Filament Spool to Hard to Pull *lightbulb?*

[staticbunny]

I'm having some issues with filament mainly ninjaflex being slowed down because of the force it takes to pull from the spool. If I manually keep the filament slack I have no issues at all and the prints come out great. I've seen only one solution so far where someone on here switched to a nice big bolt for their spool arm. Just not sure if that would work for me. I'm wondering if anyone has any other ideas, even making it motorized. I'm guessing there are the problems that need to be solved:

• 1. extruder speeds vary during print

• 2. Spool radius would cause feed to slow over time

How complicated would it be to splice into the extruder stepper cable and connect that to an arduino to add a calculation on top of that based on the spool status? I'm guessing either an algorithm you tell where the spool position or some real time data input sensing how close the filament is to the center of the spool. So the arduino would get the extruder feedrate PWM then based on a range finder it would know how full the filament would be and adjust the speed to counter the slowing down. As long as you use spools of the same center radius...

[BenTheRighteous]

Wow! If you're that dedicated that you want to build some kind of arduino solution, go for it. On the other hand, I feel like it would be a lot easier to just print a new low-friction spool arm. I'm sure there are designs with bearings available, or you could come up with your own. I think that would be a lot less effort and would probably be just as good of a solution to the problem. You know what they say, KISS and all...

[staticbunny]

Wow! If you're that dedicated that you want to build some kind of arduino solution, go for it. On the other hand, I feel like it would be a lot easier to just print a new low-friction spool arm. I'm sure there are designs with bearings available, or you could come up with your own. I think that would be a lot less effort and would probably be just as good of a solution to the problem. You know what they say, KISS and all...

haha yeah it all sounds awesome till you have to do the math... I have been looking at some of the low friction ones so i might try one out. Think of the glory behind a motorized spool though. I could be the Wade of spools!

[Captain Starfish]

The standard "clunk, clunk, clunk" arm is cheap and easy to cut from the Rostock stock melamine board. But it kinda sucks - it's not smooth, it can take some work to peel it off.

Have a look around on here and you'll find a fair few alternatives. I ended up going for a threaded rod with a hub that fit the spool, but after seeing tinyhead's good work changed to a cone on either side of the spool (to accommodate different sized spools) with a skateboard bearing pressed into it to fit into the rod, and nuts either side to hold it together.

Mine is a vertical orientation and I'd not do that again - full spools have a tendency just to dump coils off the side and down around the spindle base where it tangles up. But horizontally, even off the existing holder frame, the only problem you'll have is that it comes off too easily when you're loading filament into the extruder

This is what I use now: http://forum.seemecnc.com/viewtopic.php?f=35&t=6839
On fresh spools I put the rod into the top of my old spool tower, ignore the hubs in this one, the cones are much more universal: http://forum.seemecnc.com/viewtopic.php?f=35&t=567

[staticbunny]

thanks captain! I'll keep looking to see what is out there. I'm gonna try making one with some ball bearings i've seen or maybe modify some of the rounded replacement arms. I just hope its enough to fix the issue.

[staticbunny]

So i ended up making something by combining two different spool holders.
I took this and made one small modification so the ballbearing sit on an aluminum bar 5mmx5mm http://www.thingiverse.com/thing:408288
Then i copied the half of this http://www.thingiverse.com/thing:617857 that latches onto the top of the printer spool base and added a similiar backing as the other post so i can screw then together. Originally i was just going to add ball bearings to the standard rostock spool holder with extra height but printing it so the ballbearing hole was vertical was a pain. I'll upload some pictures tonight as well as the models i modified.

This didn't actually fix the ninjaflex issue i was having. i did get one successful print of one model but when i tried to do multiple small models the extrusion kept failing. I got my new cobra extruder from micron today so I;m going to try and add it right to my hotend for direct extrusion tonight as well.

[Captain Starfish]

Whoever put that up doesn't understand how ball bearings work - by rolling. In this design they are just sitting there and you're relying on coefficients of friction and a smooth hub inner on the spool.

One thing that might be worth trying is eliminating the spool friction as a source of ninjaflex woes by sitting through a small job and unspooling the filament manually - so there's always a loop hanging free in the air with zero friction. If it still stuffs up then you know the problem is elsewhere.

[staticbunny]

Unspooling it manually did fix the issue, which was why i went down this path in the first place. I did actually get it printing ninjaflex successfully for a few prints after upgrading to direct extruder. http://imgur.com/FQTfNnX
I did create a new spool and it totally does reduce the friction it takes to pull the filament. http://imgur.com/KEyxzT9

Here is what the direct extruder looks like http://imgur.com/9EbkNP1 . At first it was printing ninjaflex like a dream as you see in the first link i posted. Now it's hit or miss because it started getting sucked into the extruder gear sometimes. I think I'm going to talk to Micron 3DP about getting a slight bigger gear since there is to much of a gap between it and the housing. it's a seriously nice piece of hardware though, worth the money if someone is thinking of getting one from them.