...... Dündar Sofuoğlu, Kurtoğlu: Effects of Machining Conditions on Surface Roughness... Sait Dündar Sofuoğlu1, Ahmet Kurtoğlu2 Effects of Machining Conditions on Surface Roughness in Planing and Sanding of Solid Wood Utjecaj uvjeta obrade na hrapavost površine pri blanjanju i brušenju masivnog drva Original scientifi c paper • Izvorni znanstveni rad Received – prispjelo: 19. 2. 2014. Accepted – prihvaćeno: 6. 11. 2015. UDK: 630*823.121; 630*823.22 doi:10.5552/drind.2015.1406 ABSTRACT • It is important to evaluate the effect of machining and wood machining properties on surface quality to determine and upgrade the data on wood machining properties and to defi ne convenient usage areas for some native wood species of Turkey. European black pine (Pinus nigra Arnold) and cedar of Lebanon (Cedrus libani A. Rich) are two softwood species and sessile oak (Quercus petraea Lieble) and black poplar (Populus nigra L.) are two hardwood species commonly used and grown in Turkey. These trees species were selected as experi- mental material for the study. Roughness measurements are signifi cant in the determination of wood surface qual- ity for use as a fi nal product. This study evaluated roughness measurements after planing and sanding operations, and found that the highest value for average roughness (Ra) was observed as 6.780 μm. in sessile oak, followed by black poplar at 6.338 μm, cedar of Lebanon at 4.836 μm, and black pine at 4.740 μm. The average roughness values for wood in directions perpendicular to the grain and along the grain from highest to lowest were sessile oak, black poplar, black pine, and cedar of Lebanon. Key words:Wood, surface roughness, planing, sanding SAŽETAK • Istraživanje utjecaja mehaničke obrade i svojstava drva na kvalitetu obrađene površine važno je kako bi se dopunili podaci o svojstvima drva pri mehaničkoj obradi i defi nirala prikladna područja upotrebe nekih domaćih vrsta drva u Turskoj. Europski crni bor (Pinus nigra Arnold) i libanonski cedar (Cedrus libani A. Rich) dvije su meke vrste drva, a hrast kitnjak (Quercus petraea Lieble) i crna topola (Populus nigra L.) dvije su tvrde vrste drva koje se često upotrebljavaju i uzgajaju u Turskoj. Te su četiri vrste drva odabrane za istraživanje hrapavosti pri mehaničkoj obradi. Mjerenje hrapavosti važno je za određivanje kvalitete površine drva goto- vog proizvoda. U ovom se istraživanju ocjenjuje izmjerena hrapavost drva nakon njegova blanjanja i brušenja. Utvrđeno je da je najveća izmjerena vrijednost prosječne hrapavosti (Ra) iznosila 6,780 μm na uzorcima drva hrasta kitnjaka te 6,338 μm na uzorcima drva crne topole, dok je na uzorcima drva libanonskog cedra izmjerena hrapavost od 4,836 μm, a na uzorcima crnog bora 4,740 μm. Izmjerene su vrijednosti prosječne hrapavosti drva u smjeru okomito na vlakanca i uzduž vlakanaca, od najviše do najniže, na uzorcima hrasta kitnjaka, crne topole, crnog bora i libanonskog cedra. Ključne riječi: drvo, hrapavost površine, blanjanje, brušenje 1 Author is PhD at Department of Wood Works Industrial Engineering, Faculty of Simav Technology, Dumlupinar University, Simav/Kutahya, Turkey. 2Author is professor at Department of Interior Architecture, Faculty of Fine Arts and Design, Dogus University, Acibadem, Kadikoy/ Istanbul, Turkey. 1 Autor je doktor znanosti u Odjelu za industrijsku obradu drva, Tehnološki fakultet, Sveučilište Dumlupinar, Simav/Kutahya, Turska. 2Autor je profesor Odjela za unutarnje uređenje, Fakultet likovne umjetnosti i dizajna, Sveučilište Dogus, Acibadem, Kadikoy/Istanbul, Turska. DRVNA INDUSTRIJA 66 (4) 265-272 (2015) 265 Dündar Sofuoğlu, Kurtoğlu: Effects of Machining Conditions on Surface Roughness... ...... 