Computing stuff tied to the physical world

One more 3D post

In Hardware on Jan 29, 2010 at 00:01

Ok, one last post on the CupCake CNC trials before I get back to JeeNode stuff.

The raft is now very solidly stuck to the base:

DSC_0968.jpg

This thing really sticks well, with plastic pushed down into the criss-cross grooves of the acrylic base. The trick is to place a plain paper sheet between the extruder head and the base, and to lower the Z axis until the paper slides away with just a tad of friction.

Unfortunately, the next problem comes up – as seen in this first Geneva Wheel trial:

DSC_0967.jpg

It turns out that the next layer of the raft doesn’t stick well to the first one. I solved this by raising the default 230° setting to 240° for the raft.

Another serious problem was that there is a lot of plastic on the right end of the raft as the print nozzle paused (!) on each turn. And the second layer of the raft doesn’t extend all the way to the end. This was solved by adding three noise-suppressing 0.1 µF caps to the extruder motor and disconnecting all the end-stop optocouplers.

The object itself seems to come out fairly well, though there were some blobs of plastic around the nozzle during printing which clearly interfered with the X-Y motion at times.

Here are over a dozen more parts, printed using black ABS for a change:

DSC_0975.jpg

These all came out ok, but note that even these small parts take 10..15 minutes to print – each.

The biggest remaining problem is “warping” – it’s causing over half my trials to fail:

DSC_0976.jpg

This part failed to build (should have been 20 mm high), it slowly came off the base and started interfering more and more with the extruder nozzle. At some point the nozzle got stuck in fact. Note how the thickness of the part is completely uneven. This is caused by the ABS cooling down and shrinking a bit – slowly pulling itself off the raft (with considerable force). A heated baseplate seems to be the hack to solve this – but that will require a lot more tinkering.

Oh well. We’ll get there… eventually :)

Update – upgraded to ReplicatorG 0012 with Extruder firmware v1.8 and switched to Zach Hoeken’s thermistor settings (raft setting reverted to original 230°). The last change was to shine a halogen light on the platform and object, to heat it up a bit – this seems to get rid of just about all the warping, yeay!

  1. Hi,

    the Blog at http://hydraraptor.blogspot.com/ shows impressively the advantages of a heated baseplate. And this is a good entry point for some other interestingly discussions about reprap problems and solutions.

    Servus KS

  2. Yes, I saw it. The last days I read your whole blog, including the Comments. A very interesting and informative way to spend time :-) — Thanks for that. At hydraraptor it is fascinating to see, how exact the printed parts can bee, how smooth the surface. But it is also shown, what problems you have to suffer on your way to this.

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