Tuesday, January 08, 2008


First Corner Bracket

OK, so I have a Corner Bracket in PLA. Took about 10 hours to print. I'm trying a second one now, just to make sure it's not a fluke. I'll update with photos later.

As it comes out of the RepRap, the stringing within the part obscures many of the holes, and drilling is required to make the part usable. Is this considered minor refinishing? A cordless drill with 8mm or 5mm bit basically guides itself into the right position; I just hold the PLA bracket in my hands and try not to drill my fingers.

Blobs are apparent at the end of each layer, when the nozzle halts and the RepRap software figures out the next one. The nozzle oozes.

The Corner Bracket has rounded corners which will not print without overhanging, and these cause knock-on wall collapses up the side of the corner bracket. It would be better if the corners were square.

Mid-way up, the distance between hole and corner is quite small. This results in a rather fragile-looking corner. This would be strengthened by leaving the edges square, but an extra mm of wall thickness wouldn't hurt either.

Is it strong enough? Just, I think. For the moment I'll call it good enough to try and build another Darwin with. After a week I should have a full set of Corner Brackets!

Vik :v)

Excellent! Only, what, 156 more parts to go? :-)

I'd been wondering about the rounded corners on the bottom. I just recently went through the STL files, looking for bits that couldn't be made without support material and that's one of the things I'd noticed. The list is over here.
Is it possible that the holes could be made with a circular motion instead of spanning the gap across them?

Or maybe build the first layer then build a spiral to build the wall of the hole then build the rest of the part around that initial construction.

or just try building a short tube and see how clean the inside edge is.
steve: Already onto it. Several parts have been modified to print without overhang.

fjr: The process of printing does go around in a circle. But when the print head moves off to do another circle it often goes over a hole in the middle. The trail of dribble from the nozzle then goes into the hole.

Vik :v)
Let me know if you need any help with the de-overhanging process. I'm assuming you're editing the parts in AOI, right?
Yup, AoI is the tool of choice.

If you want to look at the brackets on the Z axis that hold the tensioned nuts, that'd help. I'm starting from the X axis - basically following assembly instructions - so it'll take me a while to get there:)

Hint: Check that the original prints to a nullcartesian device first. Some don't and cause you grief wondering WTF you just broke! 'Course, your exported STL should also print under a nullcartesian device.

Vik :v)
That's the one in bed-clap.stl, right? That's a nasty one. I'll see what I can do.
Just bevelling the flat internal bit to 45 degrees would probably work.

Vik :v)
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