CNC Laser Engraving 8bit Shades of Grey 445nm

The analog voltage out from the encoder is linear in either direction of rotation.

A easier solution is to use an Arduino UNO R3 and a gshield stepper driver. With the J-Tech PWM grbl hex download on our forum, it will output a 0-5v PWM signal on pin 11 for the modulation using S value commands from 0-255 in the Gcode.

http://www.picengrave.com/forum/inde...7d35442a7a0a51

That is what we are using for our Shapeoko and the J-Tech Laser now.

https://www.youtube.com/watch?v=6-Df6Iqtf1g

We have been experimenting with 3D Laser Diode engraving using our EmBlaser. We made an air assist for it and it helped considerably with the precision depths of cuts.

Here is the image we used to generate the gcode in PicEngrave Pro 5.

Attachment 47469

Here are the results on Poplar.

Attachment 47470

Attachment 47471

Here is a perspective of the 3D engraving.

https://www.youtube.com/watch?v=YcjVdznupZo

On the gray scale using a digital pot. What is driving the signal to the digital POT? A Arduino based controller? or PI? or something you have no control over? Because you can drive the Analog or TTL modulation directly from a "Analog" pin on the processor without all this circuitry. You will want to make a calibration table because the power gain in these diodes are not linear, but a $10 Arduino could do this with a resistor directly if any need at all. Assuming you are using a Driver like a FlexMod 3

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Originally Posted by JJWMACHINECO

Thank you,

To answer both of your questions, the last two engravings are 7.5” X 9.5” and running with a stepover of .007” at 50IPM and took about 3 hours and 15 minutes to engrave. I’m in process on another build with dual 2.5W 445nm diodes that will speed the engraving process up considerably. Your correct, it’s not really shades of grey because of the color of the Birch Ply, but with my setup I have 256 levels of power from wood color to burnt dark. I use a US Digital MA3 10bit analog shaft encoder that outputs 0-5V for the analog modulation to the driver in a 360 degree rotation. In my image to gcode program, it interprets the image into 256 .0001” Z axis moves (depths of cut) which my encoder is tied by a timing belt to the Z axis.

There is another electronic means using a DAC that takes the step and direction pins from Mach3 to get the 256 steps (power levels) also. Here is a PDF that was written by the author of the program I use and explains in more detail how it is done. More information about my setup is in this PDF also.

http://picengrave.com/Laser%20Setups.pdf

John, the author of Picengrave Pro is in process of building a laser diode engraver using an X&Y stage from lightobject.com. He will be using a Max5451 digital potentiometer for the 256 power levels. His program lets you select A,B,C or Z axis for the Gcode generation to control the laser diode's power levels.

I have looked at a 405nm, but what I have read, the 445nm's have more wattage and durability. My laser diode engraver mounted on a CNC router has over 800 hours on it with no failures.

Here is a video of my mini laser engraver in action. If you watch the 0-5V analog volt meter, the voltage goes up and down with the power of the laser diode.

Jeff

http://www.youtube.com/watch?v=8xGYtpW00I8

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Quote:

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Originally Posted by rMuD

On the gray scale using a digital pot. What is driving the signal to the digital POT? A Arduino based controller? or PI? or something you have no control over? Because you can drive the Analog or TTL modulation directly from a "Analog" pin on the processor without all this circuitry. You will want to make a calibration table because the power gain in these diodes are not linear, but a $10 Arduino could do this with a resistor directly if any need at all. Assuming you are using a Driver like a FlexMod 3

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Hi Rob,

We use three different means to vary the intensity of the laser. First is a MA3 analog magnetic shaft encoder driven with a stepper motor and Z,A,B or C gcode commands based on shades in an image which outputs analog 0-5v to a Flexmod. Second is a DAC circuit that takes the step & direction signals from a CNC control software like Mach3 & Z,A,B or C axis gcode commands based on shades in an image which outputs analog 0-5v to a flexmod. Third is we use a real $35 Arduino UNO R3 and S0-S255 gcode commands based on shades in an image and output a 0-5v PWM signal from Pin 11 to a Flexmod or J-Tech TTL/PWM driver.

