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Crazy Extruder Nozzle Idea

Posted by jupdyke 
Crazy Extruder Nozzle Idea
March 18, 2010 01:57AM
I just be crazy, but who knows. I was talking with a friend about the nozzle for the extruder and he was having trouble imagining how big 0.5mm was. He finally looked at me and said something along the lines of "oh like the 0.5mm lead pencils." Then he looked at me and asked why I couldn't just use the tip of a mechanical pencil, the kind that have the metal cone...

to which I said, I don't know. Why can't we. Those things are metal, and un-screw from the pencil. If the threading inside is a standard thread it might just be perfect.

I am planning on testing it out, just for fun. I will document it and post some pictures. But in the mean time, has anyone thought of this? How about tried it? Can anyone see some problems which I might be missing? I am still new to the extruding plastic game.

Josh
Re: Crazy Extruder Nozzle Idea
March 18, 2010 02:08AM
smiling bouncing smiley Cool idea - definitely worth a look see...


Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
VDX
Re: Crazy Extruder Nozzle Idea
March 18, 2010 02:41AM
... you can find similar nozzles for applying "Window Colors" - i bought a bottle of black "contour-colour" and a metallic nozzle-set with: - a threaded tube for applying to the bottle-tip, a nozzle (similar to the pencil-tips) and a steelwire for cleaning the bore ...

The problem for FDM will be the heating - the long tip is hard to heat proper ...

For testing with paste-deispensing at room-temp ist's perfect grinning smiley


Viktor
Re: Crazy Extruder Nozzle Idea
March 18, 2010 09:03AM
Cool! Another alternative use for mechanical pencils.

What's a common model with a removable, all-metal tip? A lot of the pencils you can find are just plastic.
Re: Crazy Extruder Nozzle Idea
March 18, 2010 09:35AM
The tip of a mechanical pencil might be so long that the extruder would have trouble creating enough pressure to pump the desired rate of plastic through it. But that's just a guess. In most of the nozzles people have made, they've gone to some trouble to make the final, small bore section be a short as possible.

If you try it and it works, we can put this guess into the trash.
(Figuring out fluid flow of melted plastic seems daunting from an analyitical perspective -- highly non-newtonian fluid, due to the long lengths of the polymer molecules, to say nothing for side branching.)
Re: Crazy Extruder Nozzle Idea
March 18, 2010 05:30PM
it is very fun about the result that the pencil have a mechanical cone
Re: Crazy Extruder Nozzle Idea
March 19, 2010 04:34PM
My own crazy nozzle idea came to me after browsing the McMaster-Carr catalog. They have stainless tubing in some very small ID sizes and 1/16" OD (bottom of page): http://www.mcmaster.com/#catalog/116/128

I thought of using a very short (3/8") piece of tubing, held in a suitable compression fitting as a 'chuck':



This would also make experimenting with different orifice (tubing ID) sizes very easy.

Of course, you'd probably want to chamfer the NPT end of the fitting into a nice entry cone, but that's probably a much easier task than drilling teeny-tiny 0.5mm (or smaller) orifices on truly scratchbuilt nozzles. Even so, the total length may be too much to allow reasonable performance without requiring obscene pressures.
TC
Re: Crazy Extruder Nozzle Idea
March 25, 2010 09:58PM
Here's another one...

Try searching for "graphite ferrule 0.5 mm id", or whatever diameter you want. Here's one example (look at the image)...

[las.perkinelmer.com]

[las.perkinelmer.com]

Good for up to 450 degrees C.

Apparently, these "ferrules" are used in Gas Chromatography equipment. They seem to come in multipacks, there are multiple vendors, and they appear to be relatively inexpensive.

I wonder if these could be used in the extruder tip.

TC
Re: Crazy Extruder Nozzle Idea
March 25, 2010 11:57PM
I didn't see a price listed on the website. How much do you think one of those costs?
TC
Re: Crazy Extruder Nozzle Idea
March 26, 2010 10:51AM
I didn't keep track of the various web sites I visited, or the prices I saw. But here is one...

[www.chromres.com]

$28.31 qty. 10

I'm pretty sure that I saw a site with a package of 2 for under $10.

If these would work and a simple way for mounting them could be found then it could simplify construction of the extruder. There seem to be some standard mechanical components for these (nuts, etc.) but I didn't have time to investigate.

