Sanded Wood Surfaces Research Articles

Testing the Processing-Induced Roughness of Sanded Wood Surfaces Separated from Wood Anatomical Structure

The metrology of processed wood surfaces is complex due to the presence of wood anatomical cavities, which are a factor of bias in several metrological steps, from the measuring to the evaluation of the surface quality. Wood requires special recommendations, and one regards the use of a robust Gaussian regression filter for filtering the roughness. The filter was previously tested with success on wood surfaces and was used in this paper. Furthermore, a reliable quantification of the processing roughness requires that independent wood anatomical data be removed from the evaluation. The paper presents a method of separating the roughness induced by processing from the wood anatomical structure. It was tested on different wood species, sanded with various grit sizes, and on a plastic material included for comparisons. The results showed similar values of the processing roughness for materials sanded with the same grit size, in spite of their different structures. The method could further be used for optimization of processing parameters at sanding.

Light microscopy of wood using sanded surface instead of slides

Abstract Xylem anatomy is fundamental in studies of the evolution of terrestrial plants, tree ecophysiology, forestry, and wood science. Traditional xylem anatomical studies by light microscopy utilize wood sections. However, the procedures are laborious, and high-quality histological sections have been particularly challenging to achieve from recalcitrant wood species and dry wood material. Modern microscopy offers opportunities for speeding up the xylem anatomical preparations. In this regard, the merits of using a sanded surface for wood anatomical research have been largely overlooked. Sanding of wood surfaces is practiced in dendrochronology and wood identification studies exclusively for the investigation of macro features, such as tree rings, wood porosity, or parenchyma patterns. We conducted microscopic level investigations of sanded surfaces of difficult-to-section high-density woods such as Dalbergia and Quercus species by reflected white light and epifluorescence microscopy. Reflected white light or combinations of reflected light and fluorescence could clearly show xylem micro-features in sanded wood surfaces. The resolution of cell types after sanding with 1000-grit was similar to the resolution obtained by transmitted light microscopy in histological slides. The advantages of sanded wood surfaces compared to traditional wood sections can be summarized as cost- and time-effective sample preparation, large sample area, intact cell walls and tissue structure, preservation of chemical content and extractives, and even focus of the field of view. A simple procedure of wood sanding instead of microscopic slides can be used for xylem microscopy and automatic image analysis of xylem structure.

Wettability and bonding quality of exterior coatings on jabon and sengon wood surfaces

Wettability and bonding quality of exterior coatings on fast-growing wood surfaces were studied. Samples of air-dried flat-grained (tangential surface) and edge-grained (radial surface) pattern of jabon (Anthocephalus cadamba) and sengon (Paraserianthes falcataria) woods were used. Before application of exterior coatings, the surfaces of the lumber samples were sanded. To provide wood surfaces with various degrees of roughness, abrasive papers of 120, 240, and 360 grits were used for the surface preparation. The wettability of two exterior coatings (water-based acrylic and oil-based alkyd varnishes) on the sanded wood surfaces was measured using a sessile drop contact angle method. The Shi and Gardner (S/G) model was used to evaluate and compare the wettability of the surface coatings on the wood. The sanded wood samples were coated with the two coatings (two layers each). Bonding quality of the coating layers was measured using a crosscut tape test method. Experimental results show that constant contact angle change rate (K value) of the S/G model decreased as the grit number of abrasive paper increased. This indicates that the wettability decreased as the roughness of the surface decreased (surface becomes smoother). There was no evidence of differences in wettability between tangential and radial wood surfaces. The oil-based alkyd coating generated better wettability compared to the water-based acrylic. The crosscut tests showed that the bonding quality of the coating films on both jabon and sengon wood decreased as the surface became smoother. The sengon wood compared to jabon wood provided better coating wettability and bonding quality. Wettability in terms of the K values was a good indication for determining the bonding quality of the two varnish layers.

Convergence of the robust Gaussian regression filter applied to sanded wood surfaces

The quality of a sanded wood surface is represented by its roughness, which can be separated from the originally measured data by a procedure of filtering. Past experience has shown that the robust Gaussian regression filter (RGRF) is suitable for wood surfaces because it does not introduce distortions into the roughness profiles. The filter works iteratively until a user-defined convergence condition is met. The iterations stop when the difference between two consecutive profile median values becomes smaller than a given tolerance. This paper examines the convergence of RGRF when applied to wood surfaces sanded with various grit sizes in order to establish the tolerance value, which leads to convergence with the minimum number of iterations. This study was based on monitoring the variation of roughness parameters with the number of iterations for a range of tolerance values. A tolerance of 0.01 μm was found acceptable for filtering sanded wood surfaces.

The influence of measuring resolution on the subsequent roughness parameters of sanded wood surfaces

No recommendation was found in the literature with regard to which measuring resolution should be used when measuring wood surfaces and requirements in the general standard ISO 3274 (1996) appear too stringent. Due to its variability, wood requires longer evaluation length than recommended by ISO 4288 (1996) and combined with a high resolution will increase the matrix of data and so the time for scanning and data processing. A study was conducted on roughness profiles from sanded surfaces of oak, beech and spruce measured at different resolutions to see which is the lowest resolution that still allows accurate evaluation of the roughness parameters in real time. The effect of decreasing the resolution on roughness parameters was examined as compared with a resolution of 1 μm, which was taken as a reference. Results showed that a measuring resolution of 5 μm seems reliable for all species sanded with common grit sizes.

