[Greg Q]

Hello all...I am a long time lurker here who is finally getting a few free moments to restore an old lathe*.

I have purchsed an Allen Bradley AC servo locally (ebay) to power the spindle, and I am wondering if there is a cheaper drive solution than the AB/Reliance/Electrocraft Ultra series drives?

Motor is a H-4075-R-HOOAA 6 pole three phase, 2.6 kW 3000 rpm

The motor has an encoder, and all I need is fwd/rev and speed control. I don't require indexing or step/dir. Closed loop would be great for spindle speed stability under load.

The correct AB drive is the 1398-DDM-030 or -075, neither of which seem to be all that affordable even on eBay. Connectors are another issue which I shall have to address.

*old lathe: AI Hembrug 11 X 20 toolroom. Originally had a 1965 Phillips Motronic variable speed drive and 2.5hp commutator motor, both long since dead. There is only a single speed pulley on the spindle. The original speed range was 45-4000 rpm and I'd like to get something similar with useful torque, hence the servo. The lathe does have a 4:1 back gear.

Thanks

Greg

[Al_The_Man]

You may want to confirm the type of commutation the motor has, generally AB has resolver for this, AC sinusoidal motors are a bit harder to match other drive makes compared to DC brushed or DC brushless, due to the commutation issue.
That is a big motor, so whatever make you get may be pricey and scarce.
Al.

[Jason3]

Greg, would you need the full 2.6 Kw? If not, perhaps a case could be made to buy a servo that will work with the 1398-DDM-019 drive (2.0 Kw rated), which seems to be more readily available at a reasonable price.

You may also be able to just use that motor with the 019 drive anyway, as long as you don't run it at max. power output continuously. I noticed while playing with AB's motion analyzer software that it recommended the 005 drive (0.5 Kw) paired with a .75 Kw motor for my application. I can only assume that the max. power requirement was of a short enough duration that heat dissipation from the drive would not be an issue. Perhaps someone (Al The Man?) with more experience could comment on the advisability of this.

On the issue of connectors, I haven't had any trouble getting the proper parts for my AB motors (Y series) and Ultra 100 drives. Let me check my manual, I might be able to point you in the right direction for your H series connectors too. I also have plenty of the OE power and encoder cable too, PM me if you'd like me to send some across the ditch

A question (related, but barely ) - does anybody know whether a motor with a multi turn encoder can rotate continuously to drive a lathe spindle?

Best regards,

Jason

[Al_The_Man]

A question (related, but barely ) - does anybody know whether a motor with a multi turn encoder can rotate continuously to drive a lathe spindle?

Jason

There is no problem using an encoder on a spindle motor, but if used by the CNC control for CSF or for threading etc, it is usual to put an encoder on the final spindle shaft.
In many cases, the motor encoder is used back to the drive for speed control.
Al.

[Jason3]

Greg,

I found the following for your motor (if you used the Ultra 100 series drive)

H series motor power cable P/N 9101-1382-???
H series encoder cable P/N 9101-1366-???

The last three digits are the length in feet.

These come up on Ebay regularly - sometimes cheap, sometimes not. The plug for the motor end of the encoder cable is here: http://www.mouser.com/Search/Refine....-MS3106F20-29S The drive end of the cable just uses a 20 pin Mini-D I think. The motor end of the power cable I couldn't find the plug for sorry.

There is no problem using an encoder on a spindle motor, but if used by the CNC control for CSF or for threading etc, it is usual to put an encoder on the final spindle shaft.
In many cases, the motor encoder is used back to the drive for speed control.
Al.

Thank you for that Al. I was really wondering whether a multi turn (absolute?) encoder could rotate continuously or whether it would count up to it's maximum then explode into a spectacular fiery inferno, or go back to 0?

I was planning to use a servo for a lathe spindle as Greg is, but using step/direction pulses from Mach3 to the drive for control. Would it be an acceptable compromise to use a toothed belt drive and rely on the motor encoder? I'd like to be able to use live tooling as well as do some threading.

Many thanks and best regards,

Jason

[Al_The_Man]

Thank you for that Al. I was really wondering whether a multi turn (absolute?) encoder could rotate continuously or whether it would count up to it's maximum then explode into a spectacular fiery inferno, or go back to 0?

I was planning to use a servo for a lathe spindle as Greg is, but using step/direction pulses from Mach3 to the drive for control. Would it be an acceptable compromise to use a toothed belt drive and rely on the motor encoder? I'd like to be able to use live tooling as well as do some threading.
Many thanks and best regards,
Jason

I guess incremental and absolute can be considered multi-turn, but usually if an absolute encoder is used, yes, you are going to run out of counts eventually, then you have to have a means in the controller to carry/subtract.
I do not use Mach, but AFAIK they cannot interface an absolute encoder?
The do not input an incremental even for threading, it is done by a ~1 pulse/rev of the spindle, to my knowledge.
This is not a closed loop back-to-the-controller system.
Al.

[Jason3]

I guess incremental and absolute can be considered multi-turn, but usually if an absolute encoder is used, yes, you are going to run out of counts eventually, then you have to have a means in the controller to carry/subtract.
I do not use Mach, but AFAIK they cannot interface an absolute encoder?
The do not input an incremental even for threading, it is done by a ~1 pulse/rev of the spindle, to my knowledge.
This is not a closed loop back-to-the-controller system.
Al.

