[ Closed ] Filament Extruder - Convert pellets to filament (Page 53 of 58)

I thought we already came up with an easy solution for this.  One motor to drive the take up reel.  The filament passes through a constant tension device (clothes pin with felt jaws?), on its way into the reel.  The photo cells turn the motor on and off to keep the loop in about the same place.  I don't think it can get much simpler than that.  If you want to measure the diameter also, then that is an add on, possibly combined with the constant tension device.  Since filament is supplied by the Kg, the scale idea is an interesting one.  It does not have to be an electronic scale.  That can be a teeter toter scale that trips when the weight hits a certain increase.  What am I missing?

Ian - have you thought about the whole spooler process.  Using the light senser is just right with only speed variation not stop and start operation.  Also how are you going to get a smooth layer of filament layed out on the spool.  What I was thinking about is a filament steering mechanism that uses a stepper motor to move the filament back and forth across the spool using a shuttle with hoops like a fishing pole.  And use a string with a slip tension band from the spool to the tension motor.   Like a string wrapped around the motor that drives the spool and then around a grooved pulley attached to the spool.  the attachment to the pulley is a slip fit in that the string will slip on it when a certain level of tension is present.

Bob Teeter

I've used it almost exclusively (the natural). I dunno what resin the white is, haven't used it at all.

I tried the winder using the spool motor only.  I ran the filament through the puller with the motor taken off.  Originally I had the idler bearing clamped down, but eventually took it off.  There was enough tension to the spool just letting the filament run over the bolt.  I think running the filament around a couple of guide rollers between the loop and the spool would create enough tension.

When you pull filament around a roller it acts more like a lever than a string.  It will use the roller as a pivot so if you pull the output to the left the input will try to move right.  The lower roller stops that movement to the right, so it will pull the loop up instead.  The tension of the filament against the guide rollers gives the spool some force to pull against.  In tonight's experiment, the channel in the bottom of the puller that leads up to the hobbed bolt played the role of bottom guide roller. 

The filament piled up in the middle of the spool, so some kind of guide could help, but I don't know how to configure one to move the right amount back and forth depending on how full the spool is.  I haven't had that much trouble in the past, and I think there was too much tension on the spool for the coils to be allowed to slide past each other and spread out across the spool.

The filament is getting a twist as it extrudes which is annoying.  I have it running between guide posts made from wire inside PTFE tubing.  Without them the loop would run almost sideways, maybe 45 degrees from vertical.  I put a couple of whisker guide wires sticking out from the base under the nozzle, but the filament drops between them without touching, then bends to the right.  Rather than moving smoothly against the guide posts by the laser, sometimes the filament snags, then pops further up or down.  If it moves past a sensor when it jerks like that, it is likely the shadow will not register.  Keeping the loop close to the laser makes the shadow larger, and the filament doesn't move as much up and down to shade the sensors.  That helps to keep the jerking to a minimum.

Since the sensors can fail to register if the shadow moves to fast, I definitely want to regulate the speed of the spool as it gets fuller.

If you move the winder further from the tensioner, it will more evenly distribute on the spool.

Side note - picked up a SD3 today, to accompany my SD2. They really haven't made any changes to the design in 8 months! Quite surprised.

It occurred to me that my garden hose reel has a guide that moves back and forth as you crank it.  It has some kind of 2-way worm gear-

That might be complicated to tackle, but could be cool

Ian - You are my hero! higher tension to straighten out the filament. And try increasing distance between spool and tensioner like Tim said.

I very much like the verticle drop out of the nozzle, but I got really straight OSP filament with horizontal nozzle 40" span and 12" of drop, S/D = 3.3;  Lateral movement at bottom of loop without guides was less than 1/2".  S/D=2.96 gives minimum variation of filament force at extruder as a function of loop lenth variation, (but you are regulating the loop lenght so tightly this shouldn't be much of a factor).

Don't know if this is relevant (and it probably is)...

mmorning,
You're missing the grooves in the interstices that probably allow the crank to run over and back the gear.  Not a hard addition, but may be crucial to getting this thing to work.

Is this extruding out or down?

If you want the extruder to point down, why not just tilt the whole thing up 90 degrees?  The only thing that would have to change is the input hopper.  I am sure someone could design one that worked coming out and up -- perhaps at a 45 or 60 degree angle?

That would mean you no longer have gravity helping you feed the pellets.

ian, I think I see what you mean.. but not sure if its necessary, it could be but not really sure. The groove reverses directions at each end. so if you follow it it will be and endless loop. When it gets to one end the guide should reverse directions. I am more concerned with how it will not skip into the grooves where they cross and reverse direction before it gets to the end of the shaft. That is what I am hoping to run some tests on. To see if a guide will follow it all the way down on both directions.