[ Closed ] Filament Extruder - Convert pellets to filament (Page 31 of 58)

Yeah, Taulman's stuff is neat, but Nylon carries some challenges. Primarily HCN. I don't have a HCN detector, so I prefer not to use it.

Nylon 6/6 releases ~250% more HCN than ABS does, so I think I'll pass. I trust published studies over Taulman's own potentially biased testing.

From published sources: "At 350C, HCN was detected"

Taulman's stuff might be "safe enough"... but published data shows ABS is potentially 2.5x safer, so I prefer it. Taulman's testing doesn't really represent a runaway hotend or extruder. 20w hotends can get >350C, and 40w hotends can get >550C. The latter is definite HCN territory on Nylon.

Sources:

http://nparc.cisti-icist.nrc-cnrc.gc.ca … amp;fd=pdf

http://www.osha.gov/SLTC/healthguidelin … ition.html

http://fire.nist.gov/bfrlpubs/fire86/PDF/f86013.pdf

Crap I forgot about the HCN when I ordered mine.  Can't do it with infants in the house.  Look for a fire sale if they won't take it back.

haha

This what I'm working on right now- Plug drilled and tapped to 6mm.  A Brass 6mm bolt drilled at 1.54mm with the head cut off, screwed into the plug.  A 7/16 PTFE rod drilled and tapped to 6mm a few mm deep to screw onto the bolt which is protruding from the plug.  After the threaded section, the rod is drilled the rest of the way through at 1.70 or 1.75.  I also increased the threaded rods to 18" so they reach past the end of the nozzle, and support a plate that keeps the PTFE rod pressed against the nozzle.  The threads by themselves aren't enough to keep the extruded plastic from pushing the rod off.

I realized that the brass barrel for the Solidoodle extruder is 6mm, and I had an extra hot end left over from my upgrade to the J-Head.  I screwed it in so that the plastic extruded through the barrel and out the top of the PEEK to see what would happen.  The filament was a little bigger than 2mm of course, and it was smooth and glossy from being pushed through the PTFE while soft.  Also it seem less prone to kinking.

My thought is that the plastic will swell coming out of the 1.54 opening in the bolt as usual, but be constrained by the 1.75mm ID of the PTFE.  The PTFE should be slippery enough that pressure against the walls should translate into forward motion of the plastic without creating too much backpressure in the extruder.  The PTFE would basically mold the plastic to its final dimension, and ideally be long enough that the filament would be too cool to swell any more coming out the end.

It could be guided by a PTFE tube mounted in the other end of the rod, in a roundabout way to the spooler which would keep any slight variation in pull from getting transmitted directly to the nozzle.

If you have any concerns over Taulmans 618 Nylon, please send him an email.  He is usually very happy to share all the testing results.

pen conversation going on here:
http://www.soliforum.com/topic/1384/3d-printing-pen/

Well, that was quite some read. Since I have just found this thread I feel I've been missing out.
Congrats to elmoret and the rest of you testers for getting so far so quickly.

Like most I have been thinking about creating some sort of extruder but so far just haven't had the time.

During the read I kept thinking why haven't they tried this or that only to find on the next page that you have. I did love the spool of "clear" though :-)

Probably too late top mention now but with the circuit you are working on I assume is a controller for the heater and auger driver? Did you think about adding a cold junction thermocouple IC to it so the mega could do you PID control to be able to make it a single board? I was thinking of an AD595 which I have used in the past for work which seem to be pretty good.

Ian, Have you made any progress with the laser/ccd width detector? I think that and the pull speed is going to be the way to go for reliable width.  There must be a simple and cheap way to detect the width but I haven't come across one yet. The smallest photocells I have used were still a few millimeters across which doesn't lend itself to accuracy.

I have a couple of sensors, but I haven't tried to set it up yet.  It is a strip of 128 photocells in 40mm.  You send a pulse to the sensor and it sends back a reading for the next pixel in line.  The idea is shine the line laser on it, and start checking pixels.  When one shows up that isn't full brightness, start counting, and then when another full bright pixel shows up stop counting.   You would need to start with something that has a known diameter to get a conversion from pixels to distance.

If the distances between the laser, filament and sensor are such that the shadow is almost as wide as the sensor, I get get .01-.02mm per pixel.

My hobbed bolt finally came in today, so I can test that tonight for consistency in feed rate.  I'm also trying to decide if it is easier to learn enough Processing to make an app that will show Speed, Filament count and graph the diameter, while letting you type in a feed rate?  Or would it be easier to wire up an LCD with the encoder and learn how to make an interface to do those things. 

So far for the spooler it is something like-

$17      Stepper
$25      Arduino Uno
$9        Hobbed Bolt (if it is acceptable)
$12      DC Motor for the spool (maybe driven by the Uno)
$15-20 LCD, depending on # of lines
$16      Linear CCD sensor
$10      Bag of bearings
$6        Laser

That's already about $100 for the spooler.  The electronics could maybe also drive extruder controls.  The extruder works fine by itself.  The spooler is a bonus, but it's more convenient, and it would be nice to have a feed counter.  Pulling from a larger die lets you boost the feed rate which is also a bonus.  The laser size sensor is added geekery, something to do just because you can.  Something like using an optical mouse to measure the rate of extrusion at the nozzle so the puller can sync up with the extruder would be additional geekery.   

It would be cool if those features could be added without bumping the cost too much.  $250 is a good upper limit but it would be tough to do the whole package for that price.   It's easier to swallow if the spooler is an add on.

Which linear CCD did you settle on?

PEEK/PTFE:

McMaster Number: 1595A13

Ian: I'm surprised that the PTFE doesn't deform enough to fill the angled hole the 6mm bit leaves.

Wow... that's really cool. I take it you had the camera on some sort of dolly? Looks like about 100x timelapse.

I purposely left the end of the barrel unconstrained so that it could move, just like is shown in the video. I figured there was no way to get everything aligned perfectly. If I constrained the end, then the auger-pipe forces would be much higher, as the misalignment caused rubbing. Leaving it unconstrained limits those forces. It's kinda like the z-axis on repraps, and how Nophead found constraining the top makes it worse.

Edit: It looks like you've got some oscillatory behavior on the temperature control. Autotuning your PID should help with that. Unfortunately it isn't a one size fits all sort of thing, as the heater wrap placement, heater band placement, ambient temps, fan placement, etc all change the system dynamics.

Dolly with a GoPro. 1 frame every 2 seconds.  If you look closely, I switch from clear to green mid extrusion (color looks terrible on the GoPro inside so its hard to tell).

The video definitely makes this more noticeable. Is there a procedure for auto-tuning the PID?