Roughness models for sanded wood surfaces

The understanding of the effects of variables is crucial to achieve the desired sanded surface quality at optimum condition. In wood surface evaluation, it is known that anatomies on wood surface could distort the roughness value and cause a misinterpretation of the processing performance. In this study, statistical approaches were taken to characterize the influence of sanding variables as well as to analyze the anatomical noises that were inherited from intra- and inter-species of woods. Four available roughness parameters (R a , R q , R k and R ap) were used to examine the surface of three distinct wood species, viz. kembang semangkok, red oak and spruce in wide-belt sanding. Based on the mean values, analysis of variance showed that species (anatomy) was significant to all conventional parameters except R ap which was filtered by monitoring the second derivative of Abbott-curve. In spite of this, R ap recorded a more widely dispersed deviation of random measurement values than R k and R a . The effects of grit size and feed rate were found to be significant. Empirical roughness models were established using response surface methodology, and the errors were calculated by comparing the model values to all the randomly measured values. Although exhibiting slight species-dependant effect by nature, R k showed reliable consistency by recording the lowest error values (<10%) for both intra- and inter-species measurements. Experimental results also suggested that three random measurements at each run could be sufficient. The method of constructing machinability models can be readily applied in the industry as a quality control tool for wide-belt sander.

Form error removal of sanded wood surfaces

According to ISO 3274 form errors can be removed by fitting a polynomial regression through the original measured data called the total profile to obtain the primary profile. For wood surfaces it was found that the regression was affected by the presence of deep and grouped pores. To obtain a primary profile free of distortion, the deep pores can be removed from the total profile prior to applying the regression. A method was developed that eliminated the pores entirely. The efficacy of this method was tested visually and by comparing coefficients of determination r2 between the polynomial regression according to ISO 3274 (1996) and the total profile and the modified regression line when the effect of deep pores was removed and the modified profile that had no pores. The influence of the shape of the primary profile obtained by the standard method in ISO 3274 (1996) on further digital processing was tested on roughness profiles filtered with a Robust Gaussian Regression Filter. The undistorted primary profile was taken as a reference.

Expeditious building of ring-porous earlywood vessel chronologies without loosing signal information

Chronologies of earlywood vessel size of ring- porous trees contain valuable ecological information, but long preparation procedures limit their application in eco- logical studies. Recent and fast techniques for wood surface preparation combined with automated image analysis are reducing the work needed to build chronolo- gies, but might also entail measurement inaccuracy. In this study, we aim to evaluate the effect of a possible effi- ciency-accuracy trade-off on ecological signal strength. To this end, we compare measurements of mean vessel area from two recent and fast procedures carried out on sanded wood surfaces with a reference procedure based on an accurate survey from thin sections. Measurements were performed on increment cores of 15 sessile oaks (Quercus petraea (Mattuschka) Liebl.) for the period 1956-2006. Dissimilarities in results with the reference procedure were quantified and evaluated. Our data show that the workload can be reduced by more than 20-fold when using the highly automated procedure. Signal weakening caused by mea- surement errors is negligible for vessels (6,000 lm 2 and can be easily compensated by increasing the sample size. Manual correction of misrecognized vessels hardly reduced this error further. The new procedures constitute a major step towards an efficient and accurate analysis of early- wood vessel chronologies of ring-porous tree species.

The Influence of Wood Anatomy on Evaluating the Roughness of Sanded Solid Wood

Sanded wood surfaces contain irregularities caused by both the sanding process and the anatomy, so the anatomical roughness, which is independent of any machining operation, must be excluded from measurements of surface irregularities if the processing roughness is to be properly evaluated. This paper investigates the effect of wood anatomy on surface roughness parameters of oak and spruce wood after sanding with P120 sandpaper. The wood anatomy is excluded from the roughness profile using a method developed by Gurau (2004). Total roughness parameters, which contain both the processing irregularities and the wood anatomy, are compared with processing roughness parameters. The effect of anatomy is to increase measures of roughness, particularly for oak.

Processing roughness of sanded wood surfaces

Any quantitative evaluation of a sanded surface requires that the data be filtered to remove form errors and waviness. Wood surfaces contain irregularities due to both the sanding process and the anatomy, so the anatomical roughness must be excluded from any measurement of the surface if the processing roughness is to be properly evaluated. The efficacy of a number of standard filters was examined to see if they were suitable for oak, beech and spruce surfaces sanded with P1000 grit. Filters in current standards introduced distortions, but a robust Gaussian filter, contained in a draft standard, appeared to give roughness profiles free of distortions. The processing roughness and anatomical roughness, contained in the filtered profile, were separated with an algorithm based on a threshold defined in the material ratio curve. Work is continuing to compare the properties of different grit size and species combinations.

Wood Surface Energy and Time Dependence of Wettability: A Comparison of Different Wood Surfaces Using an Acid-Base Approach

Summary Using four different wood species, the wetting behaviour of sanded wood surfaces was compared with that of microtomed surfaces. Sanding caused lower contact angles and lower total surface free energies. Electron donor components were considered to be responsible for the observed changes according to the applied acid-base approach. The time behaviour of sanded surfaces differed from the microtomed reference, insofar as the volume of a deposited drop of water decreased very rapidly as soon as it was applied, indicating fast penetration into the wood. A qualitative analysis by SEM revealed a heavily torn upper-most cell layer on sanded surfaces, which was assumed to be responsible for the increased surface free energy and enhanced penetration.