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Deb Fisher
07-09-2014, 5:29 PM
I am pretty much a newbie in the engraving business. I'm doing fine with wood and acrylic but having some trouble with engraving black granite piece. Used this site for a lot of good advice but when I engraved my first photo I have a little horizontal streaking. On my grandson's face there is a banding of darker across eyes then lighter band across the nose and mouth then little darker again across chin area. Does anyone know what is causing this? This granite oval was purchased from LaserBits company so I assumed it would be perfect for engraving.

Dan Hintz
07-10-2014, 6:53 AM
Deb,

Please put your machine/equipment list in your signature for future question reference...

Banding is most often seen on Chinese equipment, so I'll assume that's what you're using. It can come from numerous sources, so you'll need to knock these out one by one, but none of them will be the substrate itself.

During pre-processing of the image, make sure you do not change the resolution of the image once you have changed it to a single-bit B&W image... straight cropping is fine, but size adjustments are bad. Make sure your image resolution is an integer multiple of your engraving dpi... if you're engraving at 500dpi, then your image should be 500x pixels wide (where 'x' is an integer... 1, 2, 3, etc.). If your image is 501 pixels, or 1,001 pixels, etc. it'll show up as banding. Make sure your scangap (or whatever your machine calls it) is set correctly to give you an integer multiple of dpi... machines round decimal values at some point, so what seems like 0.0234 may actually only be 0.023. Don't let that bite you.

If that doesn't solve your issue, we need to start looking at mechanical issues, like loose carriages/lenses/mirrors/belts. We'll attack that next if the above doesn't solve your problem.

Deb Fisher
07-10-2014, 4:28 PM
Thank you much for your advice. I made sure that my dpi's matched and the streaking disappeared.
My machine is a Universal VLS3.5 30 watt. I'll be sure to post that from now on if I have any other questions.

Dan Hintz
07-10-2014, 5:03 PM
Thank you much for your advice. I made sure that my dpi's matched and the streaking disappeared.
My machine is a Universal VLS3.5 30 watt. I'll be sure to post that from now on if I have any other questions.

Edit your signature so you don't have to type it out each time. go to "Settings" in the tippy top right, then "Edit Signature" on the far riight middle.