Help with hip flasks, getting some areas where the laser isn't getting through the coating

Hey folks. Back around Christmas I got an Ortur LM2 20w. This is my first laser and I only got light burn about a week ago.

I burned some smaller stuff messing around but wanted to do some black powder coated hip flasks for my first project that other people would see. I have just been doing test patterns to try and find a good speed and power settings and I keep getting some weird dark lines towards the edges of the burn area. At first I thought it was just some thicker areas of coating so I narrowed the burn area but it just moved the gray lines so I’m sure it is just a setting that I don’t have right. I forgot to snap pictures of my settings but attached are images of the flasks. Any thoughts just based off the images? I’ll get pictures of the settings later.

It’s not clear to me based on the picture what you’re referring to. I don’t see any darker lines where you’re pointing.

Can you explain this further? How did you narrow the burn area? Is the before and after both represented in this photo?

Instead of a picture a screenshot would be preferable. Much easier to read.

By “narrow the burn area” I mean I went from around 3.5" w x .25" h to around 3.2" w x .25" h.

If you look at the top of the flask you can see the same dark areas where the face of the flask starts to curve down to the side. When I narrowed the burn area I was still getting the same affect, just closer to the middle of the flask

I can certainly do a screenshot. Thanks for the recommendation.

I will also mention that when I was doing the burning I was watching with my safety glasses on and the laser showed up as a yellow color through my glasses. When the laser would go over the areas where the dark spots are it would change to a blue color. Not sure if that is relevant or not.

I have to admit, I had to look at the photo for quite a long time to figure out what it was you were referring to. I didn’t realize I was looking for a vertical band. An outline of the artifact would have been much easier to understand for future reference.

This is interesting. At a minimum this tells me that it’s burning different there.

To me at first glance it just looks like you’re not fully getting through the powder coating. Why there specifically not quite sure. It might be the angle of the laser at those points or perhaps an unevenness of the powder coating.

Try burning slower or raising the power level. Or multiple passes or a crosshatch. First order of duty is to confirm that’s what it is by seeing if you can get through it. Then you can determine the best way to avoid it with the best looking outcome.

Your flasks are curved, which means the focal length gets greater as the flasks are burned. (It isn’t focused on the edge) Not sure how you can change the focal length without raising the bed as it get burned. I hope you could understand what I am referring to, as the laser will be burning outside the focal length set in the middle/center of your flask.

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So what were your settings? I’m planning on doing some . testers and this may save me time and flasks lol. :smile:

I agree with this 100%.
Because there is a slight curve to the flasks, it’s best to size your artwork so that it remains in the center of the piece and the laser doesn’t go out of focus on either side.