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Experimental investigation of tool wear in electroplated diamond wire sawing of silicon
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8th CIRP Conference on High Performance Cutting (HPC 2018) 8th 8th CIRP CIRP Conference Conference on on High High Performance Performance Cutting Cutting (HPC (HPC 2018) 2018) 8th CIRP Conference on High Performance Cutting (HPC 2018) Experimental investigation of tool wear in electroplated diamond
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wire Experimental investigation of tool wear in electroplated diamond wire Experimental investigation of tool wear in electroplated diamond wire Experimental investigationsawing of tool wear in electroplated diamond wire of silicon sawing of silicon 28th CIRP Design Conference, May 2018, Nantes, France sawing of silicon sawing a,* aof silicon a a Uygar Pala uussmaier a,* , Stefan S¨ a , Fredy Kustera , Konrad Wegenera Uygar Pala , Stefan S¨ ssmaier a,* a , Fredy Kustera , Konrad Wegenera Uygar Pala S¨ ssmaier Kuster Wegener a , Fredy a , Konrad a A new methodology to,, Stefan analyze the functional and physical of Institute Machine Tools and ETH Zurich, Leonhardstrasse 21, 8092 Zurich architecture Uygar Palaofofa,* Stefan S¨uuManufacturing, ssmaier , Fredy Kuster , Konrad Wegener Institute Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich Institute of Machine Tools and Manufacturing, Zurich, Leonhardstrasse 21, 8092 Zurich Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mailETH address: [email protected] Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 8092 Zurich identification existing products for an assembly oriented product 21,family Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mail address: [email protected] Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mail address: [email protected] a a a a
Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mail address: [email protected]
Paul Stief *, Jean-Yves Dantan, Alain Etienne, Ali Siadat
Abstract Abstract Abstract École Nationale Supérieure d’Arts et Métiers, Arts et Métiers ParisTech, LCFC EA 4495, 4 Rue Augustin Fresnel, Metz 57078, France Abstract Nowadays diamond wire sawing is used as the most efficient method for manufacturing of silicon wafers. However, experimental inNowadays diamond wirewire sawing used aswear the most efficientbased method for manufacturing of silicon wafers. However, investigation of diamond and is has process limitations and is expensive when conducted on a experimental wire saw. Due Nowadays diamond wire sawing isabrasive used as the most efficient method for manufacturing of silicon wafers. However, experimental investigation of diamond wire and abrasive wear has process based limitations and is expensive when conducted on a wire saw. Due Nowadays diamond wire sawing is used as the most efficient method for manufacturing of silicon wafers. However, experimental in*vestigation Tel.:wire +33 3and 87 it37abrasive 54 30; E-mail [email protected] toCorresponding high material consumption, is difficult identify andbased observe individual In this a novel of author. diamond weartoaddress: has process limitations and grains. is expensive whenstudy, conducted on experimental a wire saw. setup Due to high material consumption, it is difficult to identify and observe individual grains. In this study, a novel experimental setup vestigation of diamond wire and abrasive wear has process based limitations and is expensive when conducted on a wire saw. Due is proposed for rapid wear testing diamond wires, which can emulate realistic contact conditions considering to high material consumption, it is of difficult to identify and observe individual grains.grain-workpiece In this study, a novel experimental setup is proposed for chip rapid wear testing of diamond wires, can emulate realistic grain-workpiece conditions considering to high material consumption, itandis long difficult to identify andMoreover, observe individual grains. In this study, a novel experimental setup the undeformed thickness contact lengths.which the setup allows monitoring thecontact wear propagation of identiis proposed for rapid wear testing of diamond wires, which can emulate realistic grain-workpiece contact conditions considering the undeformed thickness and long contact lengths.which Moreover, the setup allows monitoring the wear propagation of identiis for chip rapid wear testing of diamond wires, canareemulate realistic grain-workpiece contact cal proposed abrasive grains throughout lifetime. The experimental validated through investigations on wires conditions used on a considering multi-wire the undeformed chip thickness and long contact lengths. results Moreover, the setup allows monitoring the wear propagation of identical lifetime. The experimental are validated investigations onwear wiresinpropagation used a multi-wire the undeformed chipthroughout thickness and long contact lengths. results Moreover, the setupthrough allows monitoring the of identiAbstract saw.abrasive Wire grains topography is analyzed applying a proprietary software application to characterize grain termson in cal abrasive grains throughout lifetime. The experimental results are validated through investigations on wear wires used on ofa change multi-wire saw. Wire topography is analyzed applying a proprietary software application to characterize grain wear in terms of change in cal abrasive grains throughout lifetime. The experimental results are validated through investigations on wires used on a multi-wire the abrasive protrusion, base area and volume. The influence wire weartooncharacterize cutting forces normal forces ofis change discussed. saw. Wire grain topography is analyzed applying a proprietary software ofapplication grainandwear in terms in the abrasive grain protrusion, base area and volume. The influence of wire wear on cutting forces and normal forces is discussed. saw. Wire topography is analyzed applying a proprietary software application to characterize grain wear in terms of change in In business the trend more product variety and unbroken. Dueand to this development, need of thetoday’s abrasive grain environment, protrusion, base area towards and volume. The influence of customization wire wear oniscutting forces normal forces isthe discussed. the abrasive grain protrusion, base area and volume. The influence of wire wear on cutting forces and normal forces is discussed. agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production c 2018 Published by by Elsevier Elsevier Ltd. © 2018 The The Authors. Authors. Published Ltd. c 2018 The Authors. Published by Elsevier Ltd. systems as well as tothechoose the optimal product matches, product analysis methods are8th needed. most on of the known methods Cutting aim to Peer-review under responsibility the International Scientific Committee of the CIRPIndeed, Conference High Performance c 2018 The Authors. Published by Elsevier Ltd. This is an open access article under theof CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of the International Scientific Committee of thehowever, 8th CIRPmay Conference on High Performance Cutting c 2018 The Authors. Published by Elsevier Ltd. analyze a product or one product family on the physical level. Different product families, differ largely in terms of the number and (HPC 2018). Peer-review under the responsibility of the International Scientific Scientific CommitteeCommittee of the 8thofCIRP Conference on Highon Performance Cutting Selection and peer-review under responsibility of the International the 8th CIRP Conference High Performance (HPC 2018). Peer-review under responsibility of the International Scientific the 8th CIRP Conference on High Performance Cutting nature of(HPC components. fact impedes an efficient comparison andCommittee choice of of appropriate product family combinations for the production Cutting 2018).the This (HPC 2018). Diamond wire, wear, wire sawing, Keywords: (HPC 2018). system. A new methodology is proposed to silicon, analyzewafer existing products in view of their functional and physical architecture. The aim is to cluster Diamond wire, wear, wire sawing, silicon, wafer Keywords: Keywords: Diamond wire, wear, wire sawing, silicon,families wafer these products in new assembly oriented product Keywords: Diamond wire, wear, wire sawing, silicon, wafer for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a1.functional analysis is performed. Moreover, a hybrid