Lasered image has background artefacts


#1

Hi All ( @Noah )

I have run many successful laser prints, however lately some of the images I have run into problems and noticing background artefacts on the burnt image, generated from SnapmakerJS

Below is the original image followed by a lasered print. Notice the dots in the background created by SnapmakersJS, you may have to zoom in. I have tried all the algorithms, with varying results. Reduced the dwell time. Any tips would be welcomed, my aim is to have a clear background to the image.

No changes were applied to Contrast, Brightness or white Clip
Dwell was set to 30, algorithm: Burks. work-speed :288

I currently have a print running with white clip value of 215 and Density of 10 and will see how that looks when finished


Have a great day

Doug


Laser Pitting/Stuttering
#2

Hi All

This was the other montage image I had problems with and had a speckled image on the background.

BTW the woman is a good friend in NY who is now Yondan (4th Dan) level and will kick my ass when she gets to me… hahaha thank goodness I am in Australia, 16,000km away.

I took a subset of this photo and tried different algorithms; Burks was best. Notice all the black dots. I have also considered this may be a sensitivity flaw of the plywood as the laser goes over it.

Doug


#3

Looks like the edge of the image has maybe a 1 pixel dark color line? I had something similar show up on different images and was able to get rid of them by editing the edges in gimp. You may get lucky though and be able to remove it just by the white clip but more than likely will need editing in inkscape/gimp/windows bitmap editor. I have been getting decent results from Atkinson and Stucki algorithms and tweaking the white clip. What you upload to the main page where you set the laser power should give you a good indication if your settings are good. If the just the kicking girls image is solid black and everything else not a part of her outline is white, then you know your white clip where it should be.

Edit -Also - I have found that sanding the wood sufficiently with a high grit helps when doing grayscale. I had several pieces of plywood that would not work correctly until i sanded them - assume its due to some film/coating on the surface. That might help get rid of your speckles?


#4

Thanks @macklebee

Yes I am aware of the side line and I will clean that from the image. My bugbear was the background dots inserted from SnapmakerJS. I realise the images are created with the methods of the old newspaper prints as a series of dots. However if you have a clean image background you don’t expect dots to be inserted.

This latest test below, was almost perfect, except fro the lower left of the image with several rows of dots. Using the standard settings, I decreased the white clip to 215 and increased the density to 10, decreased the dwell to 30, using the Burks algorithm.

I will keep tinkering, and having fun.

Doug


#5

is that a shared ie “free” file? If so the dots might be “water mark” from the maker. Lots of free paper prints have similar intended flaws. Some disappear through simple re-editing and others will not from my experience. If it’s your design then no idea with what’s going on however if you can find the design source some designers will give you a clean copy after explaining what your use is for.


#6

@Carcharoth

Good thought. The image was from Etsy that I bought for a friend. This is so intriguing. When I run Preview you will see the dots appear on the lower left and a center diagonal line. I edited the image and cut off this area and reloaded… dots were still injected. I have since played with other images and had dots injected. I used the Atkinson algorithm and it was almost perfect except for 2 injected lines’ that almost look like going to the start and returning from end. I will keep experimenting until I am educated.

The image is .PNG I will convert to .JPG and see if that makes a difference. This is an education for sure


Take care and have a great weekend.

Doug


#7

Hi all

No background artefacts, dots/lines

Fixed it, reduced white clip to 210, used Atkinson Algorithm, dwell time set fro 25 and I set density to 10. laser power was 85%, and that could come up a tad to make it bolder.

Have a great weekend

Doug


#8

So what was the problem? Was it the image that needed cropping? Was there watermarks/artifacts in the White area?


#9

Hello @jnovack

No cropping needed; that was a my newbie failure. I turned on the laser print head on before pressing the play button and as the laser positioned itself to start printing it burnt the line heading to it… a lesson for other other newbies to watch out for.

As for the image I changed the algorithm to Atkinson and kept lowering the white clip… It was interesting in using a number of algorithms the number of artifacts they left on the image to be lasered, Using Burks left a lot of dots on the background.

We live and learn.

Have a great weekend.

Doug


#10

Hi Doug,

Nice to see these tests.
The Burks algorithm however clearly results in crisper and more legible text.
What if you try to work with a PNG image with a transparent background?

For your convenience, you can find them attached.


#11

For some reason the Snapmaker forum decides to convert the PNG images to JPG when uploading.
Download here:
www.designsoul.nl/downloads/NicoleWordle.png
www.designsoul.nl/downloads/NicoleWordleS.png


#12

Hi @idzone

Much appreciated, I thank you greatly and I shall give the a whirl in the days ahead.

Take care and have a great weekend.

Doug


#13

Hi All

Another lesson learned, simply amazing. The first image was lasered with a standalone file on a USB stick loaded onto the Snapmaker. The second image was the Snapmaker connected to the PC via USB cable and has all the black dots. Seems that when the PC is running activities in the background it causes little interrupts and pauses the data being transferred to the Snapmaker leaves the laser stationary for just long enough to burn a dot.

I will do this test again with settings to lighten the image…


#14

I haven’t experienced issues like this :confused: IS there maybe a difference in the way the software on the PC and the software on the Snapmaker reads the image?

I’ve had better luck with different images depending on the methods I use (Like Sierra and stuff).

-Greg


#15

Hi All ( @Noah @whimsycwd )

I do believe the controller could do with a larger buffer that takes in the USB connected data and not suffer from communication the minor stoppages from the PC with its background task and interrupts on the USB.

Doug


#16

Hi @doug You have become expert on this. High five.

We are aware of this issue. I ran into this issue when I develop Snapmakerjs a few months ago. It’s not a simple buffer problem. The communication protocol (Marlin/GCode) is a very simple one, which is a request/reply protocol. The host software only sent another command after the previous command reply ok. or it will cause the buffer overflow in some cases, and lead to a crazy state which is very dangerous when using CNC.

Yes, The problem can be solved. if we let the controller board take of control instead of the host software. But things get really complex and error-prone. Need to think thoroughly.

For now, I suggest you use USB to do offline printing to avoid this problem.


#17

Is the Dotting problem also when you use MacOS or Linix Ubuntu ?
The background processes ar a lot diferent.
I can’t find anything about that.
I am thinking of making a Ubuntu system only for Snapmaker but i need to know if the problem with the dots is on all OS operating systems.
Hope anyone can tell.


#18

Too many variables to consider to answer, dots could also be created by the choice of algorithm and the image you are using. You will have to try a few images with different settings and see how you go. There are no hard and fast rules… just experience. All I can say is that on a Windows based PC using the cable connection can cause burn spots and I and many other use a USB memory stick instead. I can tell you that the Atkinson algorithm on my images has a lot less spotty shaded background.

Good luck

Doug


#19

Well oke thanks.
I think i am going to give it a try and make myself a linux ubuntu system.
I will make some test and hope that it will be beter than on windows.