1 INTRODUCTION (2002) studied surface roughness in planing and sand- 1. UVOD ing of Uludag fi r (Abies bornmülleriana Mattf.). Efe et al. (2003) carried out surface roughness measurements In wood fi nishing, roughness refl ects faults on a in planing experiments conducted under various condi- wood surface as a result of the operations carried out in tions on black locust (Robinia pseudoacacia L.) and production. These faults are repeated with a low prob- walnut (Juglans regia). Kilic et al. (2003) studied sur- ability and periodically. Control and monitoring of sur- face roughness in the sawing of wood from Scotch pine face roughness is required to maintain product quality (Pinus sylvestris L.) and chestnut (Castania sativa at the same level throughout the production, as this mill.). Ors et al. (2003) determined surface roughness property affects wood adhesion and changes can in- in the sanding of wood from black locust (Robinia crease loss. After solid wood undergoes machining by pseudoacacia L.) and oak (Quercus petrea L.) using a sawing, planing, sanding, etc., it becomes a fi nal prod- stylus trace method. Aslandogan (2005) determined uct. Wood fi nishing is an important factor in determin- the surface roughness after planing and sanding exper- ing the economic value of the fi nal product. Accord- iments of European black pine (Pinus nigra Arnold) ingly, surface roughness is a defi nitive property for that were artifi cially grown. Sogutlu (2005) determined measuring the success of the wood fi nish. surface roughness in sanding of black locust (Rubinia Surface roughness can be evaluated quantitative- pseudoacacia L.), European pear (Pirus communis L.), ly and qualitatively. Each approach has advantages and chestnut (Castanea sativa Mill.), oak (Quercus petrea disadvantages, such as a slower speed, sensitivity, and Lieble) and cedar of Lebanon (Cedrus libani A.Rich) the accuracy of results (Malkocoglu, 1999). There are grown in Turkey. Sonmez et al. (2005) determined sur- various methods of surface roughness measuring in the face roughness in the planing of wood from Black lo- area of woodworking. Lumber surface roughness can cust (Rubinia pseudoacacia L.), European pear, chest- be measured with an airfl ow method (Porter, 1971). An nut, oak and cedar of Lebanon. imaged light and needle-scan can also measure surface Aras et al. (2007) evaluated surface roughness in roughness (Peters, 1970). It is thought that surface the turning of walnut (Juglans regia L.), oriental beech roughness in industrial applications can be easily done (Fagus orientalis L.), largeleaf linden (Tilia grandifo- with a light-sectioning shadow scanner method (San- lia Ehrh.) and aspen (Populus tremula L.) with a stylus dak, 2005). However, the stylus trace method has trace method. Malkocoglu (2007) investigated planing emerged as the most suitable and applicable method in properties and surface roughness of oriental beech (Fa- the measurement of surface roughness (Peters, 1971; gus orientalis Lipsky.) grown in the Eastern Black sea Faust, 1987). region, Anatolian chestnut (Castenea sativa Mill.), Stumbo (1960) mentioned that a decrease in sur- black alder (Alnus glutinosa), Scots pine (Pinus sylves- face roughness will occur with an increase in the cutter tris L.) and oriental spruce (Picea orientalis (L.). It was speed and number of teeth in cutting saws. An increase observed that using veneer with tough surfaces in ply- in surface roughness will occur with an increase in wood production reduced adhesion quality (Faust, feeding speed. When planing and milling softwood 1986). Hiziroglu et al. (2013) determined surface species compared to hardwood species, roughness is roughness in the sanding of pine (Pinus strobus), bor- greater when cutting perpendicular to the grain than neo camphor (Dryobalanops spp.) and meranti (Shorea when cutting along the grain. In general, worn cutters spp). Zhong et al. (2007) evaluated surface roughness increase surface roughness. With regards to average in various commercially produced composite panels roughness