Parametric Optimization for Laser Marking Performance via Taguchi Approach

Transcription

1 Technical Junal, Univesity f Engineeing and Technlgy (UET) Taxila, akistan Vl. 0 N. II-05 aametic Optimizatin f Lase Making efmance via Taguchi Appach A. R. Khan, M. Q. Saleem, A. Ikam Industial & Manufactuing Engineeing Depatment, Rachna Cllege f Engineeing & Technlgy (Cnstituent Cllege f Univesity f Engineeing & Technlgy, Lahe) Gujanwala, akistan Industial & Manufactuing Engineeing Depatment, Univesity f Engineeing & Technlgy Lahe, akistan Engineeing Depatment, Univesity f Gujat, Gujat, akistan qaise@uet.edu.pk Abstact-This pape paametically ptimizes the lase making pcess f making stainless steel AISI 6L f making's quality and time using Taguchi methd wheein the atinale is t ensue the cmpatibility f the pcess with mateial being pcessed. Fu paametes namely lase fequency, numbe f layes emved, lase pwe and scanning speed ae investigated heein. Main effect f means and signal t nise ati have been dne t study & ptimize the effects f vaiables n stated pefmance measues espectively. The pcess is mathematically fmulated via linea egessin mdel. It is fund that amng the facts studied heein, maj cntibuting fact f making time is numbe f layes emved wheeas scanning speed effects suface ughness the mst. Optimum levels f minimizing making time ae detemined t be: level f lase fequency and numbe f layes emved, level f lase pwe and level f scanning speed. On the the hand, f minimizatin f suface ughness, ptimum levels ae fund t be: level f lase fequency, numbe f layes emved and lase pwe and level f scanning speed. The mathematical mdel develped heein is fund t be statistically significant at % cnfidence level with cntibutins f mdel tems t be 98.9% f making time and 96.8% f suface ughness. The develped mdels ae validated by the cnfimaty un wheein gd ageement between pedicted and expeimental values is btained. Keywds-Lase Making, Taguchi Methd, Suface Rughness I.INTRODUCTION Lase beam making pcess uses a highly fcused lase light that falls n the suface f the wk pat t engave mak the bject. The pcess has wide applicatins in vaius types f fd industies f engaving numbe and dates n fd packages as well as f making and pinting lgs and ba cdes n pinted cicuit bads, electnic cmpnents and the pducts f the pupse f pduct identificatin and taceability [i-iii]. The pcess pvides highe flexibility, accuacy, ease f autmatin and epducibility as cmpaed t the cnventinal making techniques such as ht stamping, mechanical scibing inkjet [i]. The nn-cntact natue f the pcess allws wide vaiety f mateials such as plastics, wd, metal and ceamics t be used as wk piece that futhes the usefulness f the pcess [ii, iv]. The pinciple f peatin is based n ablatin wheein the inteactin between mateial and the lase beam, which cmes fm a lase system and passes thugh a fcusing lens (cnvex lens), leads t the vapizatin and melting f wk mateial. As a esult, the mateial is emved fm the wk piece in layes via ablatin mechanism [i, v]. Fig. shws the pinciple f peatin f a lase making machine. Fig.. inciple f peatin f a lase making machine [i] Seveal studies have been dne n the paametic ptimizatin in de t impve the quality f maked pats [v-x]. Results f these studies shw that pcess paametes can be adjusted t ptimize the pcess f numbe f applicatins. Sme eseaches [vii] have used Atificial Neual Netwking (ANN) while ptimizing the pcess wheeas thes have used Taguchi methd t impve the quality f maked pats [v]. N cnsideable wk, hweve, culd be fund f the ptimizatin f making time. Cnsideing, that the making time is elated t the cst dynamics f the pcess it is impeative that a study is undetaken t 9

