Prusa XL Semi-Assembled: Bed Mounting Rails Not Even Close to Lining Up?
Hi all,
I have carefully assembled my Prusa XL, up through part 4, step 16. Step 17 is where one screws the heat bed down to the 2 supports that slide up and down the guide rails.
Two things aren't adding up... 1) It looks and measures square. The frame looks good. The z-screw rods look good. The panels all fit with basically even (and very small) gaps between the panel and the extrusions. And the extrusion ends are flat against the parts where they are supposed to meet (with right angles as necessary). And yet, 2) The holes on the heat plate are at least 1/4" (6mm) out of alignment on the left, and at least 3mm out of alignment on the right.
Even though the mounting holes are way out of alignment, the under-carriage/frame is evenly spaced between the guide rails (and square to it) and the heat plate/grid is evenly spaced within that, and also square to it. Everything looks perfect, except when I slide the left and right "Z-axis parts" up to screw the bed down, the holes are shifted to the right, as compared to the holes in the heat bed frame.
I notice on the left side (caution sticker side), there is a spacer between the rail bearing and the "z-axis part". It looks like if this spacer were moved to the other side, everything would fit well. Can someone look on their reliably finished XL and see if you have a spacer there? And/or does anyone have any troubleshooting thoughts?
Thanks in advance. Photos of relevant parts are attached.
RE: Prusa XL Semi-Assembled: Bed Mounting Rails Not Even Close to Lining Up?
The assembly is slightly asymmetric. The non-rotating z-support must be on the left side. In your photo it looks correct. Is the heatbed orientation correct?
RE: Prusa XL Semi-Assembled: Bed Mounting Rails Not Even Close to Lining Up?
The assembly is slightly asymmetric. The non-rotating z-support must be on the left side. In your photo it looks correct. Is the heatbed orientation correct?
Thanks for replying. Heatbed orientation was my thought too, as it sure looks like reversing it would fix the problem. But the cable attachment is to the back as in the instructions. And so are the build plate guide pins. I believe the orientation of the heat bed is correct (assuming the heat plate assembly is built correctly).
When looking at the printer, the non-rotating z-support is on the person's right (I.e. opposite side from the "caution sticker). Is that correct?
I wonder if the aluminum frame in the heatbed assembly is upside-down (flipped left to right). Would that reverse the asymmetry?
Are there any steps in the official build process where I could have installed something backwards prior to this step, that would reverse the sides of the z-axis supports?
Are there any parts that may have been reversed at the factory that might produce the same issue?
Nothing looks bent and everything looks square. So this seems most likely to be caused by an error in an earlier step that either shifted the z-axis support or more likely reversed the orientation of the asymmetry
RE: Prusa XL Semi-Assembled: Bed Mounting Rails Not Even Close to Lining Up?
Hi Jeff:
The non-rotating Z axis support has to be on the left side.
Please read the instructions again.
You should disassemble the parts and install that support on the left.
RE:
The non-rotating z-support is supposed to be on the LEFT side (see 2-base-side-frame-assembly), the side with the sticker.
On the aluminum heatbed frame the screws on the left side are a few mm closer to the edge than on the right side (see assembly manual, screws at front and back; not the marked ones for the spindles). If you followed the assembly instructions closely, then it should have been right, provided there is no mistake in parts and preassembly. The build plate pins can be screwed into the plate from either side if I remember correctly.
Yes, a flipped frame in the preassembled heatbed would cause that misalignment. If so, it is up to you whether you contact support for it. I had the heatbed completely disassembled anyway so that I could align the z-spindles without risk to damage the heatbed tiles. If you decide to do that, please note down the numbering scheme of the tiles. If you treat the tiles and the plugs with some care, it is not difficult.
Edit: somebody answered before.
RE: Prusa XL Semi-Assembled: Bed Mounting Rails Not Even Close to Lining Up?
I found it. Funny how carefully I paid attention to most of the highlighted warnings. Apparently not that one. I installed the z-axis supports on the wrong sides.
For anyone finding this in the future when searching about the same problem, it does not appear to require rolling all the way back to that step. Really all that appears to be needed is to swap the z-axis supports (including the spacer on the rotating side). The problem is that one of the screws involved is behind the z-axis threaded rod. So you need to remove the 4 screws holding that motor in so you can move the threaded rod enough out of the way to get to that screw.
I say "Appears to be needed" because the instructions from tech support was quite a bit (extremely) more involved, and I did as instructed, and it worked. The above shortcut is not directly tested and should be considered a "try at your own risk" thing. But in the process of fixing mine, I noticed that the vast majority of the procedure appeared to be unnecessary. The only meaningful thing I did, that I didn't end up putting back together as it was, was the swap of the z-axis supports. I.e. it does not appear that you have to swap the motors and cabling, etc.
Thanks all!