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Plastics extruded so far?

Posted by SOI Sentinel 
Plastics extruded so far?
September 30, 2007 01:05AM
Hi all,

just trying to jog my memory. I know we've seen PLA, polyactic acid (?), CAPA, and HDPE as materials printed so far. I know that ABS has been on the materials list, but either I'm searching wrong or I haven't found much documentation on any testing (although I think I remember references in Forrest's blog about ABS but no results).

I know that RepRap will move into a bit higher league once ABS and perhaps PC are printed. I'm curious if there's been any results.
Re: Plastics extruded so far?
September 30, 2007 01:21AM
I've extruded (not printed) CAPA, HDPE (also printed), homopolypropylene and ABS. ABS seemed to require rather higher extruder barrel pressures than the GM3 gearmotor was prepared to deliver. I could extrude it, but not for long periods of time. Homopolypropylene required high pressures and temperatures. Again, I could extrude it, but not reliably enough to do any printing with it. I've got a design for a more powerful polymer pump that I need to build to let me print ABS and homopolypropylene.
Re: Plastics extruded so far?
October 24, 2007 08:33PM
Is it possible to extrude LDPE (recycle number 04)? Its just that I end up seeing it a lot in plastic bags, and it would be nice to be able to extrude that too. Wikipedia claims that it has the same melting point as HDPE (120
Re: Plastics extruded so far?
October 24, 2007 08:48PM
I have no doubt that you could extrude LDPE. Why you would want to use that plastic, though, isn't clear.
Anonymous User
Re: Plastics extruded so far?
November 26, 2007 12:21AM
Has anyone tryed melting grocerybags to get HDPE? sounds like a goo recycling scheme to me + easy printing material.
Re: Plastics extruded so far?
December 02, 2007 03:02PM
Are there any issues extruding PET?

And the only reason I would want to extrude all of these other plastics, is because I might happen to have a random piece of trash made of that particular plastic. It would be nice to be able to just grind it up and make something out of it.

Re: Plastics extruded so far?
December 03, 2007 05:05PM
nobody has tried PET as far as i know. i'm not familiar with it, but it may have a high melting point or other things that make it undesirable. if you experiment with it, let us know!
Re: Plastics extruded so far?
December 03, 2007 05:51PM
Well, my experiences indicate that it softens quickly over a candle, but that doesn't help much. smiling smiley

That raises a good question, though. What are we looking for in a plastic? I.e. what features make a plastic usable under the current extruder design? I can tell you that pet melts at 250
Re: Plastics extruded so far?
December 03, 2007 11:13PM
By the seat of my pants I would say we are looking for a plastic that:
melts between 120 and 200 degrees C
does not manifest any undesirable fumes (or other bad behaviors) until 250 C
low viscosity
exhibits a volume change of <1% when cooling
Is relatively chemically stable and insoluble
is possessed of acceptable tensile strength and rigidity when solid
is cheap
is widely available

To my knowledge only 3 thermoplastics have been extruded by RepRaps:
CAPA melts closer to 80 degrees C but easy to work with good for proof of concept. Not Cheap or widely available
HDPA shrinks by at least 2% when cooling which deforms the printed object.
PLA moderately expensive but synthesis is reportedly easy. appears to print well but there has been no real report on the material itself.

PET is not used for injection molding (which is the closest to what we do) because its' surface tension and viscosity are too high, it won't conform to the mold. The same properties might interfere with interlayer adhesion. Commercial FDM machines use ABS. We have not extruded it yet due to its' high melting point. Polyesters are thermoplastic but generally have little rigidity. Waxes have very narrow viscose phases and high specific heat (ie are runny and take a while to harden) (although paraffin might be what you want for your "spray on" thermoplastic fabber).
Re: Plastics extruded so far?
December 04, 2007 06:51AM
ABS really hasn't been extruded?

Zach is selling it at the store, I assumed it was proven. I found this blog comment:

Forrest Higgs said: "ABS, at least the white pigmented ABS that I've used, doesn't go transparent. I don't know what virgin ABS would do. What I found is that it requires not so much a very hot extruder barrel, though that helps, as a lot more pressure from the polymer pump."

Edited 2 time(s). Last edit at 12/04/2007 07:04AM by RoundSparrow.
Re: Plastics extruded so far?
December 04, 2007 07:29AM
... i want to test with ABS at room-temp, as you can solve grinded ABS-powder in Acetone to a paste, which dries to solid ABS (~70-80% strength of origin ABS) again, when the Acetone evaporate.

