Improve acceleration algorithm

[peteruithoven]

Peter: I was trying to speed up our lasercutter for engraving.
Using the following settings it engraves around the same speed as the native hardhard (Morntech).
motion.speed 800
motion.accel: 12000
But with a motion.accel more than 3000 it makes a complete mess of regular cut jobs. And even at 3000 and 100% it's clearly inaccurate (it can't make straight rectangles). At motion.accel 1300 30% it can be kinda accurate. At motion.accel 1000 1% speed starts cutting trough 4mm wood etc etc.
So there is a huge difference between what's a useful for engraving and cutting.

Anyway we can greatly increase the acceleration when it's just doing straight longer lines?
I know we can't make a exception for an engraving mode, because there is no (proper) engrave mode, VisiCut sends it as a regular cut job.

Jaap: At this time, accelleration and speed settings are for X and Y axis at the same time. The X axis can move much faster then
the Y axis, so it makes sense to have motion.accel and motion.speed seperately (and even Z?). Line cutting and engraving would then still use the lowest accelleration, but raster engraving can use the higher X settings.

Peter: Hi Jaap, I'm not fully following your post. You mean that acceleration and speed settings for X and Y axis are always the same? You think we should have separate motion configurations per axis?
The X axis can be faster because it's motor has to move a much smaller piece of the frame than the Y axis?
Good point, that sounds like something I might even be able to implement.

How does a separate motion configurations make sure line cutting and engraving use the lowest acceleration? Because I don't believe the hardware knows it actually engraving something.

Reinoud: Well, a cutting movement is always `just' a move from XY to X'Y' with the laser either on or off where as its engraving its actually generating a very fine pulse train representing the bits. Or is the engraving implemented as a heap of linear movements of say a few steps with the laser on or off?

[peteruithoven]

One way of improving the accelleration might be to update to the latest GRBL. But since it looks like we changed grbl to enable laser control this is quite a task.

Last time I researched this there where no up to date NXP LPC ports of GRBL. Maybe Smoothieware (firmware for the Smoothieboard) uses a newer version, at least it's also for lasercutting.