Determination of the surface roughness values of Turkish red pine (Pinus brutia (Ten.)) woods

Abstract

Full Article

Determination of the Surface Roughness Values of Turkish Red Pine (Pinus brutia (Ten.)) Woods

Murat Kılıç *

The aim of this study was to determine the surface roughness values of Turkish red pine samples obtained from the seven natural growth areas in Turkey. The samples were cut with a circular saw, planed with a thickness machine, and sanded with a sanding machine (with No. 80 sandpaper). After the samples were processed as radial and tangential surfaces in the machines, their surface roughness values (R_a, R_y, and R_z) were measured in accordance with ISO 4288 (1996). According to the statistical results, the lowest surface roughness values were in the samples obtained from the Muğla and Samsun areas on the tangential surfaces that were processed with the thickness machine.

Keywords: Surface roughness; Turkish red pine; Pinus brutia Ten woods; Wood machining; Cutting directions

Contact information: Kırıkkale University, Faculty of Fine Arts, Department of Interior Architecture & Environment Design, Yahsihan, Kırıkkale, Turkey; *Corresponding author: muratkilic@kku.edu.tr

INTRODUCTION

Wood materials have many uses in construction and furniture production. While the most important aspects in the selection of wood materials for the construction sector are the mechanical properties, the aesthetic and mechanical properties are important for the material used in furniture (Aslan et al. 2008).

Surface roughness is the most important property in wood material used in furniture production. Surface roughness affects the quality of furniture because aesthetic concerns are significant in this industry (Ilter et al. 2002; Salca and Hiziroglu 2014; Söğütlü et al. 2016).

Among the methods used to minimize surface roughness, the most important one is increasing the number of machine cutters and processing wood materials in the low feed speed (Hiziroglu and Suchsland 1993; Hiziroglu 1996). Another successful method for processing wood in the direction of cutting involves usage of a down-milling machine. The results obtained in applications carried out tangentially are known to give better results compared to application carried out radially (Kılıç et al. 2006; Kılıç 2015; Kılıç 2016).

In the cutting, planing, and sanding processes of wood material, the accurate selection of processing conditions is very important to avoid undesired negative results, primarily surface roughness. Roughness on the wood surface can be minimized with additional precautions, such as increasing the knife and rotation numbers in the machines used to process wood (Pelit et al. 2015; Tiryaki et al. 2015).

The growth area of Turkish red pine (Pinus brutia (Ten.)) is expanding throughout the world and within Turkey. This species has a high economical value and is a principal tree species for Turkey. Forests covered an area of 21,678,134 hectares in Turkey in 2014, which was 27.6% of the country’s total area. Turkish red pine has an expansion area of 5,854,673 hectares (General Directory of Forestry 2014). The Turkish red pine is one of the most important primary tree species in Turkey. Therefore, the study of its basic wood properties is a top priority.

The surface roughness of wood material does not directly affect the surface roughness processes or the bonding resistance. Currently, there are no reports on the surface roughness values of Turkish red pine. For this reason, determining the surface roughness of the Turkish red pine wood is the subject of this study (Fig. 1).

Fig. 1. The importance of surface roughness in the processing of furniture

In the evaluation of surface roughness, three parameters are widely used. These are R_a, which is the average deviation of the profile; R_z, which is the average of the height of the irregularity at 10 points, and R_y, which is the highest level of the profile.

EXPERIMENTAL

The experiment materials were selected from areas in Adana-Pos, Antalya-Düzlerçamı, Burdur-Bucak, Mersin-Silifke, Samsun-Bafra, Kahramanmaraş-Topçam, and Muğla-Kıyra, which are Turkish red pine natural growth areas in Turkey. For each region, a total of 21 trees from 7 different areas were selected (3 trees per area). The trees were cut in accordance with ISO 4471 (1982). Information about the areas is presented in Table 1.

The trial materials were cut to dimensions of 60 x 500 mm and placed in an environmental test chamber until air-dried humidity (12%) was reached. (Table 2).

