Research and Development of Economical CNC Software for 2D Lean Friction Stir Welding Machine

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1 Interntonl Journl of Mechncl Engneerng nd Applctons 08; 6(: do: 068/jjme08060 ISSN: 0-0X (Prnt; ISSN: 0-08 (Onlne Reserch nd Development of Economcl CNC Softwre for D Len Frcton Str Weldng Mchne Dop Sokhn Ant Bll, Zhou Hu, Xu Ch Deprtment of Mechncl Engneerng, Donghu Unversty, Shngh, Chn Eml ddress: To cte ths rtcle: Dop Sokhn Ant Bll, Zhou Hu, Xu Ch Reserch nd Development of Economcl CNC Softwre for D Len Frcton Str Weldng Mchne Interntonl Journl of Mechncl Engneerng nd Applctons Vol 6, No, 08, pp 59-6 do: 068/jjme08060 Receved: Aprl, 08; Accepted: My 7, 08; Publshed: June 0, 08 Abstrct: Ths project s developng two-dmensonl frcton str mchne, reltvely low cost to cheve four xs frcton str weldng equpment wth rel-tme servo control, where the correspondng trjectory plnnng functon n cm s reltvely ndependent by mkng full use of Gll moton controller hs strong mult xs lnkge control cpblty nd fst rel-tme communcton cpbltes nd the Gll moton controllet G code nlyss softwre module s developped Ths pper s studyng the trjectory plnnng softwre system desgn nd development of frcton str for dfferent trjectores n the pln nd s mng to solve the moton trjectory control problem wth complex weldng pth A deep study of three polynoml splne functon trjectory plnner s done, nd the complex moton trjectory of the mult xs weldng mchne controlled by ccelerton nd speed s relzed The mcro rc trnston pproxmton method s ppled to optmze the nflecton pont wth brupt chnge of trck pth nd cheve smooth nflecton moton Keywords: Frcton Str Weldng (FSW, Gll Moton Controller, G Code, Speed Optmzton Introducton Invented n December 99 by The Weldng Insttute (TWI, Frcton str weldng (FSW s qute new process for weldng dfferent knds of mterls, whch provdes n excellent weldng qulty FSW process does not requre use of weldng mterl nd does not produce fume gs FSW cn be used to weld metls such s lumnum lloy, copper, mgnesum, znc, steel nd ttnum Regrdng to ts benefts, FSW hs been wdely used n hevy ndustres such s shp, rcrft, rlwy, ntonl defense nd mltry [] Although the reserch of frcton str weldng technology s more mture, n prctcl engneerng pplcton, reform of the trdtonl hgh grde numercl control mchne s often ppled, nd there revoluton hgh speed of frcton hed nd n extenson through the spndle nto the jont of the workpece shown n fgure, nd the reltve moton of the XY xs s formed to complete the weldng In FSW process, the weld s effectve even before mterls rech ther meltng temperture, so no porosty s observe on the weldng surfce, therefore hgh-qulty weld s obtned Sometmes t even hppens tht the weld become stronger thn the bse mterl Usully mterls propertes do not notce chnges n ther propretes [] Wth FSW process, the weldng problem of the low meltng pont lloy hs been solved successfully Fgure Prncple of FSW process But the Frcton Str Weldng method usng the exstng numercl control equpment hs hndered the populrzton of the technology n cvl feld becuse of equpment hgh cost, whch s not fclttng the ntegrton of mltry nd cvln []

2 Interntonl Journl of Mechncl Engneerng nd Applctons 08; 6(: FSW Process Mn Prmeters The FSW hed shpe, for mn prmeters whch hve consderng effect on weld formng nd jont mechncl propertes, re essentlly the rottng speed (n, the weldng speed (v nd the weldng pressure (p [] ( FSW Rotton speed (n Accordng to the str weldng hed rottonl speed, when the weldng speed s slow nd weldng surfce become brght nd smooth, but n the bck of weld cn be seen s the locl fuson nd we got emergence of shrnkge The shrnkge wll dspper whenever the weldng speed (v ncrese As well s constnt growng of the weldng speed, weld surfce