Engraving glass problem?

[Jeffrey Dewing]

I am attempting to learn how to engrave on glass, and right off the bat I noticed vertical lines down the glass in the same spots down two totally different pictures I sent over to the engraver. I'm hoping it's me not my Trotec speedy 300. Then I tried to see what it would do at the other end of the playing field and got lines as well. :confused: Anyone got any Ideas? Here are some pics...308000Here are the two totally different pics lined up.308001
308002 Thanks for any help...Jeff.

[Dan Hintz]

Two problems: 1) It doesn't look like you're processing your images correctly for engraving on a 1-bit substrate like glass (hence the single shade of white), and 2) It looks like you're using one resolution for the image but a different one for the engraving (which leads to harmonics in the image, and these appear as periodic lines).

[Jeffrey Dewing]

Thanks, Do you know what the Photo option in this job control really does? I know I have to go to a black and white 1 bit then pick a stucky, jarvis, or floyd. but was trying to find out what the photo op does. Thanks for replying Dan...

[Scott Shepherd]

Jeffrey, what was your process, as well as what were your settings?

Did you send a color photo over using the Photo mode? Black and white using the photo mode? Didn't use the photo mode at all? How many DPI did you send it over at? What was the speed/power/ppi setting? Did you have High Quality turned on?

We need to know more.

[Jeffrey Dewing]

I sent it over grey scale, 70 power 100 speed jarvis dither mode, inverted with a black background at 333 dpi on a speedy 300 80 watt. the photo op was on. Every time I tried to black and white it in 1 bit the background would come back over the black I had put behind the pic for inverting. I've done better photos on glass, but was just trying to find out what the photo op does. then I thought I had a laser problem with the vertical lines. I called Trotec about this photo mode and he didn't know exactly what it does.The tec support man said he was going to get me in touch with someone who knew a lot more. That was 5 days ago. Usually Trotec support has been very helpful, and for all I know he may have tried but somehow we got crossed. I was hoping you folks could clue me in. I was glad to here that the lines were most likely to do with my processing. Thank you Scott and Dan for your time. If you have any more info I'd be glad to listen...

[Scott Shepherd]

Jeffrey, what size was the photo (How many dpi was the photo?). That's where you can start to get vertical banding. You need to make sure your photo was at 333 dpi when you imported it into whatever you had, at the size you wanted it to be. That's not always a cure, but everything should be the same in order to eliminate any issues that that coming in from the processing of the data. I've seen it matter greatly and I've seen it not matter too much, but in trouble shooting, it's one of those things you try to make right just make eliminate that as a cause.

I don't recall ever doing a photo on glass in recent years, so I'm not much help, but I do know that photos on acrylic work amazing with that Photo mode. You just have to really get the power almost perfect and it's almost always a lot less power than you'd think.

Wish I could help more, but I don't think you have a machine issue, banding is a very common problem with lasers and especially photos.

[Jeffrey Dewing]

Thanks for the info Scott! I'm curious what the photo mode does? I'm pretty sure I know the steps required for any laser in prepping a photo. What do I not have to do with this feature? If I go through the required steps and then turn this on, Is it doing something twice? I've read here on SC, not to mix the ppi,dpi, no. up but think I may have to study a little further on that. I'm going to have to get together with Trotec's tec. staff Mon. or Tue. to get some of these answers... I'm glad to hear that the banding was ME not my machine. I'll get back on this thread with any answers I find. Thanks again Scott and Dan for your help. Jeff DBA Bellwether Laser LLC.

[Scott Shepherd]

I'm curious what the photo mode does?

To the best of my recollection at the moment, all is does is produce a halftone type file with a very different process options for the dithering pattern. I don't think it's any more complicated than that, as in it's not doing anything else special for the photo. It may also vary the power based on gray values, but I'm not sure about that one, I'd need to take another look at it. I don't use it often, but when I have, it's done a great job in comparison to other products I have used in the past.

You'd probably need to get ahold of Brett or Josh to get it answered more in depth. Josh is in the field, as far as I know, but I think Brett is still around.

[Jeffrey Dewing]

Thanks again Scott! That would make sense... I'll get back to you or this thread and let you know anything I find out. Maybe it should be on that Trotec page you made about Trotec related things where you have the video tutorials? Sticky link?

[Bill Cunningham]

It looks like your image is a positive! photos in Glass are always etched with a negative image.