The effect of three different surface processing types on Turkish red pine was determined using two cutting directions, tangential, and radial.

Two cutting directions (radial and tangential) and three surface treatment techniques (cutting by circular saw, planning, and sanding) were used in this work, and 300 measurements were taken with 50 test repetitions (2 x 3 x 50=300). In total, 2100 surface roughness measurements were performed for the seven different areas.

As the final process for the Turkish red pine, the samples were planed with a thickness machine three blades (4500 rev/min), cut with a 40-tooth circular saw machine (diameter 30 cm) (6000 rev/min), and sanded with a caliber sanding machine (with No: 80 sandpaper).

Table 1. Information Related to Origins

*(Ilter et al. 2011)

During sample processing, the feeding rate was fixed at 10 m/min. Surface roughness values were measured with a Mitutoyo SJ-301 device (Kawasaki, Japan), which measures with the stylus method, in accordance with ISO 4288 (1996) (Fig. 2). The surface roughness was measured on the fibers in a perpendicular direction with a ± 0.01 μm sensitivity (measurement speed 0.5 m/sec; cut-off wavelength (lc) 4 mm; measurement length (lt) 21 mm; diamond tip stylus; tip angle 90°/tip; and radius 2 m) in accordance with ISO 4288 (1996).

Table 2. Properties of Experimental Trees

*(Ilter et al. 2011)

Fig. 2. Surface profilometer used in this study

With the purpose of presenting the effects of Region, Machine, and Cutting Direction (the main effect, double and triple interactions) on R_a, R_y, and R_z, the Univarite General Linear statistical model was used, and analysis was carried out. For the multiple comparisons of the factors that were considered to be statistically important as a result of the overall F-test of each measurement, the Tukey HSD test was used. A statistical error with an importance level of type one has been determined as α=0.05. In terms of determining the difference effect level, Partial Eta squared statistics was used. The Partial Eta squared parameter indicates the level of effect and it is considered that as its value becomes closer to 1, the effect level increases.

RESULTS AND DISCUSSION

Evaluation of the Data Obtained for Ra (Average Roughness)

The statistical values and the results of the Tukey test according to the areas calculated for the average surface roughness (R_a) are presented in Table 3.

Table 3. Variance Analysis and Tukey’s Test for Ra According to Region

While the area, machine types, and cutting directions affected the R_a value, their double and triple effects were statistically significant in terms of the R_a value as well. In Table 3, the Partial Eta Squared effect value for R_a was found to be highest in Machine. According to the results of Tukey’s tests for the areas, the lowest average surface roughness values were in Samsun (R_a = 5.16 m), Muğla (R_a = 5.17 m), and K. Maraş (R_a = 5.30 m). There was no significant difference in the surface roughness values of these three areas.

The lowest average surface roughness value according to machine types was determined in the thickness machine (R_a = 4.54 m), followed by the sanding machine (R_a = 5.26 m), and the circular saw (R_a = 7.28 m) (Table 4). When the statistical values were analyzed in terms of the cutting directions, the average surface roughness values of the tangentially cut samples were lower than the radially cut samples (Ra_Tangential = 5.53m, Ra_Radial = 5.86m) (Table 4).

The R_a values determined in previous studies are lower in tangential surfaces than in the radial surfaces as well (Table 5).

Table 4. Statistical Values for Ra According to Machine Type and Cutting Direction

Evaluation of the Data Obtained for R_y (R_max) (Maximum Roughness)

The statistical values and the results of the Tukey test according to areas calculated for R_y are presented in Table 6. Areas, machine types, and cutting directions affected the R_y value; however their double and triple effects were statistically significant in terms of the R_y value as well.

In Table 6, when the Partial eta squared value was analyzed for R_y, it was seen that the effect of machine was higher. According to the results of the Tukey’s tests for the areas, the lowest average surface roughness values were in Muğla (R_y = 38.51 m), Samsun (R_y = 39.04 m), and K. Maraş (R_y = 39.04 m). There was no statistical difference between the surface roughness of these three areas.

