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Building and Environment 42 (2007) 2988–2992 www.elsevier.com/locate/buildenv
Comparison of surface roughness of Locust acacia (Robinia pseudoacacia L.) and European oak (Quercus petraea (Mattu.) Lieble.) in terms of the preparative process by planing Ilker Ustaa,, Selcuk Demircib, Yilmaz Kilica a
Department of Wood Products Industrial Engineering, Hacettepe University, 06532 Beytepe, Ankara, Turkey Ege Vocational School, Programme of Furniture and Decoration, Ege University, 35100 Bornova, Izmir, Turkey
b
Received 21 April 2004; received in revised form 11 July 2006; accepted 24 July 2006
Abstract Effects of number of the cutters (planing knives), feed rate (operational speed) and cutting depth (biting thickness) on the surface roughness of Locust acacia (Robinia pseudoacacia L.) and European oak (Quercus petraea (Mattu.) Lieble.) were investigated on the base of the preparative differences by planing. The specimens were prepared by planing with two and four knives at 5 and 9 m/min feed rates in 1, 2 and 4 mm cutting depths. Surface roughness was measured from the radial face of each sample according to TS 930 (1989) by using Mitutoyo SJ-301 stylus scanner device. These measurements were performed perpendicular to the fibers by the sampling length of 12.5 mm at a sensitivity level of 70.01 mm. Considering between all types of the experimental preparations, Locust acacia had the smoothest surfaces than that of European oak. Comparing the results of the surface roughness of both species, it has been obtained that the surface roughness decreases when the feed rate and the cutting depth decreases, whereas it increases when the knives on the cutter heads decreases. Therefore, it may be suggested that the perfect faces could be particularly prepared for this considered species by the greater number of the knives (four) at the slow feed rate (5 m/min) in the condition of the light cutting depth (1 mm). r 2006 Elsevier Ltd. All rights reserved. Keywords: Surface roughness; Locust acacia; European oak; Planing; Feed rate; Cutting
1. Introduction Wood finishing, which is related to the quality of the end products of wood material, is usually desirable to protect wood surfaces from accumulating dirt (or to create a surface that can be cleaned easily) and to enhance its aesthetic appearance. Although a finish on wood is achieved by the several coating techniques using different chemicals, the quality of the surface finishing involves a combination of the surface condition of the wood and the finishing treatment applied to it [1,2]. According to Hoadley [2], most finishing instructions begin with surface preparation, emphasizing such things as proper sanding and dusting just prior to Corresponding author. Tel.: +90 312 297 89 55; fax: +90 312 297 68 85. E-mail address:
[email protected] (I. Usta).
0360-1323/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.buildenv.2006.07.026
treatment. But the concern must begin long before, because surface condition is influenced by every step of woodworking, from sawing the log and drying the lumber to machining the surfaces and gluing the joints. In this case, Stumbo [3] evaluated the surface condition regarding to the characteristic of wood material (species, structure, moisture content) and its preparation (cutter geometry, cutting depth, cutting speed, feed rate, the number of the cutter and the surface smoothness by sanding, i.e. the granule sizes of abrasive paper). Burdurlu and Baykan [4] described the different cutting methods in furniture industry according to the operational process as in the following order: sawing, planing, drilling and sanding. In this case, regarding to the quality of surface finishing of wood, the most important cutting method is planing which is done with planing machines in which knives with different numbers can be attached to the cutter heads.
