26

Re: Filament Extruder - Convert pellets to filament

I agree!  A list of parts with URLS, and any custom parts (to be printed, or software for a controller) would be super!

27

Re: Filament Extruder - Convert pellets to filament

IanJohnson wrote:

How often do you need to show up to reload the hopper?


It depends. You can use a paper cup or round cardboard tube to extend the runtime. Or, I could print a taller hopper. As it sits, it holds about 4 hours of pellets. (Just the green hopper alone)

28 (edited by elmoret 2012-11-29 16:57:58)

Re: Filament Extruder - Convert pellets to filament

XaroRSA wrote:

Good work man, i had a similar idea to mount the motor like that!
Can we expect a buildlog from you perhaps? Really want to make one of these too!

I'll publish details once I'm happy with the design. I'd rather not have mk. 1 2 3 4 5 6 7 designs floating around.

Soon, maybe next week, if SD can send the replacement parts for my printer!

I can say that the total parts cost is about $155. No software needed, and the 3D printed parts total about 100g of plastic. Still no machining needed, just a drill and a dremel. Total assembly time is about 1 hour.

29

Re: Filament Extruder - Convert pellets to filament

If you can figure out how to add colorant, you may be on the way to $45,000-

http://desktopfactory2012.istart.org/

30 (edited by elmoret 2012-11-29 17:45:20)

Re: Filament Extruder - Convert pellets to filament

Yeah, I've read about that. I'm not sure what their deal is - I'd expect that the contest would be over by now. I'm thinking of submitting, once I finalize the design.

31

Re: Filament Extruder - Convert pellets to filament

There are other extruders certainly, but no one seems to have tackled the colorant.  Seems like that is the hard part, but also big part of why I would want one of these rather than getting something shipped in 2 days via Amazon Prime.

32

Re: Filament Extruder - Convert pellets to filament

IanJohnson wrote:

There are other extruders certainly, but no one seems to have tackled the colorant.  Seems like that is the hard part, but also big part of why I would want one of these rather than getting something shipped in 2 days via Amazon Prime.

What needs to be done with the colorant?

33

Re: Filament Extruder - Convert pellets to filament

One of the requirements of the Desktop Factory Challenge is that you need to be able to color the filament, and not just extrude it.  So some point after the pellets are melted you have to be able to mix in pigment or dye and still keep the cost of the machine under $250.

34

Re: Filament Extruder - Convert pellets to filament

IanJohnson wrote:

There are other extruders certainly, but no one seems to have tackled the colorant.  Seems like that is the hard part, but also big part of why I would want one of these rather than getting something shipped in 2 days via Amazon Prime.

I have half an idea of how to add color on the fly to white filament while printing, but I don't have any time to try it out.  I've been very limited in machine time as of late.  If anyone wants to give it some thought and maybe experiment PM me for details if you're interested.  It's just a rough idea at this point but I haven't shot it down in my brain yet.

35

Re: Filament Extruder - Convert pellets to filament

A normal plastic colorant process consists of adding master batch pellets (containing the colorant) plus uncolored pellets, then
"melt, mix, extrude, chop into pellets, repeat" at least 3 or 4 times.
I don't think that will be doable on the desktop without a lot of manual labor.

Liquid colorant might work, if you can get the pellets to melt sufficiently and get adequate mixing (ie: not easy).

For the time being, just having something that will convert pre-colored pellets into filament will be fine.

36

Re: Filament Extruder - Convert pellets to filament

Almost looks like it should be at least a 2 step process to 1. color the melted pellets to create colored pellets and 2. extrude the filament from the newly created colored pellets.  This, however, would be more intensive and definitely over cost for the challenge.

