I’m a relative newbie so forgive me if this topic is covered elsewhere. I didn’t find anything. AND… I really love how helpful people are. I’ve learned a lot in these forums.
I am working on etching photo images onto glass, and after a lot of testing, I feel I’m getting close. This image is a test image and is only about 1.5 inches tall. So I feel the detail is almost acceptable. But what I can’t resolve is the vertical stripes/streaks that appear. They seem to show mostly in gradations and in darker areas. There are some horizontal stripes too but those are never as pronounced (though I do need to resolve them). Does anyone have any suggestions? My settings for this image are:
Vary power (I’ve never been satisfied with converting to dots on glass)
I have cleaned and aligned the machine a couple of times with no improvement. These streaks show no matter what I use for heat dissipation. I’ve tried protective paper, a wet tissue, and dishwashing liquid.
After inverting the image to a negative, I set the blacks in Photoshop to about 80% and the whites to a max of 35. The images looks very dull in Photoshop of course, but it prints much better. I save the image as a jpeg and have the same results whether it’s full RGB or a grayscale for the color mode.
These streaks show up with other settings too and are more pronounced with higher power or lpi.
Hello and welcome to the forum! Problems and support won’t be able to assist when you’re using a non-proofgrade material, so I’m going to move your post to the ‘everything else’ catagory. I’m sure someone familiar with using glass will drop by to try helping you. Best of luck.
It’s hard to see from the picture and get perspective. One way to get some more info is to turn the image 90 degrees and do the same operations and see if the artifacts change axes too. That indicates motion induced artifacts rather than image induced.
The defocused engrave is used to eliminate share scan/raster lines. Your artifacts are wider bands of contrasting engraving, if I can read it correctly. At least in the verticle darker lines. The horizontal look different, but seem regularly spaced. Some of the bitmap jockeys might know what is going on here. Sorry I can’t help too much.
I have seen this exact result, and I’m still baffled. Using the same image that had those (which I might have scaled differently), I have had a result that didn’t display those verticle lines. That suggests it’s not the machine. WAG -An interpreted result of different resolutions between LPI/image…?
My first thought was the spacing between the cogs on the drive belt but I don’t think that’s it.
It’s been discussed many times but no definitive reason or solution. The term “banding” was used.
It seems to be a function of how the images are processed, in combination with how the machine operates. It appears the laser isn’t capable of running at anything less than full power, so it is modulated - pulse-width - at high speed. As a result, you end up with regular patterns that show up on materials that “accurately” reflect that modulation.
It occurs even with solid vector shapes, so it’s almost certainly not the image.
The “sharper” the material, the more it can be seen. Glass>Acrylic>Wood. As suggested above, a “defocused” engrave can help soften the overall image, and that works well on acrylic. I’ve never tried (or needed) on glass - I’ve only done text and small designs (on shot glasses, for example.)
Is that true? One of the GF’s early chest-thumping points was the trick power supply that would allow for variable power being delivered to the tube. They even claimed issues with that was the reason for the first big delay in shipping. But I didn’t keep track of what Scott and the OpenGlow folks found out as they tore into the machine’s guts.
That’s why I said “it appears” - the laser is absolutely modulated, whether they found a way to trigger the arc at lower power is unknown. That’s all it is, an arc lamp, and you have to cross the voltage threshold for it to fire.
Thanks everyone. All these comments have been very helpful. I think the main cause of these lines was something I should have realized right away… I scaled the image quite a bit smaller than the size of the file to print it. When I printed it at the same size as the file, the lines had diminished quite a bit, but were still there.
Defocusing and turning the image 90 degrees also helped. The quality is still not really acceptable at the level I had expected - a little disappointed in the Glowforge’s ability. That’s something I was very interested in for my fine art pieces. ::sigh::
But these suggestions from you guys has made a big difference in the quality of the etching on acrylic I’ve been doing, so thank you!!!