THE INFLUENCE OF THE TOOL POINT ANGLE AND FEED RATE ON THE DELAMINATION AT DRILLING OF PRE-LAMINATED PARTICLEBOARD Mihi ISPAS Prof.dr.eng. Trnsilvni University of Brsov Fculty of Wood Engineering Address: B-dul Eroilor nr. 29, 500036 Brsov, Romni E-mil: isps.m@unitv.ro Lidi GURĂU Assoc.Prof.dr.eng. Trnsilvni University of Brsov Fculty of Wood Engineering Address: B-dul Eroilor nr. 29, 500036 Brsov, Romni E-mil: lidiguru@unitv.ro Sergiu RĂCĂŞAN Assist.dr.eng. Trnsilvni University of Brsov Fculty of Wood Engineering Address: B-dul Eroilor nr. 29, 500036 Brsov, Romni E-mil: sergiu.rcsn@unitv.ro Astrct: Pre-lminted prticleord is wood sed composite extensively used in the furniture industry. Drilling is the most common mchining process which prepres the pnels for joining using twist/helicl drills in the solute mjority of cses. The point ngle of the drill it nd the feed speed during drilling ply mjor role in gining good surfce qulity nd minimizing the delmintion tendency of the pre-lminted prticleord. The ojective of this study ws to mesure nd nlyze the influence of the two ove-mentioned fctors on the processing qulity, evluted y de size of delmintions, oth, t the entrnce side nd the exit side of the drill it. To ssess the defect, two prmeters were used: the delmintion fctor nd the effective re of delmintion. The results showed tht, in generl, the comintion of smll point ngle with low feed rte minimizes the delmintion of pre-lminted prticleord pnels t drilling. Key words: drilling; prticleord; delmintion. INTRODUCTION Drilling is one of the most usul nd frequent type of processing in the wood industry with the most common ppliction in the furniture industry. This hs developed long yers into mssive production of cses mde of doweled joint pnels, where the min rw mteril is prticleord nd minly pre-lminted (ccording to FAOSTAT, the worldwide prticleords production in 2014 ws of pp. 110.5 mil.m 3, more thn pp. 106.3 mil.m 3 in 2013 nd pp. 97.1 mil.m 3 in 2012). The opertion of free drilling, which is common for on-line processes, rises surfce defect noticed, t the pre-lminted prticleords, to occur round the drilled holes. Delmintion is processing defect which consists of locl detchment of the coting lyer engging chips/prticles pull-offs from the prticleord surfce. This phenomenon cn occur during drilling t the entrnce side s well s t the exit side (for drilled through holes). Its mgnitude depends on the processing prmeters nd cn e used s n indictor of the drilling qulity (Dvim et l. 2008). Some long go, Rdu (1967), in his extensive study on drilling with twist drills, referred to the qulity of drilling the prticleords in terms of visul qulifictions of the surfce in the neighourhood of the processed holes. Prmeters, s tool feed speed nd tool geometry, were mongst the ones investigted, ut the qulifictions were limited to sujective qulittive ssessments s: good, wek, slight increse, slight decrese. More recently, the delmintion cused y drilling the wood sed pnels, especilly medium density fierords (MDF), ws quntittively ssessed y using prmeter clled delmintion fctor, F d. Hence, Dvim et l. (2008) investigted the reltionships nd prmetric interction etween the feed rte nd the cutting speed on the F d t entry nd exit side of the holes in drilling the MDF. Two types of MDF pnels, melmine coted nd veneered, were tested using cemented cride (K20) drills. The F d decresed with the increse of the cutting speed nd incresed with the feed rte for oth mterils. Plnikumr et l. (2009), Prksh et l. (2009) studied the performnce chrcteristics given y F d in drilling opertions of MDF ords using cride tools. The mchining prmeters considered were: the spindle speed, the feed rte nd the drill dimeter. They found tht F d decreses with the increse of the cutting speed nd increses with the feed rte nd drill dimeter. 494
