02 I 2004

Along with the continuous Ceramics Mee-ting Point display, facilities are available forholding informational and educationalevents of all sorts:

Fraunhofer meets NASA: As a contribution to thenationwide “Technology Day” in the “Year of Technolo-gy,” Fraunhofer IKTS held a seminar on June 18, 2004on adaptive structures. The 60 guests were introducedto one of the Fraunhofer-Gesellschaft’s 12 leading-edgeinnovations.

W. K. Wilkie and R. G. Bryant, leading developers atNASA Langley Research Center (R.G. Bryant, middle,with Dr. Schönecker from IKTS), reported on the originsand developmental results of “Macro Fiber Technology,”which arose to provide a solution for active control oflightweight structures using piezocomposites.

The demonstrationcenter has takenshape at all locationsof the seven partici-pating Institutes.At the Dresden loca-tion, »AdvanCer«

joint developments are already on display.News from IZD: On June 3, 2004 a ceremo-ny was held to celebrate completion ofexpansion work at FEP, IFAM-IPW, IWS andIKTS. Visit Dresden and visit »AdvanCer«!

»Advancer«Contents in Dresden

Newsletter

The name »AdvanCer« conveys a sense of foresight, progress and benefit.Ceramics manufacturers and users find in it their »Advanced Ceramics« - materialsholding great promise for the future. AdvanCer presents innovative applications forhigh-performance ceramics: systems solutions with »Ceramics inside« for todayand tomorrow.

page 2Featured over-view: fine fin-ishing of high-performanceceramics

page 32004 tradeshow highlights:Materialica,Euromold andEuroblech

page 4High-performan-ce ceramics: success stories

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Dresden is worth visiting anytime. Now that the renova-tion of the Frauenkirche church has been completed,another highlight has been added to the skyline of theold city centre.

Components made of high-performanceceramics have been increasingly used inengine manufacturing, mechanical andplant engineering and medical engineeringover the last few years. The specific advan-tages of these materials are their outstan-ding strength and wear behavior, high-tem-perature and structural stability and chemi-cal inertness. High-performance ceramicmaterials are already being mass-producedfor rolling and sliding bearings, brake disksin vehicles and medical implants. The highcost of ceramic components can be tracedback to complex and time-consuming post-machining, which is currently done byusing fine machining processes such asgrinding, honing, polishing and lapping.Current efforts of the AdvanCer team inthe area of fine machining are aimed atdeveloping or optimizing machining tech-nologies to expand the application field forhigh-performance ceramics.

Fine machiningGrinding, honing and lapping are the pro-cesses used for fine machining of high-per-formance ceramics. Because of their highhardness and wear resistance, these materi-als can only be machined using tools withdiamond or boron carbide grains. For gene-ration or finishing of functional surfaces oncomponents, a variety of technologies areemployed. Besides surface, cylindrical andprofile grinding of ceramic materials, surfacegrinding with planetary heads, double-disklapping, ultrasonically assisted grinding,abrasive-flow machining and honing aresubjects of R&D projects currently under-way at AdvanCer.

Surface grinding with planetary headsand double-disk lappingSurface grinding using planetary heads anddouble-disk lapping result in highly accura-te coplanar functional surfaces. These pro-cesses possess the same kinematics but dif-fer in the type of tool they use. For surfacegrinding with planetary heads, diamondgrains are fixed on the grinding wheel; forlapping, loose grains are used. Boron carbi-de grains are used for lapping to make theprocess more economical. In these processes, ceramic workpieces areplaced in toothed wheels and simultane-ously passed between the faces of anupper and a lower grinding or lappingwheel. The resultant functional surfaces arecharacterized by an extremely high surfacequality. Whereas lapped surfaces exhibit thecrater structures typical for this process,surfaces ground using planetary motionhave randomly oriented scratches formingcrisscross patterns. Both processes are usedin the industrial production of a variety ofsealing disks and regulating wheels, rollingbearings and tools. Double-disk lapping ofsilicon nitride produced Ra roughness val-ues on the scale of 0.05 µm. Similar levelswere achieved with surface grinding usingplanetary heads and bound abrasive grains.

Ultrasonically assisted grindingIn ultrasonically assisted grinding, a longitu-dinal oscillating motion is superimposed onthe conventional grinding motion. The fre-quency of alternation is ca. 22 kHz; usuallyit is the tool that executes the motions. Thissuperimposition of ultrasonic oscillations onconventional grinding motions significantlyreduces the grinding forces, which are qua-sistationary over the duration of the machi-ning process and enable high machiningvolumes to be achieved. For ceramics, theadvantages of this process can be exploited

in the production of complex contours suchas those of drill holes, grooves, sphericalsurfaces and freeform surfaces. This pro-cess has already found its way into suchindustrial applications as the production ofmedical implants made of high-performan-ce ceramics.