roughness vrton wll be clerly seen, the smple cut wll fnd tunnel defects long the cross secton of the weld, nd when the weldng speed s too much fst, more defectons tunnel type wll be notced, or even trench wll pper on the weld surfce [5] In FSW process there s relton between the rottonl speed nd het produced durng the weldng process whch cn be expressed s: E=πωµ F (r 0 + r 0 r + r / [5 (r 0 +r v] ( Where ω s the rotton speed, r/mn; µthe frcton coeffcent; F tool shoulder pressure, N/mm; r0 s the shoulder rdus, mm; r pn Rdus, mm; v weldng speed, mm/mn ( FSW weldng speed (v Durng FSW process, the weldng heds of prtculr type of weldng, f weldng speed nd weldng pressure remn constnt, the rottonl speed s low, the generted frcton het not enough, weld metl cnnot rech the thermoplstc stte, to form therml plstc flow lyer Tht mkes the FSW process to be not ble to form closed weld by mllng n the metl, whch ppers n the weld groove surfce Weldng het producton depends on rotton speed vrton [6] In FSW process velocty cn be express s: dmensonl weldng pth s the lest complex, requrng mnml flexblty (smll number of shfts The smplest verson of ths mchne hs only two xes (x, y Techncl Dffcultes nd Solutons The modfed mllng mchne whch s presently used for FSW process hs lmts n weldng complex pths nd t s known tht the flexblty of every mchne s defned by the number of degree of freedom present n ths mchne nd the mnmum requre on ech s t lest one dmensonl In our cse, to be ble to provde soluton n weldng dfferent trjectores, t lest three-dmensonl mchne s requred There the mn problem n FSW ndustrlzton s comng over: how to nsure the lodng cpcty to the weldng mchne n dfferent prts of the weldng for pth where we know tht prts cn be dfferent n mterl, sze, geometry, the requred precson, etc So, the weldng prts or the weldng hed re gong to be ble to move to ensure requrements for the progrm buldng by tht the degree of freedom of the mchne wll be ncresed Tht s wht not so frequently seen from conventonl mllng mchnes The dversty nd complexty of trjectores requre more flexblty from weldng mchnes Why not choosng robot rm to be the weldng hed of FSW? A robot rm system s gong to weld esly curve, crculr nd strght jonts whch request system of two degree of freedoms (DOFs t lest Further studes were lredy orented to those rm robots n order to brng flexblty n FSW weldng process But robot controllng system s not the most economc system whch s gong to help FSW process to wden ts user s world[8] v r =ωr Usnθ ( Where r s rdl dstnce from tool xs θ s the ngle between the rdl vector r nd the weldng drecton U s weldng tool constnt speed ( FSW xl shoulder pressure (p In FSW process, n enough pressure ppled s so fr enough to obtn the requre frcton weldng het between the FSW hed nd the weldng peces At the sme tme, the weldng pressure plys role n lmtng the overflow of plstc flud nd ensurng the formton of weld bed [7] Therefore, the weldng pressure sze plys bg prt n weld qulty Its nfluence mght be consdered Dffculty n FSW Weldng Process The flexblty of the modfed mllng mchne for FSW process lmts the complexty of the weldng pth (lner, curve The number of xes (degrees of freedom, the mchne hs usully estblshed the flexblty of the mchne One Fgure FSW process mchne structure