Prksh nd Plnikumr (2011) investigted the influence, t MDF, of the spindle speed, feed rte nd drill dimeter on the surfce roughness of the processed hole. The experimentl result reveled tht the most significnt drilling prmeter for the surfce roughness ws the feed rte followed y the cutting speed. Regrding the drilling of prticleords, Vlrmthi et l. (2013) dvnced the ide tht the thrust force developed during cutting ply mjor role in gining good surfce qulity nd minimizing the delmintion tendency. They studied the influence of the spindle speed, feed rte nd point ngle upon the thrust force. However, the drills they used hd geometry more specific to metls rther thn for wood sed mterils ( tip ngle 2κ r 100 ) nd the sme ws true for the processing prmeters (feed speeds v f = 75-225mm/min). These experiments led to the sme conclusions s with previous reserchers concerning the trends for the delmintion fctor. Studies on the processing PB with flt drills y Isps et l. (2014) hve showed tht, in generl, the comintion of smll tip ngle with low feed rte minimizes the delmintion of prelminted prticleord pnels t drilling. In conclusion, most of reserch on delmintion of wood sed mterils focussed minly on MDF nd less to the drilling of pre-lminted prticleords. Therefore, this pper is iming to study the delmintion defect which occurs when drilling pre-lminted prticleords, ut compred to other studies, this study employs tools nd cutting prmeters used in the woodworking industry. OBJECTIVES The ojective of this study is to evlute the influence of the tool point ngle nd feed speed on the drilling qulity of the pre-lminted prticleord. The processing qulity ws evluted y de size of delmintion mesured, oth, t the entrnce nd exit sides of the drilled holes. In order to evlute the delmintion dmge occurred during drilling, two prmeters were involved: the delmintion fctor, which ws used y previous reserchers, ut lso, the effective delmintion re mesured with n imge nlysis method, clled ImgeJ. METHOD, MATERIALS AND EQUIPMENT For the experiments, four twist (helicl) drill its with the point ngle, 2κ r, of 30, 60, 90, 120 nd one lip nd spur drill it, ll hving cutting dimeter of 10mm, were used (Fig.1). The clernce ngle of ll drills ws the sme α = 20. The symols used for those drills were tip ngle relted; T30, T60, T90, T120, respectively TLS for the lip nd spur drill. Forty squre smples, 80 mm side, were cut from single pre-lminted prticleord, 18 mm thick. They were divided into four groups of ten specimens ech. Ech specimen ws drilled with five different drills (T30, T60, T90, T120, respectively TLS) (Fig. 2). Ech group ws processed with different feed speed so tht the tooth ite, f z, ws different, hving the following vlues: 0.1, 0.3, 0.5 nd 0.7mm. The rottion speed, n, ws kept the sme for ll five types of drills, nmely 3000rpm. This led to four feed speed vlues, v f : 0.6, 1.8, 3.0 nd 4.2m/min. Fig. 1. The five types of drills used for processing pre-lminted prticleord: four twist drill its with the tip ngle, 2κ r, of 30, 60, 90, 120 nd one lip nd spur drill it (TLS) 495