values, approximately the same values are including particleboard, medium density fi breboard obtained in directions perpendicular to the grain and (MDF), and plywood in addition to ten different solid along the grain (Steward, 1970). wood species which are commonly used in furniture Roughness of various tree species has been in- production. Skaljic et al. (2009) determined surface vestigated. Gurleyen (1998) studied surface roughness roughness values of planed beech-wood (Fagus L.), in the planing of beech (Fagus orientalis L.), scotch oak - wood (Quercus L.) and fi r-wood (Abies alba pine (Pinus sylvestris L.), sessile oak (Quercus petreae Mill.) specimens. L.), and black locust (Robinia pseudoacacia L.). This study investigated and evaluated surface Demirci (1998) studied oriental beech (Fagus orienta- roughness through planing and sanding experiments lis L.), scotch pine (Pinus sylvestris L.), oak (Quercus for several hardwood and softwood species commonly petreae L.), and black locust (Robinia pseudoacacia used in Turkey. L.) in the machining of massive wooden material with circular saws. Ors et al. (1999) studied the planing and sanding operations of planed and sanded massive 2 MATERIAL AND METHODS wooden material using oriental beech and Scotch pine. 2. MATERIJAL I METODE Kantay et al. (2001) studied the surface roughness of 2.1 Wood material sliced veneer boards from tree species of walnut (Jug- 2.1. Uzorci drva lans regia L.) and oriental beech (Fagus orientalis L.) Various species of softwoods and hardwoods were in Turkey. Ünsal et al. (2002) studied the surface used for the experiments. European black pine (Pinus roughness of massive parquets from oak and oriental nigra Arnold) and cedar of Lebanon (Cedrus libani A. beech in Turkey using a stylus trace method. Ilter et al. Rich), as two softwood species, and Sessile Oak (Quer- 266 DRVNA INDUSTRIJA 66 (4) 265-272 (2015) ...... Dündar Sofuoğlu, Kurtoğlu: Effects of Machining Conditions on Surface Roughness... Table 1 Machining conditions of planing experiments Tabli ca 1. Uvjeti obrade tijekom provedbe eksperimenta pri blanjanju Number of knives Feed ratePosmična brzina Number of knife marks per cm Cutting angles, o Broj noževa m/min Broj prolazaka noža po 1 cm Kut rezanja, o Run 1 / Prolazak 1. 4 8.6 4.72 25 Run 2 / Prolazak 2. 4 18 2.36 25 Run 3 / Prolazak 3. 2 8.6 4.72 15 Run 4 / Prolazak 4. 2 8.6 4.72 20 cus petraea Lieble) and black poplar (Populus nigra L.), 2.4 Statistical methods used as two hardwood species commonly used and grown in 2.4. Statističke metode Turkey, were selected as experimental material for the Arithmetic mean and standard deviation were study. The samples were all randomly selected from used for the evaluation of the specifi c gravity and the naturally grown wood in Istanbul and Kutahya in Tur- number of annual rings per cm. In the evaluation of key. The wood was conditioned at a temperature of 20 ± roughness results, correlation analysis, analysis of var- 2 °C and 65 ± 5 % to a moisture content of about 12 %. iance (ANOVA), and also a t-test were employed to 30 specimens (25 x 102 x 910 mm) were used for each investigate whether there is a signifi cant difference be- planing and sanding test according to ASTM standard D tween the roughness values with respect to the applied 1666 (2004) (ASTM International, 2004). measurement directions. 