NordicCNC's build log

[NordicCnc]

Regards Motor brake then I can't answer that because I don't know those motors, but servos are not like steppers where they have a shaft sticking out the back, mostly because this is often used for the encoder.

JAZZ, what motors are you using to drive the ball screws and is the Z-axis motor with a brake? The Z-axis for my machine will be quite the same weight.

If you read one of my last posts in the build log http://www.mycncuk.com/threads/13448...823#post114823, I wrote that I will probably use Delta 400W servo motors and with a brake on the Z-axis. Well now I've got an offer for a full return from the supplier of those JMC 180W with integrated drivers, if I swap them for JMC 400W servo motors with integrated drivers. The problem here is that those JMC 400W servo motors does not come with a brake option.

[JAZZCNC]

JAZZ, what motors are you using to drive the ball screws and is the Z-axis motor with a brake? The Z-axis for my machine will be quite the same weight.

If you read one of my last posts in the build log http://www.mycncuk.com/threads/13448...823#post114823, I wrote that I will probably use Delta 400W servo motors and with a brake on the Z-axis. Well now I've got an offer for a full return from the supplier of those JMC 180W with integrated drivers, if I swap them for JMC 400W servo motors with integrated drivers. The problem here is that those JMC 400W servo motors does not come with a brake option.

The motors are 8Nm Lichuan closed loop steppers using 230Vac mains drives. It doesn't use a break because the gantry is vertical so Z-axis isn't fighting gravity, plus 8Nm is more than enough for this Z-axis even with heavy ATC spindle on it.

Regards the JMC then I've no experience using these motors or drives so I can't comment on how good or bad they are and I haven't looked at the specs, but if I'm honest I wouldn't use motors with integrated drives on a CNC machine. The heat and vibrations from the motors along with cutting debris, esp from aluminum coolant, etc, can't help with life expectancy but for me what's worse is the fact your running long signal wires back to the controller leaving you wide open to issues with interference from noise.

[NordicCnc]

The motors are 8Nm Lichuan closed loop steppers using 230Vac mains drives. It doesn't use a break because the gantry is vertical so Z-axis isn't fighting gravity, plus 8Nm is more than enough for this Z-axis even with heavy ATC spindle on it.

I totally missed that.. It is of course the X-axis in your case that could perhaps need a brake, but seems like its fine without.

Would there be any chance that a 400W Delta servo with brake couldn't handle my Z-axis of around 25-30kg, with a 2:1 reduction or even 1:1? I could go for 600W if that would be better.

Regards the JMC then I've no experience using these motors or drives so I can't comment on how good or bad they are and I haven't looked at the specs, but if I'm honest I wouldn't use motors with integrated drives on a CNC machine. The heat and vibrations from the motors along with cutting debris, esp from aluminum coolant, etc, can't help with life expectancy but for me what's worse is the fact your running long signal wires back to the controller leaving you wide open to issues with interference from noise.

Got it, thanks again. I will now completely forget about these servos with integrated drives.



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[jarjar]

Would there be any chance that a 400W Delta servo with brake couldn't handle my Z-axis of around 25-30kg, with a 2:1 reduction or even 1:1? I could go for 600W if that would be better.

I believe I already answered that in details...

[NordicCnc]

I believe I already answered that in details...

Gah you are right! In post #44 you did answer..

JAZZ, please ignore my repetitive question, and thanks jarjar for pointing out!

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[JAZZCNC]

Nordic: Forgot to say in the previous post when mentioned about higher-level servos requiring higher quality components. That this is also true to lower degree for cheaper servos over a Stepper system.

For instance, with motor coupling used on Stepper, you can get away with more springy coupler and it won't affect the motor in any way. Whereas a springy coupler on even a cheap servo system can cause big issues with tuning the motor. The same goes if using belts and pulleys, buy good quality belts and pulleys.

The stiffer you can make the coupling between motor and screws the better this goes right down to motor mounting. Flimsy motor mounts etc will cause resonance which you'll have to tune out of the system. This isn't always so easy with cheap servo's so the more you can do to limit resonance the better.

[NordicCnc]

Nordic: Forgot to say in the previous post when mentioned about higher-level servos requiring higher quality components. That this is also true to lower degree for cheaper servos over a Stepper system.

For instance, with motor coupling used on Stepper, you can get away with more springy coupler and it won't affect the motor in any way. Whereas a springy coupler on even a cheap servo system can cause big issues with tuning the motor. The same goes if using belts and pulleys, buy good quality belts and pulleys.

The stiffer you can make the coupling between motor and screws the better this goes right down to motor mounting. Flimsy motor mounts etc will cause resonance which you'll have to tune out of the system. This isn't always so easy with cheap servo's so the more you can do to limit resonance the better.

I have never used servos before so I am not familiar with how the tuning works. All I know is that the Delta servos and most of the other servos comes with some auto tuning software. How good auto tuning works I have no idea.

Seems like tuning manually is very difficult and requires a lot of experience to get it right. If you don't know how to do it, the servo system would end up being even worse than a stepper system. I am starting to wonder if I would be better of with a good stepper system instead of diving into the realm of servos.

To me it seems like you favor steppers at for your own builds, but I may have got this wrong. If I am right, I guess you favor steppers for the simplicity and the above reasons?

By the way what would be a good supplier for belts and pulleys? What supplier are you using?

Thanks again for your great insight!


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