Re: need help on CNC

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "stfstairbuilder"
<stfstairbuilder@y...> wrote:

> I have a CNC with servo motors but no drives or controller. I am
> hoping that you guys could give me some advice on what I need to

get

> this thing up and running. Right now all I have is a machine with
> all the mechanics attached, as well as the motors, but that is as

far

> as the wiring goes. Can any of you hook this up, or even give me
> some advice as to what goes where? I am located in central
> Kentucky. Any help is appreciated. Thanks, TK Sapp

Ok, I'll take a shot.

Knowing the kind of machine would be really helpful to people trying
to help you. Your machine sounds kinda Bridgeport BOSS like. That
means some pretty hefty servo motors and a 3 phase spindle motor.

I'm new at this BTW. My machine is about 75% done. But the spindle
turns and I have sh$#@ load of DC power!

Here's my basic parts list in big pieces:

BIG DC Power Supply. For the motors at the appropriate voltage and
amps for the motors. Hopefully there is name plate info on the motors
that you can Google and hunt down the info on the motors. If not
search these archives for info on how to put some voltage in them and
back figure the internal resistance. This will allow you to figure
out the electrical characteristics of the motor. I am NOT an expert
on this, just read the postings about it.

Obligatory Safety Blurb - If you decide to build a power supply,
watch out! These things have really big capacitors in them. If you
screw up you will probably set something on fire and you might kill
yourself. Be careful, not scared.

Motor Controllers. Pico's stuff looks good and I wish I would have
done that. I got the Gecko drives and am going to get the Pico board
that allows closed loop operation of the servos with the Geckos. The
Geckos I have are open loop to the computer but do fault after so
many missed steps based on feed back from the encoder. Geckos are
very well built however. Very impressive stuff.

A machine control computer. Lots of opinions on what works. I would
say if you can get a 2 - 3 year old Pentium class machine you should
be good to go.

Parallell Port Breakout board. A lot of people are using Bob
Campbell's. It's got good opto-isolation. But that is not a must. You
can go with a cheap break out box. The Geckos have opto isolators
built in for instance.

Sheilded Cable - Belden. Conductor configuration is up to you I
guess. You'll have to figure stuff our based on your loads. But
sheild everything. Seriously.

Variable Frequency Drive (VFD) - I will hazard a guess that you got a
big machine with a 3 phase primary or spindle motor. You probably
have 220 single phase in your garage or basement at best. Several of
these message boards have beat this subject to death. The VFD is
really the right way to go. Other less desireable options are to
change the motor, get a rotary phase converter, play games with
wiring and the windings and capacitors and ??? in some way I have
never understood, or have the motor rewound. I did the $$ and time
research and VFD is the way to go. (Warning, incoming VFD flames!)

"Little crap" - Wires, screws, nuts, bolts, electrical enclosures if
needed, mounts, etc.

Ball Screws - Maybe. If your screws are worn beyond what you want to
deal with, then you will need to replace them.

Machine Control Software - I am going with EMC. There are many others
that people like.

CAD / CAM Software

The most powerful PC you can afford to run the CAD/CAM package. All
my stuff is a couple of years old and it runs fine, but more power
just makes this easier.

Those are the big parts. I've probably left out 100 little things.

Have fun! Really.

-jd