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Author Topic: should all of my axis have the same accel. and velocities?  (Read 2484 times)

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should all of my axis have the same accel. and velocities?
« on: April 02, 2009, 05:06:43 PM »
I built my machine and it is working great, but I am just always trying to improve it.
Should all of my motors/axis use the same accel. and vel. or will Mach3 compensate for the differences?

It seems when I increase the percent function on the mach screen, my corners start to round... ???

Thanks
Ben

Offline Hood

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Re: should all of my axis have the same accel. and velocities?
« Reply #1 on: April 02, 2009, 05:19:51 PM »
Mach will compensate no problem :)
 What you are seeing there is the result of low accel values and relatively fast cutting speeds, because you have it in Constant Velocity mode(G64) the motion will merge, ie when its coming to a corner one axis will be decelerating and the other starting to accelerate. If your accelleration was good then the distance to decel one axis and accel the other would be small and the rounding minimal.

 You can do a few things to try and stop rounding on a machine with slow accel values, one is to use Exact Stop mode(G61), what will happen there is the axis will actually come to rest for a split second before the next movement starts, the drawback to this may be that your machine will judder if it is not very rigid.

 Another thing you could try is mess with the CV settings on the General Config page.

 You could also write the code so that the cutter arcs round the corner instead of going past it by the radius of the cutter before changing direction , this will give a nice sharp corner as the motion doesnt really slow so no real accel/decell.


Hood
« Last Edit: April 02, 2009, 05:21:56 PM by Hood »
Re: should all of my axis have the same accel. and velocities?
« Reply #2 on: April 03, 2009, 11:13:01 AM »
So what kind of accel. would be ideal? I should go check on my machine, but I'm not at home right now. Also I am using BobCad(it's ok) which creates my g-code for me and it is supposed to slow down in my arcs. It seems that if I program it for 100ipm, things work out pretty well. once i increase the percentage feed rate on Mach3, it starts to lose the 'crispness'. (I guess it is just my learning curve)

Thanks
Ben

Offline bowber

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Re: should all of my axis have the same accel. and velocities?
« Reply #3 on: April 04, 2009, 06:43:02 AM »
I have my Z faster than the X and Y as there is less mass on my Router, on my mill it has big steppers so they are all set the same and quite high accelerations.

I've set the CV setting to 89, this turnes off CV after this angle, it's stopped the rounding on my tests but I've not had much time to do many jobs yet as I've been very busy.
I hope to get some real jobs done next week so I'll be able to see how it does then.

Steve