BenJackson wrote:My laser's top speed has been 470mm/s (due to PC latency -- but I could have reduced microstepping to go faster) but I just got a Mesa Electronics card to drive it and I've played around with 1000mm/s with no problems. At some point acceleration becomes the bigger factor if you want to overscan your engraving enough to get up to speed. I have not been focused on speed lately so I don't really know what the top end is.
MasonAtom wrote:Yes, in my system I find that if I use speeds over 400 mm/s it actually slows things down a bit because most of the time I'm engraving across 2" or less increments. So in this sort of configuration, so in this sort of setting, if you increase the speed, the overshoots gets larger and the cumulative time increases due to that.
The overscan is to give the laser carriage time to accelerate to full speed.
If the laser is still accelerating within the field of the image then the
left/right edges will be engraved slightly darker. You can compute the
exact distance needed as 0.5 * F^2 / A where F is feed speed (in mm/s, not
mm/min) and A is [AXIS_0]MAX_ACCELERATION. Assuming you always engrave
at top speed ([AXIS_0]MAX_VELOCITY = 470mm/s) and modulate power to suit,
the value of overscan should be about 15mm. If you tune the accel faster
or engrave at a lower speed you can use smaller overscan. If you are willing
to tolerate some uneven engraving power at the edges you can turn overscan
way down to get near the edge of your work area. I have not tested with
overscan of 0, that might break the algorithm.
BenJackson wrote:MasonAtom wrote:Yes, in my system I find that if I use speeds over 400 mm/s it actually slows things down a bit because most of the time I'm engraving across 2" or less increments. So in this sort of configuration, so in this sort of setting, if you increase the speed, the overshoots gets larger and the cumulative time increases due to that.
Here's the part of the README for my LinuxCNC config for the 2.x Laser:The overscan is to give the laser carriage time to accelerate to full speed.
If the laser is still accelerating within the field of the image then the
left/right edges will be engraved slightly darker. You can compute the
exact distance needed as 0.5 * F^2 / A where F is feed speed (in mm/s, not
mm/min) and A is [AXIS_0]MAX_ACCELERATION. Assuming you always engrave
at top speed ([AXIS_0]MAX_VELOCITY = 470mm/s) and modulate power to suit,
the value of overscan should be about 15mm. If you tune the accel faster
or engrave at a lower speed you can use smaller overscan. If you are willing
to tolerate some uneven engraving power at the edges you can turn overscan
way down to get near the edge of your work area. I have not tested with
overscan of 0, that might break the algorithm.
(You can see my whole config at https://github.com/bjj/2x_laser ) I've not determined the max X acceleration, I just quit increasing it when it was pretty snappy. I'll probably go higher for a higher top speed. My Y accel is actually less than the machine can accomplish: I increased it until rapids were capable of knocking the open lid over center (!) and backed it off from there. My machine is on a table over carpet which makes it wobble more than I'd like.
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