Съдържание


Vol. X, Issue 1 2021

CHECK OF SURFACE ROUGHNESS AVERAGE OF WENGE & MAPLE MILLING SURFACES

Автори: Ioannis Ntintakis, Andreas Onoufriou

Резюме

Working in a CNC machines is one of the most popular woodworking processes. Often is more suitable to use Subtractive Rapid Prototyping (SRP) machines than classic CNC machines. In the current study the surface roughness checked for two different wood kinds, wenge and maple. For each kind of wood six specimens milling in a 3-axis SRP machine and then the surface roughness average (Ra) defined. During milling process two different tools used. For roughing phase, a square end mill and then a ball end mill for finishing. For roughness check a portable linear roughness tester instrument used to define the Roughness Average (Ra) for each specimen. During the milling process the spindle speed and fed rate varies. The spindle speed starts from 1.100 mm/min until to 2.400mm/min and feed rates starts from 9.00 rpm to 15.000 rpm. According to the results the changes in machining parameters have significant effect to surface quality. Wenge is harder than maple wood and that play an important role to surface roughness. As cutting parameters improved roughness average (Ra) is less.

Ключови думи: CAD/CAM, CNC Rapid Prototyping, Roughness Average (Ra)

EN Version

COMPATIBILITY OF HIGH SCHOOL DESK DIMENSIONS WITH ANTRHROPOMETRIC MEASUREMENTS

Автори: Mehmet Acar, Yusuf Ziya Erdil, Ali Kasal

Резюме

The aim of this study was to examine whether school desk dimensions’ match high school students’ anthropometry. Anthropometric variables (shoulder, elbow, knee and popliteal height, buttock-popliteal length and hip breadth) were measured from randomly selected 328 students who attend public high schools in Mugla/Turkey and school desk dimensions which are in use in corresponding schools were measured to match with anthropometric data. The age range of the children was from 14 to 18 years. Mean, median, standard deviations, minimum values, maximum values, were analyzed statistically. The measured anthropometric dimensions of the students were also compared with those of the school desks in use. The results of the study showed that most of the anthropometric data of students differ significantly and there exists a high mismatch between anthropometric measurements and the school desk that they use.

Ключови думи: furniture ergonomics, school desk, anthropometry

EN Version

INNOVATIVE FIREPROOF INSULATING PANELS FROM AGRICULTURAL WASTES

Автори: Yasmina Khalaf, Peter Hajj, Julia Mihajlova, Patrick Lacroix, Roland El Hage

Резюме

To reduce pollution as well as energy consumption, new insulating and non-flammable bio-panels based on the combination of different reinforcements such as Miscanthus x giganteus particles and rice husk mixed with recycled textile fibres were prepared using Chitosan as a polysaccharide natural binder. Different formulations using one or more combined reinforcements and Chitosan (7 wt%) as an aqueous binder were prepared by a thermocompression process. Mechanical, thermal and fire behaviour of the panels were examined. Results showed that the mechanical properties vary according to the size and the nature of the used reinforcements. All the panels showed sufficient bending and compressive strength for thermal insulation uses, according to European construction specifications (DIN 4108-10). The highest mechanical strengths in bending and compression have been found for the formulation with small size miscanthus particles (0.48 MPa and 0.64 MPa respectively). Fireproof panels (E rating, according to standard NF EN ISO 11925-2) with an insulating behavior (thermal conductivity vary between 0.07 and 0.09 W/m/K) and a density range between 247 and 400 kg/m³ were successfully elaborated. The prepared bio-panels show promising results and great potential to compete with the conventional insulating materials used nowadays.

Ключови думи: bio-panels, agricultural wastes, chitosan, thermal insulation, fireproof

EN Version

INFLUENCE OF HOT-PRESSING TEMPERATURE ON PROPERTIES OF ECO-FRIENDLY DRY-PROCESS FIBREBORDS WITH LIGNOSULFONATE ADHESIVE

Автори: Viktor Savov, Julia Mihajlova, Nikola Yotov, Bozhidar Madjarov

Резюме

A major challenge for the producers of wood-based panels is to achieve formaldehyde emissions at wood levels. For that purpose, various types of lignin have emerged as particularly promising substitutes for the traditionally used urea-formaldehyde resins.

Lignosulfonates are a by-product of the production of cellulose by the sulphite method. They are practically harmless to human health. The main functional groups of lignosulfonates are the hydroxyl groups and the connection with fibres is mainly through hydrogen bonds. To form these bonds, in addition to the surface with active hydroxyl groups, the temperature of hot-pressing is also essential.

This paper presents a study on the effect of hot-pressing temperature on the properties of eco-friendly dry-process fibreboards. As an adhesive was used calcium lignosulfonate in a content of 10% to absolutely dry fibres. In the experiment, the hot-pressing temperature varied from 150 to 200° C, with increments of 10° C. The main physical and mechanical properties of the panels were determined. On this basis, an analysis was made. It was found that the properties of dry-process fibreboards with only lignosulfonate as a binder are significantly affected by the temperature of hot-pressing, because of which the hot-pressing temperature should be at least 190°C.