Thank you, that answers my question - if I can use that motor at all, I'll have to use it for an axis drive then, not the spindle. I was hoping the servo drive, an AB Ultra 100 2.0 Kw DDM-019, and not Mach3, would interface a multi turn encoder, but now I think of it, I'm not even sure the drive has that capability. Might it be possible to use a multi turn encoder as an ordinary single turn incremental encoder?

Regarding threading, I will need to do some more reading I think - I had thought that Mach3 would assume the spindle was rotating at the commanded speed - which it should be, since the motor-drive loop is closed - and would drive the axis accordingly. I guess I don't really understand how a single pulse per rev gives enough accuracy to cut a thread in multiple cuts - how does it know exactly when the tool should engage the thread? Is it simply relying on consistency to hit the right start point each pass?

...Sorry, as usual I am getting off topic.

Regards,

Jason

[Al_The_Man]

I believe the Mach system looks at the pulse/rev of the spindle to sync the Z axis on each spindle revolution.
With a closed loop controller, typically the control will use the marker pulse on the spindle shaft encoder to engage the Z axis gearing, at this point, the Z axis will be directly geared off the spindle encoder for the duration of the thread operation.
Al.

[Greg Q]

Al and Jason thanks for your replies. I was away and am just now (at 1 AM) getting to read this thread.

Al, this motor's literature shows a 2000 line optical encoder. It is a sinusoidal motor, which as you say limits my options I guess.

Jason, I'll have to have a deeper look at Rockwell's knowledge base for the connector part numbers. This motor cannot use the -100 series Ultra drives according to the spec sheet...the 1398 200 series or the newer series (2098) drives are called out. I would dearly love some hand holding when it comes to wiring. Thanks for your kind offer...I'll contact you later about that.

Since I want to implement simple variable speed spindle motion I am wondering if I can use an MPG handwheel for that and the lathe's fwd/stop/rev switch for direction command. I'd like to avoid any other control especially any software imlementation, although I am unclear if the drive automatically uses encoder information to keep the motor on commanded speed, or if that requires a discreet controller.

Thanks again guys, more tomorrow.

Greg

[Jason3]

Hi Greg,

The connectors for your motor as listed in my book are as follows:

Motor power:
VAN-SYSTEM
#VCR06R20-4S

Encoder:
MS3106F20-29S

None of my usual suppliers has the motor power plug. RS components and Mouser both seem to have the Encoder plug. I guess if you can't find it anywhere you could always pull off the existing connector and change it to one you can get more readily.

I think the AB drives you mentioned will all take an analog (0-10v) input as well as digital, so you should have plenty of options for the speed control. I believe the drive does use the encoder to control speed very accurately, though I'm not 100% sure. Al might know.

Also, it's a curious thing your motor spec sheet excludes the Ultra 100 drive - the motor is listed in the motor tables for the Ultra 100 - it's no. 26, so when you set up the drive, you enter that for the motor ID. I'm pretty sure it would drive it fine, but you wouldn't get the full 2.6 Kw.

I'm intending building a lathe shortly, using a 1.8 Kw AB motor (chosen specifically because it's a good match to the ultra 100 DDM-019 drive) so will be very interested to hear how this goes for you. I'm hoping a servo drive with it's excellent speed control and good torque will give a very good result.

Al - thank you for the explanation, the threading mystery is becoming clearer...

Best regards,

Jason

[Greg Q]

Hi Jason...

With regard to connectors it appears that I might have to pay the Rockwell price for at least the motor cannon plug, although I might luck out elsewhere.

The encoder uses a simple four prong connector, so those parts you kindly spec'd should work.

I ended up with this motor purely because it was the first approximately suitable servo that I've seen locally in many months of looking, and it was new. Although it is a low inertia motor I am hoping that won't be an issue. Perhaps running big chucks or work might make for a problem mismatch but this is a 10" lathe after all.

The original commutator motor was a 2.5kW commutator (95 kg, 18" diameter beast with a 3/4" thick cast iron housing) so this 2.6kW servo should be as good I think. Better than a 2.2 kW induction motor at any rate.

I would have bought a smaller motor/drive combination if I had seen one-there was a Yaskawa 1.5 kW that went last week for cheap.

Here is a link to a 2kW servo conversion of a Monarch 10EE. The thread contains links to you tube videos of the machine in action which are very impressive:

http://www.practicalmachinist.com/vb...d.php?t=154967

Jason I'll send you a PM

Greg

[Jason3]

Hi Greg,

you might find it cheaper to keep an eye out on Ebay for the complete cables, if possible. There's a set up now, but they're dear. Generally though, those connectors are a horrible price on their own, I hope you can track something down ok.

I think the encoder plug is a 17 pin type? I double checked, but that doesn't mean I couldn't still be wrong

Thank you very much for the link - I had happened across the videos previously so I'm really looking forward to finding out more about that conversion.

Best regards,

Jason

[Greg Q]

An update to this thread...

I purchased an Allen Bradley 1398-DDM-075 drive from an eBay seller, and Jason very kindly posted some motor and encoder cable to me. I have connectors on the way too, so the project continues. Some (many) questions remain, but I am starting to see how this servo will work out.

Just to recap I am trying to avoid any control at all for the moment, instead relying on a potentiometer for speed input, a fwd/off/rev switch and an e-stop buss for the two e-stop buttons the machine will have.

I have a thermostatically controlled fan for installation too, but I have been informed that it may not be needed.


For now can anyone advise as to drive pulleys? My lathe spindle has a double B-section vee belt pulley right now...will that be OK with this 3 1/2 hp servo or will I have to make something else?