The practice of the Laboratory of Testing and Validation of Furniture at the Department of Furniture Design of the Poznan University of Life Sciences shows that most furniture defects that are revealed during testing come from design errors. Yet there are few instances of damages to the product as a result of the quality of treatment or the quality of the machine park. In general, design errors can be divided into ones that result from the following assumptions:
• construction and
The most common errors of usage assumptions include:
• adopting assumptions of climatic conditions of using furniture which do not comply with the real conditions of places where the product is exploited in the future,
• failure to take into account seasonality of the climate of the place of exploitation,
• the assumption of too liberal schemes of using furniture by future customers and
• the omission of requirements related to the infrastructure of the place of exploitation.
Among errors of functional nature, the following dominate:
• non-compliance of dimensions of places and surfaces for storing with the dimensions of the stored items,
• limited free access for fixed and moving pieces of the furniture, including a high degree of difficulty for single-person use of the item and
• the lack of functions resulting in an obvious way from the purpose of the furniture.
Errors relating to the anthropometric characteristics constitute a serious percentage of all errors made during the designing stage. The cause of this phenomenon lies in the routine of designers and basing on obsolete measurement data of the population for which the product is being created. During the certification tests, the following main errors were pointed out:
• the lack of variations in the dimensions of furniture not regulated according to the characteristics of the centile groups of relevant populations,
• improper dimensions of seating and worktops,
• dimensions of furniture mismatched to the ranges of the upper and lower extremities and
• collisions of dimensions of furniture forming sets.
Among the errors resulting from the person-technical object relation (anthropo – technics), the following usually appear:
• selecting the hardness of seats and mattresses routinely and not in accordance with the physiology of the human being,
• curvatures of the furniture parts directly in contact with the body of the user mismatched to the natural geometry of the body,
• methods of use of the moving pieces of the furniture not compatible with natural motor features of the body and
• wrong placement of important manipulating and usable elements.
Structural errors often come down to:
• the inaccurate selection of joints and connectors, as well as the inaccurate location of structural nodes,
• the underestimation of the global stiffness and local stiffnesses of individual parts of the furniture and
• the lack of stability of the furniture or its components.
The most commonly encountered technological errors include:
• incorrect selection of materials not taking into account: purpose, form, function and construction of the furniture,
• mismatching the finishing technology to the conditions of use and
• defects of performance resulting from simple technology, causing the reduction in use value and/or exposing the user to injury or damaging clothing.
Most often, these errors can be eliminated by preparing, reviewing and consulting with a wide group of professionals of all design assumptions.