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Many works have shown that the achieved surface quality of wood products may be obtained by employing suitable conditions of improvement in a considerable number of well-defined preparative processes. Extensive investigations by Richter et al. [5] have shown that wood species and its structure, cutting direction and cutting depth, number of cutter and feed rate, and the sanding process for the preparation of the end material tended to be more effective factors on the surface roughness of wood products. This phenomenon was initially described in detail by Stumbo [3], who also briefly alluded to the cutting process in surface preparations. Stumbo found that the surface roughness of the planed and sanded Weeping birch (Betula verrucosa Ehrh.) was dependent on the presence of the number of the cutter and the cutting speed. In this case, he observed that the surface roughness decreased at the slow feed rate when the number of the cutter and the cutting speed increased. It was also noticed by Stumbo that the surface roughness of the attempted wood material subjected to be increased if the material was not completely dry. The increase of the surface roughness was also related to the sharpness of the grinding materials by Pahlitsczh and Dziobek [6], and they observed that the surface roughness increased if the grinding material blunts. This observation was also determined by Stewart et al. [7] on a base of the slow feet rate with poplar (Populus spp.), Sugar maple (Acer saccharum Marsh.) and Douglas fir (Preudotsuga menziesii (Mirb.) Franco). Achieving of the smoother surfaces with planing and sanding at the slow feed rate and light cutting depth was studied by Stewart [8] on a dried sample of Large-leaved lime (Tilia grandifolia Ehrh.), European oak (Quercus petraea (Mattu.) Lieble.), Turkish walnut (Juglans regia L.) and poplar (P. spp.). The kinetics of activation and changes of the smoothness led Stewart to suggest that the considered process was the result of a conformational change of the surface roughness of all the trial species from a form with low feed rate and light cutting depth to one with high activity of the preparative process. The similar findings on the effect of slow feed rate and light cutting depth was also observed by Baykan [9] with the planed and sanded Oriental beech (Fagus orientalis Lipsky) which of its surface appeared to be more smoother than Scots pine (Pinus sylvestris L.). Baykan also determined that the tangential section formed smoother surfaces compared with the radial section when the feed rate was quite slow in a dry wood material, and hence he stated that the feed rate of the planing machine and the moisture content of the wood material were both the important factors for achieving the smoothness. This observation was also found by Yalcinkaya [10] with Crimean pine (Pinus nigra Arn. var. caramanica Schn.) which formed smoother surfaces when compared with European oak (Q. petraea (Mattu.) Lieble.). Gurleyen [11] also informed that the tangential sections of Scots pine (P. sylvestris L.), Oriental beech (F. orientalis Lipsky), European oak (Q. petraea (Mattu.) Lieble.) and Locust acacia (Robinia pseudoacacia L.)
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formed smoother surfaces than their radial sections and the smoothness was particularly observed by the planing with four knives than that for two knives. Achieving of the smoother surfaces by sawing tangent to the growth rings was also studied by several researches on different experimental design. For instance, Ors and Baykan [12] obtained this purpose for Oriental beech (F. orientalis Lipsky) and Scots pine (P. sylvestris L.), and they noticed that the surface roughness decreased at the speedy feed rate if the number of the cutter and grinding material increases. Ors and Demirci [13] sawed tangent to the growth ring and radially with different teeth numbers and feed rates for Oriental beech (F. orientalis Lipsky) and Scots pine (P. sylvestris L.). They observed that the smoothest surface was obtained in Scots pine (P. sylvestris L.) when it was sawed radially with 5 m/min feed rate by the circular saw of 24 teeth. Ors and Demirci [14] also considered to determine their initial observations in different hardwood species with European oak (Q. petraea (Mattu.) Lieble.) and Locust acacia (R. pseudoacacia L.) which of both were sawed tangent to the growth rings and radially with the feed rates of 5 and 9 m/min by the circular saw of 20, 24 and 40 teeth. According to their experimental findings the smoothest surface was obtained in Locust acacia (R. pseudoacacia L.) on tangent to the growth ring when sawed with the circular saw of 40 teeth. This preparative process was also investigated by Ors and Gurleyen [15] on Scots pine (P. sylvestris L.) and Oriental beech (F. orientalis Lipsky). They found that Scots pine (P. sylvestris L.) formed smoother surfaces compared to that for Oriental beech (F. orientalis Lipsky) if it was sawed tangent to the growth rings. In this case, Ors and Gurleyen described that increase of the number of the cutters while decrease of the feed rate was a main reason for the smoother surfaces in this species. Since neither investigation addressed whether these changes were persistent to the utilization of the experimental wood with regard to the condition of plane equipment and the way of planing process, the present study was undertaken to observe the characteristic of the surface roughness of Locust acacia (R. pseudoacacia L.) and European oak (Q. petraea (Mattu.) Lieble.) on a base of the planing with the various number of the cutters (two and four knives) at the several feed rates (5 and 9 m/min) in different cutting depths (1, 2 and 4 mm). 2. Material and methods 2.1. Preparation of the experimental samples The two native hardwood species, namely Locust acacia (R. pseudoacacia L.) and European oak (Q. petraea (Mattu.) Lieble.) which are grown indigenously in Turkey, were selected because of their wide ranges of the usage for manufacturing of the decorative furniture. The air-dried 48 defect-free sapwood stakes from each of the two species were produced in the dimensions of 50 cm
