Saturday, October 04, 2008


Building ABS on a lasercut/fabbed Darwin

I've managed to put together one extruder from the bits of lasercut prototypes Ponko have been cutting for me. It slotted straight in to the Darwin head exchange mechanism, but was a bit loose. I've got a better extruder base already being cut by Ponoko so I was expecting that and simply wrapped it with tape. The extruder motor is a little far away, so a temporary heave-to has been executed with a cable tie. Sorry, ugly. Is also fixed already.

I've loaded it with ABS and am now printing components with it, as you can see in the photo, as well as a classic Mighty RepRap Power Ring. I've fitted the ABS extruder to a Darwin to try my hand at testing out ABS, Imagin Plastics were kind enough to give me a 50m sample of 3mm ABS natural. Looks good, and I should be able to get it for under NZ$20 per 100 metre coil.

I've found ABS to be generally the hardest plastic to work with. It needs high temperatures, high pressures, and isn't that keen to laminate. You have to work in thin layers to keep lamination, which slows me down. It does score on accuracy and tidiness, however, as the paste-like exudate stops fairly rapidly even without a valved nozzle.

You need to have your nozzle mounted very rigidly, because ABS is not that easy for the hot nozzle to plough through if there are any rough bits sticking up from the surface. This is another reason I found to use thin layers and go slowly.

Getting ABS to stay down on the bed is hard too, but by accident I made one of those handy discoveries: With an eye-dropper, put a few drops of acetone (methyethylketone for the new-fangled) on a wooden extruder bed where the printing will take place. This hugely improves the adhesion to the bed, BUT IS VERY FLAMMABLE! Just bear it in mind, and keep the big can of acetone well away with the lid on just in case, eh? (PS What pen do you label little acetone bottles with? It all gets dissolved off when I spill it!)

Things bode well for an alpha release of the Ponoko lasercut components kit. I'm getting excited about that, and it should tie in nicely with the imminent arrival of Zach's new shipment of extruder motors on the RRRF site.

Oh, the curly-white wave flowing over the top of the big washer holding the extruder barrel is an ABS leak between the PTFE insulator rod and the top of the brass M6 extruder barrel. I hadn't anticipated the need to seal it, but the ABS starts pressurizing some way up the PTFE rod and squooshes out the gaps in an organic way. I'll seal the gap with PTFE tape when I install the latest extruder clamp assembly off the pending prototype lasercut run.

Vik :v)

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i am really enjoying ABS. the quality of prints is amazing.

i have a hose clamp installed at the point where the PTFE barrel connects to the heater barrel, and i've never had a spillage problem like that. i highly recommend it.

if they're called something else in NZ, here's a pic:
Based on Nophead's work, I've added stuff to the Java s/w that builds a foundation of a few layers, then makes the first layer of the actual part with a bigger Z gap. On both my and the Bath U. machines this sticks an ABS part down well, allows for slight deviations from the plane in the bed, allows the extruder to warm up and get comfortable, and allows the part to be easily separated with a penknife from those foundations.

See the preferences docs at

for the values to put in.
Can't wait for the kit! Any idea what sort of price range it'll be in?
My limited experience with PLA was that it worked better than ABS. How do you think they compare Vik?
Still early to tell, but it looks to me like PLA is the winner at this stage. If I run PLA as slowly as I have to run ABS I get the same quality. Bear in mind I'm still running my original Darwin with the PIC rig, but I'll put an Arduino into it soon and we'll see how that works. I expect PLA will still come out tops. ABS is more resistant to higher temperatures though, which may be useful for some purposes.

Just fixed Phoenix (ex-rrChild) back up again, and the lasercut design with ball-chain drive and NEMA 17's is now done, so plenty to play with.

Vik :v)

Kits are avaiable from
The BitFromBytes is available now. The Ponoko version is going to be out next week from their website.

I've done 2 versions: One is US$420 and has 2 swappable extruders, compatible with Darwin plus spare parts and a few new ideas like GM3 options for the Z axis. The other is a bare-bones kit with one extruder, no spare parts and an MDF bed. That comes in at US$299.

I'm also working on a version that only needs 2 axis motors, experimental parts for which are in the $420 kit. More on that probably later next week.

Vik :v)

I'm aware of that. It's the Ponoko kit in particular that I'm excited about.


Wonderful! Looks like my opportunity to join in the fun is nigh.
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