Wednesday, May 07, 2008


Bug fixing

Inspired by some of Nophead's experiments, this is a water filter insert made in RepRap. Actually, it's a bit of a cheat: the model for it is a simple disc. But I've enhanced the host code so that you can plot multiple outlines of an object one inside another. Add that to the fact that you can set the infill width to whatever you like and the part becomes trivial to make. It took about 20 minutes in my home Darwin to build.

In general these enhancements mean that you can make the boundary of an object thicker (therefore stronger) and do a sparse infill, thus both saving material and reducing build time overall.

If you set


in the properties file you get a single outline as normal. Setting it to bigger integers gives that number, one inside another. Setting it to 0 suppresses outline plotting altogether.

Also, if you set


negative that suppresses infill hatching.

Anyway. Here it is filtering some non-potable water as input. (Mark you, I wouldn't drink the output, either...)

RepRap water filter from Adrian Bowyer on Vimeo.

Despite all evidence to the contrary, the noise on the soundtrack is not a Sopwith Camel that has just received the coup de grĂ¢ce from the Red Barron. It is my neighbour's lawnmower. I'm glad to say that he has removed the Lewis gun...

So, do you want to print out a generator next? I've made a couple of stl files for one that I'll post in the library whenever I get a chance.

It requires some unreprapable parts though, like a skate bearing, threaded rod, copper wire, 19 mm diameter toroid magnets, nuts and bolts.
You sure seem to be having a lot of fun! :-D
Go with the generator. Look forward to seeing it. Can I ask the rough overall size?
What we actually need is a printable stepper motor. :-)
Gene Hacker,

For the generator, if you designed a spool holder and an upside horn or something else that smoothly lets wire out for the Darwin head, you could wind simple coils using Darwin.
It's about the size of a CD, just a few cm thicker though.
I just posted the STL files for my 3 phase ac generator in the forums.,11789
It seems worth note that a stepper motor and a generator like that are on a qualitative level the same device. It's just a matter of what the specific numbers are optimized for. In this case, you might want a microstepping controller, but apart from that.. could almost certainly even make one of those nifty little linear actuators. Now if I only had time to get myself a reprap and do the work... (maybe next school year.)

Now, what I think would be impressive is managing to lay down alternating layers of conductive material, bound graphite bits/something else that'll absorb ions, nonconductive polymer that will let ions move through it, and lithium iron phosphate or somesuch... print a battery, shaped to fit into whatever space is available.
Lithium ion batteries are kinda tricky; polymer electrolytes, doubly so.

I built them for a couple years, as an undegrad, though to be honest I have much more experience with the liquid electrolyte. They're very sensitive to air, so you'd need to have your reprap in a dry box or similar, and there are lots of other nontrivial issues.

Sealed lead-acid may be a better first step. If you must make lithium ion, the cost of materials won't be as large a proportion, and you're presumably doing this for the sake of performance, so I'd recommend lithium cobalt oxide as your cathode material.
Post a Comment

<< Home

This page is powered by Blogger. Isn't yours?

Subscribe to
Posts [Atom]