1 Topic by jason_

  • jason_
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Topic: Idea for spooling tension system

I've been following ians work on the spooler for a fillastruder, and while it looks like it will work and is quite impressive.  I wonder if we are taking a simple problem and making it harder than it needs to be.

It seems that there are two problems with  spooling the fillament.  You have to keep a constant amount of tension on the filament with an uneven and unpredictable extrusion speed, and you have to spread the filament across the entire spool in a way it can be easily unwound without tangling.

For the first problem I've seen microswitches, or optical switches combined with a microcontroller. 

I may be way off here but would it not be a more simple setup to use a ratcheting drive rotating backwards for the tension?  As the motor spins the spool the tension would be regulated by the ratcheting mechanism

2 Reply by ronsii (edited by ronsii 2013-09-30 00:04:01)

  • ronsii
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Re: Idea for spooling tension system

good idea but I think the ratchet system might not be as even as a sprag clutch and would give similar results without the 'ratcheting' effect on the filament... the trick would be finding one with the right amount of pull/friction which would change as the spool fills up.

3 Reply by elmoret

  • elmoret
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Re: Idea for spooling tension system

Ian has some simplifying modifications in the works, just hang tight!

Filastruder - the robust, inexpensive filament extruder
E3Dv6 All Metal Hotend - the premier 3D printing hotend

4 Reply by IanJohnson

  • IanJohnson
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Re: Idea for spooling tension system

Extrusion speed and filament tension are two separate issues.  Matching winding speed with extrusion speed is covered by the photosensors.  To maintain tension I originally had a motorized puller before the spool, then I replaced the puller with a pinch wheel adapted from a printer extruder.  Then we figured out that all you really need is something for the filament to drag against to make it a little harder for the spool to pull.  There only needs to be enough tension to make each wind slide down next to the last and lay flat against the spool.  Running the filament through a 360 degree loop of PTFE tubing when it gets to the winder creates enough drag.  If you need more tension, you can simply squeeze the loop with something to make a tighter bend.

Since the spool motor is always changing speed to keep the filament in the same position in front of the photo sensors, it will always be pulling just as hard as it needs to counter the amount of drag put on the filament.