functional and physical architecture with graph grinding (HyFPAG)process is the output which depicts the saw kinematics technology and proIntroduction saw kinematics with grinding processdesigners. technology and pro1. Introduction similarity between product families by providing design support to both, production system planners and product An illustrative vides the possibility of monitoring the wear of identical saw kinematics with grinding process technology and pro1. Introduction vides thecase possibility of product monitoring wear ofcolumns identical kinematics with grinding processthetechnology and pro1. Introduction example of a nail-clipper is used to explain the proposed methodology. Ansaw industrial study two steering of diamond at on cutting speedsfamilies up the to of75m/s. vides the grains possibility of monitoring wear ofMoreover, identical Despite some attempts in kerfless technologies, wire diamond grains at cutting speeds up the to 75m/s. vides possibility of monitoring wear ofMoreover, identical Despite Presta some France attempts kerfless wire evaluation thyssenkrupp is thenincarried out totechnologies, give a first industrial ofthe the proposed approach. abrasive grain is investigated experiments on diamond grainswear at cutting speeds upthrough to 75m/s. Moreover, sawing is still most prominent technology to generate Despite sometheattempts in kerfless technologies, wire ©sawing 2017 The by B.V.technologies, abrasive grain is investigated experiments on diamond grainswear at cutting speeds upthrough to 75m/s. Moreover, is Authors. still most prominent technology to generate Despite somethePublished attempts inElsevier kerfless wire a multi-wire saw. The results from the WWGW setup are abrasive grain wear is investigated through experiments on wafers in semiconductor industry where 30% of the total sawing is under still the most prominent technology to of generate Peer-review responsibility of the scientific committee thetotal 28th CIRP Design grain Conference 2018. a multi-wire saw. results fromthrough the WWGW setup are abrasive wearThe is investigated experiments on wafers in industry where 30% of sawing is semiconductor still the most prominent technology to the generate
manufacturing cost is accounted by where sawing 30% [1]. Even wafers in semiconductor industry of thethough total manufacturing cost is accounted by where sawing 30% [1]. Even wafers in semiconductor industry of thethough total there have been extensive research efforts on wear of diamanufacturing cost is accounted by sawing [1]. Even though Keywords: Assembly; Design method; Family identification there have been extensive research efforts [1]. on wear diamanufacturing cost is accounted by sawing Even of though mond have tools been for different and materials, of there extensiveprocesses research efforts on wear wear of diamond have tools been for different and materials, of there extensiveprocesses research efforts on wear wear of diathe electroplated diamond processes wire is still fully understood. mond tools for different andnotmaterials, wear of the electroplated diamond processes wire is still fully understood. mond tools for different andnotmaterials, wear of the electroplated diamond wire is still not fully understood. electroplated diamond wire is still not fully understood. 1.theIntroduction Because of their advantages in cutting performance and Because of their advantages in cutting performance and workpiece quality over other technologies (i.e. Becausesurface of their advantages in bonding cutting performance and workpiece quality over other technologies (i.e. Because ofthetheir in bonding cutting performance and Due tosurface fastadvantages development in the domain used of resin bonding), electroplated wires are widely workpiece surface quality overdiamond other bonding technologies (i.e. resin bonding), electroplated diamond wires are widely used workpiece surface quality over other bonding technologies (i.e. communication and an ongoing trend of digitization and in brittle materialelectroplated sawing. Thediamond wires are composed of a steel resin bonding), wires are widely used in brittle material sawing. The wires are composed of a steel resin bonding), electroplated diamond wires are widely used digitalization, enterprises are facing important wire corematerial and manufacturing diamond grains that areare fixed on the surface by in brittle sawing. The wires composed of a steel wire core and diamond grains that are fixed on the surface by in brittle material sawing. The wires are composed of a steel challenges in diamond today’s market environments: a continuing depositing the filler metal (nickel or alloys) by wire core and grains that arenickel-cobalt fixed on the surface depositing the filler metal (nickel or nickel-cobalt alloys) by wire core and diamond grains that are fixed on the surface tendency reduction of product development times means oftowards electroplating. Typical core diametersalloys) are inand the depositing the filler metal (nickel or wire nickel-cobalt by means of product electroplating. Typical core diameters are in the depositing the filler metal (nickel or wire nickel-cobalt alloys) by shortened lifecycles. In addition, there is an of increasing range ofof60-140µm with typical abrasive grain sizes 8-25µm. means electroplating. Typical core wire diameters are in the range of 60-140µm with typical abrasive grain sizes of 8-25µm. means of electroplating. Typical core wire diameters are in the demand customization, beingabrasive at the same global range ofof 60-140µm with typical grain time sizes in of a8-25µm. range of 60-140µm with typicalall abrasive grain sizes This of 8-25µm. competition with competitors over the trend, The presented research introduces a world. fast characterizaTheispresented research introducesfrom a fast characterizawhich inducing the development macro to micro tionThe method for diamond wire wear and a software tool presented research introduces a fast characterizationThe method forindiamond wire and a tosoftware tool presented research introduces adue fast characterizamarkets, results diminished lotwear sizeswires. augmenting for the characterization of wire diamond The method tion method for diamond wear and a software tool for the characterization of diamond wires. The method tion method for diamond wire wear and a software tool product (high-volume to low-volume [1]. employs a novel-design experimental setupproduction) named ”Wire for the varieties characterization of diamond wires. The method employs a novel-design experimental setup named ”Wire for the characterization of diamond wires. The method To cope with this augmenting variety as which well to be able to Wrapped Wheel”experimental (WWGW) wire employs aGrinding novel-design setupasemulates named ”Wire Wrapped aGrinding Wheel”experimental (WWGW) which wire employs novel-design setup named ”Wire identify potentials in emulates the existing Wrappedpossible Grindingoptimization Wheel” (WWGW) which emulates wire Wrapped Grinding Wheel” (WWGW) which emulates wire production system, it is important to have a precise knowledge
withsaw. results obtained actual sawingsetup process. acompared multi-wire The resultswith fromthethe WWGW are withsaw. results obtained actual sawingsetup process. acompared multi-wire The resultswith fromthethe WWGW are compared with results obtained with the actual sawing process. compared with results obtained with the actual sawing process. A MATLAB based diamond wire analysis software (WAS) A MATLAB based diamond wire analysis software (WAS) is developed for based detailed investigation of wiressoftware in terms(WAS) of diA MATLAB diamond wire analysis is developed for based detailed investigation of wiressoftware in terms(WAS) of diA MATLAB diamond wire analysis amond geometry, size, protrusion, aspect ratio, is developed for detailed investigation of wires in density terms ofand diamond geometry, size, protrusion, aspect ratio, density is developed for detailed investigation of wires in terms ofand diof the product andprotrusion, characteristics manufactured and/or distribution. Inrange addition, the method provides framework amond geometry, size, aspect ratio, adensity and distribution. In addition, the method provides a framework amond geometry, size, protrusion, aspect ratio, density and assembled in this thiscomparison context,provides theofmain in for the characterization and diamond wires distribution. In system. addition,In the method achallenge