Methods of Furniture Design and Construction

The mutual interaction of all known and unknown design parameters requires taking into account the cooperation of competent partners during designing. The experience of many national and foreign concerns and companies manufacturing furniture shows that modern furniture constructions are created by multidisciplinary teams, which, in
the course of work, solve any problems associated with placing a new product on the consumer market. High-quality furniture cannot be the result of conservative designing, based only on the work of an artistically talented person, but the result of creative marketing, design, cultural and technological discoveries emerging in interdisciplinary teams appointed for the time of preparing a new product.

An interdisciplinary design team should include the participation of a designer, a construction engineer, a technology engineer, a trader and a marketing specialist. Working in such a group has an interactive nature and is mostly assisted by CAx systems and thematic knowledge databases (Fig. 4.2).

Acronyms used in CAx technologies:

CAD Computer-aided design,

CAE Computer-aided engineering,

CAM Computer-aided manufacturing,

CAQ Computer-aided quality control,

CE Concurrent engineering,

CIM Computer-integrated manufacturing,

CSG Constructive solid geometry,

CRM Customer relationship management,

DFM Design for manufacturing,

EDM Engineering data management,

ERP Enterprise resource planning,

FEM Finite elements method,

Fig. 4.2 The structure and tools of work of an interdisciplinary design team

FMEA Failure modes and effects analysis,

MIS Management information system,

PDM Product data management and

TQM Total quality management.

The design space in such a team expands greatly and is conducive to shifting the project’s centre of gravity, gradually, from aesthetic priorities, through construction and functional priorities, to the marketing visions, aiming to confront them in order to verify again the previous parameters and obtain the best market effect (Fig. 4.3).

The structural creation of innovative furniture systems based on anthropometric design process (ADP) should have well-defined phases and methods (Fig. 4.4).

A. Purpose and place of use of the furniture: hotel, cinema, restaurant, school, office, post office, bank, apartment, living room, bedroom, dining room, kitchen, bathroom, sitting, sleeping, relaxing, eating meals, learning, work, customer service and storage;

B. Object of design: wardrobe, bookcase, dresser, chest of drawers, glass case, bar, cabinet, dining table, table, desk, bedside table, attachment, chair, armchair, bed, couch and sofa;

C. Group of users: Europeans, Dutch, Poles, Americans, Chinese, children, teenagers and adults;

D. Characteristics of the population: adults between 30 to 50 years old and school children from 14 to 18 years old;

• Problems identified and resolved,

О Problems identified and unresolved,

□ Unidentified and unsolved problems,

9 The original location of the center of gravity,

• Secondary location of the center of gravity.

Fig. 4.3 The development of the design space and shifting the project’s centre of gravity: a conservative designing without the ability to quickly identify and eliminate design problems, b multidisciplinary designing for rapid analysis of the occurrence of problems and their solution, filled circle Problems identified and resolved, circle Problems identified and unresolved, square Unidentified and unsolved problems, dark grey circle The original location of the centre of gravity, light grey circle Secondary location of the centre of gravity

Fig. 4.4 Phases and methods of designing and constructing furniture

E. Relationship between anthropometric parameters: reference of the dimensions of the designed furniture to the appropriate anthropometric dimensions;

F. Evaluation of anthropometric criteria: representativeness—characteristics of the population should correspond to anthropometric data, accuracy—statistical solutions must apply to precise calculations of the representative sample, and project error—evaluation of what percentage of the population should be excluded. It is usually accepted that from 1.5 to 10 % of the population for which a new construction of furniture is being designed should be excluded in order to avoid excessive increases in the cost of production of the future product;

G. A set of many types of data and criteria in order to adapt the characteristics of furniture to assumed use requirements, the precise realisation of the design, as well as creating a few sizes of the same product. This is especially important when designing school furniture, where there needs to be a compromise between the cost and anthropometric requirements;

H. Purpose, function, functionality and silhouette: resulting from user preferences and the type of clothes worn;

I. Critical factors: taking into account critical factors which are likely to have a significant impact on the health and safety of future users is knowledge flowing from the correlation between anthropometric dimensions, the type of popula­tion and function of furniture;

J. Anthropometric model of furniture;

K. Correlations;

L. Product idea: the source of inspiration and vision of the product;

M. Clothing and equipment;

N. Additional parameters: taking into account additional parameters which are likely to significantly improve the function and equipment of furniture;