2 Technical Junal, Univesity f Engineeing and Technlgy (UET) Taxila, akistan Vl. 0 N. II-05 minimize the making time yet maximizing the quality f the engaving. This wuld ensue the cmpatibility f the pcess with mateial being pcessed. The atinale behind this eseach is thus t ensue the cmpatibility f the pcess with mateial being pcessed. This pape epts n the ptimizatin f lase making pcess f enhanced suface quality and peatin time eductin f the case f Stainless Steel AISI 6L that has gd heat and csin esistance ppeties [xi]. It is mstly used in shafts, pumps and equipment f pcessing chemical fds [xii]. Taguchi methd is used heein while investigating fu pcess paametes namely pulse fequency, numbe f layes emved, lase pwe and scanning speed. ulse fequency is defined as numbe f pulses emitted fm lase system pe unit time, numbe f layes emved efe t the ttal numbe f layes ablated in the pcess afte multiple passes, lase pwe is the aveage pwe f the pulsed lase and scanning speed is the distance pe unit time cveed by the lase head as it scans the selected aea duing machining. [xiii-xiv]. Main effect plt f means and signal t nise ati ae used t analyze and ptimize the pcess espectively while egessin mdeling is dne t undestand the elatins between the pcess paametes. II. MATERIALS AND EXERIMENTAL SETU A. Wk piece Details A 6.5 mm (/-inch) thick plate f Stainless Steel (AISI 6L) is emplyed f the pesented wk. The mateial's chemical cmpsitin is given in Table I. TABLE I CHEMICAL COMOSITION OF STAINLESS STEEL (AISI 6L) Element C Ni Mn Si S C M Fe AISI 6L % Wt. (Actual) Balance % Wt. (Standad) [xi] Balance A. Making Details Making is dne n the wk piece using lase making machine (TuMak statin 00, TRUMF, Gemany) with Ultavilet (UV) lase as the beam. The machine used f expeimentatin is shwn in Fig.. Fig.. Lase making machine used f the making peatin n the wk piece C. Expeimental Cnditins A cnvex lens with fcal length f 6 mm is used in the way f lase beam t fcus the lase beam n the wk piece with an input vltage f 0 vlts. A mix hatching mde scanning stategy is adpted heein because in multi-laye machining cycles, suface ughness is epted t be educed by changing the scanning diectin [xv], In this mde, the lase head mves in diffeent diectins (i.e. angles) in successive passes f machining cycle t emve the layes. In the wk pesented heein, angles f the hatching patten ae fixed (as ppsed t andm hatching) s that in each expeiment a simila hatching patten can be e pduced.the hatched lines make angles f 5, 90, 5 and. Hatching mde with scanning diectins is shwn in Fig.. Fig.. Mix hatching patten with scanning diectins Thee eplicatins ae dne t ensue epeatability f expeiments as is the geneal appach [xvi-xvii] with aveage values epted heein.

3 Technical Junal, Univesity f Engineeing and Technlgy (UET) Taxila, akistan Vl. 0 N. II-05 D. Design f Expeiments Taguchi's thgnal aay L9 is used heein t ptimize the effects f fu pcess paametes. The clumn namely Wking Range shws the veall ange f paametes' values wheeas thee levels ae taken f each pcess paamete. F each paamete investigated, level is the minimum value wheeas level is the maximum value f the chsen value set. Table II lists pcess paametes with units and values f the levels selected heein. cess aametes TABLE II ROCESS ARAMETERS AND LEVELS Units Hetz - Watt Micsecnd Symbl f Units Hz - W µ-sec Wking Range The wk piece afte making peatin is shwn in Fig.. Fig.. Wkpiece afte making peatin. III. MEASUREMENT & ROCEDURES Making time is nted f each expeiment by using a stp watch while suface ughness data is taken by measuing R a using pfilmete (Fig. 5). Thee eadings ae taken with a cut-ff length f 0.8 mm and an evaluatin length f.0 mm and the aveage is epted heein Fig. 5. filmete emplyed f the measuement f suface ughness (Ra). IV. RESULTS, ANALYSIS AND DISCUSSION A. Making Time and Suface Rughness Table III lists the aveage esults f making time (T m) and suface ughness (Ra) f all the nine expeiments. TABLE III TAGUCHI ORTHOGONAL ARRAY AND EXERIMENT RESULTS FOR MARKING TIME AND SURFACE ROUGHNESS Exp. N cess aametes efmance Measues Suface filmete: Sutnic S5, Tayl Hbsn Ltd, United Kingdm Minitab 6.0 is used f the analysis B. Main Effect lts f Means The effects f individual paametes n making time and suface ughness ae calculated by using data means. The values f data means f making time and suface ughness ae given in the Table IV and Table V espectively T m Ra

