He sold the old amps. Then used the money to buy AMC servo amps off ebay.
They are top of the line and sell for peanuts. They need 0 - 10 volt from
computer, nothing else. Encoder goes to control and control software does
everything. I think EMC works the same.
I think he likes money. AMC work better and cost less. Plus, myself and
others have no interest in supporting every damn flavor of servo amp. Just
try to buy a replacement amp for your machine. I've got a dozen spare AMCs
on the self right now and can swap one in less than five minutes if a
problem is suspected.
That's cool, great to know. If I can get modern servoamps that would
be more compatible, and recoup their costs, I will do so as well. If I
do that, I just might free up enough space inside the control box to
stick the PC right in there.
I think you got brush servos, verify this. Here's one offer:
You need three. I'd get a spare.
Thanks Karl, I will verify this very soon.
I now agree with you in that the more electronics I will replace, the
better off I will be.
A couple things that may open up your options.
Copley Controls makes amps that are very similar to AMC's. I've used
both and personally prefer Copley, but most of my experience is a few
years old and the differences are pretty insignificant.
Also, some of the more recent generation amps are compatible with both
brush and brushless motors.
How familiar are you with this. I'm sniping a couple auctions where the
description is brushless servo. The check sheet says the servo amp does both
Then I go to the individual drive manual and see nothing about brush servo
connection. Brushlees servos have three hot wires, do you just use two of
the three on a brush type? There must be more, brushless is totally
different electical output.
On Sat, 13 Mar 2010 14:41:26 -0600, "Karl Townsend"
I haven't used a brush motor in a very long time, and don't remember
setting up a brushless amp to run a brush motor. I've just noticed the
brush/brushless feature showing up in the specs. I couldn't find the
setup in the manual, either, but I did find this on AMC's FAQ page...
Based on that, I wouldn't be surprised to learn that older AMC and
Copley brushless amps will also drive brush motors. Perhaps, because
of declining deamand, it's simply no longer economical for them to
produce amps specifically for brush motors.
Thanks for the excellent advice. Now I can buy up brushless drives and be
able to use them both ways. Just an FYI, I keep enough spare parts on hand
to make about three machines like Iggy's into a Galil/Camsoft machine. Right
now, I'm looking for drives to do my Matsuura bedmill. its a twin spindle
machine that weighs about 16,000 lbs. - just the thing for light home hobby
I'm looking for servo drives that run at 340 VDC with a 20 amp continous
rating to do the axis. The spindle is a real problem, I may have to mount a
10 hp 3 phase and VFD as finding a servo drive at a reasonable price is
unlikely. From there on all CNC controls are about the same. I use a Galil
card for motion control and like the Nudaq I/O cards going to Opto22 boards
for isolated I/O. A PC with Camsoft runs the whole thing.
On Sat, 13 Mar 2010 17:49:13 -0600, "Karl Townsend"
I'd check whether this is in fact true for the older drives before
buying too many. I did check, and the model numbers for some of the
current drives, that are capable of both modes, are the same as those
in a 1985 AMC catalog I had in my files. But it's possible there have
been revs to the drives that enable both modes of operation, even
though the model numbers have not changed.
I thought I had an older AMC brushless amp around that I could test,
but I couldn't find it in the obvious places.
I highly doubt that you can run a brush type motor with a brushless
servo. The power output of the brushless servo is completely different
configuration than a brush type servo.
The motors on the bridgeport tmc151 are brush type servos. I have
maintained several systems for customers and the controls as well as the
whole systems were comparatively free of problems. The biggest problem
was that the customer let the memory battery go dead and in turn it
would lose the parameters which would then have to be reloaded into the
memory after the battery was replaced. The big problem with the tmc151
is that you are limited to a three axis machine. With a new pc based
control you could add other axes including a two axis rotary table which
would really be interesting to program.
It is important to match the power of the drives to the application. If
anything you want the drives to have a little extra torque or HP so that
the acceleration/deceleration of the machine parts are reasonably fast,
otherwise you will have to slow everything down to keep the commanded
position from the PC close to the actual position of the cutting tool.
Encoder feedback to the servo will give you the best control of the
tool position. On a brushless servo the encoder has to be set to the
shaft position of the motor or it will not run properly.
It's not intuitive to me either, but AMC advertises that fact, and the
link above tells how to configure their brushless amps for brush
I assume you're talking about the commutation feedback here. Some
drives use the motor encoder to report rotor position to the amp, but
the standard, and far more common, scheme is 3 Hall sensors in the
motor supplying this information to the amp. The Hall sensors are
built into the motor and non-adjustable.
The ones that I installed all had an external encoder that had to be
timed to the rotor of the motor. The encoder was also used as feedback
for speed control. The brushless motors with the hall effect sensors
installed internally are definitely easier to set up but are less
versatile for certain applications. Most of the motors I see are AC
permanent magnet motors, mostly Fanuc. I use a some Toshiba spindle
motors and drives which work out fine. With a tool changer you have to
have spindle orientation which can get to be a problem with the wrong
I never did get into the difference between a brushless DC motor and an
AC permanent magnet motor, they seem to be basically the same.
Easier if you have the data to get the phasing between the Halls and
the motor windings right. A pain in the butt if you have to do it by
trial and error. There are, I think, six possible Hall connections
once the winding connections are made, a couple of which may appear to
run the motor, but aren't correct. I've used drives with resolver
feedback that do a little dance to determine the resolver to winding
orientation. I've also installed some very sexy Control Techniques
drives that I believe do something similar if you're using encoder
You're right, there's no difference. AC permanent magnet is more
descriptive. The motors are essentially 3-phase permanent magnet
synchronous motors with rotor position sensing added for the
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