Feed override not responding in UCCNC

[Blaise]

Hi all,

When I change the feed override upwards, nothing noticeable is happening and if I change it downwards, it only start to slow the servos down when I reach about 60% or less.

Is this normal?

I am still bench testing the electronics. For more info on my current setup, you can look at this post: http://www.forum.cncdrive.com/viewtopic ... 968&p=7294

Thanks for your help!

- Blaise

[ger21]

Is your Velocity on the Axis setup page about 70% of your commanded feedrate?

[Blaise]

Currently testing the Y axis and it’s current velocity in the axis setup is 10500 mm/min
And the commanded velocity is 6000 mm/min.

- Blaise

[cncdrive]

I don't think it is the FRO which is not responding, because your set feedrate is 6000 and your act speed is 800ish and so the speed is already not reached 100% of the FRO, 300% is very far in value.
The toolpath is not straight, but an arc and so it is possible that with your settings it is not possible to accelerate up to 6000mm/min.
Try to set your acceleration of the axes higher to get a better result, to get higher possible speeds on this path.
Also you can adjust the CV parameters for higher tolerance to let the software optimise better for set speed.

And to see if it is a FRO problem or not (which I'm sure it is not) you can test the FRO with a straight single line.

[Blaise]

Oh! Yess! I see what you are saying! I will design a larger part with long strait lines where the servos get a chance to accelerate to the full commanded speed and test again.

I have never worked with servo motors before. I still have a lot to learn. The tuning... the PID... its a lot to wrap my head around!

Thanks! Very helpful!

[Blaise]

I did the test and you are absolutely right! FRO is working perfectly right!

Thanks for the help!

- Blaise

[Blaise]

Just curious. My current acceleration is set to 200.
I don’t know if there is a relation with ppr and velocity so just in case:
My encoders has 2000 ppr.
My velocity is set to 11000 mm/min

What would be a topical acceleration setting?

Thanks!

- Blaise

[ger21]

The maximum acceleration is entirely dependent on the available power, how much weight you are moving, and how much friction is in the system.
Generally, the higher the acceleration, the better, until the machine starts shaking or flexing.

[Blaise]

I see. The machine doesn’t exist yet! The servo is sitting on a bench with no load attached, so i’ll have to wait for the tuning. It’s just that I’m trying to wrap my head around has much as possible of the system so that when I design the mechanical part of the machine, I have a good idea of how things work!

Thanks for your help!

- Blaise

[Battwell]

In metric 200 acceleration is a bit slow.
I use 500 to 800 on my machine with a very heavy gantry.
Z axis can be a bit slower if it's heavy.
My main axis xy are set at 20000 mm/ minute
Z axis 5000 mm/ min