overscan/dynamic laser power/dark edges

[mattm58]

Zax,

I'm getting dark edges on one of my machines, not the other.  It's running an endurance 10w.  Exact same settings as my other eleks 2.5w engraver (I can use the same gcode, same instance of T2 just switch com ports). 

I've got overscan enabled, dynamic laser power enabled, yet still get dark edges on that machine.  Is there some kind of delay or something or additional overscan, I'm thinking the endurance isn't turning on/off as quick as the eleks on the change of direction?  I know it can change laser power, I can burn at various power rates and get different light/dark results.

The endurance one with the problem is running on a eleks 5.2 3axis controller, the other on a regular eleksmaker 2axis controller, both running 1.1e.

Thanks!

[mattm58]

Attached is a sample.

[Zax]

I actually think the opposite may be true, it's initial pulse is higher and then it fades. Disable bi-directional scanning so it's only lasering from one direction and you'll see if it's related to the switch on or over burn when it should be turning off.

You may be able to improve it by increasing the acceleration / deceleration value although dynamic mode should eliminate that, but if it's due to power variance that's a laser driver issue.

[mattm58]

I'll give it a try tonight and see how it goes.  Thanks!

[mattm58]

Ok Zax, here's the trials:

1 - Bi-Directional Scanning On, Overscan On, Dynamic Laser Power On
2 - Bi-Directional Scanning On, Overscan Off, Dynamic Laser Power On
3 - Bi-Directional Scanning Off, Overscan Off, Dynamic Laser Power On
4 - Bi-Directional Scanning On, Overscan On, Dynamic Laser Power Off
5 - Bi-Directional Scanning On, Overscan Off, Dynamic Laser Power Off
6 - Bi-Directional Scanning Off, Overscan Off, Dynamic Laser Power Off

It appears you can't do overscan with bi-directional off.

The dynamic power is obviously a big help.  Bi-directional and overscan didn't seem to make much difference.

[Zax]

Check your Grbl parameters or upload my defaults, make sure; $30=255, $31=0 and $32=1.

Then increase the acceleration / deceleration value; $120 and $121 to 1200.

[mattm58]

Ok, box in upper right is after setting $120 and $121 to 1200 (were 200), overscan, dynamic power, bi-directional all on.  All other GRBL settings were what you listed.  I am burning at a power of 80 (speed 4000) so you can see the difference, at full power it would just be a black box of char.

[Zax]

OK, so heading in the right direction. You may be able to go higher, say 1600 or even 2000 but at some point the motors will stall as they can't accelerate the mass that quickly. I would try changing $120 only as that's the axis that needs to be fast in this case.

[mattm58]

Will do, thanks Zax! 

[Zax]

Also I would recommend to use diagonal engraving as that should reduce it too.