[Hplusroadmap] Fwd: [RAS] CNC Machine

[Evgeny Egorochkin]

В сообщении от Friday 06 June 2008 16:12:37 Antonio Marcos написал(а):
> >And these will cost much more than $100. I wouldn't get overly excited
> >at a cnc machine made of wood/MDF. It has the same deficiencies as
> >RepRap. Maybe not as much though.
>
> I disagree. We can use, and humans have done this for millennia(and i also
> say its the only way to go), more primitive tools to make more refined
> ones.. evolution... Btw, i just watched a lecture at TED, talking exactly
> about this.. how people tend NOT to think in technology(or anything else
> for that matter) in evolutionary terms.
>
> In this case, we can use it to make a better cnc ^_^

You're confusing completely different things:
Evolution of knowledge and evolution of open hardware

There's nothing to invent here. Most of technologies used in manufacturing are 
quite old and not secret by any means. So why not use the best available 
technology from the start?

You can bootstrap using commercially available stuff(ok, cnc machining centers 
are less available in countries like yours or mine, but not a big deal in the 
us&eu)

The goal is: machine that can manufacture every part of itself and something 
useful as a side effect or vice versa.

The question is: what bottlenecks do we have? Which parts are hard to 
manufacture and expensive at the same time?

And the answer is in my previous email: electronics, motors, precision 
mechanical parts(precision brearings and screws).

Electronics cost can be reduced by making pcbs and soldering components 
yourself(manual or automatic is another matter). *Reduced*, not eliminated.

Motors... you're out of luck.

Bearings? Forget it. You can only try to use as small quantity as possible.

Precision screws are possible to make at home with a good cnc machine, at 
least in theory.

This list of bottlenecks(surprise!) is exactly what will eat more than 50% of 
costs of building the project you're amazed about.

What was wrong about it is using wood instead of steel. Wood/MDF will flex, 
wear out fast and can't be precicely machined. Steel frame fixes this. Cnc 
machine with a steel frame has a much better chance of making a good steel 
frame for another machine ;)

What is absent in these open hardware designs is a technology that gets rid of 
generational quality loss. That is, these machines can produce certain parts 
for themselves, but only of a lower quality than parts they are made of.

So if you make a part for a machine, put it into the machine, make another 
part and put it in, eventually replacing all parts, you get a machine of 
lower quality. Do it several times and you end up with a *pile of junk* :(

This makes viral spread of the machine as envisioned by RepRap folks 
unrealistic.

So the problems are: tech bottlenecks and quality detoriation.

That was bad news.

And the good news is...

Tech bottlenecks can be worked around by minimizing the use of the offending 
technologies or by using [usually overlooked] alternatives.

Quality detoriation can be battled using active defect compensation 
mechanisms. Basically, machine defects are measured and accounted for during 
manufacturing process. This is possible today thanks to cheap processing 
power and sensor advances.

Oh and someone's working on fixing this. *wink*

> yet, its an amazing project =]

Didn't mean to discourage anyone. Didn't claim it was a bad project either.

Pointing out shortcoming may be unpleasant, but it's the first step required 
to actually address them. We don't want press releases, hype, whatever. We 
want stuff that actually works.

> >-- Evgeny
>
> im curious.. you're russian?! cool!

Yes :)

> I have a russian friend here, maybe you 
> know him? His parents returned to Russia if im not mistaken.


There are too many of us to know each other ;)

> []
> Mark.
>
> --- Em sex, 6/6/08, Evgeny Egorochkin <phreedom.stdin at gmail.com>
> escreveu: De: Evgeny Egorochkin <phreedom.stdin at gmail.com>
> Assunto: Re: [Hplusroadmap] Fwd: [RAS] CNC Machine
> Para: hplusroadmap at heybryan.org
> Data: Sexta-feira, 6 de Junho de 2008, 0:00
>
> В сообщении от Thursday 05 June 2008 17:46:58 Bryan Bishop
> написал(а):
> > ----------  Forwarded Message  ----------
> >
> > Subject: [RAS] CNC Machine
> > Date: Friday 23 May 2008
> > From: "Richard McClellan" <richard.mcclellan at gmail.com>
> > To: ras at ras.ece.utexas.edu, andersonrobotics at ras.ece.utexas.edu
> >
> > This is what we may be using to build robots next year:
> >
> > Pictures: http://picasaweb.google.com/richard.mcclellan/HomemadeCNC
> > Video: http://ras.ece.utexas.edu/~richard/cnc_part1.mov
> >
> > This is the result of only about three days of work, and only a little
> > over
> > a $100 for all the parts so far.  The whole thing is very smooth and
> it > looks like it's going to work pretty well.  Next step is mounting
> lead > screws, mounting motors, then electronics!
>
> And these will cost much more than $100. I wouldn't get overly excited at a
>
> cnc machine made of wood/MDF. It has the same deficiencies as RepRap. Maybe
> not as much though.
>
> -- Evgeny