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in longitudinal length 5 cm in radial width 2 cm in tangential thickness, and were then kept in the conditioning room at 2072 1C temperature and 6573% relative humidity until their weights became stable. In this way, moisture content of each stake was nominated to 12% according to [16]. The stakes were then planed from their radial surfaces with two and four knives at 5 and 9 m/min feed rates in the cutting depths of 1, 2 and 4 mm. For this purpose, the plain knives, which are generally used for planing machines in furniture industry, were preferred for planing the specimens after they were sharpened. Thereafter, to increase the number of replication in due to achieving a reasonable measurement on the roughness values of the radial surfaces of the considered wood species, each stake was marked along its length into five equal imaginative blocks in which four measurements were subjected to be taken along the stakes in question. 2.2. Determination of the surface roughness Although there are several techniques available to analyze and to evaluate the surface quality of wood, the stylus scanner method introduced by Stumbo [3] as the most suitable one for determination of the smoothness behavior of wood material. Surface roughness was, therefore, measured according to the Contact Styles Tracing Method [17] by using the device of Mitutoyo Sj-301 which exists in our laboratory at the Department of Wood Products Industrial Engineering, Hacettepe University, Ankara, Turkey. This device was operated for obtaining the roughness data according to the descriptions given in its manual as follows: measuring speed of 0.5 mm/min, stylus (skid) diameter of 4 mm, and stylus angle of 901 [18]. The evaluations of the surface roughness were determined as the sensitivity of 70.01 by the scanning length (lt) of 12.5 mm and the sampling length (lc) of 2.5 mm according to the procedure explained in [17]. In this case, the four consecutive measurements were done with perpendicular to grain on the radial section of all samples, and they were repeated if the tip of the scanning stylus was attached to the lumen. For evaluations of the roughness value for each experimental sample, the Ra (mm) value, which is the average arithmetic height from the average roughness value of the roughness values measured within the length of one sample [19], is taken due to its simplicity and acceptability for the representative behavior of the surface roughness of the tested wood material. All these measurements were also complied with the principles of [20]. 2.3. Data analysis The experimental data were analyzed by analysis of variance (ANOVA) on the base of the wood species, the number of knives, feed rates and the cutting depths. In this case, to determine the effects of the considered factors, ANOVA were performed by the data of 384 measurements which were obtained from the 96 samples of both species.
Significant differences among the mean values of the surface roughness were compared by Duncan‘s multiple range test with a least significant difference (LSD) at the Pp0.05 level. All data were analyzed by a computerized statistical software package SPSS (Release 7.0). 3. Results and discussion The results of the ANOVA (involving two wood species, two knives, two feed rates and three cutting depths) are given in Table 1. The results indicate that the number of cutters (planing knives), feed rates (operational speed) and the cutting depths (biting thickness) were very highly significant (Po0.01) on the surface roughness of Locust acacia (R. pseudoacacia L.) and European oak (Q. petraea (Mattu.) Lieble.). It can be inferred from the results of ANOVA given in Table 1 that the variation in surface roughness among the considered wood species (A) became more noticeable with the number of knives (B), feed rates (C) and cutting depths (D). It was also noticed that the interactions of all these factors were observed to be statistically significant in despite of a slight deviation in some results. For instance, apart from the interactions between wood species and feed rate (A C)—including either planing knives (A B C) or cutting depth (A C D)—and interaction of planing knives and feet rate (B C), all interactions indicated considerably strong relationship to one another. This observation can perhaps be understood qualitatively if the structure of the trial wood species has been revealed separately. In this case, as it has been described Table 1 The results of analysis of variance for surface roughness indicating significant effects for the influencing factors of the wood species (A), number of planning knives (B), feed rates (C) and the cutting depths (D) Sources
DF
SS
MS
F-value
P
Wood species (A) Number of knives (B) AB Feed rate (C) AC BC ABC Cutting depth (D) AD BD ABD CD ACD BCD ABCD Error Total
1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 744 767
649.483 100.804 8.492 20.332 0.003 6.927 4.641 13.016 22.030 43.302 41.203 19.158 7.365 45.643 64.576 855.111 1902.085
649.483 100.804 8.492 20.332 0.003 6.927 4.641 6.508 11.015 21.651 20.601 9.579 3.683 22.821 32.288 1.149 —
565.0914 87.7059 7.3889 17.6901 0.002 6.0273 4.0377 5.6622 9.5836 18.8377 17.9244 8.3343 3.2041 19.8561 28.0927 — —
0.000 0.000 0.007 0.000 0.048 0.014 0.045 0.004 0.000 0.000 0.000 0.000 0.041 0.000 0.000
DF: degrees of freedom, SS: sum of square, MS: mean of square, P: probability. Significant at Pp0.05 level. Significant at Po0.01 level. Significant at Po0.001 level.
