RepRap: Blog

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)

Labels: ABS, lasercut, ponoko, reprap