TC
TC
Re: Crazy Extruder Nozzle Idea
March 27, 2010 01:19PM
Here is some application info re: graphite ferrules that shows some of the common mechanical parts associate with their use (nuts, etc.):

[www.sigmaaldrich.com]

[www.sigmaaldrich.com]

[www.swagelok.com]

These items were pretty randomly chosen by me. There could be more relevant documents available. There seem to be many vendors. I haven't had a chance to read any of this yet, and I don't really know if this graphite ferrule stuff is of any use, or not.

TC
TC
Re: Crazy Extruder Nozzle Idea
March 27, 2010 01:33PM
This stuff also looks interesting...

[www.sge.com]
[www.sge.com]

TC
TC
Re: Crazy Extruder Nozzle Idea
March 29, 2010 06:21PM
This will probably be the end of my posts to this topic (crazy nozzle ideas).

I was trying to find existing materials that were tubes with inside diameters of 0.5 mm (or less). There appear to be a large number of extruded ceramic tubes that meet that description. There are several different ceramic materials that I saw in my searches with different properties for thermal conductivity (high to low), thermal coefficient of expansion (from low to near zero), hardness (from easy to machine to very hard), etc.

Here are a couple of examples...
[www.ortechceramics.com]
[www.accuratus.com]

Once again, I didn't keep track of the various links. However, this seems to be a pretty common material. These tubes may be interesting when combined with the graphite nozzles I previously posted.

Note that you can also purchase machinable rods of alumina ceramic which may be an interesting material to fabricate an extruder nozzle out of.

TC
TC
Re: Crazy Extruder Nozzle Idea
April 02, 2010 09:44PM
Found another interesting item for a nozzle. Do a search for:

Grex Tritium Nozzle 0.5mm

[www.grexusa.com]

Made for airbrushes, easily obtained on Amazon and other on-line retailers. Available in other sizes.

TC
Re: Crazy Extruder Nozzle Idea
April 06, 2010 04:29PM
Casting my mind back a little ways to the earlier discusions on nozel design. I think Nophead, Vik, Forest and Adrian did a bunch on this as well as measurements fo some kind.

The basics of this seemed to be that the length of the narrow part of the nozzle was critical to the amount of force required to extrude.

Basicaly the longer the exit orifice tube the greater was the force needed to extrude.

Where more extrusion force is required, you run a much higher risk of loosing grip/drive of the filament. As well as striping drive gears etc.


Necessity hopefully becomes the absentee parent of successfully invented children.
Re: Crazy Extruder Nozzle Idea
April 14, 2010 07:41AM
Another nozzle idea is usual ball-pen tip.
Ball can be easily removed with niddle from inner side. For termoisolation, we can use the concrete.

This nozzle is very fine (thin). For fine quality printing.

Probably we would use TWO nozzles in one extruder - one for massive feeling, another for fine outer surface. But this design requires the valve.

May be two extruders - thin and thick - would be better. I see software supports several extruders already.
TC
Re: Crazy Extruder Nozzle Idea
April 14, 2010 03:45PM
FYI - I got one of these today...

Grex Tritium Nozzle 0.5mm

[www.grexusa.com]


- Overall length from nozzle tip to the other end is about 9 mm.

- Inside diameter on the threaded end is about 7.5mm.

- The 0.5 diameter hole in the tip is about 2 mm in length.

- Above the tip the inside diameter slopes outward to about a 3.5 mm width within about 2 to 3 mm.

I'll have to see if I can figure out what the specifics are on the thread.