For drilling, CNC type ISEL GFV/GFY ws used, which llowed the exct set-up of the drills rottion speed nd of their feed speeds. After drilling, ech hole dimeter ws mesured with n electronic clliper, with 0.01mm precision, on two perpendiculr directions nd men dimeter ws clculted for oth hole sides (entrnce nd exit), s cn e seen in Fig. 3. All drilled specimens were then scnned on oth sides nd received codes, IN, for entrnce side (Fig. 2) respectively OUT, for exit side (Fig. 2). Fig. 2. Pre-lminted prticleord specimens drilled with the five types of drills (T30, T60, T90, T120, respectively TLS in the middle) when the tooth ite ws 0.5 mm: - the entrnce side; -the exit side The scnned imges were used to evlute the delmintions tht occurred round ech hole, on oth sides. Two methods were used for this purpose nd they re presented s follows: the delmintion ws evluted y the delmintion fctor F d, given in [ 1], where D mx is the dimeter of the circle circumscried to the defect, while D is the men hole dimeter given y cliper mesurements D1 nd D2 (Fig. 3) F d = D D mx [ 1] the second method used n imge processing softwre, ImgeJ (http://en.wikipedi.org/wiki/imgej), to mesure exctly the re with delmintion, S, the white re in Fig. 3. Fig. 3. Evlution of the prticleord delmintion cused y drilling: - y the delmintion fctor F d.; - y the ImgeJ imge processing softwre Compred to the delmintion fctor, which pproximtes the zone with defect y tking into considertion the mximum dimeter of circle tht circumscries the defect, the second method is more precise, ecuse it identifies exctly the dmge round the holes. The method ws previously 496
used for wood species identifiction nd the working principle ws descried in detil y Guru et l. (2010). The softwre is le to detect imge fetures, to select their contour nd to return msk imge where only the items of interest re kept. In this study, they were holes with delmintion surrounding them (lue res in Fig. 4). Further, numericl dt mesuring their re ws cquired in spredsheet. c Fig. 4. Exit side of pre-lminted prticleord specimen drilled with five different tool geometries nd 0.7 mm tooth ite: - specimen scnned imge; - ImgeJ detection of drilled res including delmintions; c- contour detection of drilled holes with delmintions The delminted re ws clculted for ech hole s the difference etween the hole re with defect mesured with ImgeJ nd the processed hole re, clculted with the men dimeter D otined from two clliper mesurements D1 nd D2 tken on perpendiculr directions. RESULTS AND DISCUSSION The men vlues, stndrd devition nd coefficients of vrition were clculted for oth defect ssessment prmeters: the delmintion fctor F d (Tle 1 nd Tle 2) nd the effective delmintion re S (Tle 3 nd Tle 4). Tle 1 The men vlues, stndrd devitions nd coefficients of vrition for the delmintion fctor F d, t the entrnce side of the specimens, for vrious feed rtes nd drill geometries IN f z = 0.1mm f z = 0.3mm f z = 0.5mm f z = 0.7mm T30 1.10 0.04 4.00 1.20 0.04 3.49 1.24 0.03 2.18 1.25 0.06 4.58 T60 1.14 0.04 3.14 1.22 0.04 3.56 1.27 0.07 5.74 1.28 0.05 4.04 T90 1.11 0.04 3.65 1.22 0.05 3.91 1.25 0.05 4.31 1.30 0.04 2.89 T120 1.09 0.02 2.19 1.26 0.06 4.44 1.28 0.06 4.35 1.32 0.06 4.41 TLS 1.14 0.06 4.88 1.31 0.05 3.53 1.34 0.04 3.33 1.35 0.04 2.97 Tle 2 The men vlues, stndrd devitions nd coefficients of vrition for the delmintion fctor F d, t the exit side of the specimens, for vrious feed rtes nd drill geometries OUT f z = 0.1mm f z = 0.3mm f z = 0.5mm f z = 0.7mm T30 1.01 0.02 1.75 1.02 0.03 2.95 1.05 0.08 7.68 1.08 0.05 4.96 T60 1.00 0.03 3.01 1.02 0.04 3.68 1.10 0.09 8.43 1.10 0.08 7.28 T90 1.01 0.02 2.20 1.01 0.03 2.47 1.07 0.06 5.55 1.07 0.05 4.21 T120 1.07 0.10 8.91 1.11 0.11 10.06 1.06 0.09 8.91 1.08 0.07 6.45 TLS 1.70 0.12 7.30 1.82 0.17 9.09 1.78 0.27 15.26 1.70 0.22 13.01 497
