MILLING OF WOOD MATERIALS WITHCOMPUTERIZED NUMERICALLY CONTROLLED (CNC

) ROUTER

M.Sc. Ümmü KARAGÖZKastamonu University, Faculty of Forestry,

Dept. of Forest Industrial Eng, 37100, Kastamonu /TURKEY

ukaragoz@kastamonu.edu.tr

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Preview

INTRODUCTION1

MATERIAL AND METHOD2

CONCLUSIONSCONCLUSIONS44

REFERENCES5

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1. INTRODUCTION

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Wood is a sustainable, natural, attractive and aesthetic product, with excellent properties of durability, acoustic performance and fire performance. So, it has wide range of usage.

Wood is used in the production of some aspects of internal and external decorative elements by such processes as cutting, planning, CNC milling and sanding.

Recently, Computerized numerically controlled (CNC) woodworking machinery that can automatically control the movements of a spindle and table, has been widely introduced in wood industries for automatically cutting, drilling and shaping.

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CNC Woodworking Machinery

History CNC routers were first used by the aerospace industry to

cut complex patterns out of sheets of aluminum. And then, by the early 80’s, this technology was used in

many types of machinery in the secondary woodworking industry.

New functionality and improved performance is being developed day by day which will give CNC an ever increasing role in the success of wood machining sector [6].

Lately, Cad-Cam programs also have started to improve with development of the CNC technologies and increase the importance of design. Woodworking sector has followed this development in terms of both design and engineering. Cad-Cam is the integration of the Cad (design or drafting) process with the Cam (manufacture) of the component [7].

M.Sc. Ümmü KARAGÖZ4

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CNC Woodworking Machinery

Recently, CNC woodworking machinery has been widely introduced in wood industries especially, in the furniture industry. CNC has been used for the grooving, milling, patterning of furniture material …ect

The CNC woodworking machinery is mainly focused on the achievement of high quality; in term of work piece dimensional accuracy, surface finish, high production rate, less wear on the cutting tools, economy of machining in terms of cost saving and increase of the performance of the product with reduced environmental impact.

M.Sc. Ümmü KARAGÖZ5

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The surface quality of wood machined by CNC

The surface quality; is one of the most specified customer requirements and the major indicator

of surface quality on machined parts is surface roughness. The surface roughness; is mainly a result of various controllable or uncontrollable process

parameters.

M.Sc. Ümmü KARAGÖZ6

Fig 1 Effecting factors on surface roughness

there are a great number of factors influencing the machined surface roughness

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The aim of the study

The aim of the study was to investigate the machinability of Scotch pine (Pinus sylvestris L.), Oriental beech (Fagus orientalis Lipsky.), Uludağ fir (Abies bornmülleriana Mattf.) and Carolina poplar (Populus canadensis) with the CNC router.

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M.Sc. Ümmü KARAGÖZ7

Also, wood samples were machined both tangential directions and radial direction. And then surface quality of tangential and radial direction was compared

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MATERIAL AND METHOD

In the experiments , different species of hardwoods and softwoods were used.

For Hardwoods; beech (Fagus orientalis Lipsky.), Carolina poplar (Populus canadensis) For Softwoods; Scotch pine (Pinus sylvestris L.), Uludağ fir (Abies bornmülleriana Mattf.)

o Primarily, wood samples were obtained from these species at 50x50x150 mm dimensions.

o The wood samples were conditioned in a conditioning cabin at 20±2˚C temperatures and 70±5% relative humidity to reach Equilibrium Moisture Content (EMC) throughout 8 weeks

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SpeciesMoisture

content (%)

Density(gr/cm³)

Oriental beech

12,10 0,671

Carolina poplar

11,35 0,569

Scotch pine 11,85 0,558

Uludağ fir 12,54 0,426

And then, the moisture contents and density of wood species were determined according to TS 2471 [14] and TS 2472 [15]. Table 1 shown moisture and density values of wood species

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Processing parameters;

8 mm of diameter cutterspindle speed 8000 rpmfeed rate 6.4 m min-1cutting depth 4 mm

surface roughnesswas measured by using a stylus type profilometer (Mitutoyo SJ-201).

