NordicCNC's build log

[jarjar]

Delta is Taiwanese and they make proper cheap servos. Also 400W Yaskawa servos can be found rather cheap (~$400 motor + drive + cables). Most similar sized servos have the same ratings. 6000 rpm is nothing special, same for absolute encoders.

I asked a quote for the latest ASD-A3 drives from Delta with a 750W servo, 24-bit incremental/absolute encoder. Price was $350.

But Jazz is right to warn you. Servos are more complex than steppers. I went Yaskawa just because their manual is more comprehensive than the Delta one.

[JAZZCNC]

Delta is Taiwanese and they make proper cheap servos. Also 400W Yaskawa servos can be found rather cheap (~$400 motor + drive + cables). Most similar sized servos have the same ratings. 6000 rpm is nothing special, same for absolute encoders.

I asked a quote for the latest ASD-A3 drives from Delta with a 750W servo, 24-bit incremental/absolute encoder. Price was $350.

But Jazz is right to warn you. Servos are more complex than steppers. I went Yaskawa just because their manual is more comprehensive than the Delta one.

I wasn't referring to Delta when I said Chinese servo's it was a general point between Cheap and Expensive Servo's. Regards the Yaskawa motors -drive-cable package then can you post a link to where your buying because that's a very good price. What model is that.?

Regards the speed I don't see many that are rated at 6k rpm in the lower price ranges, 3K rpm is a typical rating with incremental encoders. Yes, they can be run up to 5-6K rpm but they are not rated to run at that speed constant.!

[jarjar]

I wasn't referring to Delta when I said Chinese servo's it was a general point between Cheap and Expensive Servo's. Regards the Yaskawa motors -drive-cable package then can you post a link to where your buying because that's a very good price. What model is that.?

Regards the speed I don't see many that are rated at 6k rpm in the lower price ranges, 3K rpm is a typical rating with incremental encoders. Yes, they can be run up to 5-6K rpm but they are not rated to run at that speed constant.!

There are currently tons of offers on Ebay for SGM7J-04AF + SGD7S-2R8A00 at $450 new. I bought one like this a while back for a little less. I just asked for cables and they included them with no extra charges.
You can even buy the model with absolute encoder separately for less (SGM7J-04A7 $160 + SGD7S-2R8A00 $260)

I didn't say 6000rpm is the nominal rating, but it's still useful for short rapid moves.

[JAZZCNC]

There are currently tons of offers on Ebay for SGM7J-04AF + SGD7S-2R8A00 at $450 new. I bought one like this a while back for a little less. I just asked for cables and they included them with no extra charges.
You can even buy the model with absolute encoder separately for less (SGM7J-04A7 $160 + SGD7S-2R8A00 $260)

I didn't say 6000rpm is the nominal rating, but it's still useful for short rapid moves.

I'm surprised how much these have dropped in price, last time I looked, which must admit is quite some time ago, Yaskawa kits were like $900-$1100 range for 400W. I've never used them for this reason so I may look at these when a suitable job comes up.! . . . How easy or hard are they to setup/tune.? Do Yaskawa supply the Sigma tuning software for free.?

I'm surprised the absolute encoders are cheaper as well, not as many controllers about that can accept Absolute positioning so I would have expected them to be more. Thou absolute systems and Bus/Ethercat drives/controllers are coming down in price and more popular so maybe this is the reason.?

[jarjar]

I'm surprised how much these have dropped in price, last time I looked, which must admit is quite some time ago, Yaskawa kits were like $900-$1100 range for 400W. I've never used them for this reason so I may look at these when a suitable job comes up.! . . . How easy or hard are they to setup/tune.? Do Yaskawa supply the Sigma tuning software for free.?

I'm surprised the absolute encoders are cheaper as well, not as many controllers about that can accept Absolute positioning so I would have expected them to be more. Thou absolute systems and Bus/Ethercat drives/controllers are coming down in price and more popular so maybe this is the reason.?

Yes of course software is free. I'm not yet to the point of tuning but having read the manual multiple times I don't expect many issues. You start with the auto-tuning and fine-tune from there.

IMO rotary absolute encoders are not worth the hassle. Their only use in a router/mill context is to spare you the homing after power-up. And obviously the controller must be able to interpret the special Yaskawa protocol and I think no hobby controller can at this point. It could be done with some knowledge with LinuxCNC+Mesa.

[JAZZCNC]

Yes of course software is free.

No, it's not obvious really, it's not uncommon for high-end Servo manufacturers to charge for specialist tuning software if not using their own controllers just like it's not uncommon for PLC providers to charge for programming software.

I'm not yet to the point of tuning but having read the manual multiple times I don't expect many issues. You start with the auto-tuning and fine-tune from there.

I'd be interested in hearing how you get on with tuning. What controller and which method of control +/-10v or Step/Dir .?

IMO rotary absolute encoders are not worth the hassle.

What hassle.? Far less wiring and setting up far as I can tell, esp if using Bus type.! . . . I've not used any yet but soon will be doing so I'll let you know.

[jarjar]

I'd be interested in hearing how you get on with tuning. What controller and which method of control +/-10v or Step/Dir .?

Step/Dir is the most reliable and flexible. With analog +10V you're forced to control the servo in velocity mode.
With Step/Dir you can control it in position or velocity mode.
I'm also convinced position mode (letting the drive close all the loops internally) is the best way since the drive can do it much faster than the controller.

What hassle.? Far less wiring and setting up far as I can tell, esp if using Bus type.! . . . I've not used any yet but soon will be doing so I'll let you know.

The interface of the servo drive is a whole other topic and has nothing to do with absolute encoders. For absolute encoders you need to connect a battery and 2 extra wires to request the position data when using the standard analog/pulse-train drives. And as I said above, the controller needs to be able to read the position data for the specific servo manufacturer.

Now if you use EtherCAT drives, indeed you just need a RJ-45 cable between the drive and controller (but still need the battery). But you have 2 more problems:
- you need to actually find one of those rare EtherCat drives. Yaskawa for example doesn't sell them in the Chinese market. So you would need to go through an official reseller and pay $$$, or buy another brand: Omron / Panasonic / Mitsubishi / Delta / Estun...
- be prepared to spend weeks and write some C to make the controller talk to the drive (LinuxCNC in this case, the only one supporting EtherCAT).