2.2 Performance of planing and sanding experiments 2.2. Provedba eksperimenta pri blanjanju i brušenju 3 RESULTS AND DISCUSSION3. REZULTATI I RASPRAVA Planing experiments were carried out using a TORK brand K500-X250 model thickness planer at the Wood species with various specifi c gravity were facility of the Istanbul University, Forestry Faculty of selected: European black pine (0.6526 g/cm3), cedar of Furniture and Wood Machining. Thirty test samples Lebanon (0.5019 g/cm3), sessile oak (0.7767 g/cm3), with the dimensions 25 x 102 x 910 mm and a wood black poplar (0.3412 g/cm3). The mean for the number moisture content of 12 % were made from each tree of rings per cm was also calculated for each species: species. As stated in the above said standard (ASTM European black pine (3.484), cedar of Lebanon (1.768), D-1666), the cutting depth was 1.6 mm for all the cuts. sessile oak (4.660), and black poplar (0.780). The properties of the cutting tools used in the planing A total of 8 roughness measurements were con- tests are presented in Table 1. ducted on 4 fi xed points established on each machine A wide-belt caliber sander, Melkuc Kombi 650 in directions perpendicular to the grain and along the model, for calibrating and sanding of wood based pan- grain on 30 planed samples. A Ra (average roughness) els was used for the sanding experiments. The cutting value was used in the evaluation of results of rough- speed in sanding operation was set to 5.5 m/min. The ness measurement. samples previously used in the planing experiments There is a very weak correlation between rough- with dimensions of 20 x 102 x 910 mm were fi rst sand- ness, a dependent variable, and the number of annual ed with 80 grain sandpaper and then with a 120 grain. rings per cm and the specifi c weight, an independent variable, at 0.097 and –0.038, respectively. However, a 2.3 Roughness measurement strong positive correlation is observed between the 2.3. Mjerenje hrapavosti number of annual rings per cm and the specifi c weight, The measurement of surface roughness was done an independent variable at 0.804. The data obtained according to protocols in TS 6956 EN ISO 4287, TS from the experiments is given in Table 2. 971, and TS 2495 EN ISO 3274. An instrument for Figure 1a below shows roughness values along measuring surface roughness, Mitutuyo Surfjet SJ 301, the grain for various machining conditions and tree was used for the determination of surface roughness by species. Figure 1b shows the roughness perpendicular a contact stylus trace method. to the grain. Figure 1c provides the mean of the rough- Measurements were made in two different direc- ness values perpendicular to the grain and along the tions, perpendicular and along the grain. Gaussian fi lter grain in the form of a graph. type was used. Sampling length was 2.5 mm and the Table 3 provides average roughness values, evaluation length was Lt= 12.5 mm. Cut-off length was standard errors based on tree species, and lower and 2.5 mm. Surface roughness values were measured with upper limits based on a 95 % confi dence limit. a sensitivity of ± 0.01 μm. Tool measurement speed was With respect to tree species, oak had the highest 10 mm/min, the diameter of the measurement needle roughness average with 6.780 μm, followed by black was 4 μm, and the needle tip 90°. Care was taken to have poplar with 6.338 μm. With regards to the upper and a measurement environment around 18 °C -22 °C, away lower limits of tree species based on a 95 % confi dence from noise sources, and without vibration. The tool was level, the confi dence ranges of pine and cedar of Leba- calibrated before the measurement and the calibration non intersect. When roughness values are studied was checked at established intervals. based on machining conditions, the highest average DRVNA INDUSTRIJA 66 (4) 265-272 (2015) 267 Dündar Sofuoğlu, Kurtoğlu: Effects of Machining Conditions on Surface Roughness... ...... Europan black pine / europski crni bor Black poplar / crna topola Sessile oak / Cedar of Lebanon / libanonski cedar 7 Along the grain / 6 5 4 3 Run 1 Run 2 Run 3 Run 4 Sanding / a brušenje Europan black pine / europski crni bor Black poplar / crna topola Sessile oak / Cedar of Lebanon / libanonski cedar 10 Perpendicular to grain / okomito na vlakanca 9 8 7 6 5 4 3 Run 1 Run 2 Run 3 Run 4 Sanding / b brušenje Europan black pine / europski crni