Concept Plastruder

[Rick]

This is a concept extruder/plastruder that I recently started working
on for use with small diameter nozzles. I really did not intend for
this to look like something out of Robots or Wall-E. Form followed
function. Pretty cute though!! Have a suggestion for a name???
Stroodle? Iris? ????

Front View - http://www.flickr.com/photos/makergear/4093842147/
Side View - http://www.flickr.com/photos/makergear/4094605056/

As many of you know by now I've been experimenting with nozzles of
various diameters. I've had success with the 0.4mm and 0.35mm nozzles.
Limited success with a 0.30mm nozzle. And, nothing to report (other
than a lot of stripped filament) with the 0.25 nozzle. I think that
0.35mm is the limit for the standard, nearly-off-the-shelf MakerBot
plastruder (great job MakerBot dudes!!)

The objective with this extruder is to make something straight-forward
that does not require expensive or custom parts (beyond a standard
MakerBot style plastruder) – machining parts like nozzles and such is
time consuming enough. I've tested it using at 0.30mm nozzle and it
works but I won't be able to report any significant results until I
get a variable speed motor – it is just too painfully slow using the
standard 2RPM Kysan. Any recommendations for something that costs
about the same as the Kysan but that can vary between 6RPM and 20 RPM
and work with the existing extruder controller board? The operational
speed will likely be 6RPM with the other speeds acting as fast-forward
and reverse. (0.6mm per rotation is so painfully slow at 2RPM.)

Here is the general idea...

M6 brass threaded rod – hollowed and partly threaded to M3/0.6mm – is
rotated using two inexpensive nylon bevel gears. Filament passes
between two bearings to prevent/limit rotation and feeds into the
hollowed M6 rod. The threading in the M6 rod moves the filament along.
[There is a constant battle between advancing the filament and the
tendency for it to rotate. But since process results in threaded
filament, if the filament were pre-threaded the rotational issues
would go down considerably.] The heater is pretty standard but I used
this as an excuse to experiment with PEEK (so far so good). The upper
PEEK is threaded, the M6 rod screws in and the full length of PEEK
rotates with the upper M6 rod. The lower portion of PEEK is not
threaded (just drilled) and this allows the PEEK to rotate freely
around the M6 rod of the lower heater assembly. The upper and lower
portion are held together by the two washers/long screws. Skate
bearings are used to hold the bevel gears and M6 rod in place in the
laser cut 3/16” acrylic. It is currently a little too long to fit on
the Z platform.

I'm also following Zaggo's work with the NopHead machined brass pulley
as another possible solution. Have not looked at the MB MK5 yet. Also
interested to hear how well the needle approach works for Peter.
Anything else on the smaller nozzle radar?

Rick

[rbisping]

that is a interesting concept. one improvement i can conceive of would
be a second rotation section in the oposite direction to remove the
rotational moment.
same gear placed above the current one with the threads cut left
handed so it still pushes down.

On Nov 10, 8:39 pm, Rick <rick.poll...@gmail.com> wrote:
> This is a concept extruder/plastruder that I recently started working
> on for use with small diameter nozzles. I really did not intend for
> this to look like something out of Robots or Wall-E. Form followed
> function. Pretty cute though!! Have a suggestion for a name???
> Stroodle? Iris? ????
>
> Front View -http://www.flickr.com/photos/makergear/4093842147/

> Side View -http://www.flickr.com/photos/makergear/4094605056/

[Eberhard Rensch]

Looks very interesting. What I don't understand is, how the bearings
help to avoid rotation of the filament. Don't they only guide the
filament vertically?

After the last tests with a threaded pulley (http://pleasantsoftware.com/developer/3d/2009/11/11/maintenance/
), I'm pretty sure that feeding filament to a .3mm or even .25mm
nozzle should be no problem. I have most problems with the guidance of
the filament *after* the feeding mechanism...

Anyway, it's probably a good idea to do research on this with
different approaches. What's Peter's "needle approach", you referring
to? Do you have a link to any documentation on this?

