Thursday, 26 June 2008

Spanning a void

s0lstice requested that the next time HydraRaptor was extruding into fresh air I should post a video, so here is a video of a part with a large covered void being made: -

Spanning a void from Nop Head on Vimeo.

It is a bracket to mount a tiny stepper onto a Darwin corner bracket.

As you can see, the unsupported layer is very untidy, but the next layer sorts itself out. The reason I had to make this side the top is that there are projections on the bottom to mate with the corner bracket: -

Here is what it looks like installed. I need to sort out a shaft coupling. I have no idea if the motors will be powerful enough though.

I also made some feet for my Darwin to stop it scratching the table: -

I stuck felt pads, that I happened to have, on them, but rubber would probably be better for non slip.


  1. On this particular part, could you have made it the other way up by adding a support to the model, opposite the chevron, and then removing the support afterwards? Maybe even attach it with a thin connection so that it snaps off?

  2. The chevron would rest on the bed, eveything else on the bottom face would need to be supported if it was made the other way up.

  3. You should try a different pattern for the overhanging parts. After all, I think you still rely on the filament flattening and therefore may have a sparser pattern than necessary. Of course when making overhangs, there isn't anything that the filament could flatten against.

    Additionally, you could try to modify the part scehmatics so that the whole overhang portion is done in a single run as it most probably affects a lot. Currenlty overhang run is broken due to complexity (holes) of the part. One way you could fix it easily is with having internal filament border around the overhang part about 5mm around the overhang portion. That way the software will treat the overhang part as one continuous fillable area.

    Of course, other methods could be better for overhang parts. It might be that with thicker fill pattern the quality would get worse due to extruded filament pattern pushing the previous lines downward. Maybe a little sparser fill pattern with thinner filament will work better due to it cooling faster or just drop the extruder temperature during overhang extrusion.

  4. I forgot the golden rule: caffeine before posting.

  5. Very nice.

    I suspect that the second layer corrects itself because it has regular 'support' from the messy layer. Do you think a layer just before the overhang, with 10%-20% infill would provide enough 'support' for the 100% layer? If necessary, that 'support' layer could possibly be scraped off to clean up the part. Thoughts?

  6. BeagleFury,
    Yes I guess a 1 in 4 layer would give enough support and be easier to remove.

    I could probably remove the messy layer anyway, but in this case it simply gets covered by the motor so doesn't matter, even aesthetically.

  7. how about putting a very slight zigzag in the path of overhanging filaments so they have an opportunity to fuse with ajacent passes?

  8. Aren't adjacent passes more likely to exhert a downwards force on the still soft earlier strands? Wouldn't the best approach to be to allow more cooling time between adjacent strands? I think BeagleFury's 10-20% support layer sounds the most promising, perhaps extruded a little faster to put more tension in it, strength isn't really important as it only has to support the next layer during extrusion.