Messages

181

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

« on: April 06, 2013, 12:04:16 PM »

Brett,
Are you not hooked yet?  Guys, we need to team up on him

182

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

« on: April 06, 2013, 09:15:56 AM »

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

183

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

« on: April 06, 2013, 04:53:26 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

184

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

« on: April 05, 2013, 11:45:08 AM »

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

185

General Mach Discussion / Re: How do I assign an m-function to a parallel port pin?

« on: April 05, 2013, 09:18:39 AM »

Richpress,
M3/M5 have delays that may interfere with your laser use.  Probably better to set up a phantom axis (I use 'C') direction pin and issue a C-x to to advance the shutter, and C0 to retract it, in your code.

John Champlain

186

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

« on: April 04, 2013, 05:10:28 PM »

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

187

General Mach Discussion / Re: Rapid G1 Feed Changes (and not even changes) Causing Decel/Stutter

« on: April 02, 2013, 01:11:24 PM »

This issue has just been raised recently on two other forums, and it appears the issue is likely related to running an older version of M3.  Try updating to a newer version and see if it runs better.

I just tested some code with a feed rate on each line, and version .029 runs so badly and slowly that I am too old to wait for it to complete.  The same code with version .062 ran in 21 min. 12 sec.   For those wanting to test for themselves, the code I used can be found here: http://hobbycncart.com/forum/63-151-28 - thread # 543.

Regards,
John Champlain

188

General Mach Discussion / Re: Visual Studio 2010 or newer

« on: March 27, 2013, 04:50:12 PM »

Terry,
Never tried that with Express versions.

I have long used VB.net express versions, but compile with a separate program.  I use Inno (http://www.jrsoftware.org/isdl.php), which is a free compiler, to generate my install files.  I was just curious if it might work for your purposes. 

John Champlain

189

General Mach Discussion / Re: Visual Studio 2010 or newer

« on: March 27, 2013, 01:19:30 PM »

Terry,

May I ask why a full version is required?

John Champlain

190

General Mach Discussion / Re: Mach 3 Demo Install: "Illegal Instruction"

« on: March 20, 2013, 09:10:36 AM »

Dennis,
I don't know if this relates, but maybe.
http://support.microsoft.com/kb/245184
Regards,
John Champlain