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Tomnewry
17-04-2013, 08:28 AM
Hi guys this could be a stupid question but the problem i have is im changing my system from servos to steppers and have bought three nema 34 motors from the web and the question i have is, do i need three power supplys to run them or can i get one to run all three, the supplier says three which are 60v each but it seems to me like its gonna take up a lot of space in the control box.
Thanks for any suggestions.
Tom

Swarfing
17-04-2013, 08:57 AM
how many amps? and what supply do you have already?

JAZZCNC
17-04-2013, 11:25 AM
No only need one supply that's got enough Amps. Regards the Amps then rule of thumb is you only need 68% of total number of motor Amps IE: 3x 4.1A motors=12.3/68%= 8.4A

So 60V 8.5A PSU will be fine for 3 x motors. Max Voltage of the PSU should be roughly 10% less than drives Max voltage never run same voltage has drives else you run big risk of damage to drives.

Often with larger supplies finding just the right size is difficult often meaning some compromise on volts. Volts make big difference to stepper speeds so if it's big enough compromise then it can be less than ideal. So often it's easier and usually cheaper to build your own toroidal supply to give your exact requirements.
Unregulated Toroidal supply is also more suited to CNC/stepper motors anyway has they handle back EMF better.

Look around the forum and you'll see many examples of people building them, they are very easy to build.

Ross77
17-04-2013, 12:16 PM
What are you doing with the servos or are they Dead? I always understood servos where better than steppers

JAZZCNC
17-04-2013, 12:57 PM
What are you doing with the servos or are they Dead? I always understood servos where better than steppers

Not always.? Servos and there drives can be right Pain to setup and tune correctly.
For a simple machine that doesn't need high positional speeds or high torque then steppers are much easier and can be just has accurate if run correctly.

John S
17-04-2013, 01:25 PM
There is a post over on the Practical Machinists site where this guy has put a set of servo's on an old BOSS Bridgeport.
Now on a machine this size I'll grant you they are better but many were made with steppers, you just have to keep within limits.

However he started in Feb 2012, it's on 14 pages so far and he still hasn't got it running even though he's thrown $$$ @ it.
Currently he's looking at some more new servo drives after having blown the other up.

A stepper machine would have been cutting with a month.

Tomnewry
18-05-2013, 11:29 AM
Hi the servos are all working fine but the boards that they run of on the computer are faulty and cost 800 for new ones so I thought i would be cheaper to replace the system with steppers they seem a lot less hassle to set up, and as the drives are old and run at 10v i cant find any suitable breakout boards that do servos with encoders.
Thanks
P.s sorry for late reply have been busy at work.








QUOTE=John S;45233]There is a post over on the Practical Machinists site where this guy has put a set of servo's on an old BOSS Bridgeport.
Now on a machine this size I'll grant you they are better but many were made with steppers, you just have to keep within limits.

However he started in Feb 2012, it's on 14 pages so far and he still hasn't got it running even though he's thrown $$$ @ it.
Currently he's looking at some more new servo drives after having blown the other up.

A stepper machine would have been cutting with a month.[/QUOTE]

m_c
18-05-2013, 12:15 PM
anotherpostbitesthedust

Tomnewry
05-07-2013, 07:38 PM
Hi guys thanks for the help, i have changed to steppers and motors are running already but just need a few tweeks.