framework for the characterization diamond wires distribution. addition, the comparison method provides a with framework modelling andIn analysis isand now not only toof single fromtheseveral manufacturers going beyond the specification for characterization and comparison ofcope diamond wires fromtheseveral manufacturers going beyondofproduct the specification for characterization and comparison diamond wires products, a limited product range or existing families, usuallyseveral provided by the manufacturers. profrom manufacturers going beyondThe thesoftware specification usually provided by the manufacturers. The software profrom several manufacturers going beyond the specification but alsoimages to be able to andan to Alicona compareThe products to define cesses developed with 3D Infinite Focus usually provided byanalyze the manufacturers. software processes images developed with an Alicona 3D Infinite Focus usually provided by the manufacturers. The software pronew product families. It can be observed that classical Microscope (IFM) and comply with ISO 1101.2004 [2] and cesses images developed with an Alicona 3D Infiniteexisting Focus Microscope (IFM) and comply with ISO 1101.2004 [2] and cesses images developed with an Alicona 3D Infinite Focus product families are[3]. regrouped in function of1101.2004 clients or features. ISO 5436-2.2001 imageISO processing algorithms Microscope (IFM) and Multiple comply with [2] and ISO 5436-2.2001 [3]. Multiple image processing algorithms Microscope (IFM) and comply with ISO 1101.2004 [2] and However, assembly oriented product families arelayer hardly to find. are employed to determine a wire reference and each ISO 5436-2.2001 [3]. Multiple image processing algorithms areOn employed to determine a wire reference layer and each ISO 5436-2.2001 [3]. Multiple image processing algorithms thelabeled product family level, products differ mainly two grainemployed is the comparison of wear states throughout are tofor determine a wire reference layer andineach grainemployed is labeledtofor the comparison of wear states throughout are determine a wire of reference layerand and(ii)each main (i)on the number the their characteristics: lifetime. the measurements, statistical analygrain is labeledBased for the comparison ofcomponents wear states throughout theiroflifetime. the measurements, statistical analygrain iscomponents labeledBased for (e.g. theoncomparison ofelectrical, wear states throughout type mechanical, electronical). sis is lifetime. conductedBased and aon stochastic-geometric modeling of diatheir the measurements, statistical analysisClassical is lifetime. conducted and aon stochastic-geometric modeling of diatheir Based the measurements, statistical analyconsidering mainly single products mond wiresmethodologies madeand possible. Wire surfaces are captured sis is conducted a stochastic-geometric modeling of with diamond wires madeand possible. Wire surfaces are captured with sis is conducted a stochastic-geometric modeling of diaor existing product families analyze the the solitary, imprinting method introduced by IWF [4,5] that allows mond wires already made possible. Wire surfaces are captured with the imprinting method introduced by IWF are [4,5] that allows mond wires made possible. Wire surfaces captured with product structuremethod on a physical level by (components in-situ sampling without disrupting the experimental setup. the imprinting introduced IWF [4,5]level) that which allows in-situ samplingmethod withoutintroduced disruptingbythe experimental setup. the imprinting IWF [4,5] that allows causes difficultieswithout regarding an efficient definition setup. and in-situ sampling disrupting the experimental in-situ sampling without disrupting the experimental setup. comparison of different product families. Addressing this
c© 2018 2212-8271 Published by Elsevier Ltd. Ltd. 2212-8271 2018 The TheAuthors. Authors. Published by Elsevier cunder 2212-8271 2018 The Authors. Published by Elsevier Ltd. Peer-review the of the Scientific Committee of the 8th CIRP Conference on High Performance Cutting (HPC 2018). copen 2212-8271 2018access Theresponsibility Authors. Published by Ltd. This is an article under theInternational CCElsevier BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of the International Scientific Committee of the 8th CIRP Conference on High Performance Cutting (HPC 2018). c 2212-8271 2018 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the International Scientific of the 8th Conference Cutting on High(HPC Performance Peer-review under the responsibility of the International Scientific Committee of the Committee 8th CIRP Conference onCIRP High Performance 2018). Cutting 2212-8271 © 2017 The Authors. Published by Elsevier B.V. Peer-review under the responsibility of the International Scientific Committee of the 8th CIRP Conference on High Performance Cutting (HPC 2018). (HPC 2018). Peer-review under responsibility of the scientific committee of the 28th CIRP Design Conference 2018. 10.1016/j.procir.2018.09.038
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2. State of the Art The causal chain of process input - wear - process output is currently not prioritized by researchers, comparably little effort has been documented. Most of the work published focuses on the influence of wear on the process outputs. Three major wear mechanisms have been observed: blunting, flattening or rounding of the grains, chipping of grains and grain pull outs [6]. Graphitization of diamond grains has also been observed [7], which would contribute largely to grain flattening. Wire surface cracks, which may appear, have low effect on the machining performance however they foster pull outs by eroding the filler material [8]. Abrasive chips caught in the cutting zone wear out the bonding further [9]. Initial wire deflection is found to be positively correlated to abrasive wear [10]. Due to the reduction of grain protrusion with increasing thickness of the electroplated nickel layer, the bonding layer thickness has the largest negatively correlated influence on diamond wear, while cutting speed and feed rate are positively correlated and have a lower contribution and wire tension seems to be insignificant according to [9]. Cai [11] discusses diamond wear in the light of a diamond softening effect of high temperatures in the contact zone and hardening of the Si workpiece due to phase transitions. With progressing wear, the average protrusion of the active grains decreases, at the same time the number of active grains increases. This mechanism decreases the wear rate as well as the cutting ability [12]. It has been shown that wafer thickness increases [13] and roughness [6,10,13], kerf loss and shape deviation [10,13] decrease with progressing wear. According to [6] progressing wear further leads to a higher proportion of surface generated in the ductile cutting regime, with fewer but slightly deeper cracks and a lower average fracture strength. The influence of the grain shape and thereby of wear on the material removal mode has further been investigated in [14].
used for cooling. The elements of the force measurement system are a Kistler MiniDyn Type 9256C 3-component force sensor, a Kistler Type 5080A charge amplifier, a National Instruments NI 9222 analog-to-digital converter and a measurement laptop with Labview software. Shown in Figure 1, the wheel is rotating with a peripheral velocity vc and advances towards the workpiece in −y direction with a feed rate of v f . Process based similarities and deviations of the WWGW process and wire sawing are stated as follows: • The process is able to emulate long grain-workpiece contact lengths as in wire sawing. The geometric contact length AB in WWGW process is indicated in Figure 1. • Unlike wire speeds between 15 and 25m/s as typical in wire sawing process, investigation of cutting speeds up to 75m/s (10’000 RPM) is possible with the setup. • The wire is supported by the aluminum wheel, resulting in a stiff contact between the two elements while a wire bow prevails in sawing. • The wire motion is limited to the cutting direction unlike in wire sawing where three degrees of freedom (two transitional and one torsional) are present. • In the WWGW process, only a share of the wire circumference contributes to material removal, while in wire sawing, the complete circumference of the wire is active. Hence, a correction factor has to be applied to correlate the material removal rates with the wear.
