Re: Re: replacing feed screw with a hydraulic cylinder

Jim

Wow, you're serious enough to drag it home. I'm going to answer with the
EMC controller in mind because it allows the widest range of choices for
drives and such. If you have another controller in mind, you should
filter out of this post the things that will work with it.

The first thing to check is are the Parker brushless motors really
steppers or are they brushless servos. The specs sound more like servos
with 15 running amps 45 stall amps and 7k max rotation speed. They sound
like 180 volt motors. Those little beggars are approaching five hp
(3360/750) each.

I'd also check the speed reduction stuff and see that it has no backlash
or slippage, unless you are going to use a separate encoder from those in
the motors.

Even if they are brushless servos, you could drive them with partial
power using something like the Gecko for brushless motors. 20 amp at 80
volt would get you about half speed and partial power. I'd talk to
Mariss If you think seriously about this. Otherwise you might find a
couple of drivers big enough on an auction site. If you are really
serious about these you will need to step up to the likes of Copley or
Advanced and get a drive setup for these motors.

If they are servos, you could use full CNC servo control with the likes
of a Servo-to-Go, Vigilant, or Pico board setup. The Pico is the cats
meow If you have in mind a laptop.

A full servo setup can use an unusually slow PC. Jon Elson runs his
bridgeport sized mill with a 100 MHz processor. The servo routines are
very quick. It is the stepper pulse generators that take most of the
power of the PC so if you decide on step and direction you will need a
somewhat faster PC. I use 800 MHz with the TNG and it works well here.
I also use a 200 MHz on my little grizzly mill and can easily get 5 K
pulses per second with steppermod.o and still have plenty left over for
surfing, writing and editing code and such.

I'd wait a bit on the z motor until you decide how you are going to
handle these big motors. If step and direction pulses from a parport is
your choice, I'd at least get a 200-400 watt servo and a matching step
and direction servo drive for it. That way you can get some speed out of
coordinated motion using all three drives.

Once you settle on the motors, then I'd start to think about ball screws.
The inexpensive ones from McMaster should do OK. When you clear out
the hydraulic cylinders you will have a boxcar sized space to put screws
in so don't skimp on diameter. I'd get 1" for x and y at least and a
pair of nuts for each with some belleville disk spring washers between.
You could turn down the ends of the screws for bearings or you could turn
out some couplings that fit over the screw ends and clamp to it. The
axis end covers are massive so there should be no problem with space for
the bearings and such. You could also replace the end covers with steel
plate and mount bearings, motors, encoders, and switches to it. That
would save some screw length.

The size of the z (quill) ball screw is not critical because there isn't
much travel. I'd think that you could get away with the 5/8 stuff but
again I'd use two nuts and preloaded washers to limit backlash.

The last thing to think about is the tool changer and related spindle
orientation stuff. The Moog tool changer can be run from a spare parport
and it should be possible to write an IO driver module for the EMC that
would handle this setup. Open loop spindle drive is already in there.
Spindle orientation is done by a lever that hits a flat on the spindle
shaft. Tool clamp and unclamp are by the little Baldor motor on top.
Turn it one way and it screws the threaded rod into the tool holders, the
other way threads it out of the holder. I'd write it in Tcl/Tk right
now but a program called ClassicLadder is close to being integrated so
that you could treat this whole PLC thing like a real PLC only free and
running under Linux with no proprietary communication protocols or
programs in the way.

Caution. Moog's tool holders are a bit different from anyone elses.

Hope this helps

Ray

>    From: "blown_mgb_v8" <jblackwood5@...>
> Subject: Re: replacing feed screw with a hydraulic cylinder
>
> Thanks Ray,
> I should have the machine here in a week or two, then I'll get
> another look at the head. Any recommendations for a stepper for the
> quill? From another post I gather that I should try to put a decent
> PC on it, like maybe a 1Ghz machine, but maybe the old P90 will do
> for setting it up. Any idea what has to be done on the x-y axis to
> mount the ballscrews?
>
> I've got some more info on the steppers I got with the machine:
> Parker Compumotor brushless, coupled to 20:1 Textron cone drives.
> Motor specs are 7000rpm max, 15A/45A stall current,6.51 Nm torque,
> 3.36Kw continuous (power?) and inertia is 2312g.cm sq.
> In appearance these motors compare favorably to the ones I saw being
> used in the 70's to prototype a Bridgeport CNC using cog belt drives
> and something like a 3:1 reduction. That system worked pretty well
> for the times.
>
> So would these be suitable motors for the Moog? If so, what can I
> get to drive them with?
>
> Jim