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tinydancer

Tips for the last 3rd on filament reel?

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I have a couple of rolls of filament that seem to be creating friction in the bowden because it's the last 1/4-1/3 of the roll and since it's very tightly wound it's seems to be giving me underextrusion issues. I have no problems printing with reels that are closer to full. Was wondering what people do to relax the filament. Was thinking of maybe wrapping it around another reel that had filament on it, but figured this isn't something new so I thought I would just ask.

I know, I ask A LOT of questions. :-)

 

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When you use a better feeder you'll print to the end of the roll with no problem ... and make sure the fillament goes straight into the feeder, f.e. by putting the roll of fillament a bit lower than the printer on a loose holder.

some other options ...

https://www.youmagine.com/designs/ultimaker2-rail-system-u2rs

https://www.youmagine.com/designs/ultimaker2-spool-connector

 

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I'm having the same issue. I've noticed that as the filament gets to the end of the roll, the angle it gets pulled at forces it against the wall of the reel, increasing friction and causing under extrusion. Even with their own filament rolls this seems to be a frequent issue, and an unfortunate design oversight by Ultimaker.

It looks like moving the filament holder slightly lower and to the right would fix this, but I'm hoping there is a solution that does not require major changes to the printer.

Anyone have any tips to resolve this?

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When pushing filament manually through the whole feeding traject, I found the most friction occurs in the teflon coupler and nozzle, when near the end of the spool. Friction in the bowden tube can also be much higher than expected. Also the "unwinding force" is very high: the spool acts as a very strong spring, trying to wind-up the filament again. It is probably the sum of these that causes the problems, when using the original feeder.

With the spool normally mounted on the printer, and the filament being fed into the machine, I usually unwind 20cm of PLA, wind it in the opposite direction around a 7cm skater wheel, and release it, after which it is almost straight. Then I unwind the next 20cm and wind it around the skater wheel in the opposite direction, etc., until I have straightened a few meters. This only takes a minute or so. And it can be done easily while the printer is printing.

Then I loosely wind the filament up on the spool again (although this is not necessary, you could leave it hanging around), so now it is sitting very very loose on the spool, with a bending radius of about 50cm, and it has very little friction in the whole feeding traject. Then it does not cause underextrusion anymore.

I know, I should try another feeder. Actually, I wanted to design one myself, but I haven't come to that yet. :)

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In an attempt to loosen the shape of the last dregs of filament on a tightly-wound roll, I unwound the last (15 or so percent) of it and took it off the spool completely. Then, keeping track of the ends so they wouldn't tangle, I manually counter-wound the filament such as to reverse it's tightly-wound shape.  The filament fought back a bit, but when I got it to a larger overall size (or into a looser bunch), I tied the ends and the filament to the coil with zip ties to reinforce the new, looser and desired shape. 

 

Now, I'm putting it in the sun for several hours (~70-80 degree F weather expected during this time...). 

 

I'm waiting to see if this works...

 

I'm hoping the heat will cause my filament to relax in the new, looser shape. 

We'll see...

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Ooh.  I wouldn't do that.  If it's PLA and is at all old (has been on a shelf for a year before you got it) then this will ruin it.  More info here:

 

Basically if you even just straighten it and let it sit like that for a day or so it will be incredibly brittle and break into pieces or if it doesn't it will break going into the bowden.

 

I think you just have to leave it alone on the spool and have a good powerful feeder.  Maybe print 30% slower the last 1/3 of the spool.  Maybe.  Or get a powerful feeder like that on the UM3, the S5, the UM2+ or get a bondtech feeder.  Or a medusa feeder.

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