3. Experiments Experiments on the WWGW setup are conducted at a cutting speed of 50m/s and a feed rate of 0.9mm/min. Asahi 12-25 standard concentration wires with 140µm core diameter are used and the wear characteristics of the diamond grains are discussed as well as the influence of wear on process forces. The validation of the wear analysis on the WWGW setup is done on a Meyer Burger DW288 multi-wire saw at the wire speed of 25m/s and the average feed rate of 1.5mm/min, resulting in comparable average undeformed chip thicknesses for both processes. An overview of the WWGW setup is given in Figure 1. The setup is mounted on a Rollomatic Grind Smart 628 XS 5-axis grinding machine and consists of an aluminum wheel that is grooved on its side surface and a concave Si workpiece with a diameter equal to that of the aluminum wheel. The diamond wire wrapped on the wheel follows the wheel grooves and is fixed on the ends to prevent sliding. Tap water is
Fig. 1: Overview of the WWGW setup (large). View of the wire grooves on wheel (small)
4. Results and Discussion Figure 2 presents the heights of the unrolled wire topography in intermediate wear stages in pseudo colors. Cumulative material removal volume is increasing from top to bottom image and the dashed red line identifies the same wire position. It can be seen that the protrusion heights of abrasive structures as well as the base areas which are measured on the reference level on the wire surface are decreasing with lifetime. In addition to single grains, aggregation of several
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grains namely clusters are observed on the wire surface. A cluster can be defined as the result of a non-homogeneous distribution of diamonds on the wire surface where the distances between the diamonds are close enough and usually filled with the Ni-filler. Moreover, they influence the available chip space on a diamond wire surface. In a cluster of grains, the wear occurs as a combination of Ni-filler removal and diamond wear. Monitoring identical clusters shows that in a cluster, initially the grain with the highest protrusion wears out until the next grain becomes kinematically active. From that point on, the wear rate of the two diamonds are comparable.
Fig. 2: Pseudo color images of identical diamond wire sections and diamonds
Figure 3 shows the results of the wear analysis performed using the developed WAS. Figure 3(a) shows the change in average grain protrusion, (b) the change in the average grain base area and (c) the change in the average volume of clusters and isolated grains with respect to the removed cumulative material volume. Different geometric change is observed with propagating wear. Whereas the reduction of the protrusion and volume can be approximated with an exponential function throughout the whole process, the development of the base areas shows two distinctive ranges: In the beginning, the grain base areas experience almost-zero deviation from their initial state. As the protrusion decreases, the filler material accumulated around the base of the grain is eventually exposed to the process and starts to wear rapidly, thereby reducing the base area (ref. also to Figure 4). As the filler is being removed around the abrasive grain/cluster base, the risk of the occurrence of pull-outs increases and the software is able to identify individual grains in clusters. Furthermore, an initially high decrease of grain volume can be accounted to the removal of Ni-filler which typically covers the grains on a new wire. Further, wear stages of individual diamond grains and clusters are followed throughout their lifetime. The results show that the main wear modes are blunting-rounding or flattening of the diamond either with micro- or macro-fractures; comparably few pull-outs are observed. A typical wear sequence of a grain is presented in Figure 4. The initial and final states are shown on top and maximum cross-sections are compared in the bottom image. In the first stages, the grain loses a considerable share of its volume, and the wear rate reduces as the grain wear propagates while rounding-off the cutting edges. In some cases it is also observed that the Ni-filler can be deposited at the back of the grain, which is also indicated in the figure (shaded area).
Fig. 3: WAS measurements of protrusion, base area and volume.
Fig. 4: Initial and final wear states of a diamond (top) Maximum crosssections of the diamond through lifetime (below)
Three of the identified wear modes are presented in Figure 5, where top images show the new grains and their maximum cross-sections and lower images show the final states and their maximum cross-sections. A grain wear of blunting-rounding is shown in (a), a premature pull-out in (b) and pull-out at the end of grain lifetime in (c). Measurement of process forces are presented in Figure 6. The observed wear modes are expected to lead to an increase in cutting and normal forces, as measured. Diamond wear has higher influence on normal forces, where a higher rate of increase is noted. Validation experiments conducted on a multi-wire saw show no difference with respect to the identified wear modes
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Fig. 5: Three diamond wear modes observed on wire: blunting (a), premature pull-out (b), pull-out at the end of wear lifetime (c)
• The WWGW experimental setup is a promising and comparable method for rapid-wear testing of electroplated diamond wires. It can successfully emulate the abrasive grain wear in the wire sawing process. • The main abrasive grain wear modes observed are blunting and rounding of the diamond grains. Very few pull-outs are observed, mainly at the end of wire lifetime. • The average volume and peak protrusion of the diamonds on wire decrease considerably in the first stage of wear. At a point, the wear rate of the grain base area increases, and its value decreases with the same trend as the volume and peak protrusion, leading to a possible grain pull-out. Acknowledgements This research is conducted as a part of the KTI Project 13079.1 PFIW-IW in collaboration with Meyer Burger Wafertec. References
Fig. 6: Influence of wear on cutting and normal forces
on the WWGW setup. Pseudo color images of sample grains from wire saw experiments and the maximum crosssectional planes in cutting direction are shown in Figure 7. A premature pull-out is identified in (a) and examples of blunting-rounding of grains are shown in (b) and (c).
Fig. 7: Samples from the identified wear modes in wire sawing process. Cross-sections have an aspect ratio of 1:3.74
5. Conclusion In this study, the WWGW experimental setup is introduced as a high speed rapid-wear test method for electroplated diamond wires. The wear of diamond wire is investigated by monitoring identical grains in successive wear states applying Alicona IFM. A software application processing Alicona images is developed for wire topography analysis. Results are compared to the experimental results obtained using a wire saw where the same abrasive grain wear modes are identified.
