Re: [CAD_CAM_EDM_DRO] Re: robotic workcell design

skykotech wrote:

>Hi Dave,
>
>Thanks for the very detailed response. You gave me a new perspective
>on some parts of the idea.
>

I do hope that I'm useful :)

AS it is I'm wondering if this discusion might be a bit off topic for
this group. It is one of those things that certainly is a near
fit. In any event there are other resources on the net such as
www.CNCzone.com or the EMC site. I'm sure if we stray to far off
topic we will here about it.

>
>The requirement for only new parts was desired so that people could
>be guaranteed to be able to build the universal gantry...I like that
>term :-...in a timely manner with predictable specifications. I know
>using ebay parts would allow a cheaper design, but then compatibility
>is out the window. At that point, you might as well start the
>construction article by saying "First, obtain a gantry cnc machine."
>

I do believe that it is doable with new parts, it just limits what can
be done within the budget. All the better reason to break the machine
up into a base gantry machine and attachments. Since the fabrication
will require square and level surfaces you would have to explain how
that would be done in a limited environment. I do not think it is
asking to much to expect people, who may not be well equiped tool wise,
to go out and ask for help. At least around here ther are plenty of
machine shops, gunsniths and engine rebuilders that would be willing to
do a little boring for a small fee. For the machine to work well a
little precision work is required.

>
>Perhaps the requirement of limited machining and hand tools needed is
>too strict. Personally, I have a fairly large shizuoka cnc bedmill,
>so I could make a lot of what this gantry would need. I *know* I
>could make it for less than $2000 if I use my cnc mill, but I am
>thinking that there are quite a few people who would be interested in
>a project like this that do not have those type of tools.
>

Yes I convinced if the machine could be presented in a easy to build
manner and its usefullness fully outlined then there are people who
would build the machine. Building the machine for under $2000 is not
really a big issues, it is a matter of doing it with extreme limits on
tools. One of the advantages of using home center materials is that
one can have the parts cut for free or a very nominal fee. Personally
I have a problem with building a machine out of MDF or other 'woods" but
that is me. There is certainly other options, including ordering
extruded aluminum cut to size, many extrusion suppliers can do this and
supply the parts as a kit.

In the end though I think one will have to expect at least a few tools
in the builders shop. For instance a properly set up drill press can
certianly help. You seem to be well equiped tool wise, what you need
to do is to approach the article from the stand point of a guy with a
bunch of cheap dime store tools. That is think about what you want to
build and then go to with just a dozen tools or so and see how far you
get. No cheating now ;) The point is you will approach the problem
at first with all the specialize tooling you have at your disposal.
There is a set of books by Dave Gingery that explains how one can build
a machine shop from almost nothing, in effect this is what you are doing
with the tooling restrictions you currently have in place. Along
these lines you may be able to come up with a method of building the
machine so that it can build parts for itself, that may be a little much
for a magazine though.

Frankly I would expect that anybody involved in robotics will have more
than a few tools on hand or know people who do have the tools. So I
don't see where expecting a little more from the readers is a
problem. In the end they will end up with a large collection of tools
anyways. Much the same can be said about any hobby be it fly tieing,
model airplanes, trains or model engines. One starts out with nothing
(well often anyways) and ends up with a bunch of purchased and
fabricated tools. There is actually an article in the making right
here - that is what is needed or required, tool wise, to get into the
hobby and to progress through the various stages.

>
>The CO2 laser thing I mentioned because I happen to have several and
>have built some slow speed engravers already. They are not *that*
>dangerous..I can still see pretty clearly out of one eye :-)
>Seriously, CO2 is probably the safest wavelength laser out there.
>10,600nm is almost 100% absorbed by plastic, glass, etc., making eye
>protection as simple as a pair of $3.00 shop goggles. A plywood
>cover with an acrylic window could be made to cover the whole gantry
>for the super paranoid types. If the beam coming from the laser is
>shielded up the to focal point (which you would do since you want to
>have positive air pressure fed into the nozzle to keep smoke and
>debris off of the ZnSe focusing optic) then laser light reflected
>from shiny surfaces will diverge to non-dangerous levels in a pretty
>short distance. This assumes you would be using a short focal
>length lens, which of course you probably would since you want a high
>power density and small spot for engraving annodized or painted
>metals, wood, etc. I use a 1.75" FL ZnSe lens with a 10 watt Synrad
>CO2 laser (actually doing about 17 watts) for most of the stuff I do.
>

I've only extensively worked on one CO2 laser. I suspect that you are
grossly underestimating the dangers. Shoot that laser at a carbon
block and see what happens. Maybe your peak output isn't that high but
the flash produced on the one I worked on is blinding. Then there is
the risk of specular reflections. Not to mention are the energies
involved, I can remember crashing every computer in the room just buy
firing the laser with a cover or two off. The storage cap for high
voltage is about a foot long and about ten inches wide.

There are many safety issues that have to be addressed with lasers, it
is not impossible for the average person to build and install one
though. Just that safety can not be glossed over. There is no
recovery after getting hit in the eye with one of these machines.

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