Автор: Vladimir Mihailov

Статии

INFLUENCE OF THE APPLIED PRESSURE ON FINGER JOINED END-TO-END WOOD

Автори: Todor Petkov, Vladimir Mihailov

Резюме

In the production of finger-jointed details, it is most important to provide the required applied pressure to achieve the desired adhesion strength of the joint. The results of the study of beech wood elements (Fagus Sylvatica) are presented, with applied different pressure for the face ends of the details (0,4 and 0,7 N/mm2). The following properties have been determined of the tested samples: bending strength, modulus of elasticity and the density of wood. The pneumatic-piston system also provided for securing the bonding pressure in the longitudinal direction of the wood. In the carried – out experiments, it was used a polyvinyl acetate adhesive with a class of water resistance D3. The mechanical properties of the glued elements depend on their structure, the type of adhesive and the type of wood. The paper presents the values of strength and modulus of elasticity in static bending of elements derived from beech wood.

Ключови думи: beech wood, finger-joint, polyvinyl acetate adhesive, pneumatic-piston system

EN Version

SURFACE SMOOTHING OF THE SIDES OF PRISM-SHAPED BEECH WOOD DETAILS VIA LAPPING WITH FAST-ROTATING METAL CYLINDER

Автори: Dimitar Angelski, Andrey Kavalov, Vladimir Mihailov

Резюме

The article presents and analysis the results from laboratory experimental researches over opportunity for effective surface smoothing of cutter-processed or initially sanded surfaces of prism-shaped steamed beech samples with grit number of a sandpaper № 80. The lapping is executed by a special work instrument – cylindrical steel circlet, loaded on the milling spindle. Upon handing over and further pressure of a detail to the smooth polished surrounding surface of the rotating bushing, the lapping that occurs results in smoothing of the detail’s surface that has been in contact. It is also due to the partial heating, densification, decrease and rounding of the tops of the microgrades remaining after sanding. The purpose of the research has been to evaluate the degree of smoothing, by checking the multiple influence of the major factors on which it depends. In this particular case, we have chosen to vary the following factors: feed speed of detail U; radially directed force of pressing to the spindle q; number of impacts over the same surface n. The research results show that a quality smoothing, equal to the traditional one that is double sanded with sandpaper №180 or №240, can be reached at values of the variable factors, as follows: u = 8÷10 m.min-1; q = 6÷8 kN.m-1; n = 1÷2 impact. Apart from the quality smoothing, this lapping method results in further economy of sandpaper and lacquer of up to 20%.

Ключови думи: surface smoothing, lapping, beech, lapping regime

EN Version

INFLUENCE OF THE TYPE OF ADHESIVE ON THE PHYSICO-MECHANICAL PROPERTIES OF BEND FURNITURE BOARDS

Автори: Vladimir Mihailov, Todor Petkov

Резюме

In the manufacture of furniture structural elements from folded glued thin furniture panels, it is important to determine the parameters affecting the performance of the finished wood composite panels. The purpose of the study was to determine the effect of the type of adhesive used on laminated high-density laminated wood fiber boards (HDF) and poplar plywood. The test specimens are made of five layers of 2.8 mm thick HDF slats and 4 mm thick plywood with 260/100 mm glued plate dimensions. For bonding, three types of adhesives were used - polyvinyl acetate (PVA) dispersion adhesive Jowacoll 103.05, polyurethane (PU) dispersion adhesive - Jovapur 150.50 and polyurethane wood adhesive - SOUDAL 66A. Bending and gluing were performed in a laboratory vacuum press with a rubber membrane and a template with a radius of curvature of 150 mm. The time to achieve minimum technological adhesion strength, vacuum velocity and minimum bending radius are determined. Samples were tested by standard bending with shoulder collection. The results obtained are analyzed and presented graphically.

Ключови думи: glued bent furniture panels, HDF, polyvinyl acetate (PVA) dispersion adhesive, polyurethane (PU) dispersion adhesive, bending strength, vacuum presses

EN Version