What wattage diode is best for photo engraving if speed is not an issue

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chris190
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What wattage diode is best for photo engraving if speed is not an issue

Postby chris190 » Tue Aug 29, 2017 2:41 pm

Greetings!

A few months ago I ventured and got a 15w (8w rms) ttl+pwm laser of ebay (non focusable) and finally got everything connected and setup to my 6040 cnc router. After running some test it seems it's burning the image too much and after some researching im finding out that it may be to powerful for photo engraving. My question is what power laser would be ideal for photo engraving ? ... or can I still use the the one I have with some tricks?

Chris

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Picengravertoo
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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby Picengravertoo » Tue Aug 29, 2017 3:57 pm

Hi Chris,

Does that non focusable laser have a recommended focal length where to spot is the smallest? If so, what width of a burn line does it create? You may be able to Pulse the laser on/off using a dithered image to generate the gcode. If it has TTL & PWM control, you can throttle down the output power with the PicLaser Max. Laser Value setting and increase the feedrate.

Jeff

chris190
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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby chris190 » Tue Aug 29, 2017 4:27 pm

Hi Jeff,

Thank You for your reply. I didn't get any documentation about the focal length which is not surprising for a Chinese product off ebay, but I'm able to control the power via pulse on Axis A on my router and I lowered it where I can see the fainted blue dot..... and the dot looks the sharpest and smallest at about 10mm distance (between the bottom of laser module to material)..... If I raise the laser on Z axis the dot becomes bigger and at about 2-3" above its almost like a roughly 3mm elipse with the beam radiating sideways.... almost like a supernova explosion captured in space.... but at 10mm height is a very tiny sharp dot.

When it draws the border of the image before starting to burn the actual image.... it cuts a very very thin and fine line... I would ~ it's no more than 0.2mm thick....it's just the burning that seems to much....im at work now but I can post some images later.

Also weird thing... I also tried to set the laser min to 0.1000 and laser max to 0.2500 and it seems like it's starting with almost no burning then as more lines of code go by (after lets say 30-40 lines) the power increases and it burns the wood (mdf in my case) more and more... I also monitor the square waves on my oscilloscope and I can see it starts at around 10% then moves to about 90%.... I do see the PWM modulating the wave/ brightness output so I know it's sending pulses.

Also my machine can do up to 4000mm/min feed rate. in Piclaser if I set anything higher than 1500mm/min it starts to jerk.... this might be some settings I suspect.

Chris

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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby Picengravertoo » Tue Aug 29, 2017 5:39 pm

Hi Chris,

Your machine may be able to travel from point A to point B at a 4000mm/min feedrate, but with short incremental raster moves will slow things down, unless your accelerations are set high. Are you adding the G64 (Constant Velocity) in the precode?

The PicConvert PWM frequency is set at 1Khz for the J-Tech Laser Driver if I remember correctly. What PWM frequency range does your driver except?

I have a 6W 450nm LD on our Shapeoko 2 and when using full laser power to raster engrave photos, have to run at max 5000mm/min (confirmed) feedrate or the laser will start cutting into Poplar or Birch Ply. MDF burns even easier.

It probably does not make a difference, but we have our PicConvert board setup in Mach3 to work with A axis depth commands (Imperial 0. to -.0255) instead of retract commands. Is your PicConvert board set with 393.7 steps per in Motor Tuning for Metric units? If so, your full range without losing steps/position should be no more then 0 to .6477mm. What is your step & dir pulse set at? Ours is set at 3, or it will lose position.

Are you jogging the PicConvert board to 0v and zeroing your laser axis after powering it up each time?

Jeff

chris190
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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby chris190 » Tue Aug 29, 2017 6:01 pm

Thank you for the info Jeff. I believe I have some of those settings wrong for sure. I will try again tonight and let you know how it went.

Thanks again!! :)

Regards,
Chris

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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby Picengravertoo » Tue Aug 29, 2017 6:24 pm

Keep in mind, your X,Y & A? (laser axis) accels & velocity should be set the same, otherwise the slowest axis will cause a limit of the actual running feedrate.

chris190
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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby chris190 » Thu Aug 31, 2017 12:26 pm

Hi Jeff,
I got to try different settings but Im still having trouble with it and I really believe it’s something with steps. Here are some of my settings:
The units in my machine is set to mm
A axis : Steps Per = 393.7
Velocity = 2500
Acceleration 762 now (initially I had it set to 30 for all axis till I realised and did the math)
step pulse and dir pulse I tried both 3 and 5 for both and for all other axis.
Axis X and Y have the same exact Velocity and Acceleration with Axis A.

What I noticed is the range of A Axis appears to be way to much.
I zeroed in my A axis and lower the intensity to 0 (no pulses) then when I jog in smaller steps to full power it reaches full 100% at 19 units.. so 0.0000 to 19.0000 is no where near 0 to 0.6477. I also read that the Min Laser Value in Piclaser should be set to the value where it barely starts burning the wood....then the Max Laser Value would be 0.0256 added to the min laser value in the positive or neg direction depending on setup.

When you say “your full range without loosing steps/position should be no more then 0 to .6477mm”:
Does that mean that my range could be for example: min 0.2550 and max 0.2806 ?


Losing steps basically throws off the intensity of the pulses that come out mach3 into pic coverter box and once those are off it will not engrave correctly for the rest of the print ..correct?

chris190
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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby chris190 » Thu Aug 31, 2017 12:33 pm

here is a pic of my last attempt that pretty much skipped some lines and just burned dark:

http://imgur.com/VdigyWg

and here are 2 pictures that I had tried initially that appear burned, perhaps in reverse but also losing lines/steps:

http://imgur.com/9IgPiIi

http://imgur.com/DD7ojrG

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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby Picengravertoo » Thu Aug 31, 2017 12:55 pm

Do you have Mach3 set for Imperial Units or Metric Units? Your Velocity setting looks like it's set for Metric.

When Mach3 is set for Imperial Units, the A axis in motor tuning should be set at 10000. In PicLaser the setting should not be set no more than a range of min 0 max .0255 (8bit)

If Mach3 is set for Metric Units, the A axis steps per should be 393.7 and the PicLaser full range should not be set more than min 0 max .6477 (8bit).

The Digital Potentiometer on the PicConvert board is 8bit (256 steps), so if you go out of that range with your A axis gcode commands, it will lose steps/position.

I would set Mach3 & PicLaser to use negative Depth setting values for the A axis, not positive retracts. Think of the laser as a cutter and the deeper it goes, the darker it burns.

chris190
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Re: What wattage diode is best for photo engraving if speed is not an issue

Postby chris190 » Thu Aug 31, 2017 1:25 pm

I have mach3 setup in Metric Units.

So if I setup exactly min laser value to 0 and max to 0.6477.. this range will be broken down into 256 steps ? or do I have to chose 256steps within that range like per my previous expample .. let say min 0.2550 and max 0.2806 ?


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