[erikjgreen]

I'm working on rebuilding/updating my Lagun 250 CNC milling machine, and I have a question about the servo drives.

Specifically, for those of you with experience in both products, how would you say the Viper drives (any model) compare to the Servo Dynamics 1525 drives?

By compare, I mean do they give similar performance, how well do they work with various servo sizes, etc?

The main reason I ask is that the SD drives seem to be somewhat in demand on the used market, and I could sell them and buy vipers with some cash left over.

Also, and more importantly, would the viper drives not make that #$%*(#$ squealing and whining noise at the motor when they're on?

My servos are Baldor "Big Mho" running at 125v DC. They have an encoder and tach each (probably will disconnect the tach) and my control hardware is a Mesa 5i20 with the 4 port analog servo control board and the 8/16 IO.

Probably if I went with the vipers I'd get 3x viper 200 drives.

Thoughts or recommendations? Should I be looking at other servo drive models instead?

I did have the thought that maybe I could dump the DC servos and drives entirely, pay the upgrade cost and go with AC servos, but I'm not sure what that would buy me.

Erik

[vidio1]

You might want to look at the Dugong too......

CNC4PC

[Al_The_Man]

One significant difference is the SD1525 is ±10vdc analogue control and the Viper is step/dir.
If you got squealing from the SD's, the gain may have been a bit on the high side.
They were most likely velocity control rather than the more current torque mode?
Al.

[Larken]

Whats the continous current rating of the motors ?
Your power supply is 125 volts ?

Larry K

[erikjgreen]

Servo specs are as follows.

Baldor Big Mho Permanent Magnet Motor
> Model # 4201990
> 50 oz-in
> 120 VDC 2500 RPM
> 10 AMPs Constant, 39 AMPs Peak
> Tach output 7.0 V/KRPM
> Volt Constant Kc=40 V/KRPM
> Transducer = Encoder 1000L

The step/direction control isn't a problem, it'd just make the analog servo control board from mesa redundant... the main 5i20 board can do step/direction just fine.

So you think if I tune the servo loop once I have the new electronics in place, I'll end up with no (or nearly no) noise when the servos are idle? I was reading up on the 1525s, and it looks like they have a 16khz pwm frequency, IE audible range.

I'm planning on not reconnecting the tach, since it's not needed. If I use the existing encoders, is 1000L resolution enough? I'm going to close the loop inside EMC2 for the servos and also limit switches and e-stop, so the 1525s will just handle pwm output and nothing else.

Would upgrading to eg. AC brushless servos buy me anything? I suppose faster moves and more resistance to feedback forces, but that's probably not worth it? I suspect the mill frame is heavy enough to handle additional force.



Erik

[erikjgreen]

Al -

I'll have to look at the settings on the drives to tell what mode they were in, but I suspect velocity mode with tach feedback.

Larry -

Yes, the power supply was 83 volts AC rectified to 125.

Erik