Tle 3 The men vlues, stndrd devitions nd coefficients of vrition for the effective delmintion re S, t the entrnce side of the specimens, for vrious feed rtes nd drill geometries IN f z = 0.1mm f z = 0.3mm f z = 0.5mm f z = 0.7mm T30 4.41 1.26 28.48 7.11 2.93 41.21 9.95 1.84 18.45 10.70 2.09 19.57 T60 5.41 1.06 19.62 7.81 1.92 24.58 11.54 3.65 31.64 14.99 3.43 22.88 T90 3.63 0.57 15.66 6.93 2.43 35.12 10.20 3.13 30.70 13.37 2.01 15.06 T120 2.22 0.91 40.88 9.42 2.77 29.41 13.18 3.71 28.18 15.68 3.23 20.63 TLS 3.75 1.05 28.08 12.68 4.61 36.39 17.38 2.75 15.85 22.83 4.01 17.58 Tle 4 The men vlues, stndrd devitions nd coefficients of vrition for the effective delmintion re S, t the exit side of the specimens, for vrious feed rtes nd drill geometries OUT f z = 0.1mm f z = 0.3mm f z = 0.5mm f z = 0.7mm T30 1.04 0.31 29.59 1.98 1.51 75.99 1.77 0.84 47.53 1.37 0.86 62.69 T60 1.05 0.41 39.25 1.77 1.39 78.61 1.55 1.28 82.02 1.32 0.47 35.58 T90 1.26 0.50 39.32 1.68 1.00 59.71 1.38 0.93 66.98 1.51 0.49 32.07 T120 1.41 0.71 50.62 2.47 1.56 63.32 1.65 0.97 59.17 2.40 2.66 111.11 TLS 60.28 20.74 34.41 96.12 22.40 23.30 74.91 41.62 55.56 69.21 42.07 60.78 The vrition of oth type of delmintion prmeters with the tool feed speed nd geometry is depicted in Fig. 5 nd Fig. 6. 1.40 1.35 1.30 1.25 1.20 1.15 1.10 1.05 1.00 Fd (delmintion fctor), IN fz=0.1 fz=0.3 fz=0.5 fz=0.7 Tooth ite, mm TS T120 T90 T60 T30 Fd (delmintion fctor), OUT Fig. 5. The vrition of the delmintion fctor with the tool feed speed nd geometry (figures represent men vlues): - t the entrnce side of the drilled specimens; - t the exit side of the drilled specimens Delmintion re (verges), IN 1.90 1.80 1.70 1.60 1.50 1.40 1.30 1.20 1.10 1.00 fz=0.1 fz=0.3 fz=0.5 fz=0.7 Tooth ite, mm TS T120 T90 T60 T30 mm 2 25.00 20.00 15.00 10.00 TS T120 T90 T60 T30 5.00 0.00 fz=0.1 fz=0.3 fz=0.5 fz=0.7 Tooth ite, mm Fig. 6. The vrition of the effective delmintion re with the tool feed speed nd geometry (figures represent men vlues): - t the entrnce side of the drilled specimens; - t the exit side of the drilled specimens 498
By compring the delmintion expressed y oth prmeters, delmintion fctor nd effective delmintion re, it cn e oserved reltive similr trend, which mens tht delmintion fctor is close non-dimensionl pproximtion of the defect nd its evolution with processing prmeters. However, if n exct mesure of the delmintion re is requested, then the effective delmintion re is dvntgeous ecuse it cn give dimensionl quntifiction. Whtever the specimen (hole) side, the iggest delmintions occurred when drilling with lip nd spur drill it (TLS), regrdless of the used feed speed (exception: delmintions on entrnce side produced when drilling with f z = 0.1mm). At the sme time, it cn e seen tht for the entrnce side of the holes, the size of delmintions produced with this drill it (TLS) ws comprle to those produced y the other drills used. Not the sme cn e sid out the delmintions on the exit side of holes. In this cse, the effective delmintion re produced y the TLS drill ws, in some situtions, more thn 50 times lrger tht those produced y the other drills. Another thing tht cn e noticed is tht whichever the side of the holes there ws generl trend (stronger for the entrnce side nd much weker for the exit side) of delmintion increse with the increse of the tooth ite (feed rte), oserved y oth defect prmeters nd ll drill geometries. This result is in greement with other results from literture (Vlrmthi et l. 2013; Isps et l. 2014). The most sensitive to the vrition of the feed rte ws T120, where the delmintion size lmost douled t the exit side nd it ws 7 times lrger t the entrnce side for tooth ite of 0.7mm compred to 0.1mm. A very interesting thing, for ll drills except TLS, the defect zone ws lrger t the entrnce side of the drill compred to the exit side with the gretest mount for T60 (more thn 11 times, t f z =0.7mm), followed y T90 (lmost 9 times) nd then y the other tool geometries T120 nd T30 (lmost 8 times). For the TLS drill, the effect is opposite: igger delmintions t the exit side of the holes (more thn 16 times t f z =0.1mm nd incresingly smller with the incresing of the feed