RE: [CAD_CAM_EDM_DRO] re: gantry router

Les -

Very sophisticated! Sounds like you had a nice shop available for
constructing your gantry machine.

Yes, the egroups webpage has a "files" dropbox that you can use to
post pictures. I've never tried it, so I can't help much there.

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Les Watts [mailto:leswatts@...]
Sent: Thursday, January 04, 2001 12:03 AM
To: CAD_CAM_EDM_DRO@egroups.com
Subject: Re: [CAD_CAM_EDM_DRO] re: gantry router

> Got any pictures???
>
> Carlos Guillermo
> VERVE Engineering & Design
>

Yes some old ones Carlos.
I'm not sure where I could post them... is there a drop box or
something for
this list?

It is a welded space frame gantry machine using THK 45 mm
linear rails and preloaded ballscrews. The gantry is driven by
dual screws
through low backlash spiral bevel gearing from a jackshaft.
Rather than XXYZ control the minor pitch variation between the two
x screws
is taken out by a simple cam/rotating ballnut.
Its an old victorian trick to make a leadscrew's pitch more
accurate than it
was manufactured to.
X moving mass is 450 kg. A modular system allows conversion to 6
axis. Right
now it has an indexable theta half axis.

The linear way mounting surfaces are hand scraped flat and
parallel to plus
or minus .0005" on a good day. I say that because variations in
the concrete
foundation are often more than that with temperature gradients.

I designed it with grape finite element analysis and made all
components
including ballscrew bearing blocks and transmission components in
the shop
in chicago. I moved it down here to Georgia in my woodworking shop
and it is
just about done.

Servo amps are Copley controls 15 amp 90v. Servo motors
(not installed yet) are to be brush. About 800 oz in peak is
required for x.
Rather than inertia matching the servos are about one quarter the
mechanism
impedance to minimise
Torque requirements. Encoders are 512x4 counts per 5mm
linear travel.

It took about a year and a half to design and build in spare time.

I am now taking a respite from surface grinding and turning
and milling aand welding to review the software needs. I have
written a
collection of motion control code for other experimental stuff in
the lab. I
did some real fast servo voice coil stuff. Now I must either put
together
those routines and parsing in the final control code, buy someone
elses, or
use EMC. I am spending the next few days deciding which one of
these is the
most prudent thing to do. I need to be up and running in about
two months.
Obviously I am trying to get a high end machine on a very small
budget .
Small shops usually don't get to have machines of this size.

Having made the plunge from hobby to profession I am tending
to make too much myself and not outsource enough!!

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.rabun.net/~leswatts/wattsfurniturewp.html