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Fig. 1. Mean values of surface roughness (Ra, mm) of Locust acacia and European oak on the base of the planing with the various numbers of the cutters (two and four knives) at the several feed rates (5 and 9 m/min) in different cutting depths (1, 2 and 4 mm).
by Tsoumis [21], each wood species has its own structural properties which could affect the results in different aspects even if the similar preparative process is obtained for the same technological purpose. The results of the ANOVA also indicated that the way of the preparation by planing may play an important role on the surface roughness of both trial species. Thus several independent approaches all provide evidence to support the view that the planing process has to be essentially modified for either species before the machining of wood for achieving the smoothness surfaces on the base of the least roughness value. Mean surface roughness values (Ra, mm) in either wood species are shown in Fig. 1 according to the number of planing knives, feed rates and cutting depths. A relationship has been found in the present investigation that the surface roughness of both species decreases when the feet rate decreases, and it increases when the number of planing knives on the cutter heads decreases (Fig. 1). This situation can be explained by the definitions of [3,8] that the increases of the feed rate while the decrease of the number of knives could be the main reason for surface roughness due to the increase of the chip thickness of the wood material in a given progressive time. The number of the planing knives is, therefore, considered to be the key factor for preparation of the smoothest surfaces by the planing process. In this case, the experimental findings have demonstrated that the best results were obtained on the planing with four knives as compared to that for two knives. This is because all of the wood surfaces could be touched fully by the plenty of cutters in which the excessive chips can be wiped out consequently from the cutting area. The effects of planing knives, feed rate and cutting depth and their combinations on the surface roughness of the trial wood species are summarized in Table 2. Interactions
Table 2 The effects of planing knives, feed rate and cutting depth and their combinations on the surface roughness of the trial wood species (LSD70.5261) Factors
Sources
Surface roughness (Ra, mm) Mean HG
Wood species
Locust Acacia European Oak
4.05 5.91
A B
Number of knives
2 4
5.53 4.44
A B
Feed rate (m/min)
5 9
4.58 5.39
A B
Cutting depth (mm)
1 2 4
4.58 4.95 5.44
A B C
between the trial wood species and the prepative factors such as the number of planing knives, feed rate and cutting depth are given in Table 3. In both these tables, means within columns were separated by Duncan’s multiple range test and compared according to the value of LSD. In this case, means within the same group followed by dissimilar letters are significantly different to each other on the base of LSD at the Pp0.05 level. The considered separation is shown in the column of HG (which represents the homogeneous group for the experimental data). It can be deduced from both Tables 2 and 3 that the smoother surfaces were mainly obtained in Locust acacia as compared to European oak. It was noticed that this occurred in the all cases of the experimental design based on the preparation of the wood samples by planing. This could be due to the anatomic structure of the considered wood species which of its structural behavior has been
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Table 3 Comparative results of interactions between the wood species—Locust acacia (Robinia pseudoacacia L.) and European oak (Quercus petraea (Mattu.) Lieble.)—and number of planing knives, feed rate and cutting depth for the surface roughness (LSD70.1174)
needed to fully elucidate the machinability of this species by examining the different preparative parameters to optimize the planing process.
