The correct belt tension is essential to a coreXY motion system. A loose belt or belt slop, can cause lots of issues in 3D printing, such as circles looking like ovals.
The belt and the gantry form a mass-spring system, with the belt being the spring(k) and the gantry being the mass (m). The natural frequency of the system is f=sqrt(k/m). Having a loose belt reduces the k, and the f, which in turn affects vibration compensation.
X1 monitors belt tension through this equation f=sqrt(k/m). During calibration, the motors will generate vibrations at various frequencies and look for the resonance, which happens when the input frequency is equal to the natural frequency. We call this operation frequency sweep, and it generates quite some noise with an increasing pitch.
When the X1 finds that the natural frequency has changed, it is time to tighten the belt. It is a semi-automatic process and can be done with a simple operation.
We also made this video showing how to clean the carbon fiber rods.
This procedure can be considered as a belt tensioning and carbon rods cleaning procedure. If you follow this video, you won't need to re-do the belt tensioning procedure as shown in the previous video.