I am trying to figure out the real build volume that you can actually print on U1. Maybe this was already discussed. I have a few dilemmas:
Jogging the tool refus to go either flat zero or to flat 270 on both X and Y axis. I can jog down to 0.10 and 269.90 only. If you can print 270 cube, you would expect to be able to at least jog 0-270 fully. Though even so, for a true 270x270 you would then skip the priming action, but let’s skip this nuance.
The slicer itself warns me when printing an object 264.37x263.60. If the build volume is really 270x270, why would you get a warning for an object that fits the specs?
it will do a click when reaching the end of the G0 travel move as if it hits the physical limit of the machine. Same thing here, if you truly have a 270x270 volume, you should not bump into the case when doing “legal” moves.
I am just trying to understand what are the actual limits of this machine so I can plan accordingly. In my particular case, I can live just fine with even 250x250 (which would provide a retreat of 10mm from all build plate edges. But maybe some people already plan based on the 270x270 specs and intentionally buy it for that volume.
I’ve done some work on this (but not for the U1). In Marlin, M121 can be used to disable firmware end-stops, but apparently not in Klipper. Yes, that Z thing sounds like there is a slight mechanical restriction on the overall range of Z, but might also be a firmware setup thing.
In my experience it is never possible to print to the extreme dimensions of nozzle travel, even if the nozzle travel really does reach the headline values. Something which gets in the way is the slicer, which seems to have a built-in aversion to accepting a model which gets too close to the limits. I think it needs a little extra room for manoeuvre, so there is a path for the nozzle outside the actual print (even if we think it doesn’t need one).
I have managed to take a Tina2 to the extreme (Marlin + Cura) by tuning the mechanics to maximise the unrestricted travel, disabling firmware end-stops, and then fooling Cura into thinking the print volume is a bit bigger than it actually is by adjusting the size in the printer definition and (this is important) setting the XY datum to the centre of the bed rather than a corner (this required additional Gcode in the printer’s preamble definition).
Z remains an issue, because the slicer assumes Z offset = 0 whereas we never actually want Z = 0 (which would gouge the plate). Therefore, if the slicer could be told that Z offset = 0.2 (say), with the full travel of 270mm it should be possible to print something 270.2mm high. But you can’t, so it’s not.
My advice is just accept the useable build volume as 265x265x265 (or whatever).
Depending on shape of the bead that the nozzle will lay down, you can get an end result of 270, true. Though all the machines I worked with, be them FDM/SLA/mill/laser refer to actual axis travel when they were specifying some dimensions.
@CrazyIvan I can accept a reduction down to 265x265, no problem. I am always worried about the real temperature at the edge of the plate anyway (it usually falls short a couple of degrees, but it depends on the heat bed implementation).
Another thing that puzzles me is that Snapmaker support sent me a gcode file to run and debug my printing surface planarity (different topic, I have a dip in the top left corner). It is the regular “one layer - full surface” print. At some point, the gcode runs:
Perhaps your X “limit” switch (which triggers to define X=0) is not properly aligned? If it can be adjusted to be further in the negative direction (without making it out of range), that would free up more travel at the upper end.
Or there’s something restricting the travel when it shouldn’t be.
This is off the top of my head and I can’t be much more help than that, because my U1 is still in its box (and is staying there until I have more time).
That opens another can of worms: the U1 does not have mechanical/optical endstops. It relies on TMC`s homing feature by bumping into the axis physical limits. There are settings on how hard to bump into the physical limit to detect such obstacle through the stepper motor, how much to retract back after that, etc. All this could affect the real zero position and hence what leaves out of the expected 270mm after that.
Coming from a Bambu X1C with a advertised volume of 256x256x256 mm! Bambu take a lot more space for their fancy space tech. They use a whopping 2cm for flow calibrating. And even you don’t want to flow calibrate the space is reserved for Bambu. And it takes also some extra space on the side walls.
So i’m very happy with the extra workspace of the U1.