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Surface Roughness Parameters

M.Sc. Ümmü KARAGÖZ

Surface roughness parametersSurface roughness parameters

mean peak-to-valley height (Rz), can be calculated from the peak-to-valley values of five equal lengths within the profile

maximum peak-to-valley height (Rq) , the square root of the arithmetic mean of the squares of profile deviations from the mean line               

average roughness (Ra) , the average distance from the profile to the mean line over the length of assessment

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These parameters are characterized by ISO 4287

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RESULTS AND DISCUSSION

Species Tangential direction Radial direction

Ra Rz Rq Ra Rz Rq

Oriental beech

5,59 31,55 7,09 5,87 34,48 7,55

Carolina poplar

5,89 34,16 7,78 5,92 33,5 7,74

Scotch pine 5,51 33,59 7,34 6,13 35,55 7,93

Uludağ fir 6,93 38,73 8,86 6,05 34,84 7,64

Table 2 shows moisture and density values of wood species

From Table 2, it can be observed that, the surface roughness values average roughness (Ra), mean peak-to-valley height (Rz) , maximum peak-to-valley height (Rq) were higher in the radial direction as compared to the tangential direction

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The surface roughness of wood species according to tangential and radial direction

According to the graph, tangential direction in the CNC milling process produces a smoother surface when compared to a radial direction. At the end of the tests realized with similar conditions in the literature, it was shown that the radial direction produced rougher surfaces when compared to the tangential direction. The findings obtained in this study support the information given in literatures [17, 18, 19, 20].

Figure 3 The surface roughness of wood species according to tangential and radial direction

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• The surface defects such as raised grain, fuzzy grain and chipped grain occur in the too much moisture content of wood species.

• In order to obtain smoother surface, moisture content should not exceed 12% [10, 21]. When the studies in the literature were examined, it can be stated that there was proportional relationship both density and moisture content with the surface roughness. The values obtained in this study are in conformance with the values in literatures [2, 22, 23].

• In general, the results have shown that the hardwoods have higher processing performance than that of softwoods. In the existing literature, it was disclosed that the surface roughness values for the diffuse porous woods were lower than those for the ring porous woods [24, 25, 26].

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CONCLUSION_1

The wood surface roughness directly concerns the final use of wood products. As the surface roughness is most important quality characteristic, the factors that affect surface roughness need to know and to analyse. This factors are related to machining parameters, wood structure properties, cutting tool and cutting properties

Being aware of the machining parameters , wood properties and other factors, whether directly or indirectly, contribute to using more efficiently woodworking machinery that were invested a lot.

This stduy compered to machinability of wood species such as Scotch pine (Pinus sylvestris L.), Oriental beech (Fagus orientalis Lipsky.), Uludağ fir (Abies bornmülleriana Mattf.) and Carolina poplar (Populus canadensis).

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CONCLUSION_2

At the same machining conditions (8 mm of diameter cutter, spindle speed 8000 rpm, feed rate 6,4 m min-1 and cutting depth 4 mm), Oriental beech has shown lower surface roughness values and has the highest machinability performance, because of its high density.

Density is remarkably the factors influencing the surface roughness.

The surface roughness decrease with increasing density value. So Uludağ fir. (Abies bornmülleriana Mattf.) has low density, surface roughness values were obtained highest value in this wood species. Also hardwoods species have shown better processing performance than softwoods.

In this study, the surface roughness values (Ra, Rz, Rq) were determined to be higher in the radial direction as compared to the tangential direction.

As a consequence, in order to determine surface quality of machined wood by CNC and traditional machine, the many factors that affect on surface roughness must be analyzed separately.

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REFERENCES

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Davis, E.M., 1962. Machining and Related Characteristics of United States Hardwoods. Technical Bulletin No.1267, America.

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M.Sc. Ümmü KARAGÖZKastamonu University, Faculty of Forestry, Dept. of

Forest Industrial Eng, 37100, Kastamonu /TURKEYukaragoz@kastamonu.edu.tr

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