3 6 Dop Sokhn Ant Bll et l: Reserch nd Development of Economcl CNC Softwre for D Len Frcton Str Weldng Mchne In ths pper, the work wll consst to fnd smpler nd economcl prototype of FSW process to weld curve whch cn be good lterntve to robot rm The workng system wll be system of four xes whch hs lrge workspce nd ech xe s gong to be drven by drver where lner encoder gves hgh precson of gudng nd loclzton [9] From the mchne structure ccordng to fgure, t cn be esly seen tht the work peces cn move through X, Y xs nd there n ddtonl W xs s bult to provde more flexblty whle weldng rcs 5 Trjectory Plnner For ths pper study cse, trjectores shown s n fgure re consdered: A contnuous spce trjectory s supposed, from tme t 0 up to t f Splt nto N segments Ech segment cn be pproxmted by three polynoml splne functons, nd the trjectores on the connectng ponts of the djcent two segment boundres re kept contnuous For tht t s necessry to know the coordntes nd veloctes of the ponts t ech end [0] T T Order symbol r = (x, y,z nd r = (x, y,z, =0,,, N, The poston nd velocty vector of gven reference pont on sptl trjectory For the frst secton t t t, the reltve tme vrble s ntroduced t τ =, 0 τ t ( And t s represented by three polynoml splne functons of ponts nd ponts + τ + τ + r( τ = τ ( 6 Controllng Weldng Trjectory Velocty Dffcultes When the rottonl speed (n doesn`t rech sutble speed, there s no wy to hve rght mterl flow whch gve good weldng qulty Wth rottonl speed ncresng, the frcton coeffcent between tools nd mterls ncrese t the sme tme, there the nput het s lso ncresng by t the sme tme By het nput ncresng, the mterl wll soften fster thn norml wy Further, wth the rottonl speed (n s knd of low, the wer of the mxng hed s too fst whch ncrese the xl force [] 7 Trjectory Velocty Expresson As followng wth the lredy descrbe functon n trjectory plnner To τ The frst dervtve dr( τ V= = r(t (t = + τ + τ (5 ( Then boundry condtons re s follows: τ = τ = dr(0 0, r(0 = r, = r(t dr( 0, r( = r, = r(t Substtutng these boundry condtons nto equtons ( nd (5 cn be obtned: r r r(t (t = = = r = (b Fgure Dfferent weldng trjectores By solvng the bove smultneous equtons, the undetermned coeffcents of three polynoml splne functons,,, cn be determned

4 Interntonl Journl of Mechncl Engneerng nd Applctons 08; 6(: = r = r = r = r = r = r (t r dr( + r + r dr( = (t (t dr( + r + r r dr( + r(t dr( + r(t (6 By substtutng these coeffcents nto the equton (, three polynoml splne functons cn be obtned dr( dr( dr( r( τ = r + τ + [ r + r ] τ dr( dr( + [r + r + ] τ Or r( τ = ( τ χ r + τ( τ (r + + τ ( τ(r + τ r (7 χ dr type, χ = 8 Anlyss of the Velocty nd Contour Error t Corner How to mntn the lftng speed smooth especlly t the corner durng the process s no neglgble pont when t comes to tool lfe nd mchne workng stblty As t ppers n fgure : Fgure 5 Anlyss of velocty t the corner pont The ngle σ s the ngle of the two moton vectors, ν s the unt vector of the speed t the end of the processng secton S nd ν s the unt vector of the speed t the begnnng of the processng secton S then: Thus, t cn be obtned: σ=ν ν (8 Fgure Corner contourng To solve ths problem over, n nlyss the mxmum llowble velocty nd contour error of trnston curve When control of the contour error t the corner s done, the mxmum dstnce needed for the decelerton cn be clculted nd the mxmum llowble speed t the begnnng of the corner trnston cn lso be defned The vector trnston lgorthm tkes ccount of the velocty smoothng nd contour error n the corner trnston The hypothess wll be tht: the speed curves of ech processng secton re bsed on the trpezum velocty curve The two processng sectons S nd S, drectons of moton re ppered n Fgure 5 θ=π-σ (9 When the trnston t the corner s between the strght lne nd rc or rc nd rc re, the end of the unt vector drecton or the strtng unt vector drecton of crculr rc s the end pont or the strtng pont of the rc the tngent drecton As ppered n fgure -, decelerton through dstnce d s supposed, S velocty drop to zero; the ccelerton of the trpezod velocty curve s consdered; the shortest dstnce between the corner vertex nd the trnston curve s δ, there: dδ/cos (0 Regrdng to the hypothess, there s n blty to clculte the velocty t the pont A:

