Advice on buying servos.

[Boyan Silyavski]

Apart from the obvious, what's the difference between AC and DC servos?

The obvious. The AC servo when 230VAC does not need additional transformer. This is best. Then cheaper servos could be 80VAC then you need to feed them 80VAC. But of course depending on price availability sometimes is worth making that PSU.

[Agathon]

The obvious. The AC servo when 230VAC does not need additional transformer. This is best. Then cheaper servos could be 80VAC then you need to feed them 80VAC. But of course depending on price availability sometimes is worth making that PSU.

So it's not the characteristic of the motor itself but just the driver? So are all servos dc motors or are some ac?

[Boyan Silyavski]

So it's not the characteristic of the motor itself but just the driver? So are all servos dc motors or are some ac?

Ahh, the AC does not have brushes. The DC servos with brushes are older motors with older drives that may need Voltage control +-10v, not pulse control. That could make things bad, as this type of controllers are expensive cause their only purpose is to retrofit old machines. Hence thats why i told you to search for drives that support Pulse and Direction

[Boyan Silyavski]

http://www.ebay.es/itm/CSDJ-02BX2-CS...cAAOSw0vBUl2gB

Thats what i have / the 400w/ and where i bought it from. And what i would recommend. Just check again for the details in the manual. You will not find anything better for the money.

[Agathon]

http://www.ebay.es/itm/CSDJ-02BX2-CS...cAAOSw0vBUl2gB

Thats what i have / the 400w/ and where i bought it from. And what i would recommend. Just check again for the details in the manual. You will not find anything better for the money.

Just noticed that your Samsung drivers appear to be the same as the Omron that I have. Obviously all made by Yaskawa and branded to suit.

[Boyan Silyavski]

Just noticed that your Samsung drivers appear to be the same as the Omron that I have. Obviously all made by Yaskawa and branded to suit.

By Iskawa not, by Parker i believe. But yes...

[Agathon]

By Iskawa not, by Parker i believe. But yes...

I noticed on the RS (Rockwell Samsung) website that they started making Yaskawa inverters under license in 1989 - presumably the servo drives followed on.

[Agathon]

Ahh, the AC does not have brushes. The DC servos with brushes are older motors with older drives that may need Voltage control +-10v, not pulse control. That could make things bad, as this type of controllers are expensive cause their only purpose is to retrofit old machines. Hence thats why i told you to search for drives that support Pulse and Direction

Thanks, sorry for being so dim about this - it's begging to make sense. Also many thanks for the links.

BTW. Apart from power, is there any difference between servo motors used for positioning ie x,y,z axis motors and servos used for spindles?

[Boyan Silyavski]

Thanks, sorry for being so dim about this - it's begging to make sense. Also many thanks for the links.

BTW. Apart from power, is there any difference between servo motors used for positioning ie x,y,z axis motors and servos used for spindles?

Yes and No. Any servo motor rightly belted could serve for spindle. But then comes the RPM. The servos that are meant for spindles could spin at higher RPM and have slightly different curve. We are talking about typical motor that will be connected to BT30, etc spindle via belt. As Yes, you could gear up any servo motor but then you need bigger more expensive motor.

these are the servo spindle motors. they gto up to 15k rpm https://www.aliexpress.com/store/pro...809932059.html

[Agathon]

Yes and No. Any servo motor rightly belted could serve for spindle. But then comes the RPM. The servos that are meant for spindles could spin at higher RPM and have slightly different curve. We are talking about typical motor that will be connected to BT30, etc spindle via belt. As Yes, you could gear up any servo motor but then you need bigger more expensive motor.

these are the servo spindle motors. they gto up to 15k rpm https://www.aliexpress.com/store/pro...809932059.html

Thanks again. Not cheap then.

While I'm here. Am I right in thinking that the advantage of an absolute encoder over incremental is that the motor position is known after power-down?