bor Black poplar / crna topola Sessile oak / Cedar of Lebanon / libanonski cedar 9 Average / prosje no 8 7 6 5 4 3 Run 1 Run 2 Run 3 Run 4 Sanding / c brušenje Figure 1a Roughness values along the grain for various machining (cutting type) conditions and tree species 1b Roughness values perpendicular to grain for various machining (cutting type) conditions and tree species 1c Mean Roughness values for various machining (cutting type) conditions and tree species Slika 1. a) Vrijednosti hrapavosti uzduž vlakanaca za različite uvjete obrade i različite vrste drva; b) vrijednosti hrapavosti okomito na vlakanca za različite uvjete obrade i različite vrste drva; c) prosječne vrijednosti hrapavosti za različite uvjete obrade i različite vrste drva 268 DRVNA INDUSTRIJA 66 (4) 265-272 (2015) Surface roughness, μm Surface roughness, μm Surface roughness, μm Hrapavost površine,μm Hrapavost površine, μm Hrapavost površine, μm ...... Dündar Sofuoğlu, Kurtoğlu: Effects of Machining Conditions on Surface Roughness... Table 2 General results for the measured roughness Tablica 2. Rezultati izmjerene hrapavosti Wood species Surface roughness / Hrapavost površine, μm Vrsta drva Run 1 Run 2 Run 3 Run 4 Sanding Prolazak 1. Prolazak 2. Prolazak 3. Prolazak 4. Brušenje Europan black pine europski crni bor 3.91 4.70 4.31 5.46 5.89 5.68 4.28 4.12 4.20 4.51 4.25 4.38 3.82 6.41 5.11 Black poplar crna topola 4.87 7.22 6.05 6.17 7.73 6.95 5.03 7.61 6.32 4.83 7.14 5.98 4.29 8.46 6.37 Sessile oak hrast kitnjak 5.81 8.08 6.95 6.70 9.30 8.00 6.03 7.79 6.91 4.68 7.82 6.25 4.26 7.28 5.77 Cedar of Lebanon libanonski cedar 4.09 4.73 4.41 5.83 5.65 5.74 4.51 3.96 4.24 4.55 3.84 4.19 4.20 6.94 5.57 Table 3 Aver age roughness values, standard errors based on tree species and lower and upper limits based on 95 % confi - dence limit Tablica 3. Prosječne vrijednosti hrapavosti, standardna pogreška za pojedinu vrstu drva, donja i gornja granica za interval pouzdanosti od 95 % 95 % confi dence limits Wood species Arithmetic average Standard error 95 %-tni interval pouzdanosti Vrsta drva Aritmetička sredina Standardna pogreška Lower limits Upper limits Donja granica Gornja granica Black poplar / crna topola 6.338 0.072 6.196 6.480 Europen black pine / europski crni bor 4.740 0.073 4.597 4.884 Sessile oak / hrast kitnjak 6.780 0.072 6.638 6.922 Cedar of Lebanon / libanonski cedar 4.836 0.073 4.693 4.978 roughness values were found in Run 1 and sanding, than the roughness value along the grain). Figure 2 and the average roughness values for Run 3 and Run 1 shows the average roughness values (Ra) along and exhibited close values when the upper and lower limit perpendicular to the grain based on tree species in the values of the Run 3 and Run 1 are studied based on a form of graphs. 95 % confi dence level, the limit values for both runs Ra of poplar is 1.6077 μm higher than that of pine. overlap. It was determined that the machining condi- The average roughness value Ra of poplar is also 1.5048 tions of Run 4 had the lowest roughness average. μm higher than that of cedar of Lebanon. However, Ra of With regards to measurement direction, there oak is 0.4417 μm units higher than that of black poplar. was a signifi cant difference between the measurement The Ra of pine is 2.0494 μm less than that of oak. Al- values along the grain and measurement values per- though the Ra of pine is 0.1029 μm less than that of cedar pendicular to the grain (the average of the roughness of Lebanon, there is no signifi cant difference between values perpendicular to the grain is 1.553 μm higher the two. In other words, pine and cedar of Lebanon may Along the grain / Perpendicular the grain / okomito na vlakanca 10 8 6 4 2 0 Europan black pine Black poplar Sessile oak Cedar of Lebanon europski crni bor crna topola libanonski cedar Figure 2 Graphs of average surface roughness along and perpendicular