautomated system was approximately two hours, ora savings of 10 hours. about 80 percent,

Example: Double Helical PinionAnother chaUenging gear to deburr was the

pinion that drives the bull gear in the exampleabove. That pinion contains two helical surfaces,approxi,mately 2.5 inche . in diameter, also Ii 10-diarnetral pitch with a 35° helix angle and a three-quarter inch gap. There is also an. integra] lo.inc.bdiameter spur gear on the same shaft.

The double helical pinion was processed usingthe 31] 6-inch carbide cutter. The burrs were not anobstruction to the process and a. uniform chamferwas produced in spite of them. Time to process thegear was reduced from [50 minutes for manualoperation to' 15 minutes :for automated operation.

Chamfering Result~Another issue of interest is ,chamfering quality

and uniformity ..The automated deburring systemhas been applied to different types of aerospacegears including:.• lO-dia:metral pitch spur gears,• 35° and 45° helical gears,• 35° double helical pinions and gears, and• 4- and 5-diametral pitch. spiral bevel gears andpinions with 30° and 35° spiral8I\gles.

Figure 4 shows data on the results of cuttingsome of the more challenging gears and pinions,The plot shows the average, maximwn and mini-mum chamfer widths measured for an teeth ..Because the maximum and minimum chamferwidth did mot exceed the typical ± 0.0 Io inch tol-erances and the surface finish was good, theprocess was deemed successful,

Admjttedly, the acute edge came out smallerthan the obtuse edge for several of the gears ..Thegoal of tile testing was not to produce the correctchamfer width so much as to achieve acceptablecbamfer width lltliformi.ty and surface finish,Oneethe uniformity is achieved on each side, thechamfer widths can be matched by changing thenumber of passes across the acute or obtuse edge

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degrees of freedom for positional errors areaccommodated as follows:• Brrorsalong the axis of the cutter are accomrno-dated by symmetry along the axis of the cutter.• Errors normal to the edge are accommodatedtltrough. compliancein the head.• Errors .along the tangent to the edge are accom-modated by the fact that they are aligned with thedirection of feed.

In programming the disc cutter:• Errors tangent to tbe disc at the point of 'contactare accommodated by symmetry at this point.• Radial errors are accommodated by compliancein the head.• Errors perpendicular to those are accommodated bythe fact thatlhey are aligned with the feed direction.

It was found that a. better blendat the rootbetween the acute and obtuse sides of the toothcould be achieved with a I~yered approach. Thatcould be done, for example, by starting with a cut-ting pass on the acute side of each gear tooth. then apass on. the obtuse side of each tooth, then a finalfmishing pass on the acute side. Also very importantto achieving a good blend is that the chamfer anglesfrom the acute and obtuse passes must match asmilch as possible over the blending region.

Selectively cutting the acute and obtuse edgeshas the added benefit of permitting the operator toincorporate that selectivity into the final operatorprogram. Thus, the program could be made toallow the operator to selectively choose to makeanother pass on the acute or obtuse side, depend-ing on which looked as though it needed anotherpass. Keep in mind, though, that switching backand forth is the best way to accomplish a smoothblend. Making too many passes on one side with-out finishing with iii. final pass on the other sidecan leave a noticeable divot at the start point.Fortunately. the deeper the chamfer is. the less thechamfer opens per pass because the force is pro-portional to the area of the cut

Example: Doub e Helical BuD Geail'One of the most chalJellgillg oflhe gears tested in

this investigation was a 30-inch diameter. 1(kIiame-tral pitch, double helical bull gear. That particulargear has two helical gear surfaces, separated by a.gap

or by adjusting other parameters like the cuttingforce or feed rate. Chamfer Width of Examplelest Gears

0.06

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Futur,e WorkThe results presented here represent interim

findings of an ongoing project at INfAC. theInstrumented Factory for Gears. One of the goalsof this initial part of the project was to assess thefeasibility of developingan automated deburringsystem for aerospace gears. To that extent, thisphase has beet! considered successful. The feasi-bility of the automated system was demonstratedby deburring different sizes (from 3-incb to 30·inch diameters) of spur. helical, double helical andspiral bevel. gears and pillions. For this purpose, asix-axis robot, a programmable indexing table andcommercially available deburriog heads were uti-lized .. Such a. simple system was more than ade-quate to conduct the feasibility study. However,for such a system to operate more efficiently in aproduction setting, a number of improvements inareas like programming, fixturing, cutters and cut-ting parameters may be necessary. A brief list ofpotential areas for future work follows.

Offline p.rogramming. Programming the robotoffline caa increase the robot's productive timeand also reduce development. or prove-out timeconsiderably. since any unexpected problem infixniring, path programming., or operating therobot can be detected and resolved before therobot is loaded with the desired program.

Too.1 weal' co.mpensation.. To maintain consis-tency in the width of the chamfer. it is necessary(hat the cutting 1001 diameter remains constant.That is 110t a problem wilth cylindrical cutters.However, when very thin, fiber-bonded RexCut™discs are used, an appreciable amount of tool wearis experienced. That tool wear must be compen-sated for, and that can be accomplished by a sim-pl.e touch probe.

Application of CBN cutters. Another approachto handle the tool wear problem is to use longerCBN-coate4 disc cutters. ln the feasibility phase.such cutters were used on a limited basis. Moredevelopment is required in that area.

Brushing operations. In the case of gearsbeing deburred afte:rhardening and grinding,brushing is often necessary to remove minor sec-ondary edges and also to improve surface finish.[0 such cases, brushing is normally performedmanually. That expensive manual brushing couldalso be elimioated by integrating brushing withrobotic deburring and chamfering.

Automatic tool changes. To accommodate dif-ferent types and sizes of gears, it may be neces-sary to use various deburring heads and cutters. In

www.powerl·rensmission.com • www.geertechn%gy.com • GEAR TECHNOLOGY' JANUAAY/FES.R'UAAY 2001 25

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such cases, setup time or changeover time call bereduced and the robot's actual productive timeincreased by integrating some sort of automatedtool changing system. A nurn ber of manufacturershave developed such systems. and they could beintegrated i.nto the robotic deburring system withlittle trouble.

CouclusiodSThe following conclusions call be summarized

Cor this project, based upon work performed todate:• Robotic automated deburring of aerospace gearsis feasible and has been demonstrated on spur,helical, double helical, and spira.1bevel gears from3 inches to 30 inches in diameter.• Both deburring and chamfering of aerospacegears can be achieved with. an automated system.• A successful automated deburring system forgears can be constructed from commerciallyavailable. off-the-shelf components.• Quality and consistency of deburred and cham-fered edges were increased in gears processedwith the automated system, as compared witbmanually processed gears.• Careful cutter selection is essential to achievinghigh-quality automated deburring,• Process time for automated deburring was often asmuch as 90 percent shorter than manual deburring,• Cost savings achieved through automated debur-ring, primarily through time savings and scrapreduction, is estimated at an average of 65 per-cent, as compared with manual debarring, 0

Fig..4--Chamfer width ,amJc01U}~leru:~yfrom t(JOlh totootb for 'various ttd gearsandprocesses. -

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