4 Technical Junal, Univesity f Engineeing and Technlgy (UET) Taxila, akistan Vl. 0 N. II-05 TABLE IV RESONSE TABLE (MEANS) FOR MARKING TIME cess aametes Delta Rank Table IV shws that pcess paametes, and have a diect elatin with the making time while has an invese elatin with making time. Delta shws the intensity f the effect f pcess paametes n the espnse (making time), it is calculated by the diffeence between the maximum and minimum values f data means f each vaiable, while anking has been dne n the basis f the highe delta values f each pcess paamete [xviii]. N is, hence, fund t have an effect n the making time the mst fllwed by S. s TABLE V RESONSE TABLE (MEANS) FOR SURFACE ROUGHNESS cess aametes Delta Rank The case f suface ughness is depicted in Table V. Hee Ss affects the suface ughness f the wk pat the mst wheeas F p is fund t have a minimal effect n the suface ughness. Fig. 6 pesents the main effects plt f means f making time wheeas Fig. 7 shws the same f suface ughness. Fig. 6. Main effect plt (means) f making time. Fig. 7. Main effect plt (means) f suface ughness. The maj cntibuting fact f making time is numbe f layes emved fllwed by scanning speed. The esults can be explained; hee the numbe f emved layes epesent the numbe f cmplete hatched pattens. Highe the numbe f cmplete hatched pattens, the thicke the maked impessin. Each hatched patten takes sme time f its cmpletin i.e the time f the cmplete mvement f the lase beam. Theefe, highe the numbe f emved layes, geate will be the making time f the lase pcess. Secnd imptant fact f making time is scanning speed. Scanning speed is the speed f the lase beam duing its hatching mde. It is clea that lwe the scanning speed, me is the time that the lase beam needs t machine the suface [xiii]. F suface ughness, scanning speed is the mst cntibuting fact f suface ughness fllwed by lase pwe. The influence f scanning speed in cdinatin with lase pwe n suface ughness culd be explained n the basis that a fcused lase beam pvides enegy f vapizatin f the unwanted mateial in de t geneate a maked impessin in lase making machine. Lase beam is esult f light amplificatin f mnchmatic lights. The highe the intensity f lase, highe wuld be the pwe and hence thicke will be the maked impessin [i, xix]. Theefe, pwe f the lase beam inceases the suface ughness but it may nt affect the suface ughness as much when mvement f the lase beam i.e scanning speed is fast. On the the hand, when mvement is slw, suface quality deteiates. C. Main Effect lt f Signal t nise Rati (SNR) The type f the Signal t Nise Rati analysis used heein is smalle the bette f bth making time and suface ughness. This indicates that the smallest values f bth making time and suface ughness ae pefeable. The fmula f measuing smalle the bette signal t nise ati (SNR) is given in the Eq () [xvii]. 5

5 Technical Junal, Univesity f Engineeing and Technlgy (UET) Taxila, akistan Vl. 0 N. II-05 () Whee SNR is epesented by ç and y is the ith i eading [xvii]. Table VI and Table VII list the aveage SNR values f making time and suface ughness using the abve equatin. TABLE VI RESONSE TABLE (SIGNAL TO NOISE RATIOS) FOR MARKING TIME aametes TABLE VII RESONSE TABLE (SIGNAL TO NOISE RATIOS) FOR SURFACE ROUGHNESS aametes Optimum Optimum Results fm the espnse tables using signal t nise atis (Table VI and Table VII) have been used t plt the making time (Fig. 8) and suface ughness (Fig. 9). Fig. 9. Main effect plt (signal t nise) f suface ughness Since Taguchi appach is built n the basis that selectin f apppiate levels f the pcess paametes wuld weaken the effects