37

Re: Filament Extruder - Convert pellets to filament

this is looking really nice .. silly question, has anyone considered a hopper or feed tube to the extruder and somehow skipping the filament all together and extruding from pellets ? i can foresee many a problem with this of course, complexity makes it overkill.

so failing that .. feeding the machine with filament created as it is required. problem there would be getting consistent diameters as it is extruded at different speeds..

but yeh, i love the look of this one. i even have a couple of PID controllers sitting here doing nothing, the feed screw seems to be the trickiest bit to obtain i imagine. i have a cast iron meat mincer i could lobotomise smile

38

Re: Filament Extruder - Convert pellets to filament

there is a guy who's trying to do this, however on if the things that he found was that for best results pellets really need to be fed one at a time. trying to feed loads either leads to mechanical jams, or impossible retraction.

given the non-uniform size of the pellets feeding them one at a time is no easy feat either sad

39

Re: Filament Extruder - Convert pellets to filament

The guys at Filabot seem to be able to do this, albeit for closer to $700; I doubt that the "one pellet at a time" issue is a show stopper.

40

Re: Filament Extruder - Convert pellets to filament

jon_bondy wrote:

The guys at Filabot seem to be able to do this, albeit for closer to $700; I doubt that the "one pellet at a time" issue is a show stopper.

Filabot also completed their kickstarter 11 months ago, and to my knowledge have not shipped a single unit.

41

Re: Filament Extruder - Convert pellets to filament

elmoret, what did you make of my PM'd idea?  PM me back when you get a chance.

42 (edited by elmoret 2012-11-30 20:24:40)

Re: Filament Extruder - Convert pellets to filament

cmetzel wrote:

elmoret, what did you make of my PM'd idea?  PM me back when you get a chance.


Done! Sorry!

EDIT: Sometimes things don't go according to plan. I didn't screw down the filament guide, as I was adjusting its positioning, and I came back to find this:

https://dl.dropbox.com/u/1786359/Photo%20Nov%2030%2C%203%2007%2001%20PM.jpg

The diameter of that particular piece did not fit the +/-0.05mm goal.

43

Re: Filament Extruder - Convert pellets to filament

Well, I found this weakest link. Here's a clue:

https://dl.dropbox.com/u/1786359/IMG_3820.JPG

Let's take a look at that thrust bearing:

https://dl.dropbox.com/u/1786359/IMG_3821.JPG

Welp.

That bearing is rated at 33lbs dynamic. I have no way of calculating what the thrust force is besides an order of magnitude ballpark. I could install strain gauges on the threaded rods, but that seems silly. I was running the bearing as it came, without lubrication, and under a variety of loads (torque/extrusion temp). I've lubricated and installed a new 33lb bearing, now that I have the torque/extrusion temps dialed in. We'll see how long it lasts.

Anyway, I found a thrust bearing more suited to this, rated at 585 lbs dynamic, for just $3 more. I'll order some and test them out.

Exciting times!

44

Re: Filament Extruder - Convert pellets to filament

The simple way i can see you printing "directly" from pellets with both good retraction and hopper style feed would be to have the filament extruder and the printer talk to each other and just run the output of the filament extruder directly into a bowden system. give it an open loop area so the filament extruder isnt being pulled on directly.
Never told me your feed screw design... Is it just basic V-groove threaded rod?

45

Re: Filament Extruder - Convert pellets to filament

I do not know anything from personal experience, but their web site says "By the end of this year, we are optimistic about having all of our 67 kickstarter systems completed and on their way. Once we are done with our kickstarter backers, we will then proceed with launching to the public."

elmoret wrote:
jon_bondy wrote:

The guys at Filabot seem to be able to do this, albeit for closer to $700; I doubt that the "one pellet at a time" issue is a show stopper.

Filabot also completed their kickstarter 11 months ago, and to my knowledge have not shipped a single unit.

46

Re: Filament Extruder - Convert pellets to filament

Cwalster wrote:

The simple way i can see you printing "directly" from pellets with both good retraction and hopper style feed would be to have the filament extruder and the printer talk to each other and just run the output of the filament extruder directly into a bowden system. give it an open loop area so the filament extruder isnt being pulled on directly.
Never told me your feed screw design... Is it just basic V-groove threaded rod?

The trouble is, to control extrusion rate, you have to modify either the temperature or the auger speed. Both result in a change in filament diameter.

