Connecting a 4th axis - Centurion VI/VM16

I have a 4th axis with a servo drive available and I'm wondering if I can connect it to my VM16 with Centurion VI. There are two sets of axis connectors available in the electronics, although I think one of them is used partially by the front panel encoder.

I know it's possible to set up an indexer with the system using the external event wait line, but that's not what I'm looking for.

Can the Cent VI controller manage a 4th axis in coordinated movement with the existing 3?

I'm guessing it's possible to do this with the newer controllers from Milltronics, but my Cent VI is working fine otherwise, and I'd be nice to just add it on.

Thanks,
Erik

You just need to wire up a drive and get an appropriate encoder and set the parameters.

I did this on my Cent 5, do you have the schematics for your machine?

It will show you the wires you need to run.

Ron

Quote:

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Originally Posted by rl49

You just need to wire up a drive and get an appropriate encoder and set the parameters.

I did this on my Cent 5, do you have the schematics for your machine?

It will show you the wires you need to run.

Ron

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I do have it... I can see how I'd connect the wiring, but is there anything that has to be set in the control, like encoder counts, or to enable the axis?

Thanks!

Erik

Yes I had the original parameter sheet from factory and that will show you the areas you need to change when you have the 4th wired up.

To enable the axis you go into the power parameters and change from three to 4, then power off and restart control.

Don't do that till you have rest of drive parameters set and verified your wiring is correct thru the diagnostic screens.

Do a search on this forum on adding a 4th axis you will need to set the counts for pulses per unit which is determined buy gear ratio of 4th and your encoder counts.

Do you have DC drives? if so you have to set on the 4th axis drive card the axis position jumper. per your parameter sheet.

I am not familiar with AC drives my 2 Milltronics have DC servos.

If to intimidating PM Sporty Bob, he will help you get it functional for a very reasonable fee.

Ron

Quote:

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Originally Posted by rl49

Yes I had the original parameter sheet from factory and that will show you the areas you need to change when you have the 4th wired up.

To enable the axis you go into the power parameters and change from three to 4, then power off and restart control.

Don't do that till you have rest of drive parameters set and verified your wiring is correct thru the diagnostic screens.

Do a search on this forum on adding a 4th axis you will need to set the counts for pulses per unit which is determined buy gear ratio of 4th and your encoder counts.

Do you have DC drives? if so you have to set on the 4th axis drive card the axis position jumper. per your parameter sheet.

I am not familiar with AC drives my 2 Milltronics have DC servos.

If to intimidating PM Sporty Bob, he will help you get it functional for a very reasonable fee.

Ron

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I do have AC drives. I'll review the parameter sheet for the ones I need to change - that's probably in the printed manual that came with the VMC. It's a direct drive 4th, so no gear ratio, or rather a 1:1.

I'll experiment and see how far I get. Great to know the controller is capable of this, I was worried I'd have to upgrade before I could use the 4th.

Erik

You may be 1:1 on the belt drive, but most units run a worm gear internally to spin the platter. Usually 60:1 or 90:1, then you need to know the encoder count per revolution of the motor so you can calculate encoder counts per 360º. You will also need to find/figure out backlash adjustments. It's not rocket science, but it's not trivial either.

Quote:

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Originally Posted by Brian L

You may be 1:1 on the belt drive, but most units run a worm gear internally to spin the platter. Usually 60:1 or 90:1, then you need to know the encoder count per revolution of the motor so you can calculate encoder counts per 360º. You will also need to find/figure out backlash adjustments. It's not rocket science, but it's not trivial either.

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There is no belt drive and no gearing. This table is essentially a large high torque/low rpm direct drive servo with a mounting plate attached. It was originally shop made for a factory purpose - it came with a very large collet chuck attached that was obviously professionally made.

So, it's zero backlash, and repeatability/accuracy should be <10 arc seconds. It's really nice, and rather heavy.

Mostly I think I'll need to tell the controller counts per revolution, and possibly set up to use one of the index pulses as a home location.