5 6 Dop Sokhn Ant Bll et l: Reserch nd Development of Economcl CNC Softwre for D Len Frcton Str Weldng Mchne There: v ( d= ( ( The speed of the trnston t the corner s ntroduced by the formul ( nd (: v /cos ( When the feed speed s less thn or equl to the strvton vector trnston wll strt From the bove know δ nd the mxmum llowble speed t the corner trnston s proportonl Therefore, the trnston speed cn be controlled by controllng the profle error δ, so tht the shpe error control cn be done 9 System Components Expermentl equpment nd pltform wll ncludes PC, moton control crd nd weldng tble On the PC, provdng humn-mchne nterfce by softwre progrmmng, moton controller s selected by the Amercn GALIL compny moton control crd, usng hgh performnce mcroprocessor s the core processor, cn complete weld n pln wth meet of the rel-tme poston t the very sutble weldng speed, ll control wth servo control flterng nd other functons, cn be developed n the Wndows pltform pplcton softwre, whch s composed by vrety of control system The purpose of ths experment through X nd Y moves, weldng hed tool s gong to be ble to weld dfferent trjectores n pln, Y curve n X plne The weldng tble s drven by servo motors n two drectons, X nd Y, nd cn be crred out wth GALIL crd And the Z xs ensures the up down move of the weldng hed [] 0 Concluson Frcton str weldng process s qute new process tht hs bg potentl of use becuse of ts chrcterzton of beng frendly wth the envronment: no fumes nd no use of fllng mterls Only for the mn reson to protect our envronment whch gettng worse nd worse due to dly use chemcl we must fnd wy to mke wdely use of FWS process To study ts flexblty to weld pths by low cost s gong to ntroduce t n others felds not only hevy mnufcturng References [] Dong Chun Ln, Lun red, off the brdge frcton str weldng: Weldng n erospce, prospects of pplcton nd development of the ndustry, 009 (: 5- [] Bbu, A S nd Devnthn, C, An Overvew of Frcton Str Weldng, Int J Res Mech Eng Technol (, (0 [] XIA Luosheng, ZHU Shuhong, LU Dunmn, the Study of Open CNC System for Two-dmensonl FSW Equpment Bsed on PMAC Zhngjje Insttute of Aeronutcl Engneerng, Zhngjje 7000, CHN; Centrl South Unversty, Chngsh008, CHN Chn Acdemc Journl Electronc Publshng House [] G C Jdhv, R S Dlu, Frcton Str Weldng Process Prmeters nd ts Vrbles: A Revew, Reserch Scholr, Mechncl Deprtment, Govt Engneerng College, Amrwt-60, Ind; Deprtment of Mechncl Engneerng, Govt Engneerng College, Amrwt-60, Ind IJECS Volume Issue 6 June, 0 Pge No [5] Ammour, A nd Hmde, R, On the selecton of consttutve equton for modelng the frcton str processes of twn roll cst wrought AZB, Mterls & Desgn 57, (0 [6] W R Longhurst, A M Struss, nd G E Cook, Enblng utomton of frcton str weldng: the odulton of weld sem nput energy by trverse speed force control, J Dyn Syst Mes Control ( [7] Xng L, Koll dwn, Lun Guo Hong, Dong Chun Ln, The nfluence of the shpe of the strrng needle on the formton of the S curve of the weld sem of frcton str weldng (FSW Nnchng Aeronutcl Unversty, Nnchng, Jngx 006; Chn Frcton Str Weldng Reserch Center, Bejng 000 [8] Tbtbepour, M, Hettler, J, Delrue, S nd Vn Den Abeele, K, Non-destructve ultrsonc exmnton of root defects n frcton str welded butt-jonts, NDT & E Interntonl 80, - (06 [9] Jfeng Wu, Ru Zhng, Gungxn Yng, (05 "Desgn nd experment verfcton of new hevy frcton-str-weld robot for lrge-scle complex surfce structures", Industrl Robot: An Interntonl Journl, Vol Issue:, pp -8, doorg/008/ir [0] Ts M S, et Al Development of n ntegrted look-hed dynmcs-bsed NURBS nterpoltor for hgh precson mchnery [J] Computer-Aded Desgn, 008, 0: 55~566 [] Yeh S, Hsu P Adptve-feed rte nterpolton for prmetrc curves wth confned chord error [J] Computer-Aded Desgn, 00, : 9-7 [] Yeh S, Hsu P The speed-controlled nterpoltor for mchnng prmetrc curves [J] Computer-Aded Desgn, 999, : 9-57