f nise facts [xviii] s the pint is t select the level f pcess paamete with highest SNR. Cespndingly, f making time, level f the fist tw pcess paametes ( and ) is egaded as the ptimum level, f it is level wheeas level is the ptimum level f the last pcess paamete S. F suface s ughness n the the hand, level is the ptimum level f F p, N and wheeas level is the ptimum level f. D. Mathematical Mdelling Geneal linea egessin analysis has been used in de t fmulate the pcess. The egessin equatin f the making time has been given in Eq (). () T detemine the statistical significance f the develped mdel and t quantify cntibutin made by each individual pcess paamete, analysis f vaiance (ANOVA) has been dne f the egessin mdel f making time as shwn in Table VIII. The cntibutin f egessin tems accunt t 98.9% against the e cntibutin f nly.08%. Meve, -value f the egessin mdeling cmes ut t be which is less than the selected á value f 0.05 that thus validates the statistical significance f the mdel with % cnfidence level. Fig. 8. Main effect plt (Signal t nise) f making time. 5

6 Technical Junal, Univesity f Engineeing and Technlgy (UET) Taxila, akistan Vl. 0 N. II-05 TABLE VIII ANOVA FOR REGRESSION ANALYSIS OF MARKING TIME Suce Regessin E Ttal F suface ughness, the egessin analysis pvides the mathematical fmulatin as given be Eq (). () Hee t analysis f vaiance (ANOVA) has been dne f the egessin mdel f suface ughness (Table IX) t detemine the statistical significance f the develped mdel and t quantify cntibutin made by each individual pcess paamete. A -value lwe than selected á f 0.05 shws the statistical significance f the egessin mdel at % cnfidence level. The cntibutin f egessin tems accunt t 96.8% against the e cntibutin f nly.6%. TABLE IX ANOVA FOR REGRESSION ANALYSIS OF SURFACE ROUGHNESS Suce Regessin E Ttal DF 8 DF 8 Sum f Squaes (SS) Sum f Squaes (SS) Mean Squaes (MS) Vaiance Rati (F) Mean Vaiance Squaes Rati (MS) (F) E. Cnfimaty Expeiment In de t validate the cnclusins dawn fm the egessin analysis, the cnfimaty uns invlve pedictin and veificatin f the pefmance measues unde ptimal levels f pcess vaiables. Cnfimaty expeiments wee pefmed with the ptimum levels f pcess paametes and esults wee Cnt. (%) Cnt. (%) cmpaed t the pedicted values. Results f cnfimaty expeiments f making time, suface ughness ae shwn in Table X. The cnfimaty uns shw vey gd ageement (e.% f making time and.7% f suface ughness) between pedictedand expeimental esults. The esults f the cnfimaty un validate the paametic ptimizatin btained f the lase making pcess with paametes investigated heein. TABLE X CONFIRMATORY TESTS FOR MARKING TIME AND SURFACE ROUGHNESS efmance Measues Making time Suface Rughness V. CONCLUSIONS Lase making pcess has been investigated f ptimizatin f pcess paametes f making time and suface ughness f stainless steel AISI 6L using Taguchi methd. Fu pcess paametes i.e. lase fequency, numbe f layes emved, lase pwe and scanning speed ae investigated in this study. Main effect plt f means and signal t nise atis have been dne t analyze the pcess while egessin mdeling is used t fmulate the pcess. Fllwing cnclusins can be dawn fm the eseach study: F making time, numbe f layes emved is fund t be the maj cntibuting pcess paamete fllwed by scanning speed. F suface ughness, scanning speed is fund t be the maj cntibuting fact f suface ughness fllwed by lase pwe and numbe f layes emved whilst pulse fequency is fund t be the least cntibuting fact. Signal t nise ati esults shw that Test cnditins (ptimum paametes) F N S p s F N S p s Expeimental value.8.0 edicted value.08.5 Relative e.%.70% Making time is minimized at the ptimum level f pcess paametes which f (lase fequency) and N (numbe f layes emved) is level, f (lase pwe) it is level and f S (scanning speed) it is level. s Suface ughness is minimized at the ptimum level f pcess paametes which f F p(lase fequency), N (numbe f layes emved) and (lase pwe) is level wheeas f S (scanning speed) it is level. s Mathematical mdelling pvides useful mathematical elatins amng the pcess paametes f making time and suface 5

