Okay, I finally had a chance to do some tests on some fabric. (It’s nice to be working again and not on furlough, but less chance to play with my snappy)
If you want to cut to the chase, skip to my summary at the end.
Test material: Basic canvas cotton bag I happened to have on hand .8mm thickness Looks very similar to sample on SM sight (No idea what the strength/weight of cloth was.)
I first needed to figure out a speed/power ratio. I created the word ‘test’ in luban and repeated it 8 times in vector with fill at max density, speed 1500mm/m. Then set power on each from 5 to 80%.
As you can see the 80% got a little well done.
(First time setting something on fire with my SM) If this was wood I probably would’ve gone with the 50%, but fabric was splitting on the ‘t’'s. So I chose 30% as my preferred setting.
I then ran the same test varying speed while adjusting power to keep around the same ratio.
There wasn’t as much difference as I expected in darkness but the 30% at 3000 caused less damage through the fabric than 30% at 1500. However all of the passes weakened the fabric. The 't’s on the 40&50 went all the way through and the 1500’s tore with little effort.
Maybe it would be possible with thicker fabric (like canvas duck cloth) but I wouldn’t recommend using vector (or b&w) with fabric. The repeated passes just cause too much damage.
I then decided to move on to trying greyscale. I was wondering if the way it uses dots and not a constant beam would be less damaging.
For the test material I used this picture (converted in GIMP from color)
I resized it to 50mm wide in Luban, Floyd-steinburg algorithm with default settings.
Repeated 3 times 30% @ 3000mm/m and varied the dwell time to 3, 5 & 8
Really happy with quality but you can see how much the image came through on the back and with very little effort the dark areas tear.
Then decided to see what happened if I reduced dwell to 1 and varied power 30, 20, 10%:
Definitely the least through damage and what you see was only after I pulled fairly hard. So for display it would be fine, but I wouldn’t want to be trusting it as an actual bag.
Lastly I did some tests setting the density to half. It really didn’t change much. To get the equivalent image darkness it needed twice the power and the fabric damage didn’t change while sacrificing detail (although on this test material it wasn’t that obvious).
Yes it is possible to get results equal to those of the “Mr. Tiger” bag from the first post.
However the durability of the fabric is compromised and it may not be practical in real world use. (need to acquire some thicker material to verify this) At the very least fabric density and strength should be considered when choosing materials.
Faster speeds and lower dwell time causes less burn through/fabric damage.
The dots of grayscale are less damaging than the repeated passes of vector.