Author Topic: no success etching in greyscale  (Read 4890 times)

dindunuffin

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no success etching in greyscale
« on: May 21, 2016, 11:21:58 AM »
Has anyone else had trouble etching in greyscale?  I have no trouble etching in B&W, I've been learning on stencils, and everything works fine.  I finally decided to do some greyscale etching, but I haven't been successful.  I changed the jumper on my L5 board, so the PWM should be working on the hardware, and I'm using the T2Laser software with the J-tech hex file, so I have the correct software.

I'm wondering if it might be the L5 board, which seems to be rare, or is it simply in my settings.  I get the laser light on, but its at such a low power that its not making a mark.  I've been using soft pine wood which is usually very easy to etch.

What are you guys using as the minimum power when you do greyscale? 

Zax

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Re: no success etching in greyscale
« Reply #1 on: May 21, 2016, 11:36:29 AM »
Have you tried manually pulsing the laser with different power levels?

Perhaps it has a non linear response as some others have reported.

dindunuffin

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Re: no success etching in greyscale
« Reply #2 on: May 21, 2016, 03:24:25 PM »
I used the sketch function in T2laser and drew a small square with a letter in it.   I ran it at 250, 240, 230, etc. down to 220.  I could not tell any difference until I got down to 220, then from 219, 218, and at 217 it barely left a mark.  So, it looks like it goes from full power on 200 to not enough to etch at 216.

I will do some more testing, but that gives me a good start.


Zax

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Re: no success etching in greyscale
« Reply #3 on: May 21, 2016, 03:59:44 PM »
You could try LaserInk firmware instead of J-Tech, it has a much higher PWM frequency so may produce a more analog/linear response.


dindunuffin

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Re: no success etching in greyscale
« Reply #4 on: May 21, 2016, 04:03:02 PM »
I will give that a try and report back. 


QuietMike

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Re: no success etching in greyscale
« Reply #6 on: May 21, 2016, 04:32:42 PM »
For me it seems to be a very narrow window of powers that encompass white (no marking) to black (burning wood away)  and it seems to be from about 225 to 230
If you burn an actual grey scale , the one I tested on had 6 steps, you can figure out what your setting can be to get the different shades

dindunuffin

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Re: no success etching in greyscale
« Reply #7 on: May 21, 2016, 04:46:13 PM »
I ran my test image at speed of 3000 and took the power down as low as 200, and so far all I get is black anywhere there is anything other than white.  I've attached my test image in case there is something wrong with it.

Are you setting your max at 230 and min at 225?

Zax

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Re: no success etching in greyscale
« Reply #8 on: May 21, 2016, 05:14:19 PM »
In the G-Code window, can you see that it is sending different power values (the number after the S)?

X0.08 M03 S32
X0.09 M03 S142
X0.1 M03 S146
X0.11 M03 S141
X0.12 M03 S143
X0.13 M03 S139

dindunuffin

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Re: no success etching in greyscale
« Reply #9 on: May 21, 2016, 06:47:01 PM »
Yes, the G-code shows numbers from S180 down to S0, so it appears to be sending varying power values.

When running at higher speeds like 1000 and power 0-255, I get black anywhere there is color.  And if its slower its just blacker.
I've tried so many settings from slow to fast, and max power down to 170.
When I run it really fast, at a speed of 3000, and a lower power, it almost resembles greyscale, but its blurring. 
Here are a few test burns to see what I'm getting, which to me all appears black and white, not greyscale.

Zax

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Re: no success etching in greyscale
« Reply #10 on: May 22, 2016, 04:38:45 AM »
It appears your system either isn't capable of PWM or the response is so non-linear that you aren't getting grey scale.

Just a thought... the results from T2Laser using dithered and medium to high resolution are actually pretty close to grey scale, you may want to give that a try. It works best for photos and then use black/white for artwork, depending on your required application that may suffice rather than swapping the Eleks Board and/or laser driver.

dindunuffin

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Re: no success etching in greyscale
« Reply #11 on: May 22, 2016, 07:30:07 AM »
I've already ordered another board, the one from banggood.com that you have referred to in other posts.  We will see what board they ship, its a crapshoot, and I'll see if that works.  It should be here in a few days since its coming from a U.S. warehouse.

Could you give me an example of settings (speed,power,resolution,size) you would use on your 2.5K mw laser if you were doing greyscale.  If I'm using a 2K mw laser, then my settings shouldn't be too far off from yours IF it is possible.  Just for a reference point.

I would like to be able to etch kids photos and things like that for gifts, otherwise its all for fun and education.

Zax

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Re: no success etching in greyscale
« Reply #12 on: May 22, 2016, 08:50:07 AM »
The values in T2Laser are what I use as a starting point, but the actual values depend on the image and material.

A good image with good contrast and not too much background noise will produce the best results.

Some material doesn't work well with grey scale (plastics, anodized aluminum etc.) as it produces a binary result, in that case I use dithered. Wood generally burns light to dark with increasing power (fairly linear) but others don't.

ROSS

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Re: no success etching in greyscale
« Reply #13 on: May 22, 2016, 08:54:39 AM »
 produces a binary result, ///

Care to explain that  Zax for those of us dummies  ?...................
.
Lasers are wonderful machines..not ONLY  can they cut a finger off BUT  they can also cauterise it at the same time.....

SAFETY -  IS NO ACCIDENT

Zax

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Re: no success etching in greyscale
« Reply #14 on: May 22, 2016, 09:05:11 AM »
Binary... as in 1 or 0, on or off.

For example, when you are etching anodized aluminum (aluminium - I've been in the US too long) it doesn't really produce a linear response to the laser. Low power doesn't do much, just changes the gloss perhaps but as the power increases it quickly removes the coating and exposes the bare metal but more power has no effect - hence the on or off result. Using dithering is much better in this case as that is an on or off method to simulate grey scale.