Saturday, October 24, 2009

No posts here for a while, been putting my energies into the cubespawn website, and the cubes themselves
also, trying to figure out the google ad crap...

I personally hate ads and would skip the whole thing - but the tiny revenue stream is enticing and must be ideally engineered to exploit a human weakness, otherwise why would so many people put annoying ads on thier site?

power mulling...
more blogs?
politics and opinion are a mire of time wasting dreck - so stick to factual stuff
One for the cubes
One for the modular robots, (this one, eventually)
One about the stone house,
One for the Solar Cabin
Possibly one for a rainwater capture/de-humidifier supplemented water system - part of the solar cabin design - but with enough technical information thats independant it MAY justify its own blog...

Friday, September 25, 2009

WHERE the cubes spawn

A couple of updates: Finally got my (Very Crude) website started and have the first iteration of the X, Y, motion for the 1/2 meter cube.

It appears its going to work like this:
assumes no access to a machine shop for the first step

make the first cube using hand and (common) power tools, use simple mounts and brackets appropriate to that developement enviroment.

Induce as much accuracy as possible to overcome shortcomings of the manufacturing process

use the machine itself to make better mounts and brackets

lather, rinse, repeat!

so, I see mark I, mark IV etc... implementations on a few basic cells, once these are built though, then "standard" designs can be used for more advanced/more specialized cells.

More Later!

Thursday, September 10, 2009

The Cubes are Spawning!

YAY! Finally got the (wrong) hardware to assemble the little cube, but the right stuff is on its way - meanwhile, this'll do...
Also got a 60 tooth aluminum blade for the miter saw - so, much better finish on the cuts...

Thus far: it looks like this ( a scale model of the 1 meter cube... ;0) )
You may note the corner connector-cubes are missing at this point, as they are outrageously priced (IMHO) at $17.50 ea (!) with 8 required they'd cost 50% of the whole shebang... not acceptable! The triple connectors for the 1 meter cube where $5.60 each so for now I'll get by without till I can make some.

Sunday, September 6, 2009

Shiney Things

The Linear Bearings for the little cube have shown up - there sooo LITTLE!

and the electronics from the Mcwire are now operational again - turned out to be a scrambled arduino IDE install.
Upgraded to 0017 added the sanguino files and away we went...

More soon - as these components are integrated


Wednesday, September 2, 2009

Isn't it Cuuuuute..?....
Several updates: the "Little Cube" is coming along nicely, but as I construct it, several questions pose themselves:

Given the crude construction techniques, how can I insure that the machine will have adequate precision to make parts as good as those used to make the first one i.e accuracy won't decline with each copy...
The most likely problem is parallelograming the frame during assembly - out of parallel linear bearings are easier to spot - and a significant error will cause binding in the travels.
This can be addressed during assembly with some measurement and a proper bolt tightening sequence, but a subtle parallelogram will be harder to detect and correct.
Applying this principle, can I make the machine MORE accurate at each iteration? If so, to what limit?

I think I have an answer to this as well:

Yes, using a technique from land surveying - if a test program is built with measurement points in a rectangular grid and the error for each point is logged, then a compensation table can be emplaced to counter irregularities in positioning accuracy due to out-of-square or non-parallel problems.

Two approaches then present themselves: do all compensation with the control software , or iteratively suggest adjustments - then retest until certain tolerances are met and compensate between those tolerances and the practical limit of the positioning system - this should yield the best accuracy a given system is capable of...

The main caveat to this is such a system would compensate for static errors, I can think of no practical way to compensate for dynamic error due to deflection, sag, or harmonics although proper telemetry would likely allow for all that - this may seem to be overkill - but if this form factor of machine is to make its own parts some of them may call for very precise positioning (I'm thinking SMT pick and place f'rinstace... ;-) ) so I believe it is a problem meriting careful consideration

And where all these maunderings lead me is:

What positioning system? This first cube will be a ball screw/stepper positioning system, but I think machine 2 will be a Linear stepper solution.
For the attractive merits of greater mechanical simplicity, much more precise positioning, and potentially closed loop operation inherent in a linear stepper system.

the questions posed above are satisfied by this solution and the upper threshold for accuracy becomes potentially very high if a mechanism to loop the accuracy upwards iteratively is implemented.

Tuesday, August 18, 2009

Hippity-Hop! every time I look at this project it sprouts several rabbit trails to (mis) lead me to more solutions! or problems... as perspective sometime defines them.

I was told once that "a thoroughly defined question IS an answer" so this question popped unbidden into my whirling brain. :
"why not make your repstrap JUST like your router?"

As anyone who has built the McWire has doubtlessly discovered, it has a large number of mechanical quirks, and several designed in oversites, even so, I have dutifully built it very similarly to that shown in the plans with an eye to interjecting my take on things that could be improved, but, it appears to have stalled as a project as those involved went on to other things.

with that in mind, if this 1/2 meter cube turns out to be cheap enough to build - I may document that and advance it as yet-another-way to build a RepStrap

So, then, since I have some 1x1 extrusion lying around I'll be assembling a 1/2 meter cube with the sanguino electronics/repstrap project in mind - I found some inexpensive brackets online today and this will keep my tinkering reflexes sharp while I save money/wait for parts/etc... I may set it up useing the 1/4 inch drive threads while I decide if I am feeling bold enough to try for linear stepper drives, or if they turn out to be cost prohibitive

Baldor Linear Steppers

I'm sure it'd take thier lowest rating motor, given the forces involved...
yadda yadda, I've said enough for this post

and so it goes...

Wednesday, August 12, 2009

Just a quick post: The frame is together and checked for straightness, and squareness...

The space between the top bar and the next one down is the data/electric bus and external connector area the wide bar below will support the precision guide rails for the "X" axis of the motion control assembly "Y"'s parts are on order for the coming week.