A robotization of assembly is the real implementation of Industry 4.0 in the furniture industry. The robotization objective is to obtain favorable values of production process parameters (performance, productivity, quality) and to improve human wellbeing at work. Our aim was to present and compare the quality parameters of a selected furniture production process, performed in a very long series, containing more than 30 thousand products. The analysis included the results of the long-term measurements of the quality level of upholstery frames produced by the modified and improved, on the basis of operational conclusions, robotized line for the serial production of upholstery frames and by the simultaneously used nonrobotic line for assembly of frames of the same construction. The results obtained show that robotized assembly leads to a much lower percentage of defective products than in the case of the nonrobotic technology, the causes and types of defects in the products are also different, and it is easier to prevent these defects and remove them. The cognitive findings identified problems and challenges, not found in traditional technologies, caused by the using of manufacturing robots in furniture production.

This paper presents an approach to the design of an upholstered furniture frame using the finite element method and empirical studies. Three-dimensional discrete models of upholstered furniture frames were developed taking into account orthotropic properties of solid pine wood (Pinus sylvestris L.) without and with details strengthening their structure in the form of glue joints and upholstery staples. Using the CAE Autodesk Inventor Nastran finite element method, linear static analyses were performed by simulating normative loading. The finite element method was performed considering the experimentally determined stiffness coefficients of the PCAC adhesive and staple joints. As a result, stress, displacement, and equivalent strain distributions were obtained for upholstered furniture frame models with stapled corner joints. The deformation and strength behavior of the upholstered furniture frames was improved by reinforcing with a wood strip. A new approach to the design of upholstered furniture frame frames using the FEM method with stapled component connections was developed and tested. The results of the study can be applied in the optimization of upholstered furniture construction.

T-nuts are factory installed in the holes of the ready-to-assemble furniture components. There is a risk that the t-nut spontaneously falls out during transport or storage and get lost; the t-nut can also be pushed into inaccessible spaces during assembly. These complications can make furniture assembly impossible. For this reason, sufficient force to hold the t-nut in the hole is essential. The article presents the test results of the forces holding the t-nuts in five furniture materials (softwood, Oriented Strand Board, plywood, and particleboard in two variants). The M6 t-nuts with four prongs were installed in predrilled 8 mm holes. The resistance to withdrawal of the t-nuts was measured with a universal testing machine. The tested materials could be divided into three groups in terms of the risk of the t-nut falling out: softwood and plywood – low risk, F = 1113.2-1158.0 N; OSB and particleboard – moderate risk, F = 592.3-645.5 N, particleboard with a pad – high risk, F = 645.5 N. The results show that the withdrawal resistance is not correlated with the density of the wood material, and that it decreased with the degree of wood material processing – the less processed the material, the greater the resistance to withdrawal of the t-nuts.

Influence of technological parameters of the upholstery seams in furniture. Based on the real problem of weak seams in covers of wooden furniture, a multifaceted analysis of the issue was performed. As a result, it was decided to carry out comparative laboratory strength tests of seams made with the use of various technological parameters. For the production of test samples, we used different yarn threads to find the best and sufficiently strong seams for used fabrics. The test results show that not only the thread and fabric used, but also the sewing technology parameters have a significant influence on the seam strength. Overall, these results indicate that to increase the seam strength, it is necessary to choose thread type B with very high strength and low elongation at break. This solution will minimize the risk of broken threads in case of deviation of material features and technological parameters, which can be variable in the long duration of large-scale production.

Impact of upholstered furniture structures on the comfort of long-term use. The main objective of the study was to analyze the impact of changes to the structures of upholstered seating furniture to measure the comfort of new furniture and after long use. Tests were conducted with the use of a Force Sensitive Applications sensing mat to record contact pressure, and a profiled cavity pressed into the seat with a force of 760 N. The period of 5 years of long-term use was simulated by the cyclic load of 1000 N x 25,000 repetitions. Based on the analysis of the test results obtained, a decrease in the discomfort factor D by 12.7% for seat I and 11.5% for seat II was observed. This means an increase in the feeling of comfort in using these seats during the period of use. This is associated with a decrease in seat stiffness. Seats with less rigidity ("softer") cause less pressure on the human body due to the larger usable area.