[nzlug] reprap

[Simon Bridge]

Drat that Vik Olliver!
I've just spent two days heaving and coughing and all I could think
about was different reprap designs!

eg. The Darwin is much bigger that it needs to be, but the design
scales... the reprapable components are the corner-bits, wheels and
connectors (head assembly is probably the most complicated bit). One can
choose frame rods to any length. (Will the software adjust to suit?)

A self-reproducing machine only needs to be a bit bigger than the
largest of it's own components. (Note - anything which *needs* a
circular hole can be made in two parts.)

A smaller machine won't need as much metal to maintain it's strength -
so it can make it's own support struts. That leaves the z-axis screws
and the x-y rods.

If the connectors stay the same size, then larger machines can be made.
But the smaller size implies the "mini-darwin" needs only smaller
connectors... which are quicker to make.

If the z-axis is used to move the head instead of the base, then the
base is no longer part of the machine. One can place the machine over
the build site. It also scales better as it means arbitrarily large (and
heavy) components can be made without additional strain on the motors.

Now the tricky part - adopting a more organic design allows the
connectors and struts made by the mini-darwin to be both lighter and
stronger. And quicker to make.

An academic analysis:
http://alumni.media.mit.edu/~saul/PhD/index.html
... but different design paradigms.

Amnday! It appears I may be building one of these things sometime
soon-ish. I hate you Vik ;)

Q. What is the shortest time for the existing machine to build all it's
own components, if run continuously?

Oh - and the dripping issue - what's wrong with a spring-loaded
contact-board at the rest position? The nozzle then sits pressed against
the board, which won't bind. (The standard solution is to use a
spring-loaded cap which slides out of the way when in use. The motor
which drives the material could also shift the cap.)

BTW: apologies to anyone else who went to the AuckLUG meeting, it seems
I was sicker than I thought. As I had started manifesting symptoms, I
may not have been contagious - but I'm not that lucky. So, if you feel
ill, I'm so sorry.