Can PhotoVcarve be used to Laser engrave on a CNC Router????

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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby dlgabry » Tue Feb 28, 2012 11:13 am

Nice job!
I'm thinking of trying this probably at first with black/white, controlling the laser with a photointerruptor (combination of photodiode and photocell with a gap between the two) and some sort of opaque flag mounted on the stepper shaft.
Mach3 has a digital control plug-in for laser control with modulation, but I'm a bit worried about direct drive from the parallel port so that's going to wait until I can get a breakout board.
Probably the first smoke I'll see here will be from some electronic component :)
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby JJWMACHINECO » Tue Feb 28, 2012 1:34 pm

Yea, I have a index pulse card and looked into using it to turn the laser on and off. One of these.

http://www.cnc4pc.com/Store/osc/product ... cts_id=129

But since I started off trying to implement variable voltage for the analog modulation, I had already mounted the potentiometer board on my router. I did do some testing with the index pulse card and just powered it with the 5V from my PC USB port. This style just needs a slot or hole in a disk to turn it on/off.

When I started looking into converting my CNC router to a laser engraver, I played around with the plugin in Mach. It did not give you any preview of the image it will laser like PhotoVcarve does and I already had the Vectric software. I started to do a search to see if anyone else had done it and only found this thread where someone asked this question before back in 2009.

http://www.vectric.com/forum/viewtopic.php?f=7&t=7117&start=0

By Brian's statement, this can not be done using PhotoVcarve and can't has never been in my vocabulary. :idea:

I could not find where anyone has done this before in my search of there forum. Also this statement on the PhotoVcarve Overview page drove me to see if I could make an inexpensive laser marking system using PhotoVcarve to drive it. "PhotoVCarve has been developed to allow CNC machines to carve and engrave in a way that until now could only be done using an expensive laser marking systems."

I am very happy with the PhotoVcarve software and it was a very reasonable investment compare to other software out there. I also just wanted to make my investment grow to it's maximum potential and I that is really what I have accomplished. This setup and and the PhotoVcarve software will not only work with inexpensive laser diodes, but will work with a CO2 laser mounted on a CNC router also.

Maybe this new use for there software will bring this part of there forum back to life again in the near future. It's seems to have slowed down considerably since there release of the Aspire software.
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby JJWMACHINECO » Mon Mar 05, 2012 3:17 pm

Well Dave, the potentiometer finally crapped out. I was wondering how long it would last rotating back and forth millions of times. I would say it ran for about 100 hours total. I still don't have my other laser back yet with the analog modulation, so later I will look into some kind of encoder circuit to vary the voltage.

I went ahead and installed my pulse card with the photo interrupter and made a disk with 16 slots and mounted it to my servo motor shaft. It now switches on and off within .0001". I did 16 slots so I can calibrate Z zero allot easier based on the thickness of the material I'm engraving and were the rotation of the motor shaft is. Went back and set up my steps for the Z axis to what it was before I started all of this experimenting with the laser. With the disk, I get .0031" on and .0031" off, so the Z+.0015" and Z-.0015" settings in PhotoVcarve still works perfectly. I know how far the laser focuses off the material, so made a plastic spacer that height to locate from the bottom of my heat sink on the laser diode to the material. I set the spacer on top of the material, then run the Z axis down until it just touches the spacer and then come back up .0001" incrementally until the red LED goes off. That is where I zero the Z axis. I did a video of it engraving and here is a link. Excuse the video quality, as I'm not very good at that yet. :roll:

http://www.youtube.com/watch?v=VJvmtEmLEpg

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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby dlgabry » Mon Mar 05, 2012 4:13 pm

Sorry to hear about the demise of the potentiometer Jeff. I've been giving some thought to using a hall effect sensor like one of the SS49 family. Looks like one could mount a magnet on the stepper shaft and the sensor would give a linear output based on the magnet position. No clue if I can make that work though. There's a mess of different types, some linear, some digital with or without latching. Not sure if these would drive the modulation input directly or if it would need a transistor to do that.
I've got some photo interruptors here, I can always go that way if I need to. No sign of a laser in the mail here either, so there's time to play.....
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby JJWMACHINECO » Mon Mar 05, 2012 4:54 pm

Actually I'm glad the potentiometer failed. The photo interrupter setup is working allot better by it's allot more precise on switching the laser on and off and not having to deal with the slip clutch anymore to zero the Z axis. Now I can use my home switches and fixture coordinates again too. :D
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby dlgabry » Sun Mar 18, 2012 12:27 pm

My modulatable 1.7 watt laser arrived last week, and it's way more powerful than I expected!
For the modulation, I'm using an itr9606 photo interrupter, which consists of a photo diode on one side, and just an npn photo-transistor on the other, both are being powered by a 5 volt dc regulated supply. This particular photointerrupter doesn't have a digital output. The phototransistor has an aperture slit that's narrow but about .050" tall. The output varies from 0-5 volts depending on how much of the aperture slit is blocked in the tall direction, and the light vs output curve is fairly linear over most of it's range.

