A specific print image has been causing discussion in the 3D printing community for a few weeks now: Vertical lines on the outer walls of models, also known as Vertical Fine Artifacts (VFA), are visibly appearing on Prusa’s CORE One. According to the manufacturer, the cause is not clearly attributable to a single problem, but rather a combination of several mechanical and electronic factors. Now the CEO and founder of Prusa is speaking out.
VFAs are regular micro-irregularities along the Z-axis that become clearly visible on close inspection – especially with glossy materials and direct lighting. These artifacts are caused by minimal fluctuations in the extrusion, which add up visibly over many layers. The typical deviation is in the range of 10 to 40 micrometers. Although so fine, they are disturbing for demanding applications such as prototyping or design.
According to the manufacturer’s technicians, there are three main causes: Motor resonances, vibrations due to acceleration and inconsistencies when the timing belt engages with the drive pulley. The influence of the motors was excluded following internal tests. The drivers and voltage values used come from the proven MK4 platform and are considered to be well tuned.
Other indications point to the so-called “belt meshing” problem: When switching a timing belt from pushing to pulling, minute delays can occur. These occur primarily at certain belt tensions and engine speeds – regardless of the actual printing speed. A more precise belt tension and adjustment of the printing parameters could provide a remedy here.
The CoreXY kinematics are also a factor. As every movement affects both axes, effects can overlap or weaken depending on the direction and speed.
Prusa is currently working on new guidelines for belt adjustment and extended diagnostic aids. A software solution for optimizing the settings is also to follow. The aim is to make the problem manageable for users without time-consuming manual error analysis.
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