For my micro-fabbing-experiments i have trouble with very thin nozzles, when the extruded material is to viscous or change viscousity drastically, when cooling down on the way trough the syringe-needle, so i'll try with solved pastes and heat-curing after extrusion.

I tried with drilled nozzles, but the quality of needle-extruding is much better with trays thinner 0,2 mm ...

Re: Plastics extruded so far?
December 04, 2007 10:05AM
forrest has done some experimental work with ABS using a custom extruder. once i get through with my work on the mcwire bot and the new electronics, i'd like to revisit the extruder and see if i cant modify it to be able to handle higher temperatures so that it can safely extruder things such as ABS. that would be awesome.

keep in mind, not everything on the RRRF store is sold because its ready to use... some of the things such as the ABS plastic are there to help people who are interested in researching things. i try to mark them as such, but sometimes i miss stuff. as always, make sure you research things and that you fully understand the things you're purchasing before you purchase them from the RRRF (or anywhere else).
Re: Plastics extruded so far?
December 04, 2007 11:22AM
I am still confused, I did research this (ABS extruding) winking smiley

1. Show original post on this link: [www.blogger.com] Adrian Bowyer posted in that Blog that ABS melts at around 110 C.

2. Forrest in a blog reply [www.blogger.com] saying that it is pressure more than temp that matters.

2a. Forrest says here on another blog reply [crnano.typepad.com] : "I recently redesigned the extruder barrel for RepRap's Mk 2 extruder so that it could be made out of hard copper tubing with a bit of braising. That has worked out very well and the Mk 2 can handle several engineering plastics like HDPE, ABS and polypropylene in addition to the polycapralactone that it was able to extrude before."

3. And most authoritative to me, the RepRap Wiki says only _positive_ things about ABS. [reprap.org] . "A very nice plastic that is stronger, more durable, and more resistant than HDPE. Its a bit pricier, but it also holds its shape out of the nozzle better, so it can produce finer detail parts." The Wiki entry suggests suggests finding a source for it.

This thread
I overlooked Forrest's reply in this very thread (September 29) that implies there are still unresolved problems with ABS extrusion.

Zach, the RepRap Wiki ABS page referenced in #3 could be updated. I suggest a statement like: "Darwin 1.0 Extruder built to specification can not extrude ABS".

Will the real ABS extruding factors please stand up [is it not 110 C melting point]?

Edited 13 time(s). Last edit at 12/04/2007 02:24PM by RoundSparrow.
Re: Plastics extruded so far?
December 04, 2007 01:20PM
sorry if that post implied that we've been using HDPE... i changed it to not imply that.
Re: Plastics extruded so far?
December 04, 2007 02:34PM
ok, I overlooked another Wiki page that discusses the very topic of this forum thread.

[reprap.org] <- WiKi page "PrintingMaterials"

From the Wiki page:
"In this section we will discuss a number of materials that can be used with RepRap and the ways to use them, as well as the core information needed for their successful application."

So this is basically the RepRap Owner Manual / Assembly Manual, I'm trying to draw attention that it doesn't say anywhere that ABS won't work... ? I'm not complaining, I'm trying to bring up the topic so we can get out on the table what needs to be updated/added to that page.

To me, I suggest something like a table of materials with editable wiki pages for each material. People can put up 1) actual test results, 2) which extrusion head they used, 3) notes on modifications to head or special steps required.

Edited 2 time(s). Last edit at 12/04/2007 02:57PM by RoundSparrow.
Re: Plastics extruded so far?
December 05, 2007 05:35PM
I'm actually doing some research on extruding higher temperature materials... I'm still working on getting my initial extruder up and running, but I've got a friend in the construction industry that I've been working with on a concrete based solution to the heat barrier...

It'll be 'fragile' compared to what we've got now... but I was told that what we're looking at will work until we try and extrude at higher than 900c... then we've got to put some additives in to up the temperature... it's also got a durability problem and won't last more than 4 years... but I figure I'll have a concrete extruder by the time I need to replace it... (well... this stuff might not lend itself to extrusion... but I'm still looking for the right 'concrete' for an extruder! smiling smiley)

One of my goals is to be able to extrude parts for model rockets, and those need to be able to withstand the heat from the motor... so I'm looking at things like Teflon...
Re: Plastics extruded so far?
December 06, 2007 01:29AM
Hi lordcat,

> ... higher than 900c ...

That seems not practicable with an extruder!

Aluminum melts at over 600
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