ABS cracking between layers

I just printed a minimug out of ABS after getting frustrated with dealing with the warping of HDPE as it cools. Came out mostly ok, still need to do some tuning, but for a first try it's pretty good. Unfortunately, when I squeezed it laterally to see how much it flexed it cracked between two layers. Not good!

I'm wondering if anyone else has seen this, and what their solution was. I'm printing at 230C, though I have little confidence in the accuracy of my reading. HDPE was extruding fine at 240C according to my system, and it was completely translucent when it was extruded, then cooled to opaque withing ten seconds or so (as long as it wasn't in a big glob in the middle of a part, in which case it took longer- and shrunk while cooling). Does ABS become more brittle if it exceeds some temperature? Since it seems to be fluid enough during the extruding process I don't think that it's not hot enough, so I'm thinking that I'm overheating it and that's causing crystallization or whatever it's called when a thermoplastic becomes brittle.

Any advice would be much appreciated.

See my blog post about this here: [makerhahn.blogspot.com] with links to pictures.

Thanks folks!
-Adam

Running it high apparently causes it to be quite brittle.. I think the metareprap guys, reprap.soup.io and nophead (hydraraptor.blogspot.com) have been extruding ABS at 210C, so you may want to just try dropping your temp a bit.

Generally I find the hotter it is the better it bonds. I accidentally made some objects at a very high temperature when my thermistor fell off and they were rock hard, but a little brown.

Too low a temperature or the layer height too high for the filament diameter will cause delamination with ABS. It never fuses as well as HDPE does.

---

[www.hydraraptor.blogspot.com]

Hey nophead-
I read (I think in one of your posts here) that you're extruding ABS at 230c- is that right? Are you getting usable parts, or are they too brittle? I'm worried that I'm going to get parts which are no less brittle than the lasercut acrylic parts I'm trying to replace.

Hmm, that's a tough one- the way HDPE fuses is nice but I keep getting objects messed up on the infill layers because they warp on cooling. Maybe I need to try extruding HDPE with the fan on again to see if I can work around the contraction problem.
Thanks folks,
-Adam

Adam,
Yes I am currently using 230C with black ABS. The parts are not as strong as plain ABS. I would not describe them as brittle. ABS is not a brittle plastic, like acrylic. The parts split along the layers, which is a different thing. They are very strong in other directions.

Ways to increase the bonding: -

Increase the temperature, I think Adrian told me Stratasys use 290C but the extruder is only really useable to 240C. I think when my thermistor fell off I was probably over 300C. There is no way these objects will delaminate:- [bp3.blogger.com]

Slow down the head movement.

Reduce the layer height. I use filament diameter * 0.8.

Use the double shell option in Skeinforge.

Edited 1 time(s). Last edit at 10/23/2008 07:49AM by nophead.

---

[www.hydraraptor.blogspot.com]

... another way for fabbing homogenous objects from ABS is solving ABS-dust in Acetone to receive a dispensable paste and then prnt at room-temperature.

The Acetone dries fast away, so the actual layer would be rigid enough to support the next one, but the Acetone in the current output-tray is enough to wet/solve the surface of the dried layer and fuse the actual tray with the surface ...

Another benefit with this method is the reduced warpage - the tray shrinks a bit while drying, but this causes only a reduction of the layer-thickness, not warpage at the edges.

But you have to ventilate your building-area ...

Viktor

Non smokers only
and you should make sure that all electronics a perfectly isolated,
one spark and you win a free flight to barbados

Did you already tried that Viktor?
if yes can you post a picture of the process and the result?
if not... can you try and then post a picture

I'm eager to see some roomtemp fabbing results other than the uv curing pastes fab@home recently uses

'sid

Hi sid,

i tried this some years ago when developing housings and the assembly of micro-sensors.

Some tests with ABS-paste went fine (i tried then with laser-drying and -sintering too), but finally we changed to high-temp-sensors and i built complex bodies out from flexible 'green' ceramic-foils and selfmade ceramic- and gold-paste and some types of soldering-glass.

I didn't have the images, but i have some of the materials and wanted to start with paste-fabbing when finished an exact enough paste-dispenser.

My actual pneumatic-driven dispensers weren't exact enough for my needs, so i broke them down and started with linear-motor driven pistons as in the f@h-dispenser.

I hope to get some of them running before Dezember ...

Viktor

PS: beside ... the 3D-milling runs fine

Yay! I printed another mug, all the same settings except this time at 250c, and it seems to be holding together quite well. I can squeeze it as hard as I can by hand, and the layers don't come apart.
Still have some ooze problems, that comes next.

Theoretically, because ABS shrinks while it cools, there is nothing to do about warping and cracks. The volume will become less, no matter what...
You might be able to reduce the effect on the part. Like a certain structure in your part or something. But the volume schrinking effect will always be present.

I do not believe people who print 100% flat (as some say).... I guess they have mistaken (literally) a role of PLA instead of ABS

I like the idea of ABS dust / paste, sounds like a great idea. I was unaware that parts could be produced this way cold. Is it just like a very thick version of ABS Juice and could you recycle your old parts by just dissolving them in a vat?

Any more details about this would be appreciated.

This would mean you could mix in fillers easily to experiment with various compounds. Perhaps by altering the % of dust to acetone we could get both a print material and a more dusty support material that you can break easily.

Flashing the acetone off quickly would be easy by warming the paste as you extrude. OK the acetone vapor might be an issue, but I could see an enclosed machine with an extractor.

You could recover the acetone from the vapor by condensation and recycle it back in. This "homebrew" technology was developed in the days of prohibition! Perhaps a name for the machine could be "Moonshine" reprap!

... I've dispensed some ten layers of 'ABS-juice' on ceramics with a square-size below 40x40mm and didn't notice any warp - when fabbing greater parts, then check first for warping caused by drying ... or explicite reheat every printed layer, so it dries complete and won't add excessive stress.

The solidified paste has maybe 50% to 70% stability of original ABS, but this should be similar with extruded parts too.

The % of solved ABS only affects the viscosity and height of the solidified track - you need dispersed additives or chemistry for defining the brittleness/stability of the part.

With laser-fusing dry black ABS-powder I've received different stabilities with changing the power and timing settings - could be the amount of air-bubbles remaining in the molten phase ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Has anyone tried larger ABS priints in a heated enclosed space. It would seem that most of us are printing in rooms < 73F, which is a shock to material coming out at 230C+.

solved here - [forums.reprap.org]

Edited 1 time(s). Last edit at 11/19/2014 10:51AM by abuharsky.

I had terrible problems with large ABS prints cracking. I built a heated chamber and now the problems have gone. I have a 300x300x280mm build space and run the chamber at 50 degrees and all my cracking issues have been fixed. It's the only way to do large prints in ABS.
See the attached picture for the effect of the chamber on preventing cracks. The right hand print is without the heated chamber.