Cheers,
Eberhard (MakerBot #127)
Blog: http://pleasantsoftware.com/developer/3d/

[Zach 'Hoeken' Smith]

It appears that they can be tightened to pinch and flatten the filament which would prevent it from rotating.

very cool design!

[Rick Pollack]

@rbisping - great idea but there is a catch. Once the filament passes through the threads it is threaded. So, if it passes through the left-hand threads and then enters the right-hand threads the friction against the right-hand threads will be significantly less. Regardless, I am trying to find a 3mm/0.6 pitch left-hand threaded tap...thanks for the feedback!!

@Zaggo - Zach is correct on the bearings being tightened to manage the rotation. Even with enough tension to prevent rotation the filament moves reasonably easily through the bearings. I can rotate the assembly by hand...

I have no doubt that that the threaded brass pulley will produce enough push to get the plastic through the smaller nozzles. What I am wondering is if the design can move slowly enough to coordinate the flowrate with the feedrate.

Here are some quick flow rate calculations:

0.5mm nozzle area: 0.25 * 0.25 * 3.14 = 0.19625 mm^2

filament diameter: 2.88 mm
filament area: 1.44mm * 1.44mm * 3.14 = 6.51 mm^2

pinch wheel pulley diameter: 10.30 mm
pinch wheel pulley circumference: 2 * 3.14 * 5.15 = 32.342 mm (per rotation)

32.342 / 30 = 1.08mm/s (mm per rotation / seconds = rate/sec)
6.515mm^2 * 32.342 mm * 2 RPM = 421.1 mm^3/min (filament area * flowrate * RPM = plastic flow per minute)
421mm^3 / 60sec = 7mm^3/s (plastic volume / second)

Extruded filament from 0.5mm nozzle has a 0.6mm diameter
area = 0.3 * 0.3 * 3.14 = 0.2826 mm^2
7mm^3/s / 0.2826mm^2 = 24.77mm/s (plastic volume through nozzle / nozzle area = throughput in mm/s). My actual measurement of the output was closer to 22mm/s at 215C.

Assuming the above calculations are done correctly, I'm estimating that a 0.6mm thread pitch will move 8.3 mm/s through a 0.25mm nozzle. Hence my thinking that 6RPMs should work.

@Zach - Thanks!!

[Peter Charles]

Eberhard-

I am experimenting with using 316 Stainless Spinal needles for nozzles (mine are from BD, but any supplier should work).  They have Luer locks on the ends, so I can interchange extrusion sizes. Have not actually done a run with them yet- still figuring out how to machine the end of the extruder barrel to accept them.

peter

On Wed, Nov 11, 2009 at 6:49 AM, Eberhard Rensch <ma...@pleasantsoftware.com> wrote:

[Rick Pollack]

Peter -

What are the diameters and needle lengths that you are going to test initially? Is the needle 100% metal (any plastic or other materials)? There is going to be a lot of pressure involved and I'm wondering how you are going to get the plastic through anything small than 0.3mm.

Rick

[Peter Charles]

Rick-

100% 316 medical Stainless.  Luer Locks are pretty sturdy- I have never had one come off unintentionally.  Granted, most of my experience with them is in the medical setting! For sizes, see: http://en.wikipedia.org/wiki/Needle_gauge_comparison_chart.  I am going to test 20-28 ga (0.603- 0.184 mm ID).

peter

[Rick Pollack]

Thanks! Maybe you could cut the end off a syringe and mount that rather than fabricate the end. Also, typically how long are the needles?  Or what length of needle do you intend to use?

[Peter Charles]

I use the shortest needle I can get- 0.25".  May need to cut them. have looked far and wide for a barrel, or male Luer fitting I could re-purpose.

peter

[Andrew Plumb]

If they can handle the pressures involved, don't cut them! That's 10mm
of narrow-diameter towering room.

You could do some really smooth, steep-ramped/contoured surfaces using
one of those.

Andrew.