to the grain based on tree species Slika 2. Prosječna hrapavost površine istraživanih vrsta drva uzduž vlakanaca i poprečno na njih DRVNA INDUSTRIJA 66 (4) 265-272 (2015) 269 Surface roughness, μm Hrapavost površine, μm Along the grain Perpendicular to the grain Average Along the grain Perpendicular to the grain Average Along the grain Perpendicular to the grain Average Along the grain Perpendicular to the grain Average Along the grain Perpendicular to the grain Average Dündar Sofuoğlu, Kurtoğlu: Effects of Machining Conditions on Surface Roughness... ...... Europan black pine / Black poplar / Sessile oak / Cedar of Lebanon / 9 8 Run 1 7 6 5 4 3 Along the grain / Perpendicular the grain / 10 9 Run 2 8 7 6 5 4 3 Along the grain / Perpendicular the grain / 9 8 Run 3 7 6 5 4 3 Along the grain / Perpendicular the grain / 9 8 Run 4 7 6 5 4 3 Along the grain / Perpendicular the grain / Figu re 3 Average roughness values under machining conditions of runs 1, 2, 3, and 4 based on measurement directions and tree species Slika 3. Prosječne vrijednosti hrapavosti u uvjetima obrade nakon 1., 2., 3. i 4. prolaska noža za različite smjerove mjerenja hrapavosti i različite vrste drva 270 DRVNA INDUSTRIJA 66 (4) 265-272 (2015) Surface roughness, μm Surface roughness, μm Surface roughness, μm Surface roughness, μm μm μm μm μm ...... Dündar Sofuoğlu, Kurtoğlu: Effects of Machining Conditions on Surface Roughness... Europan black pine / Black poplar / Sessile oak / Cedar of Lebanon / 9 Sanding / 8 7 6 5 4 3 Along the grain / Perpendicular the grain / Figure 4 Roughness graph for sanding operation (cut type) based on measurement directions and tree species Sika 4. Izmjerena hrapavost nakon brušenja za različite smjerove mjerenja hrapavosti i za različite vrste drva be gathered together under the same group with regards occurred i n the sanding operation. Although it was ex- to roughness value. The Ra values for black poplar and pected that black poplar would have smoother surfaces oak are higher than those for the other tree species. during sanding, since the machining method affects According to statistical analysis results, the Ra surface quality, an increase in the roughness was ob- for Run 2 was by 1.1737 μm higher than for Run 1. served. It is believed that this result is signifi cantly af- Although Ra for Run 1 was by 0.0218 μm higher than fected by the type of procedure. Cedar of Lebanon ex- for Run 3, there was no signifi cance between them hibited values close to black pine with regards to (Sig: 1,000) and Run 1 and Run 3 can be put into the average roughness, displaying the lowest average same group with regards to roughness averages. While roughness values amongst the tree species studied. The the value of Ra for Run 1 was by 0.2375 μm higher values for black poplar and sessile oak were found to than for Run 4, it is by 0.2677 μm less for sanding. The be higher. Cedar of Lebanon was in the same group as Ra for Run 2 exhibited a signifi cant difference since black pine in regards to surface roughness and exhib- they were higher compared to all the other machining ited the highest roughness value. conditions. The Ra for sanding conditions have a slightly higher Ra compared to all the other machining Acknowledgement – Zahvala conditions except for Run 2. Sanding machining condi- This study is a part of Doctorate Thesis prepared tion can be shown as a separate group with regards to by Sait Dundar SOFUOGLU, Institute of Sciences, Is- Ra. At the same time, although Ra for Run 3 was by tanbul University, Istanbul, Turkey. 0.2158 μm higher than for Run 4, these two machining conditions are shown under the same group with re- 5 REFERENCES gards to roughness averages. 5. LITERATURA According to the statistical analysis results, there was no signifi cant difference in roughness with regards 1. 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