Messages

1

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 07, 2013, 09:24:43 PM »

Yanxin

Too early to say that, it shows up as it burns more, sounds like the lead screw problem.
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Yanxin,
You might try to chase the threads of the lead screw with a sharp (new) thread die if you have one.  It might help. 

John Champlain
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I do not have the tools, I actually swapped the X and Y axis by swapping X and Y within the gcode and run it again, the lines is still the same direction, so my Y axis does have problems, it does not produce even lines, sometimes the spacing is larger. X is fine, no lines.

Yanxin

2

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 07, 2013, 09:21:33 PM »

Yanxin,

I'm the one that developed/invented this process by varying the power to laser engrave 8bit shades and I do have to say, very good job!

Why don't you jump over to the Hobby CNC Art laser diode thread and post your results? This is a CO2 laser build thread that Tweakie started. Just a suggestion.

Jeff

Thanks Jeff, I read your threads before, lots of my ideas are coming from you, have not got a chance to say hi! I tried to register the forum you and John mentioned but I do not understand the language(hungarian?), will try again, I'll move to that thread once registered.

Yanxin

3

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 07, 2013, 09:39:18 AM »

Lines are gone once I reduced the line spacing half, in order to retain all shades, I had to burn MDF darker, it's still burning, will take 4 hours to complete.

Yanxin

Too early to say that, it shows up as it burns more, sounds like the lead screw problem.

4

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 07, 2013, 08:18:44 AM »

Lines are gone once I reduced the line spacing half, in order to retain all shades, I had to burn MDF darker, it's still burning, will take 4 hours to complete.

Yanxin

5

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 06, 2013, 10:32:02 PM »

Yanxin,

Yes to Tweakie's comment - a really excellent beginning.  MDF burns dark, but your image shows very good image tonality.

The lines are something I also have a problem with.  Are you using 1/4-20 (or similar) lead screws?   That's what I believe is causing the lines, and I have just started building a small belt-drive machine to see if I can eliminate them.  Our friends who use ball screws don't have the lines.

John Champlain

Yes, I am using 1/2-13 lead screw, Y axis is not stainless steel lead screw, I have been planning to replace it and now I think it's time to do it, the other two are high quality stainless steel lead screws.  Maybe next build will be ball screws.

I reduced the power and bias current, de-focused the laser a little bit, burned another MDF, lines are still there, image is better but it's losing details at lighter color because of the lower bias current(I'll definitely implement your DAC circuit soon). Next will try de-focus more, reduce line spacing to see if I can make it better. Maybe it's the way this piece of MDF reacts with laser, will try one other type of wood too to see if lines are still there. I am having a lot of fun:)

See below picture. Sorry the MDF was a little dirty, some marks on it, looks like there are three flies on Dew's nose.

Yanxin
 

6

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 06, 2013, 10:14:52 PM »

  Yanxin, your coming right along............ makes me happy.

Brett

Thanks Bret, still a long way to go, those genius setup a really high standard, hard to keep up with:)

7

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 06, 2013, 10:12:37 PM »

My congratulations Yanxin, this looks like you are well on your way to producing some stunning images. 

A really excellent job my friend. 

Tweakie.

Thanks, Tweakie, you are the one that always motivating me. A good start:)

8

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 06, 2013, 07:02:21 AM »

Hi Dan,
Losing a few bits from the bottom of a 256 bit image is not the same as reducing total bit depth of an image.  To me, my images were burning darker with the lower bits missing, but YMMV.  When I was able to use the full 256 bits, my results seemed to improve, hence my recommendation.  In truth, image engraving with analog modulation of laser diodes is still evolving, and we are all learning new things frequently.

Yanxin,
If you increment (jog) your diode control by one step at a time until your diode current starts to increase from your set minimum, this will tell you how may bits (if any) are being 'lost'.  Your driver may respond differently than mine, and you may not need the full 0 to 5 volt signal to get good results.

More here about my circuit (message #320): http://hobbycncart.com/forum/63-151-16

Best Regards,
John Champlain

Thanks John, now I understand. I was assuming the current will start to increase based off the bias current at 1st step, looks like it's not, steps will be lost, I will prove that later.

I burned my first MDF today, no practice at all, first laser burned wood in my life, very excited, not good quality but at least it proves my DAC,driver and diode works as expected, and shades look good. See below pictures, burned too dark, and lines not merged(need to de-focus laser?), and possible backlash.

Yanxin

9

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 05, 2013, 03:24:02 PM »

Yanxin,
Dave's circuit works slick, but you will lose the lower bits of output because of the threshold requirements of laser diodes.  I added a second op-amp to the output from the DAC so I could set a bias of about .2(?) volts minimum.  This lets me have the complete 256 bits usable over the full range of the 0v to 5v signal.  I typically modulate my diode between .3 amps min. and 1.6 amps max.  I'm not sure if I could go higher or not - don't want to risk blowing another diode.  I have a 0 to 2 amp meter hard wired in the leads to my diode so I can monitor its current draw.

Hope this helps,
John Champlain

John, thanks so much for your suggestions, will try that later. The driver board I built has a bias pot too, I have set it to 0.16a(probably should set a little higher) minimum for my M140 diode, would that have the same effect of adding a second op amp at DAC side? The max current I am getting from the driver is around 1.55a, very similar to yours, increasing the bias current will increase the  max current too.

- Yanxin

10

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: April 05, 2013, 02:10:01 AM »

Tweakie,
Nice job, as is always the case with your work.  I don't know much about ceramics, but wondering if burning an image before firing in a kiln would allow lower power to be used - ala laser diodes  .   I have some old greenware (?) left by the previous owner of my weekend home that I didn't want to throw away, so it looks like another experiment has now been added to my list.


Yanxin,
Nice work indeed.  It looks like your DAC is similar to what a couple of us are also using, just with a different IC.  If you haven't already, please join our group at: http://hobbycncart.com/forum/63-151-29.

Regards All,
John Champlain

John, thanks for your kind words, I am getting closer:)
Yes, I am using Dave's DAC circuit, it's simple and I can get 8bit 0~5V output. I have to say I am surprised by soldering skills while building those circuits, I have soldered 4 tiny cop-8 chips without any problems. 
Just checked your forum, sounds like another great place having fun, will register soon.

Yanxin