Stippling/poor texture during light engraves


#1

Hi all,

Thanks in advance for any help. I’ve had this issue since I’ve started using my GF. All light-engraved prints have stippling on them, or little random dots scattered in the engrave, which is very unflattering. Is there a way to reduce or remove them?

File preparation:
I create vector images on Adobe Illustrator using #000000 for engrave fill and hairline thick lines for cut-outs. They are saved as vector-enabled PDF, then upload to the GFUI.


Sort of difficult to photograph, but noticeable in person (especially on colored transparent acrylic and some other non-PG stuff)

In the GFUI they look perfectly fine. After printing they look either like there are little dots everywhere (esp. noticeable for ~0.5" tall prints I’ve done) or textured badly (they should be able to turn out smooth like on other lasercutters)

While troubleshooting I tried to raster then upload, and then you can see the stippling.


left: rastered at 680 dpi (varying this doesn’t change it much)
right: vector PDF

The settings I used are:
1000 speed
15 power
340 lpi
.18" focus (defocusing improved some details on the engraves for specific prints)
On PG medium cast acrylic.

I know there is a “vary power” and “convert to dots” setting for engraving grayscale images. I wonder if that is related to this issue.

On previous laser-cutting machines, I’d get a mostly smooth engrave. Sometimes you can see the horizontal lines, a grid (vertical and horizontal), or complete smoothness.


#2

Have you tried saving them as an SVG file type instead of a PDF?

PDF might have some sort of compression artifacts built into the format - that looks like something along those lines. Try one from an SVG file and see.

Settings should look like this when you use Save As:


#3

SVGs were the first thing I tried. For my small prints (~.5" wide) they actually messed up all the details and offset the cut line from the raster image. It was so bad that I switched to PDF.

I engraved with SVGs before and also had the same issue with stippling/weird texture.

edit: example of weird stuff happening in SVG v.s. the original/PDF


#4

What version of AI are you running? If you want to upload a file or two that you are having issues with, I can try it on some scraps.

Okay for the text, are you converting it to outlines yourself before you try to export the SVG file, or are you letting Illustrator do it?

For something that small, I’d pre-convert, just to make sure the quality was maintained.


#5

One thing to remember for GF and svg is that it mostly knows about fills for engraves, but it does boundaries by where the path goes. So if you have a stroke with some thickness in the original, you won’t get that same effect.


#6

Ai CC 22.0.1

Yes, I outlined the text. The weird issue in the screenshot is already solved, by using PDF instead of SVG. The real issue the texture, which is present across different material types and file types (both different designs and different file type uploads.)

My paths are fill-only and not stroked. If stroked, I outline + merge into a fill-only shape. I have not encountered any problems related to stroke thickness.

Here’s a file to try. I am trying to engrave lightly across the surface instead of super deep.

z_vector.pdf (754.4 KB)


#7

No, if you would please, load the AI format file. I have Illustrator.


#8

OK, attached. The PDF still opens in Ai with editing capabilities. I think this one will save as SVG fine, but I still had the same texture issues.

z.ai (1.5 MB)


#9

Okay, I’ll take a look at it and see if anything pops.


#10

Stand by…still testing, and I want to try one other thing to see what happens before showing the results.


#11

A few observations here…

I loaded up both of your documents and neither of them used #00000. I suspect this is because they are both CMYK defined color spaces, not RGB. The PDF is using 020301 and the AI file was using 020201.

As a vector, that won’t necessarily matter because the color just defined a job operation and you assign a power value to that.

As a raster, I could see where that could possibly impact the dot spacing versus having a true 0,0,0.

I’d be leery of saving a PDF with AI editing capabilities being enabled; that’s basically saving an extra copy of the information in the file in a different language, so that it can reserve the AI editing capabilities. Plus, there are ton of different PDF options that can impact a file…

As for your SVG, it looks like you might not be saving with enough decimal point accuracy so it’s impacting the placement of each point, which, when working with a very small design like this becomes very, very noticeable.


#12

Okay, here’s what I got…

Nothing wrong with the AI file, I saved it as an SVG (without converting it into a raster image) and ran five test prints on a Proofgrade Medium Black acrylic scrap.

Since I’m going to discuss settings here, I’ll need to shift the thread to the Beyond the Manual section after I’m done.

Z

  1. Ran the SVG file at default SD graphic settings. This yielded a fairly deep engrave, but no bubbling or stippling that i could see.
    1000/FP(pro)/270LPI/0.125"FP

  2. Brought down the power so it wouldn’t engrave so deeply. Everything else remained the same. Results looked good, cut was not as deep, nice and smooth.
    1000/78/270LPI/0.125"FP

  3. Brought the power down further. Even better results, less engrave depth.
    1000/59/270LPI/0.125"FP.

  4. On the last one, I wanted to see what a defocused engrave at low power would do to the last results, so I ran a second pass with a higher LPI, very low power and changed the focal point by 0.10". For this one, I finally saw some bubbling in the results, but it’s still fairly uniform in appearance and got darker, which I kind of like.
    1000/59/270LPI/0.125"FP then 1000/10/340LPI/0.225"FP

They all look fine to me, just different effects. So you might want to try a few tests on whatever acrylic you’re using to see if you can’t tighten down the settings for it.

Keep in mind, the Glowforge defaults take masking into account, so you would probably want to reduce power a bit in order to not overmelt it if you are not using masking, and make sure you have your focal point set correctly for the material. I’m not sure which of those factors affected the outcome of the last one.


#13

Thanks for the follow-up. I was hoping to keep it in the normal issues to see if a GF staff can solve this, but if it requires tweaking beyond the manual then I guess it will end up here no matter what.

For your #3, I am currently trying lower powers to get what I want on non-masked cast acrylic. Previously, I’ve tried to vary the power and wasn’t able to avoid the texturing.

I guess in the end, it is still “look for your own settings”. I’ve experimented with dozens of setting combinations and still haven’t found anything as pristine as the default settings on an Epilog or Universal machine. It’s been super frustrating.


#14

I made a post about defocused engraving. It should solve the majority of the texturing problem for you. I’ll see if I can find it


#15

Small update:

One day I removed my lens to clean it and all my previous focus settings yielded some pretty awful engraves. I subtracted 0.03" across the board for all materials and it seems to be the same quality as before (for 1/8" acrylic, it’s 0.15".) I also set vector to the same focus as the engrave, cuts through with the same settings. I don’t think it’s worth my time to measure the exact thickness for 40+ varieties of material and create pre-made settings for each. This one-size-fits-all approach works just fine! I noticed that the engraving could be sharper on some materials but not sure if it’s a thickness variation or material color thing.