I'll release the details of the build once I am comfortable with the design as a whole.

47 (edited by elmoret 2013-02-17 18:14:25)

Re: Filament Extruder - Convert pellets to filament

Ready for Beta Testers!

https://dl.dropbox.com/u/1786359/Extruder.png

I've worked out most of the bugs I think, and am ready for beta testers. Here's where things are at:

Specifications:

  • Extrusion Rate: 6-18 inches/minute (2-5 lbs/day)

  • Extrusion Temperature: tested with 170-210°C (others may be possible)

  • Size: 24”x6”x6”

  • Noise: 58dBA @ 3ft

  • Power: 110VAC, 175 watts peak, 50 watts average


Revision notes:

  • Upgraded thrust bearing from 33lb max load to 555lb max load. New version is sealed.

  • Deleted thermal insulator. Hopper area is not getting too hot without it - roughly 35C above ambient. Thermal insulator was adding calcium silicate dust to the plastic, causing a clog in my Solidoodle, eventually.

  • Redesigned hopper. First hopper revision split open. Second hopper revision split open. Third hopper revision did not feed consistently. On the fourth revision now, which seems good.

  • Filament diameter seems to be quite consistent. I have not seen extrusions with greater than +/-0.06mm variation, as long as hopper feed was consistent

  • Entire assembly is grounded for safety, and main power connection is fused.

I would like to offer a limited beta at this time. When I set out designing this, I realized that there was some decent savings to be had by purchasing in bulk, so I bought 5 of everything. That leaves me with enough parts for 4 more extruders. I have these parts already, so kits will be ready to go out this week.

I plan on offering one option for now:

Barebones Kit - $150 + shipping

Requires:
•    Drill (#1 bit, 1/8” bit, 5/16” bit, 5/8” bit)
•    Dremel with cutoff wheel
•    3D Printer
•    SAE allen wrench set
•    7/16” wrench (dbl chk this)
•    Pliers
•    Wire cutters/strippers
•    Phillips screwdriver

The reason I am only offering a barebones kit is that I would prefer that the beta testers have the above tools on hand to make tweaks/modifications. In the future, I may offer kits that require fewer tools.

Here's what comes in the kit:

•    Pipe Coupling
•    Shaft Collar
•    24 Hex Nuts
•    24 washers
•    3 inch pipe nipple
•    4 inch pipe nipple
•    Brass plug/nozzle
•    5 amp fuse
•    Fuse block
•    6 female spade terminals
•    M5-.80x40 motor mount bolts
•    PID controller
•    Thermocouple
•    Auger
•    9mm hex socket
•    40mm fan, 12v
•    12v gearmotor
•    2 switches
•    Heater
•    4 flanges
•    1/2"x1/4" bushing
•    4 threaded rods
•    Shaft coupling
•    555lb thrust bearing
•    Power Cord
•    12v power supply
•    3 wood supports
•    Filament guide parts
•    Header Wrap
•    3 SS zip ties
•    8 wood screws
•    1/2lb of ABS pellets to get you started!


I've written up and am finalizing assembly instructions.

If you are interested, please contact me at [email protected]. Thanks!

48

Re: Filament Extruder - Convert pellets to filament

RSandven wrote:

What a great project!
What about air bubbles, is this then consistent?

I've extruded 2kg, and only saw one air bubble. it happened when powering up the extruder from cold - I hadn't even turned the auger motor on.

49

Re: Filament Extruder - Convert pellets to filament

Excellent news! I've already sent you an email.

50

Re: Filament Extruder - Convert pellets to filament

I've got a few questions:

How far does your auger bit extend into the heated tube? is it all the way or are you pushing against  a molten "block" of filament with pellets, (in the same way that the printers extruder just squishes cold filament against the hot blob to squeeze out plastic.)

out of interest, what's the motor that you're using


I'm just starting out building a similar design, (but a bit different as I want to crack the colourant addition) and am wondering if there are any gotchas I should be particularly looking out for?