Re: [CAD_CAM_EDM_DRO] How naive am I?

20,000 holes! Anything you buy is probably going to cost a lot more than
something you can make with a welder yourself because they know there are
people who either lack the motivation to do it themselves or can't. Many of
the cutters are quite easy to make if you look at them. They're mainly the
bed itself, which is however big you need it and just made of slats that you
can replace after a while when they get cut to shreds. On either side of the
bed, along it's longest side usually, you have two rails supported a few
tens of centimetres off the bed. These rails can be as simple as cold angle
iron turned upside down to make a pyramid shape. You then make two seats to
sit on these angle iron rails, support these seats using bearings, if you
know what I mean. So it looks like so:

SSSSSSSSSSS
B B
B /\ B
B / \ B
/ \

B = Bearings, S = Seat

Four bearings, two either side that rest flat against the angle iron, will
support it quite securely and you have now made something that looks like a
skate with it's wheels bent inwards. Now you add a stepper with a rubber
wheel perhaps on top of the seat angled down to meet the angle iron like the
bearings do. Now when the stepper's spindle starts the rubber wheel
propellers the seat back and forth along the rail. There is a chance that is
going to slip as it accelorates if you don't force it to meet with the rail
hard enough and then you're adding lots of drag, so other possibilites like
very long toothed belts or rack and pinions are an idea. Now you have two
seats you connect between them with a ridged beam (I think Torchmate uses I
section or something like that doesn't it?), and add two angle iron rails
along this. All together this means you can move in one direction, let's say
it's X on your bed. You make another thing similar to the two first seats
which will now cover the Y axis. It must sit on two angle iron rails going
between the ones that make the X axis otherwise it will slip off, or atleast
be very unstable. Add a stepper etc, now the cutting bit will move in X and
Y. Now you need to make a bit to sit on that last seat to hold the torch or
router. This is mounted to the last seat you made so it can travel in and
out along the Z place, perhaps two or more solid bars to form the rails. A
stepper on a screw that passes into this support for the router or torch
will let you move the tool into arc striking distance with the work. I've
seen rack and pinions used for this movement as well, even soleniods since
it only has to move in to a set distance or pull back a set distance with
plasma cutting. Done. Plasma cutting is not going to be micron accurate
obviously so there isn't really such a problem with building the machine
yourself by hand so long as it's accurately done. Instead of angle iron
rails you might prefer to use solid metal rods and linear bearings? It'd be
more expensive but it'd probably be quite easy and more accurate. There
isn't much on the internet about home built tables, I remember seeing one
that looked particularly good using a Thermal Dynamics cutter and it was
painted a light blue colour. If you search around you'll probably find just
about all the sites there are on the cutters in a few afternoons. It is
easily within your grasp to make a table for your garage. One guy built the
table then used the table to build a tractor and the tractor to knock a tree
down in his yard. Talk about the long way round!

John H.

> I am joining this group to find out how difficult it would be to
> build a CNC router/plasma cutting table. My application is geared
> towards homebuilt aircraft. My goal would be to accurately cut
> aluminum sheet to size and drill holes for rivets, and perhaps even
> to deburr and dimple the holes too. One of the most time consuming
> task of building an all-metal airplane is measuring and drilling the
> some 20,000 rivet holes. I am looking at multi function table that
> would be able to handle a plasma cutter and router. My design
> inspiration is the Torchmate table but this design seems somewhat
> expensive to me. Any thoughts? Thanks.
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Manager
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>