7 Technical Junal, Univesity f Engineeing and Technlgy (UET) Taxila, akistan Vl. 0 N. II-05 Rughness. The mdel is fund t be statistically significant at %cnfidence level with e cntibuting t nly.08% f the mdel develped f making time and.6% f the mdel develped f suface ughness. Cnfimaty tests ae cnducted t validate the mathematical fmulatins. A gd ageement (.% e f making time and.70% e f suface ughness) was fund between the expeimental and pedicted esults. ACKNOWLEDGMENT The auths acknwledge the suppt f Gujanwala Tls, Dies and Mld Cente (GTDMC), Gujanwala, akistanf making this eseach wk pssible. [i] [ii] [iii] [iv] [v] [vi] [vii] REFERENCES S. Kalpakjian and S. R. Schmid, Manufactuing Engineeing and Technlgy, easn Educatin, 009. J. ete, B. Dli and B. Bhattachayya, Analysis n the chaacteistics f Nd:YAG lase making n alumina ceamic based n RSM, Intenatinal Junal f Mateials and duct Technlgy, vl. 6, n., 0, pp. -8. J. F. Ready, Industial Applicatins f Lases, Academic ess, 997. M. Chen, Y. Wang and W. Hsia, Finite element analysis and veificatin f lase making n eggshell, Junal f Mateials cessing Technlgy, vl. 09, n., 009, pp S. L. Campanelli, G. Casalin, N. Cntuzzi and A. D. Ludvic, Taguchi ptimizatin f the suface finish btained by lase ablatin n selective lase mlten steel pats, cedia CIR, 8th CIR Cnfeence n Intelligent Cmputatin in Manufactuing Engineeing, 0, pp S. L. Campanelli, N. Cntuzzi, G. Casalin and A. D. Ludvic, Analysis f the mateial emval ate f nansecnd lase ablatin f aluminum using a paallel hatching mde, Applied Mechanics and Mateials,0, vl. 0-0, pp S. L. Campanelli, G. Casalin, A. D. Ludvic and C. Bnsei, An atificial neual netwk appach f the cntl f the lase milling pcess, Intenatinal Junal f Advanced Manufactuing Technlgy 0 (nline); DOI0.007/s [viii] S. L. Campanelli, A. D. Ludvic, C. Bnsei,. Cavalluzzi andm. Cinquepalmi, Expeimental analysis f the lase milling pcess paametes, Junal f Mateials cessing Technlgy, vl. 9, 007, pp. 0-. [ix] S. L. Campanelli, A. D. Ludvic and C. Deam, Dimensinal accuacy ptimisatin f the lase milling pcess, Intenatinal Cngess n Applicatins f Lases and ElectOptics (ICALEO), 007, Oland, Flida. [x] D. T. ham, S. S. Dimv,. V. etkv and T. Dbev, Lase milling f mic-tling, ceedings f VIII LAMDAMA Cnfeence, 005, pp [xi] peties and selectin: In, steel and high pefmance allys, Ameican Sciety f Mateials (ASM) Handbk, USA, 00. [xii] H.Lelieveld, M. A.Mstet, B. White and J. Hlah, Hygiene in Fd cessing: inciples and actice, Elsevie, 00. [xiii] D. Teixid, I. Fee, J. Ciuana and T. O zel, Optimizatin f pcess paametes f pulsed lase milling f mic-channels n AISI H tl steel, Rbtics and Cmpute-Integated Manufactuing, vl. 9, 0, pp [xiv] Cheent Inc. ( easuinglasepwendenegyutputfinal.pdf), Accessed 5-May-05 [xv]. etkv, Lase milling: suface integity, emval stategies and pcess accuacy, Cadiff Univesity, UK, 0 [xvi] A. Ikam, N. A. Mufti, M. Q. Saleem and A. R. Khan, aametic ptimizatin f suface ughness, kef and MRR in wie electical dischage machining (WEDM) using taguchidesign f expeiment, Junal f Mechanical Science and Technlgy, vl. 7, n. 7, 0, pp. -. [xvii] A. Shah, N. A. Mufti, D. Rakwal and E. Bambeg, Mateial emval ate, kef, suface ughness f tungsten cabide machined with wie electical dischage machining, Junal f Mateials Engineeing and efmance, vl. 0, n., 0, pp [xviii] D. H. Bestefield, C. Bestefield-Michna, G. H. Bestefield and M. Bestefield-Sace, Ttal Quality Management, easn Educatin Inc. & Dling Kindesley ublishing Inc., 00. [xix] E.Kannatey-Asibu, J., inciples f Lase Mateials cessing, Jhn Wiley & Sns, 009. F = Lase fequency p NOMENCLATURE N = Numbe f layes emved = Lase pwe S = Scanning speed S T = Making time m Ra = Suface ughness 55