TC
Tim
Re: Crazy Extruder Nozzle Idea
May 06, 2010 12:49AM
Here is another potential extruder option I came across: stainless steel luer lock needles (example at [www.victor-g.com]). These can be had very inexpensively from farm/veterinary supply vendors (or much more expensively from the science/industrial sector), and feature various gauges of needle on the end of a standardized twist-locking hub, typically aluminum or stainless. I'm new to this and haven't really found a good document on how extrusion is meant to work at the physical level or what makes a "good" extruder (ideal taper, transition region/length, transition point relative to the nozzle, etc.), but the inside is generally tapered nicely, and the hub ID just a bit wider than a piece of 3mm filament. My quick test of one (needle cut off at the hub to minimize back pressure; hot soldering iron tip laid against it) seemed to work all right, although I don't really know what constitues "all right".
Re: Crazy Extruder Nozzle Idea
July 01, 2010 06:46PM
I'll toss out one more nozzle idea that I've had - trying to drill such tiny nozzle holes isn't easy, especially for those wishing to experiment with orifice diameters smaller than 0.5mm. What if the standard brass nozzle was to be electroless nickel plated by flushing the plating solution through the nozzle until the desired orifice diameter is achieved? The hardness and corrosion resistance of the nickel plating would obviously be a plus.
Re: Crazy Extruder Nozzle Idea
July 07, 2010 06:11AM
OK another idea for you to try.

On my old machine which was a pseudo Darwin affair I was experimenting with making Glass nozzles.

Take a length of glass tube - 1/4" OD seemed to work OK and heat a short length in the middle of a tube with a blow lamp. Once the glass becomes soft - stretch it. It's how they make needles small enough to inject stuff into cells, so 0.5mm is no problem. Just snap bits off the end until the inner diameter is what you want.

It gives a nice smooth, tapered bore.

To heat it, I used a pair of 20W 12v Halogen bulbs inside an Aluminium tube with a polished bore to reflect as much light back to the glass tube and it's contents as possible.

The glass is a poor conductor - but transmits the IR energy to the filament OK. The upshot is not needing an insulator between the glass tube and the machine. The Aluminium sleeve did get very hot though. If you attach a tube to it and connect that to a vacuum cleaner - drawing air through it cools it, and what you are printing a bit.

By masking the glass tube with foil, you can control the heating zone to limit the back-melt.

I gripped the fat end of the glass tube in a plastic tube with a slot cut in it using a hose clip. When you tighten the clip - it grips the glass. A bit like a collet-chuck. The fat end stayed quite cool - cool enough to hold between your fingers.

The thermistor mounting was a problem which I had not entirely solved. The best was to use a tiny copper collar with a hole in the side for the thermistor. It had a hole in the middle perhaps 2mm in diameter and was glued to the glass with heat-sink compound. It sat below the Aluminium tube reflector and had no light shining directly on it - but picked up enough heat through the glass to measure. The measured temperature was 10 to 20 deg below that of the molten plastic.

Now I've built a Mendel - there is just no space in the X Carriage to fit something like this - although you might be able to do it with an IR laser down fibre-optic to heat the tip of the nozzle? That would also move the hot light-source somewhere it will not melt your machine!

Ironically - the only bit of my Mendel I'm really struggling with is the extruder nozzle / hot end. It just refuses to work for more than a few seconds before it clogs!

Si
Re: Crazy Extruder Nozzle Idea
July 08, 2010 12:58AM
Hey Simon

Your glass nozzle sounds very interesting.

Do you have any drawings or photos?
Re: Crazy Extruder Nozzle Idea
July 09, 2010 11:33PM
I'll have a look! I lost the actual extruder head when my Land Rover caught fire (nothing to do with the extruder - more to do with the exhaust on a V8 glowing cherry red!).

I'm bound to have the original sketches though.

Si
Re: Crazy Extruder Nozzle Idea
July 10, 2010 11:24AM
Sorry to hear that eye popping smiley Trust no one was hurt.

Did you ever get the nozzle to work or had it not yet been mounted?
Re: Crazy Extruder Nozzle Idea
July 10, 2010 09:43PM
In the boating industry they use brass nozzles to spray Gelcoat. I am not sure of the size so I will take a look. There are probably nozzles used in other industries such as spray painting (cars comes to mind).

I am presuming therefore that the extruders are still not perfect.
Re: Crazy Extruder Nozzle Idea
July 10, 2010 11:33PM
There's also these, although at ~$10 they're a little bit pricey:

[www.mcmaster.com]

(Precision tube orifices from McMaster-Carr, in sizes down to 0.016" = 0.4 mm)
Re: Crazy Extruder Nozzle Idea
July 12, 2010 08:20PM
These are probably even better:


[www.mcmaster.com]

Luer-lock stainless steel dispensing needles, 1/4" (6.35mm) long, in diameters as fine as:

0.016" = 0.4mm # 6710A72
0.012" = 0.3mm #6710A74
0.010" = 0.25mm #6710A76

Just $2.61 each.