Try your method using an "analog" pin on a processor and post here.

I am wondering about what controls the type one and two. I am assuming this is based on the operators/designers level of comfort with mechanical or electrical, or programming :) I was wondering in the wheel version, what is converting the code to stepper motor. Because if you had access to the firmware the third type of z axis mod could be skipped... You are taking digital -> analog -> digital -> analog to flexmod. Also the flexmod and any diode the gain curve is not linear, in your software or can do in the arduino firmware a grayscale attenuation map should be creates. 90% of the gain is in the first 50% input voltage of the Flexmod, but there is a threshold starting at 6-7% This can be done with a 16 step gray scale bar, or a power meter for example.

Quote:

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Originally Posted by JJWMACHINECO

Hi Rob,

We use three different means to vary the intensity of the laser. First is a MA3 analog magnetic shaft encoder driven with a stepper motor and Z,A,B or C gcode commands based on shades in an image which outputs analog 0-5v to a Flexmod. Second is a DAC circuit that takes the step & direction signals from a CNC control software like Mach3 & Z,A,B or C axis gcode commands based on shades in an image which outputs analog 0-5v to a flexmod. Third is we use a real $35 Arduino UNO R3 and S0-S255 gcode commands based on shades in an image and output a 0-5v PWM signal from Pin 11 to a Flexmod or J-Tech TTL/PWM driver.

Try your method using an "analog" pin on a processor and post here.

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... I'm avoiding analogue driving of lasers without a calibration-curve ... and mostly even then - it's simply not precise enough ...

My engraving lasers are all driven with pulsing -- from 1W/2W diodes up to 120W CW fiber-lasers ;-)

Viktor

Quote:

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Originally Posted by VDX

... I'm avoiding analogue driving of lasers without a calibration-curve ... and mostly even then - it's simply not precise enough ...

My engraving lasers are all driven with pulsing -- from 1W/2W diodes up to 120W CW fiber-lasers ;-)

Viktor

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Try 3D engraving with your Laser Diode engraver. Is it precise enough?

Quote:

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Originally Posted by rMuD

I am wondering about what controls the type one and two. I am assuming this is based on the operators/designers level of comfort with mechanical or electrical, or programming :) I was wondering in the wheel version, what is converting the code to stepper motor. Because if you had access to the firmware the third type of z axis mod could be skipped... You are taking digital -> analog -> digital -> analog to flexmod. Also the flexmod and any diode the gain curve is not linear, in your software or can do in the arduino firmware a grayscale attenuation map should be creates. 90% of the gain is in the first 50% input voltage of the Flexmod, but there is a threshold starting at 6-7% This can be done with a 16 step gray scale bar, or a power meter for example.

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We can adjust for any power curve there may be by adjusting the Feed Rate Change (variable feedrate) percentage in our software when we generate the gcode from an image.

Quote:

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Originally Posted by JJWMACHINECO

Try 3D engraving with your Laser Diode engraver. Is it precise enough?

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... yes it is ;) -- I'm actually developing a laser-engraving application for printing plates, but this is under NDA, so no images to post, sorry.

But will try this on my own with another machine+controller I'm actually reactivating, so can test with the 445nm-diodemodules and with the fiber-lasers ... but this can take a while ...

Viktor

Quote:

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Originally Posted by VDX

... yes it is ;) -- I'm actually developing a laser-engraving application for printing plates, but this is under NDA, so no images to post, sorry.

But will try this on my own with another machine+controller I'm actually reactivating, so can test with the 445nm-diodemodules and with the fiber-lasers ... but this can take a while ...

Viktor

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Will printing plates be 2.5D (flat top) or 3D (full contour)? Yea, I can't post all our experimenting information either because of the few NDA I have also, so I do understand.