Abrasive-flow machiningAbrasive-flow machining is used on compo-nents made of high-strength materials withinaccessible, complicated geometries toreplace productivity-hindering manualdeburring and polishing operations. Themachining effect is achieved by a polymerfluid in which abrasive particles are bound.

Boron carbide or diamond is used as thegrinding medium. The fluid is made tomove in alternating cycles over the contourof the workpiece. This motion, in combina-tion with the abrasion caused by the grin-ding media, leads to material detachment.Results depend on grain size, viscosity andcomposition of the grinding medium aswell as operating pressure and the numberof cycles. With abrasive-flow grinding, thesurfaces of ceramic components can bereproducibly and accurately formed. Inter-nal geometries benefit especially from theadvantages of this process, which is cur-rently being used for finishing nozzles withcomplex geometries and thread guidesmade of high-performance ceramics. Abra-sive-flow grinding of silicon nitride producedRa roughness values of less than 0.01 µm.

HoningLong-stroke internal cylindrical honing canbe used for machining of internal ceramiccomponents subjected to extreme tribologi-cal conditions. Surfaces with high degreesof contacting profiles can be producedusing this process. Honed surfaces exhibitcrisscross scratch patterns, which facilitatelubricant absorption and thereby result insurfaces with outstanding tribological pro-perties in sliding conditions. Long-strokeinternal cylindrical honing can be used toachieve high machining volumes and isthus more economical than internal cylin-drical grinding is. Thus far its potential forproducing internal contours has been utili-zed industrially in machining of ceramiccylinder barrels for high-performance engi-nes and in production of ceramic slidingbearing races.

Making life easier: Alumina washers for single-handlefaucets – mass-produced with high-tech finishing.

The author of this contribution, Dipl.-Ing. Tom Hühnsfrom IPK (right), presenting a ceramic cutting blade for acranial perforator at Materialica.

Featured overview:Fine finishing of high-performanceceramics (Part 1)

To experience the flexibility and performan-ce capabilities of the CT-Mini firsthand, visitAdvanCer at Materialica on September 28-30, 2004 in Munich. You will find us atStand 109 in Hall C1 (joint stand with TASK).We will also present at Euromold onDecember 1-4, 2004 at the Fraunhofer Alli-ance for Rapid Prototyping joint stand(Stands N112 to L115 in Hall 8).

Using results of investigations performed onthe tribological system consisting of a cera-mic, a lubricant and a sheet material, suita-ble drawing die and sheet materials wereselected for deep-drawing. Friction andwear in this system depend not only on thematerial pairs used but also on the surfacestructures and internal stress states of theactive surfaces created by machining.The service lifetime of ceramic drawing diesused in three stages was 100% greaterthan that of coated hardmetal drawing diesin application conditions during ironing ofsleeves made of CrNi steel sheet. Results offractography indicate potential for furtherimprovements in tool quality.Optimized tools guarantee:

• higher service capacities• lower forming forces• better product qualityIn shearing tests with a closed cutting curve(hole diameter: 8 mm), ceramic cuttingpunches produced a 10-20% improvementin amount of smooth cut and an improve-ment in surface quality over HSS and hard-metal cutting punches during punching ofsteel and nonferrous sheet metal. Hardme-tal tools are required for shearing high-strength sheet steel (TRIP, dual-phase orcomplex-phase steel). Here, research isaimed at optimizing hardness, strength andcutting geometry, as well as at developingsuitable lubricants and determining condi-tions in which a film of lubricant exists con-tinually in the gap between the punch andthe die.Visit AdvanCer at Euroblech on October26-30, 2004 in Hannover. At the jointFraunhofer stand (Stand G14 in Hall 11),you can meet representatives from IKTS,IPT, IWM and IZFP as well as from the ZEUSdemonstration centre.

Thread guides for the textile industry possess complexfunctional surfaces that need to meet demanding requi-rements.

Fiber composite investigated on the CT-Mini: Pixel edgelength = 5.55 µm; matrix material not shown on theright.

Ironing of sleeves made of CrNi steel sheet withdrawing dies made of Si3N4, �’-SiAlON, ZrO2(MgO),Al2O3/ZrO2, LPS-SiC and Al2O3.

Stemps of the manufactoring of cutting stamps of thetool materials zirconia, silicon nitride and a cementedcarbide

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For industrial applications, 3D X-ray compu-ter tomography has an advantage overother testing methods in that it deliversinformation about spatial relationships bet-ween internal structures of an objectwithout damaging the specimen or beinggeometry-dependant. Despite its uniquefeatures and undisputed advantages fordetecting internal defects and checkingassembly of complexly constructed parts,the 3D CT system is not yet being widelyused as an on-site analysis system in indu-strial environments, since many potentialusers are deterred by the high price of alarge stationary universal CT system.The CT-Mini, developed jointly by Fraunho-fer scientists and the company Procon, ful-fills all requirements of an industrial 3D X-ray computer tomography system.

