Long Bowden Tube Length

I'm building a large CoreXY printer with a build volume of 20"x26"x26". So the hotend can be very far from the hotend at max size (which obviously won't be used too much but i'm designing for when it does). I don't have a good grasp on how well Bowdens work, esp for flexible filaments, which is leading me to my questions:
How long can a bowden tube be to successfully print flexible filaments? How about normal inflexible ones?
Do you think I should go direct drive with that size and a bowden tube will just be too long?

Preferably 1.75mm filament but will take advice on 3mm as well.

Thanks

Edited 1 time(s). Last edit at 04/24/2019 05:18PM by shortyski13.

I'd design an x carriage with removable pkates so you can build one with either system and mount whatever is needed. You can then also add a plate with a laser diode or dremel attachment.

It also depends on the type of flexible filament. Tpc flex is stiff enough to be used (at least in 3mm form) but if the filament is more compressable it could fold back upon itself in the cold end drive and retraction would not be practical. Mine is about 60cm and has trouble getting good results with pressure advance compensation, even with pla or abs filament. I decided not to use it.

With a large build volume you'll need speed, which needs the moving parts to be stiff and low on mass.

A toolchanger could automate swapping direct drive and bowden. That:s something I'd want to add to my diy 3d printer.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

An alternative is to use a remote direct drive, like the Zesty Nimble.
It gives you a direct extruder with hardly any of the weight penalties you normally associate with direct drive.
We have a couple of customers using it on very large printers.

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Lykle
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Co-creator of the Zesty Nimble, worlds lightest Direct Drive extruder.
[zesty.tech]