Artwork and raster engraving question...

[Jeff Bromagem]

Hello,
I am fairly new to the laser engraving business, been in printing of all kinds for 40+ years though.
I am having problems with certain pieces of art, which have portions of the art having a "white" fill.
I am using Corel X7, Windows 7, Epilog Legend laser, using vector files (like eps).
The problem is that when raster engraving, the white fill seems to print a very faint halftone dot pattern, as if it were a very light shade of gray.
I have checked the color of the white, R=0, G=0, B=0. My thought is that since it has no color, it shouldn't print any dots at all.
I have also had a similar occasional problem with these faint halftone dots appearing outside of the image as though it is trying to print a background on the "page", or portion of it around the image/art. As an example, 2" x 2" artwork top left corner, on a 8x11" page layout, the area to the right of the image will print with a faint halftone, making the laser scan across a much larger area. No art of any kind in the blank area. This crops up from time to time.
The problem art is usually a supplied file or clip art, and trying to change white to NO fill doesn't always work very well or at all, in keeping the art looking right.
I have tried a few things to eliminate this, but no sure solution yet.
Printer profile in Corel?
Computer problem?
Anyone have ideas or a solution for me?
All help is appreciated.
Thanks,
Jeff

[Mike Null]

Can you post a file that has been giving you the problem. I believe the problem is with the file.

[Tony Lenkic]

Have you tried to separate image into layers?
Move all unwanted sections of image to layer and check off printing for that section (white part).

[Kev Williams]

Depending on the software, many lasers "see" everything on the screen even though it may be buried under something else. My LS-900 for example, if I want a black square with a smaller square hole in it (non-engraved), I can't simply place a smaller square within the black square and paint it white. What will engrave is an all black square, because it 'sees' the black under the white. The only way to not engrave the small square is to combine the 2 squares so that the smaller square actually becomes a hole.

But then there's my Explorer, which totally ignores ANYTHING below the 'top' graphic. Makes it impossible to automatically run 2 identical passes of something at different settings (a first run, then a lower power/faster cleanup pass) which I do a LOT, especially with red/white rowmark. I have to send 2 separate jobs to the laser. But, it prevents accidentally engraving something you can't see!

Your software might be trying to combine what it 'sees' into what it thinks is the closest grayscale result... ?

I get what appears to be wonderful vector art from customers, only to find out that while it LOOKS wonderful, it's actually layers and layers and more layers of colored shapes superimposed on previous colored shapes, until it looks like they want it to look. (think police badges, oh, man...) These graphics are great when sending it to a color printer, as they just print the visible colors. But they're impossible to work with if I need my LS900 to engrave a black/white version...

Only advice I have is to stop using white objects and turn them into holes. It can be a pain...