O. The project’s centre of gravity, leading direction: deciding on the definitive anthropometric requirements and going onto technical designing;

P. Defining the technical problems, including the disposal of the product and recycling;

Q. The synthesis of construction solution: a summary of the concept of the development of the construction, joints and dimensioning used;

R. Calculations and optimisation: carrying out calculation of strength, stiffness, stability of furniture and its elements, as well as optimisation of the results of these calculations;

S. Synthesis of technological solutions: a summary of the concept of technology development in terms of selecting the material, machine park, tools, etc.;

T. Synthesis of function and functionality: a summary of the concept of function and functionality development of furniture in terms of meeting the stated requirements; and

U. Product design.

Unlike the furniture produced using craft methods, furniture manufactured industrially should be done according to a specific, repetitive technology, in the conditions of mechanized unit production, small or large series. It imposes a number of important structural, technical, organisational and commercial require­ments, unknown to crafts factories and furniture workshops. These requirements have become an essential stimulus to the overall mechanization and technical development of furniture production. They have also contributed to increased awareness of producers of the need to prepare partial or detailed project docu­mentation. Engineering design methods, without which it is hard to imagine building, aviation and machine construction, have never been systematically or on a large scale introduced into furniture production. The implementation of these methods requires the gathering of detailed information concerning:

• the functions of furniture and maximum operational loads resulting from them, or also in extreme cases, unusual loads, especially when it concerns children’s and teenager’s furniture;

• elastic properties of materials used, taking into account the orthotropic char­acteristics of wood and wood-based materials, together with indicating maxi­mum stresses; and

• elastic and strength properties of normalised glued and separable furniture joints and connectors, hinges and accessories carrying operational loads.

The development of the proper structural version of furniture, ensuring durable and safe use, is one of the components of the design process (Fig. 4.5). Certainly, however, designing the function of furniture has a unique practical importance as it provides the most effective possible fulfilment of the assumed functions of use. The purpose of aesthetic activities is shaping the proportions and spatial forms of fur­niture and the choice of surface colour, texture and drawing to the satisfaction of the most sensitive tastes of the potential user. This part of the project in many cases, however, clearly dominates the whole design works, shifting functional and dura­bility features further away. In this situation, the functional requirements should have strong preference, sometimes at the expense of aesthetic or durability values.

In a properly planned process of manufacturing furniture, the stiffness of certain products is evaluated already at the designing and construction stage (Fig. 4.5). This helps eliminate any construction errors by setting the correct parameters for indi­vidual components, subassemblages and assemblages in accordance with the pre­scribed criteria of stiffness and durability. Formulating the engineering process of designing furniture in such a way enables to limit destructive tests of finished products and shorten the cycle of implementing furniture to production, limit the number of complaints in continuous production and save a significant amount of time and material.

The presented methods of designing clearly require teams of partners of an interdisciplinary education. In particular, this fosters ousting sequential methods by concurrent designing methods. Sequential designing (Fig. 4.6) limits the effec­tiveness of the work of constructors, with the necessity to deal with emerging and mounting technical conflicts in the design. With this approach to designing, only the first engineer enjoys the comfort of creatively using his working time to solving specific tasks. Other engineers, before they start to carry out their tasks, must become familiar with the project, eliminate the errors of predecessors and agree on the future modified solutions. The time spent on these activities is sometimes unproductive, lost, due to the incorrect selection of methods and tools assisting designing. Replacing this system with a system of concurrent designing reduces the designing time and increases efficiency in achieving the objectives of the project through access to a common knowledge database (Smardzewski 2007) (Fig. 4.7).

In concurrent designing, interdisciplinary designers participate, who can more quickly and efficiently satisfy customer requirements than is the case in traditional sequential designing. After all, often a product expected by the customer does not

Fig. 4.5 Constructing furniture

necessarily mean the best construction or technological values and does not always need to satisfy all the needs of the consumer, but should always optimally solve the current market expectations. Concurrent designing guarantees a high quality of designing activities because it significantly shortens the time for the emergence of a new model of furniture (mock-up, model, prototype), optimises technological processes and reduces to a minimum the time necessary to manufacture the product,

Fig. 4.6 Example of sequence designing

Engineer D

Fig. 4.7 Example of concurrent designing

increases customer satisfaction, informs and warns about the costs of the designed furniture at the stage of its virtual development, and minimises the costs both of the designing and construction process itself, as well as the cost of making furniture.