Interactions
References
Surface roughness (Ra, mm) Mean
HG
Wood species and number of planing knives Acacia 2 knives 4.31 Acacia 4 knives 3.79 Oak 2 knives 6.75 Oak 4 knives 5.08
A B C D
Wood species and feed rate Acacia 5 m/min Acacia 9 m/min Oak 5 m/min Oak 9 m/min
3.77 4.35 5.40 6.44
A B C D
Wood species and cutting depth Acacia 1 mm 3.67 Acacia 2 mm 4.15 Acacia 4 mm 4.35 Oak 1 mm 5.48 Oak 2 mm 5.74 Oak 4 mm 6.55
A B B C C D
described in detail by Panshin and de Zeeuw [22]. On this basis alone it is essential that the preparative process should be adequately characterized according to the wood species before the machining by a plane. In summary, it can be stated that the results (of the surface roughness of both Locust acacia and European oak) described in this paper would be consistent with the previous findings of [11,14]. This means that the perfect faces tended to be observed for either wood species by the greater number of the planing knives (four) at the slow feed rate (5 m/min) in the condition of the light cutting depth (1 mm). For this reason, instead of the production of wood by planing at high feed rate, it is better to use the plane at slow feed rate by using the plural cutters with a considerably light cutting depth. 4. Conclusions The evidence presented in this study confirms the importance of planing that the smoothness of the radial surfaces of wood material could be adequately created by the suitable preparative process at relatively early stage in the process of planing. In this case, the experimental results fit the previous findings that the surface roughness decreases when the number of cutters (number of planing knives) increases at the slow feed rate. Based on the observations of this study, we, therefore, suggest that both Locust acacia and European oak should be prepared by planing with four knives at 5 m/min feed rate in 1 mm cutting depth for obtaining the smoother surfaces in terms of the surface quality of the end products of wood material. However, further investigations will be
[1] Hand J. How to do your own wood finishing. New York: Popular Science/Harper & Row; 1976 170pp. [2] Hoadley RB. Understanding wood: a craftsman’s guide to wood technology. Newtown: The Taunton Press, Inc.; 1980 256pp. [3] Stumbo DA. Surface texture measurements for quality and production control. Forest Products Journal 1960;10(12):122–4. [4] Burdurlu E, Baykan I. Cutting theory in wood working and the machines of furniture industry (in Turkish). Ankara: Bizim Buro Basimevi; 1998 690pp. [5] Richter K, Feist WC, Knaebe MT. The effect of surface roughness on the performance of finishes. Forest Products Journal 1995;45(7):91–7. [6] Pahlitszch VG, Dziobek K. Einflu¨sseder bearbeitungsbedingungen auf die gu¨te vorgeschliffener holzober flachen. Holz Als Roh-und Werkstoff 1962:121–34. [7] Stewart HA, Murmari L, River BH. Surface and subsurface characteristics related to abrasive: planing conditions. Wood and Fiber Science 1986;18(1):107–17. [8] Stewart HA. Abrasive planing across the grain with higher grit numbers can reduce finish. Forest Products Journal 1976;20(4):49–51. [9] Baykan I. The research on surface roughness of the planed and sanded solid furniture (in Turkish). PhD thesis, Institute of Science and Technology, Karadeniz Technical University, Trabzon, 1996, 98pp. [10] Yalcinkaya O. Studies on surface roughness values of European oak (Quercus petraea (Mattu.) Lieble.) and Crimean pine (Pinus nigra Arn. var. caramanica Schn.) (in Turkish). MSc thesis, Institute of Science and Technology, Hacettepe University, Ankara, 1997, 74pp. [11] Gurleyen L. Comparison of surface smoothness in the materials of solid wood using in furniture industry (in Turkish). MSc thesis, Institute of Science and Technology, Gazi University, Ankara, 1998, 62pp. [12] Ors Y, Baykan I. The effect of planing and sanding on surface roughness of massive wood. Turkish Journal of Agriculture and Forestry 1999;23:577–82. [13] Ors Y, Demirci S. The effect of number of tooth, cutting direction and feed rate on surface roughness at wooden materials. Journal of Polytechnic of Gazi University 2000;2(4):1–5. [14] Ors Y, Demirci S. The effect of number of tooth, feed rate and cutting direction at the circular saws on surface roughness for European oak (Quercus Petraea Lieble.) and Locust acacia (Robinia Pseudoacacia L.). Journal of the Institute of Science and Technology of Gazi University 2001;14(3):857–67. [15] Ors Y, Gurleyen L. Effect of the cutting direction, number of cutter and cutter type on surface smoothness of wood material by planing. Journal of Polytechnic of Gazi University 2002;5(4):335–9. [16] TS, 2471. Determination of moisture content for physical and mechanical tests. Ankara: Turkish Standards Institution; 1976. [17] TS 930. Instruments for the measurement of surface roughness by the profile method—contact (Stylus) instruments of progressive profile transformation: profile recording instruments. Ankara: Turkish Standards Institution; 1989. [18] Anon. Mitutoyo SJ-301 using guide. Tokyo: Minoto-Ku; 1993 108pp. [19] TS 6956. Surface roughness: definitions. Ankara: Turkish Standards Institution; 1989. [20] TS 6212 EN ISO 4288. Geometrical product specifications (GPS) surface texture: profile method the assessment of surface texture. Ankara: Turkish Standards Institution; 1999. [21] Tsoumis GT. Science and technology of wood: structure, properties, utilisation. New York: Van Nostrand Reinhold; 1991 494pp. [22] Panshin AJ, de Zeeuw C. Textbook of wood technology, 4th ed. New York: McGraw-Hill Book Co; 1980 728pp.