Erik

Not sure if you are going to get 10 arc seconds unless the encoder count is up around 130,000 per revolution. You'd have to check my math...

Quote:

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Originally Posted by Brian L

Not sure if you are going to get 10 arc seconds unless the encoder count is up around 130,000 per revolution. You'd have to check my math...

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My bad, actually... I looked it up, and the manufacturer claims +/- 30 arc seconds.

It doesn't have an encoder exactly, it has a resolver that feeds back to a position loop in the servo drive. The drive turns resolver position into a simulated encoder output with up to 819,000 ppr.

In case you're interested, max RPM is 30, torque is 295 ft-lbs.

How about a picture and brand id?

I don't have a picture handy, but the motor is a Yokogawa DR1400A direct drive servo with a Litton Industries UR1A-400N drive. It's an older servo, I think surplus from its previous life in a factory. The entire rotary axis consists of this servo, a table mount, and a mounting plate. The collet chuck I mentioned was previously mounted on the plate.

The chuck is honestly a thing of beauty, I almost wish I was using it. It's entirely stainless steel, made to hold some collet or similar that's almost three inches across. The nut on the thing is about four inches across and five tall. Combined with the hollow bore motor, you could put one end of a long bar in it as easily as a small work piece.

Needless to say, I'm hoping the whole thing works out.

It is also possible, depending on the era of control that the chip for the 4th and 5th axis were left out of the break-out board. Beside the pots on the breakout board in the card cage, you will notice 3 long chips soldered to the board beside the 1,2, & 3 axis pots, and 2 chip sockets beside the 4th and 5th axis pots. If those chips are missing, it will NOT work. Milltronics keeps the chips on hand, $50 Last time I checked. If they are missing, the control will just send a 12V signal to the added drive making it go wide open all the time.

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Originally Posted by allen mullis

It is also possible, depending on the era of control that the chip for the 4th and 5th axis were left out of the break-out board.

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Thanks, I'll have a look. My control seems to have been upgraded to an SBC or otherwise is on the newer side of hardware revisions if that matters. If the chips are missing, I'm pretty comfortable replacing them.

I'll post back with what I find out.

its easy to do, but as far as I know, they are out of production, so milltronics new old stock is the only place to get them. I've looked...

I would also recommend getting a Yaskawa Sigma 2 drive and motor. At least with that, all the parameters are known and should be about the same as your other drives.

Not really possible. The motor IS the rotary table, so that would defeat the purpose entirely.

Thanks, though.

so youre going to depend on the motor bearings and shaft to hold up to the pressures of machining? mmm, sounds sketchy, besides that, I hope they are big angular contact or something super rigid, axially and radially, otherwise it'll never be consistent. If the axis of the machine is capable of 1200# thrust, how do you think it'll hold up to shoving a face mill 3" from the centerline?

Quote:

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Originally Posted by allen mullis

so youre going to depend on the motor bearings and shaft to hold up to the pressures of machining? mmm, sounds sketchy, besides that, I hope they are big angular contact or something super rigid, axially and radially, otherwise it'll never be consistent. If the axis of the machine is capable of 1200# thrust, how do you think it'll hold up to shoving a face mill 3" from the centerline?

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I've been considering this. The bearings in this motor are designed specifically to do this, although machining may or may not have been beyond the original design.

The motor specs are on page 2-2 of this manual if you want to have a look, the type (in this version of the manual) is DR1A-400

https://web-material3.yokogawa.com/1..._end_en_01.pdf

I would point out that the bottom of the line koma 8" rotary had 3X's the torque, but the worst thing it'll do is fault the drive or crash, how bad could it be.?

Quote:

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Originally Posted by allen mullis

I would point out that the bottom of the line koma 8" rotary had 3X's the torque, but the worst thing it'll do is fault the drive or crash, how bad could it be.?

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I think you might be confusing clamp torque with rotary torque.

I know this is kind of an experiment, that's part of what makes it interesting. The newer Tsudakoma tables are direct drive like this servo, and their specs are similar.

Should be interesting.