Ключови думи: eco-friendly dry-process fibreboards, calcium lignosulfonate, hot-pressing temperature

EN Version

POSSIBILITIES FOR UTILIZATION OF WASTE WATER AND RESIDUAL WOOD FIBRES IN THE PRODUCTION OF HARDBOARDS

Автори: Viktor Savov, Petar Antov, Nikolay Neykov

Резюме

Despite the continuous introduction of new materials and technologies in the production of wood-based composites, hardboards (HB), remain in the range of wood products, due to their good consumer and exploitation properties. The production of these products is characterized by the intensive consumption of raw materials. In the wet production process, much of the raw material used is taken up by water involved in the formation of the wood-fibre mat. It forms a significant share in the value of the finished product, resulting in a smaller added value. At present, the utilization of wastewater from the production of the HB is unsatisfactory. Its high fibre content creates sludges that can be recycled or thermally utilized. The present study is aimed at reviewing the possible methods of utilizing the wastewater and fibre sludge in it. This will provide the Bulgarian producers with a means of enhancing production efficiency and applying the circular economy principles.

Ключови думи: utilization, wastewater, wood fibres, circular economy

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

THE KINDERGARTEN INTERIOR AS AN IMPORTANT FACTOR FOR THE HEALTHY DEVELOPMENT OF PRESCHOOL CHILDREN

Автори: Boris Iliev, Danijela Domljan

Резюме

An important factor for the healthy growth and development of children is the proper organization of interior space and the use of adequate equipment tailored to their age. Analyzing psycho-physical activities of children in kindergartens and the functions they perform during the day, an environment should be designed to fit their social, cognitive, psycho-physical and other developing needs. Organization of environment or design of kindergarten playrooms is the key factor as well as furniture design. The paper presents the environment of 27 public kindergartens in towns Skopje, Zagreb and Sofia and analyses current state of interior and furniture design in their playrooms. The new suggestions based on observed environments are given.

Ключови думи: kindergarten, pre-school children interior design, playroom, child development, health

EN Version

THE DEVELOPMENT OF THE ENGINEERING DESIGN PROGRAM AT THE UNIVERSITY OF FORESTRY FROM THE VIEWPOINT OF ITS GRADUATES

Автори: Pavlina Vodenova, Desislava Angelova

Резюме

The article represents a unique view at how the “Engineering Design (Interior and Furniture Design)” Program developed from its inception to the present times. The authors of the article hold a Master Degree in Engineer Design from the first cohort; later, they defended their PhD thesis in the same field. Nowadays, they act in the position of Lecturers, training students of the same Program. All of this gives a unique look at the various achievements and problems that have arisen during the Design Program's development period. Aspects such as the kind of studied courses, teaching methods, facilities, opportunity for creative expression, and students' career prospects are considered. For better objectivity, the opinion of other alumni who graduated the Program over the years has been studied.

Ключови думи: Engineering Design Program, design education

EN Version

OPPORTUNITIES FOR PRODUCT SERVICE SYSTEM DESIGN IN THE PROCESS OF TRANSITION TO A CIRCULAR ECONOMY

Автори: Maya Ivanova

Резюме

This paper combines literature on Circular Economy, Business Innovation and Product Service System Design (PSSD) to outline different opportunities on the application of PSSD in the process of transition to a new economic model. Moving to a closed-loop industrial model would naturally introduce new opportunities for development of PSS because of the essential principles of the Circular Economy. These would include the ideas of delivering capability rather than ownership, extending product value (remanufacturing), shared ownership, reverse logistics etc. Value for the user and the environment is found in product but mainly in service content and serves as an example for the positive effect PSSs can have in the process of transition to a circular economy model. The argument is supported with case studies that serve to illustrate the potential success of circular services and systems.

Ключови думи: circular economy, circular design, business innovation, systems thinking, service design

EN Version

PROJECT ASSIGNMENT AND PHASES OF IMPLEMENTATION IN INTERIOR DESIGN – THEORY AND PRACTICE

Автори: Pavlina Vodenova

Резюме

During the direct work in teaching interior design of residential and public objects with students in the specialty "Engineering Design" at the University of Forestry, in Sofia, Bulgaria it was found that they have particular difficulties in applying the design methodology in practical briefs and work. For this reason, the present work was made. The report clarifies the stages of project assignment implementing, which accompanied by the basic concepts in the design assignment theory and practice in Bulgaria gives the key to the successful creation of a harmonious interior composition, both in public and in residential buildings.

Ключови думи: interior, project, design, project assignment

EN Version

AUGMENTED REALITY (AR) IN PUBLIC INTERIORS

Автори: Stela Tasheva

Резюме

Augmented Reality (AR) is developing technology for merging interactive virtual forms and shapes into the real-world environment. The AR products in interiors today require lightning and sometimes, spatial conditions, as well as access to some software and hardware elements, provided either by the viewer, or by the host of the location.

The study is following some public interiors of the 21st century and investigates the methods of creating and applying of AR sets in their structures. A systematization of AR versions according to the existing relations to the public interiors is presented. The focus is on the evaluation of the use of AR products in interior design, and on the future evolution.

The expected results are in the fields of architecture and interior and furniture design.

Ключови думи: Augmented Reality, interior design, 21st century, public buildings

EN Version