Material extrusion or Fused Filament Fabrication (FFF) is a common additive
manufacturing technology, where a filament is molten and deposited on the build
surface according to a CAD-defined contour. After each layer the build platform moves
one layer height down, so that the next layer can be deposited. A decent amount of
studies has been investigated on the strength of the interlayer cohesion. However, nearly
no study has dealt with the adhesion of this first deposited layer on the build platform,
although it is a very critical step, as the print cannot be finished in a proper way, if the
part detaches during the print. The present work aims at understanding and optimising
the adhesion of different filaments (poly(lactic acid) and acrylonitrile butadiene styrene)
on two commercially available build platform materials (glass and polyimide). The
adhesion forces are measured by means of a self-constructed adhesion force testing
device, in which printed strands are sheared-off and the maximum adhesion force is
recorded, as a function of the build platform temperature. Additionally, contact angle
measurements and investigations of the surfaces of the sheared-off strands complement
the results. It was found that best adhesion is given, when the temperature of the build
platform is slightly higher than the glass transition temperature of the deposited polymer.
Furthermore, the investigations show that solely the surface tension and topography of
the contact partners are not sufficient to fully describe the complex adhesion
mechanism in FFF. Especially for the development of novel materials, the knowledge
gained in this work is essential to improve the reliability or optimise the printing process.