First time Core XY Build using Duet Hardware
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Hello all, I'm looking for input on a new Core XY build (350x350x350). I have a lot of experience with other printer builds, but this is my first step into the Core XY kinematics. This will be a non stop, High temp printer (Up to 135C) chamber temps. Core XY would make it much simpler to put the motors for XY motion outside of the chamber enabling me to use either servos or closed loop steppers and water cooling the E stepper and Cold end.
My main concern at the moment is the extra little belt tension added after heat soak (Causing thermal expansion) pulling the XY axis out of square.
Is this warranted and does anybody have any experiences or input to share? Also other things a CoreXY beginner should be mindful of? I own CNC machine tools for my business so this will not be an extrusion based build.
Thank you!
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@gwatson90 I don't know if the belts expand significantly at elevated temperatures. Most belts have glass cores and glass tends to be pretty stable over temperature. I would think that since both belts will be at the same temperature there won't be any tension differential causing the X axis to tilt relative to the Y axis, bit I'm just speculating. It shouldn't be too hard to test it. You could always tension the belts at the print temperature to make sure the X axis is square. Make sure you buy belts that are specced for high temperature operation.
The most critical thing about setting up CoreXY is to ensure that the pulleys are positioned accurately to keep the belts parallel to the linear guides. Any error in that will result in belt tension varying with extruder position in the XY plane and will lead to distorted prints, especially as the extruder gets closer to corners of the build space.
You will also want to use quality drive pulleys that have properly sized and centered holes, and quality idler pulleys. Don't buy the cheapest crap that is marketed to 3D printer hobbyists. Gates makes quality drive pulleys that you can buy from Filastruder. I recommend stacked ball bearings for idlers. The cheap, crappy 3D printer idlers have too-tiny bearings that wear out quickly.
Finally, don't stand pulleys up on posts. The belt tension will cause them to tilt. Make sure pulley shafts are supported solidly at the top and bottom.
See: https://drmrehorst.blogspot.com/2023/07/corexy-x-axis-wobble-revisited.html
and https://drmrehorst.blogspot.com/2020/12/x-axis-wobble-in-ummd.html -
@gwatson90 Most electronics are rated at 80°C, and typically have some level of self-heating, and running at that temperature drastically reduces their life time. So electronics in chambers that reach more than 60°C should be avoided. This includes toolboard, probes (like the BLTouch) and even some connectors. Use wires and connectors that are rated for the expected temperature.
Ian
TronXY X5S with Duet 3 MB6HC and Roto toolboard : Cartesian bed-slinger with Duet 3 Mini 5+ WiFi and 1LC : RRP Fisher Delta v1 with Duet 2 Maestro : Polargraph with Duet 2 WiFi
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@mrehorstdmd Thank you for the input and for your excellent write up on Core-XY layouts. I've been looking through it over and over again. It really made me consider the trade off between using toothed idlers vs bearings.
I generally agree with you about standing idlers and pulleys on posts or shoulder bolts. However it may become necessary due to form factor constraints (admittedly self-imposed and arbitrary) and machining less parts. My plan there was to counter bore the holes (with either a boring bar or reamer to keep the tolerance tight) for the shoulder bolts. This would minimize moment loads and add rigidity. If reality strikes then I'll go back to the drawing board.
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@droftarts That is why I'm really looking into Core-XY. I can at least get the XY motors out of the build chamber. The heat-break and extruder motor will be water cooled.
I think the toolboards are great, but I have never used them because all of my other machines are enclosed. I usually just run one or two multi-conductor cables (Either Igus or Molex) to my tool head to keep the clutter down. Currently my highest temp machine is 90C chamber. However the kinematics are Cartesian so the motors are inside the chamber. I haven't had any issues yet and honestly the motors aren't that expensive and I'm willing to write them of as Somewhat-consumable.
However at over 120C it becomes a reliability issue so that's why I want em out! As well as the fans. Thankfully most E-Motors are so short that a well made water cooling block can do well enough to keep the heat down.
This has been and excellent replacement for a BL-Touch in a heated chamber too:
https://mandalaroseworks.com/products/strykepoint-probe
