Change acceleration while linuxcnc is running?

Todd wrote:

There are some practical higher end limits to what the new planner can do for you. They are briefly mentioned in the other thread. I didn't devote enough thought to fully comprehend it. Something to do with the interaction of the servo period time length, the number of lines necessary to calculate the path, and acceleration rates creates a practical upper boundary to what is possible.

It might help to use the Z axis as your power control as Andy mentioned, this will give you the ability to have the numbers interpolated during moves possibly allowing you to reduce your line count. You said you still wanted Z for focus, I would suggest using W for that instead. The reason I suggest this way around is to get around the fact that only XYZ are currently included in the new TP. If you add a movement in another axis it reverts to the old plan. (G64s Q also is ineffective on movements including any axis other than XYZ in the old planner as well). I am told this is on the list of things to work on with the new TP, I am patiently waiting and hoping someone gets to it. I work with several XYZW machines that would benefit.

I think I might have to play with the new INI parameters a bit for the very fast machine simulation, since all I did so far was following the instructions blindly - didn't have much time to read the whole thread and understand what is written there yet! Maybe changing the lookahead depth or something ..
I might try the W axis approach in the future, but right now I want to finish what is needed to make the laser actually write something first and maybe make some custom program for the rastering. Since the M67 method is pretty straightforward for what I need and the actual machine testing (only with axis movement, not the laser yet) shows amazing speed improvements, I will focus on this for now.

How are you using the W axis? I'm asking because we are currently in the progress of finishing a Lagun mill retrofit for a friend of mine and we use the W axis for moving the table up and down for short or long tools. I'm not really into mills and don't know much yet.

andypugh wrote:

I don't really like the idea of using Z as laser power. The reason being that changes in Z height enforce acceleration constraints on the XY axes. This can be mitigated a bit by using a very loose path-following mode, but why would you do that? In the worst case (exact-stop, perfect path following) the XY axes would stop for every change in Z height.

Agree 100%. But I understand that for some people this is necessary since they can use a CAM program and have results immediately or something? Also, I understand that with very high acceleration and very short moves for the Z axis, this would not be a problem. Or would be?

DaBit wrote:

Weird?
I always thought M-codes like M64, M67, M68, etc. were queue busters, and in that case the new TP would not help. But maybe that is only valid for the non-motion-syncronised M-odes?

And yes, M68 is a real queuebuster, as expected! About 30mm/min, compared to 6000mm/min with M67!

The machines I have using a W axis, are 4 axis routers (XYZW), with 2 spindles, each mounted on their own axis. One of them is Z the other is W.

Todd wrote:

The machines I have using a W axis, are 4 axis routers (XYZW), with 2 spindles, each mounted on their own axis. One of them is Z the other is W.

Completely different from our setup, then ..

I would like to see some photos of the machine though (if you can and like), seems interesting and haven't seen anything like this so far.

Here is a pic of one.