Pretty darn fast! Rastering can be 35 inches/sec and 100 dpi or more (more dpi is questionable, the beam is typically 0.008" dia). So, KHz changes.
Rastering is done in two modes- one, you're modulating the power to make shades or depth. Two, you're doing dithering and turning the laser on-off for longer periods, with "on" being a fixed intensity, with the intent of leaving untouched areas and burned areas. So note this- you can have TWO periods here. e.g. "I want to burn my greyscale at 50% power, using dithering". So like you're modulating power at 25KHz when in the "on" phase of dithering, and then 0 when "off", switching on and off the 25KHz fixed-period 50% PWM at 3.5KHz with variable periods to achieve dithering. On the Universal Laser Systems, that dithering didn't go so well with the periods they chose. My plan became to convert my graphics to "1-bit" which allowed my photo software to use better dithering. But then the ULS turned around and resampled it in its own resolution, leading to very obvious interference patterns. So I figured out the ULS's resolution and set the 1-bit conversion resolution to be a multiple of that, and got better success. I can imagine handling bitmaps WAY better than what ULS did, but it seems like it has to happen in the printer drivers. Danny ---- andy pugh <bodge...@gmail.com> wrote: > On 24 October 2016 at 19:06, <dan...@austin.rr.com> wrote: > I like to do fine-detail rastering. This does require rapidly changing the > power level, so it's quite a different task that just turning on the laser > with "Z". Rastering with LinuxCNC doesn't work as well as it could. Do you have a feel for how frequently the laser power needs to be adjusted? I think that the best way to do rastering would be with a special-purpose raster-generator component which also knows where in an image file it currently is, and has an independent power output to HAL based on the current pixel value. I thing that involving G-code at all is a mistake. I did make a start on making a set of HAL components to do this. But it was purely an academic excercise, and I got bogged-down in trying to make a finite-jerk rastering planner. (un-necessary to make it work). -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1916 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
