Laser Engraving

Hi Andy and cncbasher. The diode I have is a 2W M140 blue 445nm diode laser from Jordan Ramey' DTR laser shop in the US (see sites.google.com/site/dtrlpf/home/diodes/445-m140-didoes ). Mine came with copper module and glass focussing lens. I also bought a 1.8A Buck X-drive driver for the laser( sites.google.com/site/dtrlpf/home/flexdrives/x-drive ). But I subsequently found out that the driver will only serve to provide a fixed output to the laser whereas I wanted to vary the output to perform different burning strengths. Contacting Jordan on this - he told me in reply to this question " can I control the output from the laser with the X-drive or do I need external control onto the power supply side of the X-drive" - and I quote "Yea the SXD has TTL input but the X-drive does not. You can lower the output of the X-drive by varying the input voltage under 6V manually if that works for you". The SXD is another driver that he supplies - and I probably should have got that but didn't.
I've ordered a 12V TTL 445nm power supply called the Walye Power A-10 from ebay. This has laser and TTL outputs
Now where I go from here I don't know - I evidently need to control the A-10 power board voltage output from within linuxcnc to vary the laser diode output but at this stage I don't have a manual for the A-10 so I don't know what other inputs/outputs it has until it arrives. The board has output voltage and current pots. Until it arrives I don't know whether it is feasible to replace these with digital pots and control their output from linuxcnc. According to Jordan I only need to vary the voltage. But I'm currently (pun not intended) out of my depth in terms of what I need to learn with regard to lasers. Luckily the Walye power board was cheap - so If its wrong it's not a great concern - bound to find some other use for it. Do you think it possible to put a PWM driver on the output of the A-10 before it goes into the X-drive and control the laser output that way? PWM drivers are easy and cheap enough to get on ebay. I will contact Jordan now for his input into PWM control of the laser.
If none of the above answers your questions - I can contact Jordan again with questions posed by you - I'm guessing that this PWM

Micromet wrote: I've ordered a 12V TTL 445nm power supply called the Walye Power A-10 from ebay. This has laser and TTL outputs

The TTL is almost certainly an input rather than an output. You would use this to turn the laser on and off from the parallel port.
Turn it on and off fast enough, and you have variable intensity control.

If you get the system set up so that you can control the laser on/off with coolant on/off (or whatever) then we can help you adapt that to use Z-axis height to set intensity.

i dont see a problem ,
i'll look at the setup you have later today once i arrive home . so don't Panic !

Hi Andy,

Yes - I had thought about using Z-axis positioning to moderate the laser output - but I came to the conclusion that (a) the change in intensity would be very small over the Z-height range of 100mm; (b) you couldn't move the Z-axis fast enough when going from dark highly burnt areas to light unburnt areas (e.g. inside/outside strong shadows); and (c) it would change the focus of the laser leading to blurring of the burned image - analogous to increasing the pixel size within the image from small concentrated pixel burns to large lightly burned pixels - although that might be an artistic option that could work.

Micromet wrote: HYes - I had thought about using Z-axis positioning to moderate the laser output - but I came to the conclusion that (a) the change in intensity would be very small over the Z-height range of 100mm;

Some confusion here...

Image-to-Gcode outputs G-code where Z height is proportional to black-level. So I don't mean actual physical Z-height but the Z-value output by the G-code, which probably would not be connected to a physical axis at all.

changing z pos does not work , as essentialy you will move out of the focus point of the laser
you need to control the diode for the best performance