Try this one - I removed the stroke completely: https://drive.google.com/open?id=0B7LY8p6DmhEAUTNVdGJzWDVFZjA
@Jason_Dorie thank you! I’ll be able to try to burn the image tomorrow. I’ll let you all know
Hi to solve this issue i change M3 for M4 to start laser this change make that the laser power is inverse proportional to the speed between stop to feed param.
@Alfonso_serrano I don’t think this is the issue, because all the interior lines are dark as well.
with m3 the laser power is 100% in the start and in the end of each trace ( when the speed is more low than the interior of each trace so, it burn more dark when the head change direction.
That doesn’t explain why the lines on the edges in the middle of the drawing are also dark, or why they are the same thickness vertically, at the bottom and top of the design. All of those things point toward him scanning the stroke in addition to scanning the fill.
I’ve tried the file passed me from @Jason_Dorie . The first left part is made using my previous settings, the second part is made using the setting suggested from @Alfonso_serrano . I can’t see much difference … should I try a PNG image instead?
When it’s doing fills, does it look like this? If so, try enabling the “overscan” option:
The operation seems to produce a consistent preview with what you are getting out (i.e. unblocking the Show Documents and clicking the Show Laser show the same image that is getting burned. I have modified the SVG as recommended above (Setting stroke paint to none and stroke fill to 60%) and added a laser raster merge operation and see the laser preview matching 100% with no black outline. That being said I don’t think the “filter fill” and filter stroke options work the way (at least I) would expect them to - at least for this operation. If you want it all “grey” make the stroke grey or have no stroke.
Here’s a workspace with the modified SVG and the original (with the original disabled):
https://drive.google.com/open?id=0B0bthNAR9o1rNm1YRUtsdzQ2cXc
I’ve tried again with the file I downloaded from @Michael_Audette repository. I still have the same issue. At this point I think it is a sort of driver / gcode instruction issue. I see that if I do a laser cut job, the joint of the poligon are more burned than the rest of the lines… I’ll try another tool like T2Laser and see if I face the same issue.
Just making sure you loaded the same workspace as I sent (there were 2 in the zip file - the original and a new one.) You should see this on the screen with the checkmarks after you press generate GCODE. If you do you have the correct one loaded and the problem is then likely with the laser. What version of GRBL are you running on there and what are your acceleration settings?
Keep in mind laser cannot move immediately from zero mm/sec to 1500 mm/sec - this is dictated by other settings in the firmware. If your acceleration is low you might see this burning near the edge. That’s where overscan comes in. If your screen does not look like mine in the screen shot below you didn’t load the intended workspace. You should see it overshoot the image by 2-3 mm - this will allow the laser to get up to full speed before firing.
The other possibility, if you are not using GRBL 1.1 is that you are encountering an issue that was in earlier versions (stuttering/pause on spindle speed changes - this was remedied in later versions of GRBL with laser mode controlled with $32=1 in newer firmwares). What version of GRBL are you running?
My current Firmware is: grbl 1.1f
I checked my $ parameters, and $32 is 0 … I’m going to set it =1 and try again the cut 
I made another run after updating the $32 parameter to 1, It works fine now! thank you @Michael_Audette !
