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rnr107
08-11-2012, 05:02 PM
Hi all,
I am trying to build something like this:
Mini Machining Center - final design 4th axis - scratch built servo powered - YouTube (http://www.youtube.com/watch?v=b2-Kdud7eiA)

It seems fairly easy to buy stepper motors and drives but
I can't find any place to by a Servo motor + controller for a resonable price...

Where do you guys buy your Servos + drives from ?

I tryed with a stepper, but it is far too slow in RPM to be usable as a spindle...


Thank you,
Laurent

Jonathan
08-11-2012, 05:31 PM
Brilliant commentary on that video!

I'm planning on getting servos when I make the new gantry for my router since it will be too heavy for steppers to be economical. Recently I contacted the following supplier in China and they are the cheapest place I have found so far:

Find All China Products On Sale from Hangzhou Mige Electric Co., Ltd. on Aliexpress.com - 2 sets of 750 watts AC servo motor kits and 1 set 750W servo motor drive with brake with 6 sets 10 meters cables,2 sets 400w ac servo kit and 1 set 750w servo k (http://www.aliexpress.com/store/100742/search?SearchText=750W&minPrice=&maxPrice=&filterAllSearch=false&freeShipCountry=)

She quoted:

750w servo motor cost US$145 EXW per piece
600w servo motor cost Us$140 EXW per piece
740w and 600w use the same model driver
SDB08NK0 driver cost US$230 EXW per piece
per set (motor and driver) include 3 meters cables and connectors free of charge

That's not including shipping, so I asked for the price for 3 of the 750W motors and drivers with 6m cables and shipping was $120 so $1245 total, which is 260 per motor/driver pair. They run directly from the mains, so that's everything you need.

Also at the end of this year they can supply the motors with 17-bit encoders, which would be brilliant for a 4th axis. That does however add $80 to the cost of the driver and $80 to the motor. It's going to be a long long time until I can afford to get anything like this, but I'm researching now so I know what is the best option when the time comes. I'm also thinking of getting one of the larger motors, around 2kW, for my lathe to do something like in the video you linked to...

Another option is DMM servos in the USA.

Which stepper and driver did you try?

rnr107
08-11-2012, 07:21 PM
Hi Jonathan,
Thank you for the reply ! :-)
I use the 2M880N Microstepping Driver from Zapp and the stepper is a 3Nm I got from a Boxford CNC mill a while ago...

Not a bad price at all! The servos, do they come with encoders ?
Also, I see they have motors with DC brakes ? What are these for ?

Laurent

Jonathan
08-11-2012, 07:40 PM
Not a bad price at all! The servos, do they come with encoders ?

Yes they come with quadrature encoders, standard 2500.


Also, I see they have motors with DC brakes ? What are these for ?

To stop the motor moving when the power is switched off, which is useful if for instance the motor is running a Z-axis which could drop with no holding torque. The brake is rated for slightly greater than torque than the motor, so it's not much use as a spindle lock unfortunately.

rnr107
08-11-2012, 11:09 PM
OK, What about Mach3 control ? Do the drivers come with DIR & Pulse inputs as stepper drives or.... ?

Jonathan
08-11-2012, 11:13 PM
OK, What about Mach3 control ? Do the drivers come with DIR & Pulse inputs as stepper drives or.... ?

Yes they do.

rnr107
08-11-2012, 11:25 PM
Thanks ! :wink:

rnr107
19-06-2013, 12:33 PM
Hi Jonathan,
Have you bought any of these servo's kit yet ? :-)
I just bought 1x 750W AC servo kit for my 4th axis. Been saving for it for a long time, hope all goes well...

Laurent

Jonathan
23-06-2013, 03:28 PM
I've decided to wait until I've upgraded the rest of my CNC router before buying the servos. This is because I'm intending to try and make my own and if that fails then they might get cheaper with time in which case it's better to wait. How much did the one you got cost with postage and everything, if you don't mind me asking?

What type of drive are you planning to use between the servo and rotary axis?

rnr107
23-06-2013, 08:44 PM
I've decided to wait until I've upgraded the rest of my CNC router before buying the servos. This is because I'm intending to try and make my own and if that fails then they might get cheaper with time in which case it's better to wait. How much did the one you got cost with postage and everything, if you don't mind me asking?

What type of drive are you planning to use between the servo and rotary axis?

The servo + Drive + shipment cost me 360 ths seems a resonable price for a 750W AC + drive I think...
I am hopping there won't be any Duties to pay on top..... :(

Between the servo and the rotary axis I am planing on using timing belt (T5) with a ratio of 2:1
I'll see if it gives enough torque... If not I may need multiple pulley ratios...

RNR