Re: How do I add CNC to a lathe? - To James and others

James (and the others), thanks for the help

In answer to your question about advice on how to convert a
Bridgeport, I can start by showing how I proceeded with mine. There
seem to be an infinite number of permiatations of non-standard
equipment which has been hung on various Bridgeports over the years.
Mine has an aftermarket table (the Position Wizard - why?, I don't
know), a very nice custom Z axis, and a pneumatic Brake, Spindle lock
which were a challenge to reverse engineer without schematics and by
using an ohm meter on their toggle switch and relay contacts.

I've posted some photos of my conversion in the Photos section of
Master5@yahoogroups.com in
a folder called "Washcomps CNC Bridgeport" that might help some of
you out.

This is a stepper motor based design. While servos do have some
advantages, the steppers came with my machine (so its stepper
based). It is now designed to take advantage of MACH1 controller
software, but should be compatable with most others. The old NC
controller was removed and the parts salvaged were from the power
supplies (completely reconfigured), the enclosure and the front panel
switches. I also kept the wiring harnesses going from the controller
to the Bridgeport and the stepper motors as they were covered with
liquid proof flexible conduit (Sealtite) and went to convenient Mil-
Spec amphinol connectors. The mill had the X, Y, Z axis attached and
ballscrews so I of course took advantage of them. I'm using a
parallel breakout box which puts 12v D.C. on some of its output pins
which I'm using for my control relays. The Brake and Clamp circuits
are run off of a 24v AC power supply which came with the original
machine (and I saw no reason to re-invent the wheel). I am currently
using a wireless keyboard and will probably add a wireless game
contoller shortly.

If you have problems reading the downloaded copy of the schematic,
let me know and I'll send you either the original JPEG or the
original Visio copy so you can modify it.

Among other things it has a schematic that shows:

Limit and home switch setup with a safety interlock
Power brake and clamp with safety interlocks (these came on the
machine and were fun to "reverse engineer", but are probably unique
to my Bridgeport). Forced "Start" Button as safety after software is
initiated Stepper motor drives do not receive motor power until
after "Start" button is pushed simultaniously with the screen RESET
button so both hands are needed to start the motors. For those of
you who are already one handed, taking the contact out of the limit
switch circuit will allow startup with just the START button. An
added advantage of this circuit is that the steppers are not powered
unless a program is executing. This reduces heat generated as well
as allowing manual cranks (I don't have any ;( ) to be used will the
control software is active.

Stepper motor wiring shown for NEMA 42 Sigma SloSyn motors used by
Bridgeport
(Different terminals than Superior Electric)

Front picture of controller shows large white heat sink (20"x10")
onto which stepper drives (API CMD-260, similar specs to the Gecko
210, but can go a little higher on the current rating) are mounted
There are two fans blowing up (from PC compartment) across the bridge
rectifiers, one directly mounted on the drive drawing the most
current and two fans in the door of the cabinet to get rid of the
heat. The two Y axis limit switches and one of the X axis switches
are shown mounted in a photo

Have Fun!

Regards,
Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "James Owens"
<wotisname@l...> wrote:

> Hi,
>
> I uploaded some pictures of my Harrison CNC/Manual lathe to the

TurboCNC

> group, give them a look and I'll be happy to answer any questions

you have

> now that it is all working. There are a number of fail-safe bits

that stop

> you running it in manual power feed when it is in CNC mode and vis-

versa.

>
>

http://photos.groups.yahoo.com/group/turbocnc/lst?.dir=/Harrison+280+M
anual+

> CNC_Trainer&.src=gr&.order=&.view=t&.done=http%

3a//photos.groups.yahoo.com/g

> roup/turbocnc/lst%3f%26.dir=/%26.src=gr%26.view=t
>
> I'd like to know how you went about converting your Bridgeport as I

have a

> clone I'm just starting work on.
>
> Regards,
>
> Terry
>
> > OK I'm hooked. I just finished the hardware end of converting my
> > Bridgeport to CNC and now I'm ready to tackle my lathe. Problem

is,

> > I'm clueless from a mechanical standpoint (I'm OK now with stepper
> > electronics and control circuits - I think) where to begin.
> >
> > I have a Logan lathe circa 1943. The max swing from the center of
> > the chuck is 5.5" (does that make it an 11" lathe?). The gears to
> > make various threads have to be hand changed on this model. It's
> > belt driven. It does have motor driven feed on the carrage and

the

> > cross feed. Any guidance on where/how the motors should be

mounted,

> > as well as any other mechanical things to look for would be
> > appreciated. Any place I can look for diagrams? Is this project
> > even worth it or should I leave well enough alone?
> >
> > Thanks and regards,
> > Jeff