Laser Advice and Guidance - Mesa Card
- Project_Hopeless
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20 Jun 2021 18:49 #212507
by Project_Hopeless
Laser Advice and Guidance - Mesa Card was created by Project_Hopeless
With my primary project/mission complete in large part to the help I've received on this forum I'm now looking at adding a laser etch/engraver head to my CNC router.
With a Mesa 7i96e card or similar, can I etch in grey scale?
I've read some posts from circa 2013 and the method was to use G67 plus a phantom Z motion to control the laser. Is there a more refined method today?
I use Fusion 360 as a one stop shop for CAM and generating g-code. Is there a better work flow and software option for laser engraving?
I currently use the Axis GUI as it does everything I need it to do as a beginner/novice. Is there a better suited interface/GUI for lasers?
Any advice is appreciated.
With a Mesa 7i96e card or similar, can I etch in grey scale?
I've read some posts from circa 2013 and the method was to use G67 plus a phantom Z motion to control the laser. Is there a more refined method today?
I use Fusion 360 as a one stop shop for CAM and generating g-code. Is there a better work flow and software option for laser engraving?
I currently use the Axis GUI as it does everything I need it to do as a beginner/novice. Is there a better suited interface/GUI for lasers?
Any advice is appreciated.
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20 Jun 2021 21:22 #212516
by PCW
Replied by PCW on topic Laser Advice and Guidance - Mesa Card
You could certainly use the Z axis for setting a PWM value
You would want to set very high accel/velocity values for Z or alternatively
set a very high z scale number so that the range of numbers used for PWM control
were a small fraction of the (imaginary) Z axis position range
You would want to set very high accel/velocity values for Z or alternatively
set a very high z scale number so that the range of numbers used for PWM control
were a small fraction of the (imaginary) Z axis position range
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21 Jun 2021 12:15 #212552
by andypugh
Which is possibly inelegant, but does mean that image2gcode can be configured so that you can simply open a bitmap file in the Axis UI and it will "just work"
www.linuxcnc.org/docs/html/gui/image-to-gcode.html
Replied by andypugh on topic Laser Advice and Guidance - Mesa Card
You could certainly use the Z axis for setting a PWM value
Which is possibly inelegant, but does mean that image2gcode can be configured so that you can simply open a bitmap file in the Axis UI and it will "just work"
www.linuxcnc.org/docs/html/gui/image-to-gcode.html
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- Project_Hopeless
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21 Jun 2021 21:52 - 21 Jun 2021 21:52 #212602
by Project_Hopeless
Can I leave the Z axis as is and use a phantom A axis set to a high value or does LinuxCNC need to see hardware (stepper motor)?
Replied by Project_Hopeless on topic Laser Advice and Guidance - Mesa Card
What if my Z axis can't achieve fast enough accel values? Will the motor just stall and hum? And wouldn't the heat build up be bad?You would want to set very high accel/velocity values for Z or alternatively
set a very high z scale number so that the range of numbers used for PWM control
were a small fraction of the (imaginary) Z axis position range
Can I leave the Z axis as is and use a phantom A axis set to a high value or does LinuxCNC need to see hardware (stepper motor)?
Last edit: 21 Jun 2021 21:52 by Project_Hopeless.
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21 Jun 2021 22:14 #212604
by PCW
Replied by PCW on topic Laser Advice and Guidance - Mesa Card
I assumed Z was driving the laser PWM value so there are no velocity
or accel limits
Not sure A is a good choice for modulation due to blending/lookahead
limitations of the standard TP
or accel limits
Not sure A is a good choice for modulation due to blending/lookahead
limitations of the standard TP
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22 Jun 2021 00:41 #212627
by Project_Hopeless
I read through this wiki Rastering_With_A_Laser probably need to read it a couple more times. Know of any other examples?
Replied by Project_Hopeless on topic Laser Advice and Guidance - Mesa Card
I'm still trying to wrap my head around this implementation.I assumed Z was driving the laser PWM value so there are no velocity
or accel limits
I read through this wiki Rastering_With_A_Laser probably need to read it a couple more times. Know of any other examples?