Table 5. The R_a Values Determined in Previous Studies

The lowest average surface roughness value according to machine types was determined in the thickness machine (R_y = 35.84 m), followed by the sanding machine (R_y = 40.78 m), and the circular saw (R_y = 50.46 m) (Table 7). When the statistical values were analyzed in terms of the cutting directions, the R_y surface roughness values of the tangentially cut samples were seen to be lower than the radially cut samples (R_{y Tangential} = 41.58m, R_{y Radial} = 42.73m) (Table 7).

Evaluation of the Data Obtained for Rz (Mean Peak-to-valley Height)

The statistical values and the results of the Tukey’s test according to areas calculated for R_z are presented in Table 9. The areas, machine types, and cutting directions affected the R_z value; however, their double and triple effects were statistically significant in terms of the R_z value as well.

In Table 9, the Partial Eta squared effect for R_z was found the highest in Machine. According to Tukey’s test for the areas, the lowest average surface roughness values were in Samsun (R_z = 30.44 m) and Muğla (R_z = 30.48 m). There was no statistical difference between these two areas’ surface roughness values.

The lowest average ten-point height surface roughness values (R_z) in terms of machine types were found in the thickness machine (R_z = 27.59 m), followed by sanding machine (R_z = 29.78 m), and the circular saw (R_z = 41.19 m) (Table 10). When the statistical values were analyzed in terms of the cutting directions, the R_z surface roughness values of the tangentially cut samples were lower than the radially cut samples (R_{z Tangential} = 32.50 m, R_{z Radial} = 33.22 m) (Table 8).

Table 6. Variance Analysis and Tukey’s Test for Ry According to Region

Table 7. Statistical Values for Ry According to Machine Type and Cutting Direction

Table 8. Statistical Values for R_z According to Machine Type and Cutting Direction

Table 9. Variance Analysis and Tukey’s Test for R_z According to Region

CONCLUSIONS

1. Turkish red pine trees were selected from areas in Adana, Antalya, Burdur, Mersin, Samsun, Kahramanmaraş, and Muğla, which are natural growth areas in Turkey. The lowest surface roughness values were obtained from the samples taken from the Muğla and Samsun areas.
2. The samples obtained from the Turkish red pine were processed with the most common surface processing techniques in the wood processing sector: sawing with a circular saw, planing with a thickness machine, and sanding with a sanding machine (No. 80 sandpaper). After the samples were processed radially and tangentially, their roughness values (R_a, R_y, and R_z) were determined. When the statistical results of surface roughness values were analyzed, the lowest surface roughness values were obtained in the Turkish red pine samples that were processed with the thickness machine.
3. The Partial Eta Squared effect level values for R_a, R_y, and R_z were the highest in Machine type. The variable with the second highest value level after Machine type was Region.
4. In Muğla and Samsun regions, the reason why the lowest surface roughness values were obtained might be related to density and the growth area of the samples. In future studies, it might be useful to analyze the red pine trees in these areas anatomically.
5. The roughness values of the tangentially cut surfaces were determined to be lower than the radially cut surfaces. Burdurlu et al. (2006) have also determined that the R_a values of tangentially cut samples of red pine trees were lower than the values of radially cut surfaces. In the same manner, the R_a values of surfaces processed with the thickness machine were found to be lower compared to surfaces sanded with no: 80 sandpaper (Table 5). The results are in line with this study.
6. An important aspect of this study lay in determining the surface roughness of Turkish red pine samples selected from the seven natural growth areas in Turkey and introducing these results to literature.

ACKNOWLEDGMENTS

The author is grateful for the support of the Turkey General Directorate of Forestry, Central Anatolia Forestry Research Institute, Grant. No. 23.7132/2009-2015.

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Article submitted: September 10, 2016; Peer review completed: October 29, 2016; Revised version received: November 1, 2016; Further input: December 22, 2016; Accepted: December 27, 2016; Published: January 4, 2017.

DOI: 10.15376/biores.12.1.1216-1227