[Dennis] of [Made by Dennis] has been building a Voron 0 for fun and education, and since this apparently wasn’t enough of a challenge, decided to add a number of scratch-built improvements and modifications along the way. In his latest video on the journey, he rigorously calibrated the printer’s motion system, including translation distances, the perpendicularity of the axes, and the bed’s position. The goal was to get better than 100-micrometer precision over a 100 mm range, and reaching this required detours into computer vision, clock synchronization, and linear algebra.
To correct for non-perpendicular or distorted axes, [Dennis] calculated a position correction matrix using a camera mounted to the toolhead and a ChArUco board o…
[Dennis] of [Made by Dennis] has been building a Voron 0 for fun and education, and since this apparently wasn’t enough of a challenge, decided to add a number of scratch-built improvements and modifications along the way. In his latest video on the journey, he rigorously calibrated the printer’s motion system, including translation distances, the perpendicularity of the axes, and the bed’s position. The goal was to get better than 100-micrometer precision over a 100 mm range, and reaching this required detours into computer vision, clock synchronization, and linear algebra.
To correct for non-perpendicular or distorted axes, [Dennis] calculated a position correction matrix using a camera mounted to the toolhead and a ChArUco board on the print bed. Image recognition software can easily detect the corners of the ChArUco board tiles and identify their positions, and if the camera’s focal length is known, some simple trigonometry gives the camera’s position. By taking pictures at many different points, [Dennis] could calculate a correction matrix which maps the printhead’s reported position to its actual position.
Leveling the bed also took surprisingly deep technical knowledge; [Dennis] was using a PZ probe to detect when the hotend contacted the bed in various places, and had made a wiper to remove interfering plastic from the nozzle, but wasn’t satisfied by the bed’s slight continued motion after making contact (this might have introduced as much as five micrometers of error). To correct for this, he had the microcontroller in the hotend record the time of contact and send this along with the hit signal to the Raspberry Pi controller, which keeps a record of times and positions, letting the true contact position be looked up. This required the hotend’s and the printer’s microcontrollers to have their clocks synchronized to within one microsecond, which the Pi managed using USB start-of-frame packets.
The final result was already looking quite professional, and should only get better once [Dennis] calibrates the extrusion settings. If you’re looking for more about ChArUco boards, we’ve covered them before, as well as calibration models. If you’re looking for high-precision bed leveling, you could also check out this Z sensor.
Thanks to [marble] for the tip!