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23 Jun 2021 13:09 #212736
by andypugh
If you have an actual height adjustment axis then I would suggest configuring that as W and using a "phantom Z" to control PWM. Also set the Z so it moves a _tiny_ virtual amount between 0 and 100% PWM to minimise the effect on the trajectory.
M67 ought to be the correct way, but rumours are circulating here that it slows the motion (though it shouldn't)
Replied by andypugh on topic Laser Advice and Guidance - Mesa Card
Can I leave the Z axis as is and use a phantom A axis set to a high value or does LinuxCNC need to see hardware (stepper motor)?
If you have an actual height adjustment axis then I would suggest configuring that as W and using a "phantom Z" to control PWM. Also set the Z so it moves a _tiny_ virtual amount between 0 and 100% PWM to minimise the effect on the trajectory.
M67 ought to be the correct way, but rumours are circulating here that it slows the motion (though it shouldn't)
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29 Jun 2021 16:43 - 29 Jun 2021 16:50 #213248
by chris@cnc
Replied by chris@cnc on topic Laser Advice and Guidance - Mesa Card
I like the idea of controlling laser power via Z-axis.
But I'm not sure how to connect it.
Maybe you can help me.
For the test, I loaded the PWM bitfile onto my 7i76e simulator.
The following lines are written in the hal.
I have now loaded a picture in linuxcnc and started the program.
I think I can get a finer structure on the lasered picture, which there is still to try.
On TB3 pin 2 and 3 I now measure 20Khz and a nicely fluctuating voltage between 0-12V depending on the height of the Z-axis.
So I can easily adjust the power of the laser with the engraving depth.
Now two questions.
Why 12V? I thought PWM was only 5V. Background: the Borad once had a short circuit. Are that 5V on a healthy board? Because laser has only 5V PWM connection.
And how can I connect the laser to the board? I only have 3 cables on the laser. PWM, GND and 12V
But I'm not sure how to connect it.
Maybe you can help me.
For the test, I loaded the PWM bitfile onto my 7i76e simulator.
The following lines are written in the hal.
setp hm2_7i76e.0.pwmgen.pwm_frequency 20000
setp hm2_7i76e.0.pwmgen.pdm_frequency 6000000
net z-enable => hm2_7i76e.0.pwmgen.00.enable
net z-pos-fb => hm2_7i76e.0.pwmgen.00.value
I think I can get a finer structure on the lasered picture, which there is still to try.
On TB3 pin 2 and 3 I now measure 20Khz and a nicely fluctuating voltage between 0-12V depending on the height of the Z-axis.
So I can easily adjust the power of the laser with the engraving depth.
Now two questions.
Why 12V? I thought PWM was only 5V. Background: the Borad once had a short circuit. Are that 5V on a healthy board? Because laser has only 5V PWM connection.
And how can I connect the laser to the board? I only have 3 cables on the laser. PWM, GND and 12V
Last edit: 29 Jun 2021 16:50 by chris@cnc.
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29 Jun 2021 17:37 - 29 Jun 2021 17:37 #213251
by PCW
Replied by PCW on topic Laser Advice and Guidance - Mesa Card
The step/dir outputs (being used for PWM now) on a 7I76e are 5V signals
I suspect a measurement error
I suspect a measurement error
Last edit: 29 Jun 2021 17:37 by PCW.
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29 Jun 2021 18:52 #213258
by chris@cnc
Laser PWM -> TB3 Pin 2
Laser GND -> -12V Powersupply
Laser 12V -> +12V Powersupply
Or should i better use a level converter between Laser PWM and TB3 on mesa board to not share the ground?
Replied by chris@cnc on topic Laser Advice and Guidance - Mesa Card
Okay i measure now TB3 Pin 1 an 2 and got 5V max. I would wired laser this way but have fear to share thre ground.The step/dir outputs (being used for PWM now) on a 7I76e are 5V signals
I suspect a measurement error
Laser PWM -> TB3 Pin 2
Laser GND -> -12V Powersupply
Laser 12V -> +12V Powersupply
Or should i better use a level converter between Laser PWM and TB3 on mesa board to not share the ground?
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