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8th CIRP Conference on High Performance Cutting (HPC 2018) 8th 8th CIRP CIRP Conference Conference on on High High Performance Performance Cutting Cutting (HPC (HPC 2018) 2018) 8th CIRP Conference on High Performance Cutting (HPC 2018) Experimental investigation of tool wear in electroplated diamond
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wire Experimental investigation of tool wear in electroplated diamond wire Experimental investigation of tool wear in electroplated diamond wire Experimental investigationsawing of tool wear in electroplated diamond wire of silicon sawing of silicon 28th CIRP Design Conference, May 2018, Nantes, France sawing of silicon sawing a,* aof silicon a a Uygar Pala uussmaier a,* , Stefan S¨ a , Fredy Kustera , Konrad Wegenera Uygar Pala , Stefan S¨ ssmaier a,* a , Fredy Kustera , Konrad Wegenera Uygar Pala S¨ ssmaier Kuster Wegener a , Fredy a , Konrad a A new methodology to,, Stefan analyze the functional and physical of Institute Machine Tools and ETH Zurich, Leonhardstrasse 21, 8092 Zurich architecture Uygar Palaofofa,* Stefan S¨uuManufacturing, ssmaier , Fredy Kuster , Konrad Wegener Institute Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich Institute of Machine Tools and Manufacturing, Zurich, Leonhardstrasse 21, 8092 Zurich Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mailETH address: [email protected] Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 8092 Zurich identification existing products for an assembly oriented product 21,family Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mail address: [email protected] Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mail address: [email protected] a a a a
Corresponding author. Tel.: +41-044-632-4526; Fax: +41-044-632-1125. E-mail address: [email protected]
Paul Stief *, Jean-Yves Dantan, Alain Etienne, Ali Siadat
Abstract Abstract Abstract École Nationale Supérieure d’Arts et Métiers, Arts et Métiers ParisTech, LCFC EA 4495, 4 Rue Augustin Fresnel, Metz 57078, France Abstract Nowadays diamond wire sawing is used as the most efficient method for manufacturing of silicon wafers. However, experimental inNowadays diamond wirewire sawing used aswear the most efficientbased method for manufacturing of silicon wafers. However, investigation of diamond and is has process limitations and is expensive when conducted on a experimental wire saw. Due Nowadays diamond wire sawing isabrasive used as the most efficient method for manufacturing of silicon wafers. However, experimental investigation of diamond wire and abrasive wear has process based limitations and is expensive when conducted on a wire saw. Due Nowadays diamond wire sawing is used as the most efficient method for manufacturing of silicon wafers. However, experimental in*vestigation Tel.:wire +33 3and 87 it37abrasive 54 30; E-mail [email protected] toCorresponding high material consumption, is difficult identify andbased observe individual In this a novel of author. diamond weartoaddress: has process limitations and grains. is expensive whenstudy, conducted on experimental a wire saw. setup Due to high material consumption, it is difficult to identify and observe individual grains. In this study, a novel experimental setup vestigation of diamond wire and abrasive wear has process based limitations and is expensive when conducted on a wire saw. Due is proposed for rapid wear testing diamond wires, which can emulate realistic contact conditions considering to high material consumption, it is of difficult to identify and observe individual grains.grain-workpiece In this study, a novel experimental setup is proposed for chip rapid wear testing of diamond wires, can emulate realistic grain-workpiece conditions considering to high material consumption, itandis long difficult to identify andMoreover, observe individual grains. In this study, a novel experimental setup the undeformed thickness contact lengths.which the setup allows monitoring thecontact wear propagation of identiis proposed for rapid wear testing of diamond wires, which can emulate realistic grain-workpiece contact conditions considering the undeformed thickness and long contact lengths.which Moreover, the setup allows monitoring the wear propagation of identiis for chip rapid wear testing of diamond wires, canareemulate realistic grain-workpiece contact cal proposed abrasive grains throughout lifetime. The experimental validated through investigations on wires conditions used on a considering multi-wire the undeformed chip thickness and long contact lengths. results Moreover, the setup allows monitoring the wear propagation of identical lifetime. The experimental are validated investigations onwear wiresinpropagation used a multi-wire the undeformed chipthroughout thickness and long contact lengths. results Moreover, the setupthrough allows monitoring the of identiAbstract saw.abrasive Wire grains topography is analyzed applying a proprietary software application to characterize grain termson in cal abrasive grains throughout lifetime. The experimental results are validated through investigations on wear wires used on ofa change multi-wire saw. Wire topography is analyzed applying a proprietary software application to characterize grain wear in terms of change in cal abrasive grains throughout lifetime. The experimental results are validated through investigations on wires used on a multi-wire the abrasive protrusion, base area and volume. The influence wire weartooncharacterize cutting forces normal forces ofis change discussed. saw. Wire grain topography is analyzed applying a proprietary software ofapplication grainandwear in terms in the abrasive grain protrusion, base area and volume. The influence of wire wear on cutting forces and normal forces is discussed. saw. Wire topography is analyzed applying a proprietary software application to characterize grain wear in terms of change in In business the trend more product variety and unbroken. Dueand to this development, need of thetoday’s abrasive grain environment, protrusion, base area towards and volume. The influence of customization wire wear oniscutting forces normal forces isthe discussed. the abrasive grain protrusion, base area and volume. The influence of wire wear on cutting forces and normal forces is discussed. agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production c 2018 Published by by Elsevier Elsevier Ltd. © 2018 The The Authors. Authors. Published Ltd. c 2018 The Authors. Published by Elsevier Ltd. systems as well as tothechoose the optimal product matches, product analysis methods are8th needed. most on of the known methods Cutting aim to Peer-review under responsibility the International Scientific Committee of the CIRPIndeed, Conference High Performance c 2018 The Authors. Published by Elsevier Ltd. This is an open access article under theof CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of the International Scientific Committee of thehowever, 8th CIRPmay Conference on High Performance Cutting c 2018 The Authors. Published by Elsevier Ltd. analyze a product or one product family on the physical level. Different product families, differ largely in terms of the number and (HPC 2018). Peer-review under the responsibility of the International Scientific Scientific CommitteeCommittee of the 8thofCIRP Conference on Highon Performance Cutting Selection and peer-review under responsibility of the International the 8th CIRP Conference High Performance (HPC 2018). Peer-review under responsibility of the International Scientific the 8th CIRP Conference on High Performance Cutting nature of(HPC components. fact impedes an efficient comparison andCommittee choice of of appropriate product family combinations for the production Cutting 2018).the This (HPC 2018). Diamond wire, wear, wire sawing, Keywords: (HPC 2018). system. A new methodology is proposed to silicon, analyzewafer existing products in view of their functional and physical architecture. The aim is to cluster Diamond wire, wear, wire sawing, silicon, wafer Keywords: Keywords: Diamond wire, wear, wire sawing, silicon,families wafer these products in new assembly oriented product Keywords: Diamond wire, wear, wire sawing, silicon, wafer for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a1.functional analysis is performed. Moreover, a hybrid functional and physical architecture with graph grinding (HyFPAG)process is the output