Has anyone worked with bridgeport Interact CNC mills?

I'm currently consulting with a fella to refit one to Camsoft. Strictly a consult by phone and email job for me.

Karl

So, what is that guy replacing? Just the controls? Or servoamps too?

thanks Karl

i

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.

Karl

Karl, do you know why he sold the old amps?

i

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.

Karl

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

I think you got brush servos, verify this. Here's one offer:

You need three. I'd get a spare.

Karl

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.

i

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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.

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Ned,

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.

Karl

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 use.

Karl

Karl, so, in a retrofit like that, what would you use?

i

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.

Karl

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.

John

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.

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 operation.

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 drive. 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 feedback.

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 electronic commutation.