Cantilevered print bed on 500mm square printer.

[Jack Flash]

Coming along nicely on my CoreXY printer.

Basically have the frame design figured out and now I'm looking at the print bed support and drive.

Eyeballing the cantilevered layout and I can't help but feel that this design is the most simple.

Yet on the forum I see repeated comments "Don't use the cantilevered design".

My idea is a pair THK type linear bearings with the drive screw between them.

Looking for some input, debate, technical data on why this can or can't be used??

Thanks

[Viesturs Lācis]

And do you mean to tell that none of those  "Don't use the cantilevered design" answers did not provide any arguments? The problem is that there is lack of structural stiffness in vertical direction - the outer edge can wobble easily and that will dramatically affect your print quality, _especially_ if you want to go for 500 mm size print bead.

The best thing you can do is add two more drive screws approximately at corners of the outer edge so that all three screws create a nice large triangle and with 2 linear slides on the other two corners you will be just fine. And couple all the screws and Z axis motor with a timing belt. The overall result might look something like this (although this guy placed corner drive screws right next to linear slides, that does not matter that much, it allows for some savings in materials):

http://www.thingiverse.com/thing:588277

Please do _not_ copy the solution for motion in xy plane - unsupported round rails for 500 mm print size require very large diameter to avoid any flexibility in them, so use aluminium support structure and some linear rails for both horizontal axes.

[Eric Pavey]

My bot has a 305mm square cantilevered platform.  It works (dual rear leadscrew), but I think I'll upgrade it to a triple leadscrew design (two in the back, one in the front):  Better bed stability under load, and reduction in vibration during fast toolhead movements.

My printer's build volume is roughly 12x12x18" : Could easily eat up a few spools of filament on a big print (so, 4kg on the platform, not counting the platform's weight itself).  That seems surprisingly heavy when I just set the spools on there, and would be even moreso for your printer.  Cantilever on my Makerbot Replicator 1:  Good to go.  Something as big as yours:  Simplest solution, yes.  But probably not a good idea. 

[adam paul]

If you put the single leadscrew in the front, it may interfere with part removal. I turned my whole bot around, with the z cars in the front and the strippers in the back.

[Eric Pavey]

Good solution!