which depicts the saw kinematics technology and proIntroduction saw kinematics with grinding processdesigners. technology and pro1. Introduction similarity between product families by providing design support to both, production system planners and product An illustrative vides the possibility of monitoring the wear of identical saw kinematics with grinding process technology and pro1. Introduction vides thecase possibility of product monitoring wear ofcolumns identical kinematics with grinding processthetechnology and pro1. Introduction example of a nail-clipper is used to explain the proposed methodology. Ansaw industrial study two steering of diamond at on cutting speedsfamilies up the to of75m/s. vides the grains possibility of monitoring wear ofMoreover, identical Despite some attempts in kerfless technologies, wire diamond grains at cutting speeds up the to 75m/s. vides possibility of monitoring wear ofMoreover, identical Despite Presta some France attempts kerfless wire evaluation thyssenkrupp is thenincarried out totechnologies, give a first industrial ofthe the proposed approach. abrasive grain is investigated experiments on diamond grainswear at cutting speeds upthrough to 75m/s. Moreover, sawing is still most prominent technology to generate Despite sometheattempts in kerfless technologies, wire ©sawing 2017 The by B.V.technologies, abrasive grain is investigated experiments on diamond grainswear at cutting speeds upthrough to 75m/s. Moreover, is Authors. still most prominent technology to generate Despite somethePublished attempts inElsevier kerfless wire a multi-wire saw. The results from the WWGW setup are abrasive grain wear is investigated through experiments on wafers in semiconductor industry where 30% of the total sawing is under still the most prominent technology to of generate Peer-review responsibility of the scientific committee thetotal 28th CIRP Design grain Conference 2018. a multi-wire saw. results fromthrough the WWGW setup are abrasive wearThe is investigated experiments on wafers in industry where 30% of sawing is semiconductor still the most prominent technology to the generate
manufacturing cost is accounted by where sawing 30% [1]. Even wafers in semiconductor industry of thethough total manufacturing cost is accounted by where sawing 30% [1]. Even wafers in semiconductor industry of thethough total there have been extensive research efforts on wear of diamanufacturing cost is accounted by sawing [1]. Even though Keywords: Assembly; Design method; Family identification there have been extensive research efforts [1]. on wear diamanufacturing cost is accounted by sawing Even of though mond have tools been for different and materials, of there extensiveprocesses research efforts on wear wear of diamond have tools been for different and materials, of there extensiveprocesses research efforts on wear wear of diathe electroplated diamond processes wire is still fully understood. mond tools for different andnotmaterials, wear of the electroplated diamond processes wire is still fully understood. mond tools for different andnotmaterials, wear of the electroplated diamond wire is still not fully understood. electroplated diamond wire is still not fully understood. 1.theIntroduction Because of their advantages in cutting performance and Because of their advantages in cutting performance and workpiece quality over other technologies (i.e. Becausesurface of their advantages in bonding cutting performance and workpiece quality over other technologies (i.e. Because ofthetheir in bonding cutting performance and Due tosurface fastadvantages development in the domain used of resin bonding), electroplated wires are widely workpiece surface quality overdiamond other bonding technologies (i.e. resin bonding), electroplated diamond wires are widely used workpiece surface quality over other bonding technologies (i.e. communication and an ongoing trend of digitization and in brittle materialelectroplated sawing. Thediamond wires are composed of a steel resin bonding), wires are widely used in brittle material sawing. The wires are composed of a steel resin bonding), electroplated diamond wires are widely used digitalization, enterprises are facing important wire corematerial and manufacturing diamond grains that areare fixed on the surface by in brittle sawing. The wires composed of a steel wire core and diamond grains that are fixed on the surface by in brittle material sawing. The wires are composed of a steel challenges in diamond today’s market environments: a continuing depositing the filler metal (nickel or alloys) by wire core and grains that arenickel-cobalt fixed on the surface depositing the filler metal (nickel or nickel-cobalt alloys) by wire core and diamond grains that are fixed on the surface tendency reduction of product development times means oftowards electroplating. Typical core diametersalloys) are inand the depositing the filler metal (nickel or wire nickel-cobalt by means of product electroplating. Typical core diameters are in the depositing the filler metal (nickel or wire nickel-cobalt alloys) by shortened lifecycles. In addition, there is an of increasing range ofof60-140µm with typical abrasive grain sizes 8-25µm. means electroplating. Typical core wire diameters are in the range of 60-140µm with typical abrasive grain sizes of 8-25µm. means of electroplating. Typical core wire diameters are in the demand customization, beingabrasive at the same global range ofof 60-140µm with typical grain time sizes in of a8-25µm. range of 60-140µm with typicalall abrasive grain sizes This of 8-25µm. competition with competitors over the trend, The presented research introduces a world. fast characterizaTheispresented research introducesfrom a fast characterizawhich inducing the development macro to micro tionThe method for diamond wire wear and a software tool presented research introduces a fast characterizationThe method forindiamond wire and a tosoftware tool presented research introduces adue fast characterizamarkets, results diminished lotwear sizeswires. augmenting for the characterization of wire diamond The method tion method for diamond wear and a software tool for the characterization of diamond wires. The method tion method for diamond wire wear and a software tool product (high-volume to low-volume [1]. employs a novel-design experimental setupproduction) named ”Wire for the varieties characterization of diamond wires. The method employs a novel-design experimental setup named ”Wire for the characterization of diamond wires. The method To cope with this augmenting variety as which well to be able to Wrapped Wheel”experimental (WWGW) wire employs aGrinding novel-design setupasemulates named ”Wire Wrapped aGrinding Wheel”experimental (WWGW) which wire employs novel-design setup named ”Wire identify potentials in emulates the existing Wrappedpossible Grindingoptimization Wheel” (WWGW) which emulates wire Wrapped Grinding Wheel” (WWGW) which emulates wire production system, it is important to have a precise knowledge
withsaw. results obtained actual sawingsetup process. acompared multi-wire The resultswith fromthethe WWGW are withsaw. results obtained actual sawingsetup process. acompared multi-wire The resultswith fromthethe WWGW are compared with results obtained with the actual sawing process. compared with results obtained with the actual sawing process. A MATLAB based diamond wire analysis software (WAS) A MATLAB based diamond wire analysis software (WAS) is developed for based detailed investigation of wiressoftware in terms(WAS) of diA MATLAB diamond wire analysis is developed for based detailed investigation of wiressoftware in terms(WAS) of diA MATLAB diamond wire analysis amond geometry, size, protrusion, aspect ratio, is developed for detailed investigation of wires in density terms ofand diamond geometry, size, protrusion, aspect ratio, density is developed for detailed investigation of wires in terms ofand diof the product andprotrusion, characteristics manufactured and/or distribution. Inrange addition, the method provides framework amond geometry, size, aspect ratio, adensity and distribution. In addition, the method provides a framework amond geometry, size, protrusion, aspect ratio, density and assembled in this thiscomparison context,provides theofmain in for the characterization and diamond wires distribution. In system. addition,In the method achallenge framework for the characterization diamond