The CT-Mini is delivered as a complete,ready-to-use compact system. After beingconnected to a power supply and to a localcomputer network, the CT-Mini must beadjusted once - then it is ready for use.Hardware and software were coordinatedto enable many important parameters to beoptimized automatically, making the systemextremely user-friendly.

2004 trade show highlights:CT-Mini at Materialica and Euromold

Ceramic forming tools atEuroblech

View of the CT-Mini system at Fraunhofer ERTZ.

Success stories: High-performance ceramics informing technology

Fraunhofer »AdvanCer« DemonstrationCenterBusiness OfficeDr. Tassilo MoritzWinterbergstraße 2801277 DresdenGermany

Telefon: +49 (0) 351/25 53-7 47Telefax: +49 (0) 351/25 53-6 00Mail: tassilo.moritz@ikts.fraunhofer.dewww.ikts.fraunhofer.de

Publication information

• Newsletter of the Fraunhofer Alliance for High-Performance Ceramics »AdvanCer« project – a joint effort of IKTS Dresden, IPK Berlin, IPT Aachen, ISC Würzburg, IWM Freiburg, IZFP Saarbrücken and LBF Darmstadt

• Published three times a year • Orders should be sent to: Business Office, Dr. Tassilo Moritz, Publisher’s liaison: Dr. Reinhard Lenk,

Editing manager: Dr. Udo Gerlach• Articles displaying authors’ names do not necessarily represent the views or opinions of the publisher• Reproductions or copies in whole or in part of this newsletter only by express written permission of

publisher and with reference to source

Whether in your car, PC or householdappliances, components made using cera-mic tools from BeaTec are probably part ofyour daily life. BeaTec GmbH, established in1999, has had great success in producingceramic forming tools, thanks in part toexperiences gained via the Fraunhofer-Gesellschaft. BeaTec tools are now beingused successfully in countless forming ope-rations for sheet, pipe and bulk materials.Continuous development, including coope-rative efforts with various Fraunhofer insti-tutes, has pushed BeaTec into a leadingmarket position.Ceramic forming tools have the fundamen-tal advantage of possessing excellent tribo-logical properties. They offer lower frictio-nal forces and better wear resistance thanconventional tool materials such as steel orhardmetals do. These advantages are parti-cularly useful for the increasingly commonapplication of shaping parts made of hard-to-form multiphase and stainless steels. Forinstance, deep-drawing of austenitic sheetmaterials using a ceramic tool resulted in asignificantly lower tendency for welding,and thereby a better product surface. Insome cases, ceramic tools eliminated theneed for chlorine-containing oils or reducedthe need for lubricants – important results

in the light of ever-stricter environmentalregulations. Application-based knowledge was used todevelop appropriate tool designs to addressthe problem of high mechanical loadsgenerated in the forming process. Usingthis know-how, BeaTec produces customi-zed ready-to-install ceramic tools: Thesetools can usually just be installed in place ofthe old tools, with no changes to the pro-cess or the machine being necessary.With respect to the cost-benefit ratio, pre-vious experience has shown that for cera-mic tools in comparison with hardmetaltools, slightly higher procurement costs aremore than compensated for by a longerservice lifetime and higher product quality.This especially applies to tools for mass pro-duction, in which a long service lifetimeand the ability to make use of new techno-logical possibilities play major roles in ensu-ring competitiveness.

When it comes to making ceramics, manu-facturers are no longer thinking small.Advances in shaping technologies andmaterial quality have increasingly madeproduction of large parts possible. Hardmachining of these parts now poses newproblems: Not only must the respectivemachines be optimized but also the machi-ning processes themselves must sometimesbe optimized. In grinding of ceramic rollingtools, for example, despite the fact thatparts have relatively large dimensions, theystill must meet close shape tolerances andhigh standards for surface quality.Recently hard machining of rollers wasoptimized for the manufacture of highlyalloyed high-grade steel wire.Grinding must produce high-quality rollerswithout compromising surface quality. At

TE-KO-WE, a new grinding process called“stepwise grinding” has been developed toaccomplish this.Profiling is no longer done using a profiledtool in which the entire profile of the grin-ding wheel is used at once; now sidewaysmotions are made along the part by a smal-ler tool to produce the desired profile. Thisresults in significantly less damage in near-surface regions of the workpiece and there-by allows the part‘s original materialstrength to be retained. An important sideeffect of the use of this grinding process isa considerable increase in service lifetimeand process reliability, which also resultsfrom the fact that cooling is facilitated onaccount of a smaller contact zone. Rollersmanufactured using this process are cur-rently being used by Böhler Edelstahl.

Dr.-Ing. Andreas Wagemann,CEO of BeaTec GmbH.

Joachim Kozlowski,CEO of TE-KO-WE GmbH.

Production of ceramicrolling tools

The successful example of ceramic rollers shows that con-tinuous user-oriented development of individual proces-ses creates great potential for optimization of ceramicmanufacturing processes - and ultimately for applicationof ceramics.

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