On 11-Nov-09, at 12:31 PM, Peter Charles wrote:

> I use the shortest needle I can get- 0.25". May need to cut them.
> have looked far and wide for a barrel, or male Luer fitting I could
> re-purpose.
>
> peter
>
> On Wed, Nov 11, 2009 at 12:20 PM, Rick Pollack
> <rick.p...@gmail.com> wrote:
> Thanks! Maybe you could cut the end off a syringe and mount that
> rather than fabricate the end. Also, typically how long are the
> needles? Or what length of needle do you intend to use?
>
> On Wed, Nov 11, 2009 at 12:10 PM, Peter Charles <peterc...@gmail.com
> > wrote:
> Rick-
>
> 100% 316 medical Stainless. Luer Locks are pretty sturdy- I have
> never had one come off unintentionally. Granted, most of my
> experience with them is in the medical setting! For sizes, see: http://en.wikipedia.org/wiki/Needle_gauge_comparison_chart

> . I am going to test 20-28 ga (0.603- 0.184 mm ID).

--

"The future is already here. It's just not very evenly distributed"
-- William Gibson

[Zach 'Hoeken' Smith]

here's a spreadsheet i use for calculating extruder stuff: http://spreadsheets.google.com/ccc?key=0Ar78SYuXDzRMcG1FTXhZUmNRenpCMjFtZEs4R3ZvR3c&hl=en

[Rick Pollack]

Excellent! Thanks!

[Peter Charles]

Some of the needles I am using for ultra-fine printing, and the partially assembled extruder:

http://twitpic.com/qvloq

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--
Best regards,

peter

Peter C. Charles, PhD
Director,
Research and Technology Division
CyberBiota, Inc.
4022 Stirrup Creek Rd.
Suite #315-11
Durham, NC 27703

Professor of Anatomy and Physiology
College of Arts and Sciences
Durham Technical Community College
Rm. 821 Collins Building
1637 Lawson Avenue
Durham, NC 27703

Web: http://cyberbiota.com
Email: pcha...@cyberbiota.com
Office: 001.919.308.3839

[Andrew Plumb]

Sweet! (...and yeah, 0.25" = 6.35mm).

So you got those from McMaster? What were the part numbers?

Andrew.

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[Peter Charles]

McM parts:

1	6710A11	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 5 GAUGE, .189" ID, .219" OD, 2" LONG	2 EA	2	0	4.58 EA	9.16
2	6710A63	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 14 GAUGE, .063" ID, .083" OD, 1/4" LONG	2 EA	2	0	3.21 EA	6.42
3	6710A65	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 16 GAUGE, .047" ID, .065" OD, 1/4" LONG	2 EA	2	0	2.67 EA	5.34
4	6710A67	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 18 GAUGE, .033" ID, .050" OD, 1/4" LONG	2 EA	2	0	2.67 EA	5.34
5	6710A69	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 20 GAUGE, .0235" ID, .0355" OD, 1/4" LONG	2 EA	2	0	2.67 EA	5.34
6	6710A72	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 22 GAUGE, .016" ID, .028" OD, 1/4" LONG	2 EA	2	0	2.49 EA	4.98
7	6710A74	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 24 GAUGE, .012" ID, .022" OD, 1/4" LONG	2 EA	2	0	2.49 EA	4.98
8	6710A76	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 26 GAUGE, .010" ID, .018" OD, 1/4" LONG	2 EA	2	0	2.49 EA	4.98
9	6710A38	REUSABLE TYPE 304 SS DISPENSING NEEDLE, 30 GAUGE, .006" ID, .012" OD, 2" LONG	2 EA	2	0	4.33 EA	8.66
10	51465K151	NICKEL-PLATED BRASS QUICK-TURN TUBE COUPLING, MALE, 10-32 MALE UNF THREAD SIZE	2 EA	2	0	5.72 EA	11.44
11	7590A41	REUSABLE SS NEEDLE W/PIPE THREAD MOUNTS, 10 GAUGE, .106" ID, .134" OD, 1/8" NPT THRD, 2" LG	1 EA	1	0	7.21 EA	7.21
12	7590A45	REUSABLE SS NEEDLE W/PIPE THREAD MOUNTS, 22 GAUGE, .016" ID, .028" OD, 1/8" NPT THRD, 2" LG	1 EA	1	0	6.62 EA	6.62

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