wires distribution. addition, the comparison method provides a with framework modelling andIn analysis isand now not only toof single fromtheseveral manufacturers going beyond the specification for characterization and comparison ofcope diamond wires fromtheseveral manufacturers going beyondofproduct the specification for characterization and comparison diamond wires products, a limited product range or existing families, usuallyseveral provided by the manufacturers. profrom manufacturers going beyondThe thesoftware specification usually provided by the manufacturers. The software profrom several manufacturers going beyond the specification but alsoimages to be able to andan to Alicona compareThe products to define cesses developed with 3D Infinite Focus usually provided byanalyze the manufacturers. software processes images developed with an Alicona 3D Infinite Focus usually provided by the manufacturers. The software pronew product families. It can be observed that classical Microscope (IFM) and comply with ISO 1101.2004 [2] and cesses images developed with an Alicona 3D Infiniteexisting Focus Microscope (IFM) and comply with ISO 1101.2004 [2] and cesses images developed with an Alicona 3D Infinite Focus product families are[3]. regrouped in function of1101.2004 clients or features. ISO 5436-2.2001 imageISO processing algorithms Microscope (IFM) and Multiple comply with [2] and ISO 5436-2.2001 [3]. Multiple image processing algorithms Microscope (IFM) and comply with ISO 1101.2004 [2] and However, assembly oriented product families arelayer hardly to find. are employed to determine a wire reference and each ISO 5436-2.2001 [3]. Multiple image processing algorithms areOn employed to determine a wire reference layer and each ISO 5436-2.2001 [3]. Multiple image processing algorithms thelabeled product family level, products differ mainly two grainemployed is the comparison of wear states throughout are tofor determine a wire reference layer andineach grainemployed is labeledtofor the comparison of wear states throughout are determine a wire of reference layerand and(ii)each main (i)on the number the their characteristics: lifetime. the measurements, statistical analygrain is labeledBased for the comparison ofcomponents wear states throughout theiroflifetime. the measurements, statistical analygrain iscomponents labeledBased for (e.g. theoncomparison ofelectrical, wear states throughout type mechanical, electronical). sis is lifetime. conductedBased and aon stochastic-geometric modeling of diatheir the measurements, statistical analysisClassical is lifetime. conducted and aon stochastic-geometric modeling of diatheir Based the measurements, statistical analyconsidering mainly single products mond wiresmethodologies madeand possible. Wire surfaces are captured sis is conducted a stochastic-geometric modeling of with diamond wires madeand possible. Wire surfaces are captured with sis is conducted a stochastic-geometric modeling of diaor existing product families analyze the the solitary, imprinting method introduced by IWF [4,5] that allows mond wires already made possible. Wire surfaces are captured with the imprinting method introduced by IWF are [4,5] that allows mond wires made possible. Wire surfaces captured with product structuremethod on a physical level by (components in-situ sampling without disrupting the experimental setup. the imprinting introduced IWF [4,5]level) that which allows in-situ samplingmethod withoutintroduced disruptingbythe experimental setup. the imprinting IWF [4,5] that allows causes difficultieswithout regarding an efficient definition setup. and in-situ sampling disrupting the experimental in-situ sampling without disrupting the experimental setup. comparison of different product families. Addressing this
c© 2018 2212-8271 Published by Elsevier Ltd. Ltd. 2212-8271 2018 The TheAuthors. Authors. Published by Elsevier cunder 2212-8271 2018 The Authors. Published by Elsevier Ltd. Peer-review the of the Scientific Committee of the 8th CIRP Conference on High Performance Cutting (HPC 2018). copen 2212-8271 2018access Theresponsibility Authors. Published by Ltd. This is an article under theInternational CCElsevier BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of the International Scientific Committee of the 8th CIRP Conference on High Performance Cutting (HPC 2018). c 2212-8271 2018 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the International Scientific of the 8th Conference Cutting on High(HPC Performance Peer-review under the responsibility of the International Scientific Committee of the Committee 8th CIRP Conference onCIRP High Performance 2018). Cutting 2212-8271 © 2017 The Authors. Published by Elsevier B.V. Peer-review under the responsibility of the International Scientific Committee of the 8th CIRP Conference on High Performance Cutting (HPC 2018). (HPC 2018). Peer-review under responsibility of the scientific committee of the 28th CIRP Design Conference 2018. 10.1016/j.procir.2018.09.038
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2. State of the Art The causal chain of process input - wear - process output is currently not prioritized by researchers, comparably little effort has been documented. Most of the work published focuses on the influence of wear on the process outputs. Three major wear mechanisms have been observed: blunting, flattening or rounding of the grains, chipping of grains and grain pull outs [6]. Graphitization of diamond grains has also been observed [7], which would contribute largely to grain flattening. Wire surface cracks, which may appear, have low effect on the machining performance however they foster pull outs by eroding the filler material [8]. Abrasive chips caught in the cutting zone wear out the bonding further [9]. Initial wire deflection is found to be positively correlated to abrasive wear [10]. Due to the reduction of grain protrusion with increasing thickness of the electroplated nickel layer, the bonding layer thickness has the largest negatively correlated influence on diamond wear, while cutting speed and feed rate are positively correlated and have a lower contribution and wire tension seems to be insignificant according to [9]. Cai [11] discusses diamond wear in the light of a diamond softening effect of high temperatures in the contact zone and hardening of the Si workpiece due to phase transitions. With progressing wear, the average protrusion of the active grains decreases, at the same time the number of active grains increases. This mechanism decreases the wear rate as well as the cutting ability [12]. It has been shown that wafer thickness increases [13] and roughness [6,10,13], kerf loss and shape deviation [10,13] decrease with progressing wear. According to [6] progressing wear further leads to a higher proportion of surface generated in the ductile cutting regime, with fewer but slightly deeper cracks and a lower average fracture strength. The influence of the grain shape and thereby of wear on the material removal mode has further been investigated in [14].
used for cooling. The elements of the force measurement system are a Kistler MiniDyn Type 9256C 3-component force sensor, a Kistler Type 5080A charge amplifier, a National Instruments NI 9222 analog-to-digital converter and a measurement laptop with Labview software. Shown in Figure 1, the wheel is rotating with a peripheral velocity vc and advances towards the workpiece in −y direction with a feed rate of v f . Process based similarities and deviations of the WWGW process and wire sawing are stated as follows: • The process is able to emulate long grain-workpiece contact lengths as in wire sawing. The geometric contact length AB in WWGW process is indicated in Figure 1. • Unlike wire speeds between 15 and 25m/s as typical in wire sawing process, investigation of cutting speeds up to 75m/s (10’000 RPM) is possible with the setup. • The wire is supported by the aluminum wheel, resulting in a stiff contact between the two elements while a wire bow prevails in sawing. • The wire motion is limited to the cutting direction unlike in wire sawing where three degrees of freedom (two transitional and one torsional) are present. • In the WWGW process, only a share of the wire circumference contributes to material removal, while in wire sawing, the complete circumference of the wire is active. Hence, a correction factor has to be applied to correlate the material removal rates with the wear.
