I’ve been kicking around the idea of building my own take on a CoreXY printer for a few years now. I’ve looked at many of the existing options (HyperCube, VzBot, HevORT, RatRig, RailCore, Voron, etc etc) and have read through a lot of build blogs for other personal projects (Like Mark Rehorst’s UMMD). The end result of all that reading is that I decided none of the existing designs quite scratched this particular itch so I went about designing my own take on the CoreXY printer while incorporating as many “clever” ideas that I have gleaned from other builds as possible.
Here is a (non-exhaustive) list of aforementioned clever/bad ideas:
- CoreXY motion
- Frame does not rely on carefully cut and assembled aluminum extrusions
- Parallelism of the critical belt-sections is not dependent on very precise assembly of frame/motion components
- Belt-path will avoid cantilevered belt pulleys as much as possible.
- Entire build will not rely on extremely high-tolerance parts of any kind (save the ubiquitous “MGNX” linear motion components).
- Rely as little as possible on structural printed parts.
- Eschew toothed/smooth idler pulleys for stacked sets of flanged bearings (taking a page out of the Voron playbook).
- Use an ultralight carriage (Sherpa Micro extruder and very low-profile/weight accessories, or a bowden extruder) to allow the use of an unsupported (or minimally supported) X rail.
- Utilize Klipper Firmware (with input shaping) to loosen the requirements on axis rigidity somewhat.
- etc. etc. etc. (but that probably covers most of the “big ideas”.
Taking all of that into consideration the end result is something close to this:
XY motion is via three linear rails (Y is MGN12, X is MGN9). All of the pulleys are pairs of F695 bearings (like the Voron 0). Pretty much everything is sandwiched between two sheets of 1/2" MDF so all of the motor mounts and idlers are supported at both ends (nothing cantilevered). The XY pulleys are stacked on a single M3 bolt (with 5mm bushing) rigidly connected to the Y rails (and the X rail is rigidly connectec to the two X rails. Those are not cantilevered, but being rigidly attached to the steel carriages they shouldn’t be prone to ‘creep’ like a printed part. The ‘critical’ CoreXY belt sections are kept parallel with the help of eccentric pulley idlers at the four corners providing +/- 2mm of adjustability to make sure things are lined up even if I end up drilling the holes in the plates by hand. I’m still playing around with the carriage design but currently I’m trying a Sherpa Micro, Ender-3 style hotend, and a part cooling fan.
Here is a recent render of the X carriage. The fan duct is being reworked to actually cool the part without crashing into it and the rear blower fan has been relocated.
Here are the stacked pulleys on the Y carriages:
Once I actually get a working CoreXY motion I’ll continue on with all the bad ideas I have for a Z axis .