Open Core One++

Let's improve and fix the Prusa Core One(+) by leveraging the openness it was built upon.

This website serves as an information hub for the Prusa Core One (some solutions applicable to other printers) owners, who found out that the printer doesn't behave as they'd have expected it to. Many problems were fixed over the time, but many still remain and must be fixed in order to have the printer perform up-to the contemporary standard.

Every product is a product of its environment and conditions (Conway's law). While Prusa Research possibly could be held responsible, it is not the job of this website to be the judge or to incite any harm to the company. Rather the goal is to provide enough rigorous technical detail about the problems the community encounters. Our belief is that only by being open about the problems and technical decisions, we can actually make the situation better for everyone.

This page is not meant to be any basis for harassment or targeting Prusa Research or its employees. Be nice and civil.

Documented problems

Actual bed temperature is 10 deg C lower than the printer shows

As of May 2026, the printer's target temperature is about 10 degrees lower than what the display shows, causing possible problems with high-temp materials and likely with PLA on C1L.

MK3.5 MK4 CoreOne CoreOneL

"Absorbing Heat" takes significantly longer than needed

The firmware's frame temperature estimation violates Newton's law of cooling — the step rate slows down as the bed gets hotter, exactly when physics says it should accelerate. How much extra wait time this causes depends on the unmeasured frame time constant (τ).

CoreOne

Essential mods

Hole covers

Improve thermal insulation of the chassis by covering slot-shaped holes in the panels.

Essential tools

Tools specified here should be available at hand when attempting to do any modification to the printer itself, either they are essential for assembly or help with calibration/setup significantly.

Z leadscrew alignment tools

Alignment of the Z leadscrews reduces resonance of bed movement.