3. Experiments Experiments on the WWGW setup are conducted at a cutting speed of 50m/s and a feed rate of 0.9mm/min. Asahi 12-25 standard concentration wires with 140µm core diameter are used and the wear characteristics of the diamond grains are discussed as well as the influence of wear on process forces. The validation of the wear analysis on the WWGW setup is done on a Meyer Burger DW288 multi-wire saw at the wire speed of 25m/s and the average feed rate of 1.5mm/min, resulting in comparable average undeformed chip thicknesses for both processes. An overview of the WWGW setup is given in Figure 1. The setup is mounted on a Rollomatic Grind Smart 628 XS 5-axis grinding machine and consists of an aluminum wheel that is grooved on its side surface and a concave Si workpiece with a diameter equal to that of the aluminum wheel. The diamond wire wrapped on the wheel follows the wheel grooves and is fixed on the ends to prevent sliding. Tap water is
Fig. 1: Overview of the WWGW setup (large). View of the wire grooves on wheel (small)
4. Results and Discussion Figure 2 presents the heights of the unrolled wire topography in intermediate wear stages in pseudo colors. Cumulative material removal volume is increasing from top to bottom image and the dashed red line identifies the same wire position. It can be seen that the protrusion heights of abrasive structures as well as the base areas which are measured on the reference level on the wire surface are decreasing with lifetime. In addition to single grains, aggregation of several
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grains namely clusters are observed on the wire surface. A cluster can be defined as the result of a non-homogeneous distribution of diamonds on the wire surface where the distances between the diamonds are close enough and usually filled with the Ni-filler. Moreover, they influence the available chip space on a diamond wire surface. In a cluster of grains, the wear occurs as a combination of Ni-filler removal and diamond wear. Monitoring identical clusters shows that in a cluster, initially the grain with the highest protrusion wears out until the next grain becomes kinematically active. From that point on, the wear rate of the two diamonds are comparable.
Fig. 2: Pseudo color images of identical diamond wire sections and diamonds
Figure 3 shows the results of the wear analysis performed using the developed WAS. Figure 3(a) shows the change in average grain protrusion, (b) the change in the average grain base area and (c) the change in the average volume of clusters and isolated grains with respect to the removed cumulative material volume. Different geometric change is observed with propagating wear. Whereas the reduction of the protrusion and volume can be approximated with an exponential function throughout the whole process, the development of the base areas shows two distinctive ranges: In the beginning, the grain base areas experience almost-zero deviation from their initial state. As the protrusion decreases, the filler material accumulated around the base of the grain is eventually exposed to the process and starts to wear rapidly, thereby reducing the base area (ref. also to Figure 4). As the filler is being removed around the abrasive grain/cluster base, the risk of the occurrence of pull-outs increases and the software is able to identify individual grains in clusters. Furthermore, an initially high decrease of grain volume can be accounted to the removal of Ni-filler which typically covers the grains on a new wire. Further, wear stages of individual diamond grains and clusters are followed throughout their lifetime. The results show that the main wear modes are blunting-rounding or flattening of the diamond either with micro- or macro-fractures; comparably few pull-outs are observed. A typical wear sequence of a grain is presented in Figure 4. The initial and final states are shown on top and maximum cross-sections are compared in the bottom image. In the first stages, the grain loses a considerable share of its volume, and the wear rate reduces as the grain wear propagates while rounding-off the cutting edges. In some cases it is also observed that the Ni-filler can be deposited at the back of the grain, which is also indicated in the figure (shaded area).
Fig. 3: WAS measurements of protrusion, base area and volume.
Fig. 4: Initial and final wear states of a diamond (top) Maximum crosssections of the diamond through lifetime (below)
Three of the identified wear modes are presented in Figure 5, where top images show the new grains and their maximum cross-sections and lower images show the final states and their maximum cross-sections. A grain wear of blunting-rounding is shown in (a), a premature pull-out in (b) and pull-out at the end of grain lifetime in (c). Measurement of process forces are presented in Figure 6. The observed wear modes are expected to lead to an increase in cutting and normal forces, as measured. Diamond wear has higher influence on normal forces, where a higher rate of increase is noted. Validation experiments conducted on a multi-wire saw show no difference with respect to the identified wear modes
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Fig. 5: Three diamond wear modes observed on wire: blunting (a), premature pull-out (b), pull-out at the end of wear lifetime (c)
• The WWGW experimental setup is a promising and comparable method for rapid-wear testing of electroplated diamond wires. It can successfully emulate the abrasive grain wear in the wire sawing process. • The main abrasive grain wear modes observed are blunting and rounding of the diamond grains. Very few pull-outs are observed, mainly at the end of wire lifetime. • The average volume and peak protrusion of the diamonds on wire decrease considerably in the first stage of wear. At a point, the wear rate of the grain base area increases, and its value decreases with the same trend as the volume and peak protrusion, leading to a possible grain pull-out. Acknowledgements This research is conducted as a part of the KTI Project 13079.1 PFIW-IW in collaboration with Meyer Burger Wafertec. References
Fig. 6: Influence of wear on cutting and normal forces
on the WWGW setup. Pseudo color images of sample grains from wire saw experiments and the maximum crosssectional planes in cutting direction are shown in Figure 7. A premature pull-out is identified in (a) and examples of blunting-rounding of grains are shown in (b) and (c).
Fig. 7: Samples from the identified wear modes in wire sawing process. Cross-sections have an aspect ratio of 1:3.74
5. Conclusion In this study, the WWGW experimental setup is introduced as a high speed rapid-wear test method for electroplated diamond wires. The wear of diamond wire is investigated by monitoring identical grains in successive wear states applying Alicona IFM. A software application processing Alicona images is developed for wire topography analysis. Results are compared to the experimental results obtained using a wire saw where the same abrasive grain wear modes are identified.
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