Pulling filament through long tubes

Question

I'm setting up my printer in a small room, and I thought I'd come up with a system for more easily swapping filaments, but I'm not yet sure it is feasible.

Rather than physically replace the spool, I'd like to hang most of my spools on the wall, where they can rotate, and only swap filament leads in the (direct drive) extruder. The spools would be placed at some distance from the extruder, and at various angles. So to make sure the filament is pulled from the spool at the proper angle, and to avoid breaking it, I think it should probably run through a flexible tube to reach the printer.

I know such tubes are used for Bowden style extruders, but what I'm proposing is different in at least two ways: [1] the extruder motor would be pulling (not pushing) filament through the tube and [2] the tube would be longer than normal, e.g., between 1 and 2 meters.

Is this plan feasible? Or are the problems I am not foreseeing?

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Edit 1: I don't know where I got 1-2 meters from. The distance is actually closer to 50cm.

Edit 2: To clarify my proposed setup, here's a crude mockup:

Answer 1

I would say it's not the best approach.

In the situation you've described I would rather install some kind of vertical ring a bit above your printer. This ring would organize your filament going from any direction.

So let's assume you got one spool on the right and one on the left of your printer, both are 1m away from the printer itself. If you get filament and put throught the ring then to your extruder.

In my opinion the ring should be around 15..20cm over the printer, it should have around 10..15cm diameter and spools should not be too low.

The only issue I see is unwinding spools which are too far from the printer because then filament would be unwinded angular but the same issue would be with and without teflon tube.

[edit] Here is a simple change of your design

[edit2] Please also note that you can assure proper angle of unwinding filament by installing small rings ("eyes") next to spools. These eyes will direct filament out of spool and then filament will turn to your big ring mounted on the printer. This is common solution in textile industry

Answer 2

This is somewhat similar to a question I asked a while back. Pay attention to Ryan Carlyle's response in the question I posted. His post essentially explains various ways that guide tubes may hinder extrusion due to drag. In regards to the length of your guide tubes, ensure that the tube is relatively straight.

If you are holding the filament above the machine, chances are that you wont really need the tubes anyways and the distance between the spool and the extruder won't matter either. The point of tube is to ensure the filament doesn't bind coming from the back of the machine, thus potentially clogging your extruder.

Update Based on the OP's drawing, I think it would benefit to change the design to drop the tubes all together. The tubes can provide many point of contact and managing so many lines at once may become problematic. So, possibly drop the tubes and intend on not drawing your filament unless they are fed into the extruder. You could install smaller ends of tubes at either end of assembly (one at the storage rack, the other above the extruder) to ensure the filament is being fed/pulled straight. The space between the storage rack and the machine doesn't matter. Here's a basic edit of your design that might be easier to manage. For kicks, here's a design I made for my own machine as a "quick-change" design.

Answer 3

I would like to add to the already great discussion, that this general approach is prone to filament degradation by water intake. That is, if you are using filament for which this is an issue (PLA as the most prominent example).

Also, your goal is to exchange more quickly, that is without (un-)mounting whole spools each time. Basically you want to have a multi-filament spool holder, if I understand correctly. If you design an enclosed box with a single outlet you could incorporate silica gel inside and a reduced effort to swap the filament. I would still avoid a nice free-hanging spool solution due to the degradation issue.

Answer 4

Yes, this is feasible. You should constrain the tube at both ends, this prevents the spool from pulling up on the extruder. This approach is known as reverse bowden setup.

Answer 5

This shouldn't be too much of an issue, as long as:

1. You guide the filament properly to avoid breakage (at both ends as Tom mentions)
2. You avoid too much friction between the pulling extruder motor and the spool itself.

You mention that you consider using a 1-2 meter teflon tube to guide the filament. Although this might work, long teflon tubes will increase the friction from pulling the filament. Furthermore, I really doubt having such a long tube will be beneficial at all; quite on the contrary, I think it could be rather impractical. Most likely, having simple guides at both ends (whether its tube stubs or rings) will suffice.

Answer 6

Your idea is actually good, but i would add some edits to it. First of all, to keep your equipment clean, you would like to add little foam rubbers to clean the filament at the entrance of the tubes, to clean out the dust that will be accumulating over the rolls.

Another thing that i would recommend is to hang the tubes on a separate support for them and not on the extruder head, as it would add some additional friction to it and can cause the 3d model with additional friction making it distorted.