I'm now determining whether the Luer-lock fitting is appropriate for use in an extruder, and what other parts would be needed to mate with it.

Edited 2 time(s). Last edit at 07/12/2010 08:22PM by jbayless.
Re: Crazy Extruder Nozzle Idea
July 23, 2010 04:09PM
Luer-Loc needles are a great idea! Tricky to make the internal thread and tapered tube it attaches to - but if you could, I think they would be a good solution!

Si
Re: Crazy Extruder Nozzle Idea
July 23, 2010 11:11PM
Thanks!

You can also buy Luer Lock tube fittings from McMaster-Carr that mate to the needle. They call them "quick turn fittings". The trick is finding the right combination of parts to put together, because they don't have much variety...

[www.mcmaster.com]

Right now I'm thinking of this combination:

[www.mcmaster.com]
[www.mcmaster.com] or [www.mcmaster.com]
[www.mcmaster.com]
Re: Crazy Extruder Nozzle Idea
July 27, 2010 11:41PM
Copy of an email sent to Pegasus Glass (http://www.pegasus-glass.com/)

Quote

Dear Pegasus Glass,

I have a question about the cost and minimum order size of custom glass pieces, and would be very grateful for your assistance. I've attached a drawing of the necessary part. I don't have any previous expertise in glass drawing, so I'm not sure whether this part is easy or difficult to make. Unlabeled dimensions are not critical, but the overall length of the tube should be somewhere between 40 and 60 mm, and the narrow needle end should be as short as possible (less than 4 mm if possible). The length of the transition zone is not important, but a reasonable length is 10 mm. I have not been able to find any off-the-shelf parts that are similar.

For a part like this, what would you estimate the minimum order size to be, and the per-unit cost?

For some background: I'm currently building a "RepRap" (Replicating Rapid Prototyper, www.reprap.org ), which is an open-source affordable 3D printer meant to be built by hobbyists. One of the major points of failure for the RepRap is the extruder nozzle. This is a chamber that heats up 3mm plastic rod to its melting point and extrudes it through a narrow hole, creating a fine molten plastic filament to print objects. The RepRap has a very large online community.

Many designs have been proposed for the extruder nozzle, but none have had truly satisfactory performance. A typical nozzle is made from an M6 brass screw drilled through at 3mm, with a dome nut screwed to the end, and an 0.5mm hole drilled in the nut. Heating wire is wrapped around the outside of the screw. One problem with this design is that the high heat conductivity of brass causes the entire extruder to become heated, meaning plastic melts in undesirable locations. Also, it is difficult to drill a fine hole precisely, and there can be leakage problems from plastic extruding through the screw threads. When a jam occurs, it is difficult to tell why, because the tube is opaque.

I believe that a borosilicate glass tube would be far superior. The greatest benefit would be the ability to see the conditions inside the extruder nozzle, to verify that the plastic is melting properly, and check for jams. The thermal conductivity of glass is much lower than brass, meaning that the melting zone could be confined to one end of the tube. The end could be drawn into a fine needle without drilling, creating a smooth change in internal diameter.

If the minimum order quantity is small, I would certainly order some parts like this and encourage others to do so as well. If the minimum order is large, I would recommend a part like this to one of the RepRap parts vendors (such as www.makerbot.com or www.reprapstores.com) for resale.

Thank you for your help,

Jacob Bayless
Engineering Major, University of British Columbia
Attachments:
open | download - ExtruderNozzle.JPG (6 KB)
Re: Crazy Extruder Nozzle Idea
July 28, 2010 01:08AM
Has anyone looked at Macor? (Machinable Glass Ceramic) to do this.

Ok it's not clear, but has a nice spec 1000 deg C, strong and can be machined with normal metalwork tools, non porous and you can both metalise it, and epoxy it.

No idea how expensive it is, but if someone with a metal lathe could get hold of some and try it?

[www.ceramic-substrates.co.uk]


It's expensive, but available from RS - [uk.rs-online.com]

6mm x 100mm Rod is £30+vat

15mm x 100mm Rod is £51+vat

[uk.rs-online.com]

Edited 1 time(s). Last edit at 07/28/2010 01:22AM by richrap.
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