Must you dither?

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inbrissy
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Must you dither?

Postby inbrissy » Mon Dec 19, 2016 6:27 pm

Perhaps a total dumb noob question, but do you have to dither your images before burning them? I can't seem to find an answer to that anywhere. I've seen the original photos and then results people have posted, but it doesn't say anything about the dither options used.

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Picengravertoo
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Re: Must you dither?

Postby Picengravertoo » Mon Dec 19, 2016 8:13 pm

What type of CNC controller & Laser do you have?

inbrissy
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Re: Must you dither?

Postby inbrissy » Mon Dec 19, 2016 9:46 pm

I have an L-Cheapo 3.5W laser module running on an Arduino Uno with a CNC Shield.

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Picengravertoo
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Re: Must you dither?

Postby Picengravertoo » Mon Dec 19, 2016 10:08 pm

L-Cheapo? I have not seen any grayscale laser engraving examples done with one of those. The only reason to Dither an image is if your laser engraving a black & white logo/image, your material is hard to burn grayscale on wood that has allot of grains like Oak, or your laser driver is only TTL and will not except a PWM signal.

What grbl firmware is flashed to your UNO?

inbrissy
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Re: Must you dither?

Postby inbrissy » Mon Dec 19, 2016 10:38 pm

the J-Tech grbl firmware.

I may be the first to publish some greyscale engravings from the L-Cheapo then :)

Ok that makes sense. I assume that if its a black & white logo that it might be easier to vectorise it and engrave that. Only use raster with dithering if vectoring is too hard to do?

I'll learn through experience which materials are hard to burn on, I'm sure. I'm glad I was pointed to this forum. I think I'll learn a lot. Hopefully you guys won't get sick of all my questions LOL.

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Picengravertoo
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Re: Must you dither?

Postby Picengravertoo » Mon Dec 19, 2016 11:20 pm

We are the experts at laser engraving grayscale with varied intensity as we are the ones that invented/developed it.

Our programs will only generate raster code, however they work very good with Dithered B&W logos. But, make sure the image is at least 100DPI (higher the better) because Dithering will pixelize a low resolution image.

Yes, the grayscale example in your other thread is the first we have seen with a L-Cheapo. ;)

There is a new MultiMode grbl 1.0c that works better then the J-Tech LaserMode grbl 9g. It can be downloaded from here:

https://discuss.inventables.com/t/xcarv ... 2016/28943

Make sure you backup your grbl settings before flashing the new grbl.

inbrissy
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Re: Must you dither?

Postby inbrissy » Mon Dec 19, 2016 11:41 pm

Oh.. i'm talking to a legend! ;)

Ok. I generally only work with images 300dpi or higher. Luckily I have a daughter who is a graphic designer, so when I need something I just get her to do it for me LOL. Is there a benefit with using raster vs vectors? I know vectors generally are much faster to engrave.

I'll post the one that is nearly finished now for a completed one with my L-Cheapo. Please feel free to give me any tips on making it even better.

I'm currently running Xcarve_JTech_grbl_11_12_2016. How do you backup and restore settings? I've never had to do that.

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Re: Must you dither?

Postby Picengravertoo » Tue Dec 20, 2016 12:16 am

I know how to backup the grbl settings with our PicSender streamer, but I don't even know which streamer your using. $$ command brings them up, so try that and if they appear somewhere, copy/paste them in a text file. Open the text file like a gcode file and send it should make the changes.

I made these grbl settings changes to increase the performance of our Shapeoko 2. You may have to experiment with the accels on your machine though.

$0=30 (step pulse, usec)
$1=255 (step idle delay, msec)
$10=18 (status report mask:00010010)
$11=0.005 (junction deviation, mm)
$120=12000.000 (x accel, mm/sec^2)
$121=12000.000 (y accel, mm/sec^2)

inbrissy
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Re: Must you dither?

Postby inbrissy » Tue Dec 20, 2016 12:24 am

well I might just copy those and see how it goes :)
I'm not even sure what most of those mean.. I understand the accel for x and y as its similar to 3D printers.

I had my laser connected to my Wanhao Duplicator i3 before I built this machine. I'm still needing to design and build the Z. At the moment it only has X and Y and I manually can adjust the Z but I'm working on the Z axis at the moment.

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Re: Must you dither?

Postby Picengravertoo » Tue Dec 20, 2016 1:11 am

Explanation of the grbl settings.
https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9

Our EmBlaser just uses a gauge to set the focal height from the top of the material which is something you could do also.


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