Friday, October 31, 2008


Exponential Growth?

Here's a nice diagonal tie bracket (Thanks to Nophead for the updated design) I made Tuesday night. It's far from perfect, but it seems to be pretty functional.

After some tweaking and a few messed up builds, I awoke to this view on my webcam Thursday morning:

Getting better! A wayward G28 code caused a minor head collision, but everything survived.

I've still got room to grow though, so here's what I saw on my webcam first thing this morning:

That I like! There's actually build room for another row and column yet, but I've got enough diagonal tie brackets for now; next up are corner brackets!

Interestingly, Skeinforge and ReplicatorG both reported build times of about 4.5 hours for the 9 part build, but the actual build took over 6.5 hrs, give or take half an hour. That would explain the discrepancy I'm seeing between 8mm/s and 16 mm/s feed rates - I actually get too much plastic (densities above 1.0) at 16mm/s. Probably something to do with the many short moves along the curves causing a bit of a slowdown in the head feedrate. At any rate, my real limiting factor is now the extrusion rate; 3 mm^3/s is about as fast as I can reliably extrude at with my current extruder.

Either way, things are working smoothly now. My parts bin now has 43 usable Darwin parts in it, and with these longer builds I'm getting more and more parts with less and less effort (on my part at least).

Unfortunately, right now my Darwin only likes my favorite dual CPU computer and it's not at all happy sharing it. So, until we get offline printing working, I have to find another computer to work on while I'm printing.

Full resolution pics are over here:

Hopefully my next post will involve something about viral distribution. :)

Wade Bortz

"My parts bin now has 43 usable Darwin parts in it"

Well done! VERY well done! :-D
Great progress Wade.

I also get about 3 mm^3/s, pi actually, it makes the calculations easier.

Is that acrylic you are using for the base material? Is it reusable?
Thanks for the encouragement guys!

Yes, it's 1/4" acrylic (plexiglass), and it's very reusable. Old compact discs were my first successful base material, and thin plexiglass would warp too much. 1/4" plexi is strong enough to resist warping though.

You can print parts directly on to it, but they don't remove well - I shattered the 1/4" plexiglass and destroyed the part trying to remove it. The rafts enable me to get the parts off using an 8" monkeywrench, and then I scrape the raft off with a utility knife.

I also give it a wipe with 99% isopropanol before building; some builds don't stick well if I don't. It could be just the oils from my hands interfering with the bond.

You can see tiny cracks developing from the thermal stresses as the raft is laid down, so it won't last forever, but it will last a very long time. I've probably put down and removed over 20 rafts from the same area near my homing switches.

My first corner block had some issues with warping - the part separated from the raft after the first 4 layers or so. I'll have to see about getting a stronger bond between the part and the raft.

I've found that it's a fine line between not strong enough, and too strong of a bond though! :)
Yes it is a fine line. 5C or 10C change to the first layer temp can make all the difference and so can 0.05mm first layer height difference.
Very nice work Wade, very nice indeed!
My prints to date have been single objects and so far I have not printed on a raft!
Are you running ABS?

Yes, these are all ABS. Might order some HDPE with my next plastic order, just for fun. I have to use the rafts; without them ABS sticks to the base so well I can't get the parts off without destroying them.

Interestingly, I wasn't able to get ABS to stick to the MDF base at all; that fact held me back for quite a while.
you have a webcam pointed to your darwin??

Share the link! :)

Leav, yes, and the really cool part is that I can watch it from my phone. Unfortunately, at the moment I'm using a VNC session to view it, so I can't share it yet. I'll post when I get it set up properly.

Webcam support is astonishingly bad in Linux. Both my webcams are barely useable due to color and brightness problems.
wow you have been creating some very interesting things here. I usually write code and never get to actually produce something like this. Its fascinating!
How did you convience skeinforge/replicatorg to print out multiple of the same object at once?
How did you convience skeinforge/replicatorg to print out multiple of the same object at once?
Daniel, on those ones I printed the parts sequentially, by editing the gcode file manually. You move the head out of the way of the first part, use G92 X0 Y0 to reset the X and Y homes, and then cut and paste in the entire Gcode file. Painful, but it worked.

Skeinforge now has a Multiply option, which will build multiple parts simultaneously, but if you have a problem mid build, all the parts are half built, which isn't as useful.
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