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Offline DMBGO

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Re: Servo Motor question
« Reply #20 on: March 17, 2011, 04:18:41 AM »
Still haven't made a servo decision, I am thinking of running the machine on 240v single phase, which I think is doable with 1kw AC servos, but not with bigger ones. I could also use Gekko 320X drives, but it means a beefy DC supply, and probably different servos.

Please feel free to tell me what you would do.

The manufacturer recommends that I buy their sheetmetal guarding, but I am trying to get the machine from Tiawan to my shed for under $20,000.00 and the guarding is a a few grand  more.

I am trying to do this as cheaply as possible, but end up with a really good machine. If I can get this system running the way I want I may end up supplying a few of these systems

Any suggestions about the servos I should use based on the machine details below? I feel a bit lost here.

Cheers
Dave
Cheers

David
Re: Servo Motor question
« Reply #21 on: March 17, 2011, 07:58:37 AM »
Hi Dave,
  I scrounge and salvage most all of my components as I'm in it mostly for fun.
 But if I were to buy new, I would try these from Automation Direct.
http://www.automationdirect.com/static/specs/sureservomed.pdf
They have 1,2 and 3KW 230V systems and pretty decent prices. All cables and breakouts ready to go.
Iv'e used their small PLC's and VFD's and have had good service with both, great support also (the little I required).

Offline DMBGO

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Re: Servo Motor question
« Reply #22 on: March 17, 2011, 02:38:48 PM »
Thanks Overloaded, I read through the PDF on the link you provided, it was nicely laid out and easy to understand, but unfortunately, the prices were a it high. I am in Australia and once I pay freight they would cost substantially more than the others I was looking at.

Cheers
Dave
Cheers

David

Offline Hood

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Re: Servo Motor question
« Reply #23 on: March 17, 2011, 04:26:00 PM »
As Russ said you can get up to about 3Kw on single phase, the Allen Bradley motors I have on the lathe are that size.

Geckos are for DC motors and I think you were looking at AC servos so they will be no use. If you do go with DC servos then be careful as a lot of places that are selling them are quoting the peak torque rather than continuous.

Hood

Offline DMBGO

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Re: Servo Motor question
« Reply #24 on: March 17, 2011, 07:26:39 PM »
Thanks Hood,
I hear what you are saying, but the biggest single phase servo drives I've seen are around the 1kw mark.

The ones that Russ mentioned are 240V, but once you get over 1kw they need a 3 phase input.

Not really sure why this seems to be the case, 5kw single phase VFDs  are readily available and you can draw 30 amps from a single phase 240V supply if needed which is 7kw.

If you take 25% off 7kw for inefficiency in the motors and drives and then convert the result to HP for no particular reason, other than the fact that we started life in imperial and then changed to metric, you should be able to get 7HP from single phase.
Do you estimate things in feet and mm? ie.. 2ft and about 15mm

 
Cheers

David

Offline Hood

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Re: Servo Motor question
« Reply #25 on: March 17, 2011, 07:38:41 PM »
Have a scout on eBay and see if you can pick up some Allen Bradley or Giddings and Lewis drives and motors. The ones to look for are Allen Bradley DSD or Giddings and Lewis DSA drives, they are the same. The ones I have on the lathe are DSD-030 which are 3Kw 240v Single phase.

No being an ex fisherman anything over a meter and I think in Fathoms ;D

Hood

Offline Hood

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Re: Servo Motor question
« Reply #26 on: March 17, 2011, 07:41:47 PM »
Oh but check that they are not HV drives as they are 3 phase 440v.
The older drives, DDM/DSD may also be worth looking for, the biggest again for single phase is the 030 although the DDM-075 can be run single phase but it is derated from 7.5Kw to 3Kw if you do so.

Check with me before you buy any though as I will keep you straight as there are many variations of them.
Hood

Offline DMBGO

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Re: Servo Motor question
« Reply #27 on: March 18, 2011, 06:52:38 PM »
Well after a fair bit of research I am nearly back where I started servo wise. Please have a look at this and see what you think. If you think I'm making a mistake pls let me know :)

I've pretty well decided on the GSK 1kw AC servos and the GA98B controller. I will use non braked motors on the X and Y axis and a braked motor on the Z. The servos accept single or 3 phase 220v +- 10% so they should be fine with our single phase supply.

The GA98B servo drive accepts and I quote:
"Position mode(Position command mode: ① pulse + direction; ② CCW pulse/CW pulse; ③ A/B two phases orthogonal pulse) and External speed mode (Two external speed commands: ①-10V~+10V analog voltage command speed and direction; ② 0V~+10V analog voltage command speed of which the operation direction is selected by the input signal). "

max speed of the servos is 3000rpm with 2500rpm continuous, torque is 4nm cont 10nm max

The drive will accept pulses up to 1mhz in speed, has a 5000 lline encoder and apparently is accurate to 0.018 degrees of rotation, which should be rough enough. ;D
 
These are almost the same as the first ones I posted Hood, which were GSK GA98As
Just waiting on final pricing for the mill, then it's all go, or should I say it's all wait for factory wait for shipping then go.

Cheers
Dave
Cheers

David

Offline Hood

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Re: Servo Motor question
« Reply #28 on: March 18, 2011, 07:00:36 PM »
Specs sound good and the numbers seem to work out, I seem to recall the first motors mentioned seemed a bit dodgy on the numbers?
Drives too will be fine as pulse/direction is just another way of saying Step/Dir.
Encoders are quite high res, 2000 or 2500 being sort of normal but that wont cause an issue if you are planning on using something like the SmoothStepper.
Hood

Offline DMBGO

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Re: Servo Motor question
« Reply #29 on: March 18, 2011, 07:27:43 PM »
Those earlier motors with the dodgy specs were from adtech here are the brochures for the GSK motors and drive. I am a really big smoothstepper fan, since I sorted out the noise issues a few months ago the SmoothStepper has been a model of integrity. I am just about to buy another for the new mill. I was going to share a controller between the lathe and Mill, but I think that's being stingy.

Cheers
Dave
Cheers

David