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TECHNOLOGY 31
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volumes for individual designs are often relatively low. Teemu
However, FDM-printed connectors should not simply be
produced with the highest possible amount of material. Higher
infill density or thicker walls increase printing time and material
consumption, but they do not always lead to a proportional
improvement in joint performance.

In furniture applications, the best connector is not necessarily
the strongest one, but the one that provides adequate
mechanical performance with reasonable material use and
production time. Therefore, it is necessary to understand
how perimeter count and infill density affect the mechanical static load tests without structural failure.
response of the joint. These studies confirm the practical potential of printed
Several studies have already shown that 3D-printed connectors, while also showing that their stiffness and reliability
connecting elements can be used in furniture structures. require further optimisation.
Petrova and Jivkov investigated polylactic acid (PLA) based The finite element method (FEM) has been used to support

3D-printed connectors for detachable end-corner joints made the design of furniture joints and demountable fasteners.
of plywood and MDF panels and showed that connector Podskarbi and Smardzewski used FEM to analyse innovative
geometry, internal cavity filling and wall thickness affected furniture fasteners, while Krzyżaniak et al. compared numerical
joint behaviour. predictions with experimental results for demountable joints.
Uysal studied the screw withdrawal strength of 3D-printed FEM is also relevant for FDM-printed parts with internal
PLA+ specimens with different infill patterns and infill densities. infill, where explicit modelling of the internal structure can be
PLA+ (polylactic acid plus, an enhanced-grade PLA material computationally demanding.

with improved mechanical properties and printability compared For this reason, the internal geometry can be replaced
to standard PLA) was used in that study as well as in the by equivalent homogenised material properties. Bhandari
present work. and Lopez-Anido developed a homogenised FEM model
The results showed that increasing the infill ratio did for a 3D-printed part with a cellular internal structure, while
not produce a proportional increase in performance, which Gonabadi et al. investigated the effects of raster angle, build
is important for material-efficient design of printed furniture orientation, and infill density using microstructural modelling
components. and homogenisation techniques.
Printed connectors have also been studied in chair Bean et al. numerically and experimentally evaluated the
construction. Nicolau, Pop and Coșereanu developed an FFF- effective elastic properties of 3D-printed gyroid infill, and Galvez

printed connector for joining a chair leg with two stretchers et al. used a shell-infill FEM approach for a 3D-printed structure.
and demonstrated its potential to replace a conventional glued These studies support the use of simplified or homogenised
mortise-and-tenon joint. FEM models when the aim is to compare configurations,
In a later study, Nicolau et al. tested an improved PLA evaluate global stiffness and identify critical regions rather
connector in L-type joints and complete chair prototypes. The than to reproduce filament-level damage.
chair with printed connectors showed larger displacements Other studies have examined printed furniture connectors,
than the traditional reference chair, but it passed the required dowels, and related load-bearing components from the