speed). Whtever the side of the holes the influence of the tool geometry on the delmintion size did not hve cler trend. In generl, T30, T60 nd T90 gve similr processing qulity, etter thn T120. TLS gve the worse qulity y fr. However, ecuse of its elongted tip geometry, processing with T30 in cse of thin ords is limited to mnufcturing through holes rther thn with limited depth (Fig. 7). Fig. 7. Limittion of T30 drill it nd its elongted tip geometry when mnufcturing thin ords Therefore, considering the delmintion occurred t the entrnce side s well s t the exit side, drill type T90 seems the est option for getting the est qulity nd for hving the flexiility of choice for holes with or without limited depth. At the opposite, the drills types T120 nd especilly TLS seem to hve worsened the drilling qulity. CONCLUSIONS Free drilling is common opertion for pre-lminted prticleords in the furniture industry. The qulity of this opertion cn e ssessed y the delmintion occurring round the hole. This pper exmined this defect y mens of two prmeters: non-dimensionl one used lso y other reserchers, the delmintion fctor, nd one mesuring the effective re of defect with n imge processing method. The influence of the feed rte (tooth ite) nd tool geometry (tip ngle) ws ssessed y the ove qulity prmeters. Both prmeters showed similr trend with the dvntge of the ltter for giving dimensionl informtion out the defect re. Generlly, the delmintion incresed with the increse of the tooth ite (feed rte) for ll drill geometries. The defect zone ws lrger t the entrnce side of the drill compred to the exit side with the gretest mount for the lip nd spur drill, followed y the other drills. 499
The results showed n increse in the delmintion defect with the increse in the drill tip ngle, ut the influence wsn t very cler for the 30, 60 nd 90 tip ngle. If delmintion nd flexiility of hole depth is considered, helicl drill with 90 tip ngle gve the est qulity. The lip nd spur drill nd the drill with the gretest tip ngle, 120, do not seem pproprite for processing pre-lminted prticleords. Further studies my complete these results for vrious rottion speeds nd other types of drills to optimise the process qulity t drilling pre-lminted prticleords. REFERENCES Dvim JP, Clemente VC, Silv S (2008) Drilling investigtion of MDF (medium density fireord). Journl of Mterils Processing Technology 203:537 541. Issues 1 3 Guru L, Timr MC, Cionc M, Olrescu A, Dumitrscu R (2010) An ojective method to nlyse some microscopic chrcteristics of two secondry eech wood resources. PRO Ligno 6(1):35-45. Isps M, Guru L, Rcsn S (2014) Study Regrding the Vrition of the Thrust Force, Drilling Torque nd Surfce Delmintion with the Feed per Tooth nd Drill Tip Angle t Drilling Pre-lminted Prticleord. PRO Ligno 10(4):40-52. Plnikumr K, Prksh S, Mnohrn N (2009) Experimentl Investigtion nd Anlysis on Delmintion in Drilling of Wood Composite Medium Density Fier Bords. Mterils nd Mnufcturing Processes 24, Issue 12 Prksh S, Plnikumr K (2011) Modeling for prediction of surfce roughness in drilling MDF pnels using response surfce methodology, Journl of Composite Mterils 45(16):1639-1646 Prksh S, Plnikumr K, Mnohrn N (2009) Optimiztion of delmintion fctor in drilling medium-density fierords (MDF) using desirility-sed pproch. The Interntionl Journl of Advnced Mnufcturing Technology 45:370-381. Issue 3-4 Rdu A (1967) Contriutions to the estlishment of the optiml prmeters for wood drill its (in Romnin); PhD Thesis. Institutul Politehnic Brşov Vlrmthi TN, Plnikumr K, Lth B (2013) Mesurement nd nlysis of thrust force in drilling of prticleord (PB) composite pnels, Mesurement 46:1220 1230. Issue 3 http://en.wikipedi.org/wiki/imgej http://fostt3.fo.org/rowse/f/*/e 500