The interrupting disk is unslotted with it's hub offset by the .050" aperture height, and is mounted on the z-axis stepper motor shaft (picture an oval shaped cam). It takes 1/4 of a shaft rotation to completely block the phototransistor, which is .025" of z-carriage movement on my machine. That amount doesn't appear to affect the focus of the laser very much. Grayscale image results look promising. I need to play around with image enhancing and PVC to try to get better results - nothing worth bragging about yet.

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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby JJWMACHINECO » Sun Mar 18, 2012 2:09 pm

That's interesting on how you are getting the variable voltage output from a photo interrupter. It must be all in the electronics your using. Any details on the circuit? I finally received my 1.7W laser back recently, but have not mounted or done anymore experimenting with the analog modulation yet.

What 1.7W laser did you end up purchasing? Is the same one I posted a link to? If so be careful with your max voltage to the modulation input. I have to send mine back twice for replacement diodes because he claimed a voltage spike to the modulation input took them out. I have used the same power supply for modulation on the 1W laser without frying the laser diode. At least not yet. :lol:
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby JJWMACHINECO » Sun Mar 18, 2012 3:29 pm

I just re-read your description and the specs. on the itr9606. Your are getting the variable voltage 0-5 directly from the photo interupter itself, correct? Can not get any simpler then that. 8) Thanks for that info? It looks like I need to make a cam instead of a slotted disk and order an Everlight itr9606.

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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby dlgabry » Sun Mar 18, 2012 4:29 pm

Hi Jeff,
Yes, I am using just a transmissive type photointerrupter and two resistors - a 220 ohm on the photodiode side, and 7.2k ohm on the phototransistor side, connected from the emitter to ground. The laser modulation input is connected accross the 7.2k resistor. The itr9606 has an analog output.
Power supply is a 5vdc regulated wall-wart from bgmicro.

www.mouser.com has a number of transmissive photointerruptors, I picked the itr9606 one just because it was one of the cheeepest. Note that some photointerrupters have a digital-only output so they won't work with this setup. Some datasheets show the light vs output ranges, but the 9606 doesn't. Guess I just got lucky ;)

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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby dlgabry » Mon Mar 19, 2012 2:00 pm

Oops, must be getting color blind in my old age. The phototransistor emitter-to-ground resistor is 5.6K, not 7.2K. I'll try to add a diagram - I reversed the phototransistor to make it easier...
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby P.Passuello » Wed Mar 21, 2012 10:04 am

Hi Jeff,

Thanks for sharing your adventure in laser engraving with PhotoVCarve.
I am hoping to do set up a laser myself and have a few questions about your setup if you don't mind.
I am not looking at analogue control but simple on off using TTL on the Laser PSU.
If I understand correctly you have set up PhotoVCarve to move a small distance up and down. The down movement turns the laser on and the up movement turns the laser off. I have watched the video but cannot tell for sure but I assume the Z motor is not spinning but only moves enough to uncover the slot then moves back to cover it up.

If this is right would it not be easier to have a separate stepper motor in a box somewhere with it's own driver to do the pulse job instead of modifying the Z axis.

Another thought is if Z down turns the laser on and Z up turns it off would it not be simpler to use the direction pin on the Z axis stepper driver to turn the laser on and off?

Would this not also give a form of grayscale not by adjusting the power but by changing the length of time the laser is on in a particular spot. ie the length of time it takes for the Z to plunge so the longer it takes, the longer the laser is on. I am assuming a low power laser so it doesn't instantly burn the wood. The virtual cutter could plunge about 1 inch and the IPS rate would determine the duration. The second the virtual cutter starts to rise the laser would turn off.

I hope I have got it right but at present I am in the planning stage and trying to learn.

Any comments would be appreciated as I want to get it right before I commit to buying.

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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby JJWMACHINECO » Wed Mar 21, 2012 2:15 pm

Hey Peter,

Actually the setup I'm using right now that is in the video is TTL modulation. The Lasers Analog modulation is not working properly and as I described I have to short out the positive and negative every time to get the laser to turn off. A Triac is normally for AC power because AC goes to 0 volts every cycle, but by me having the + and - of the modulation connections across MT1 and MT2 on the Triac, it does go to 0 volts every time the 2.5V signal from my pulse card that is connected to the gate turns off. When the signal from the pulse card goes to 2.5 volts, it puts that voltage to the modulation on the laser. This setup is only needed for my particular laser. The pulse card actually is a TTL signal of 2.5 volts and is 0 volts when nothing is blocking the photo interrupter and goes to 2.5V when it is blocked. Like I said before, I'm just powering the pulse card with the 5V coming from the USB port. A regulated 5V wall wart, like Dave is using would work also.

I have servos on my router, not steppers, so it may be more complicated to tie to an output pin in Mach to pulse the laser because the servo has to have an encoder feedback to Mach. I never really did any testing with tying to any output pins coming from Mach and was just wanting to make it as simple as possible by adding an external circuit. Dave has come up with the simplest setup for analog or TTL modulation for the laser if you want to use an external circuit that senses the Z axis movement. 8) For TTL, you just need the Photo Interrupter to be blocked or not quicker based on your slotted disk or cam.

One thing I did notice is the shorter the Z axis moves generated from PhotoVcarve, the smoother the motion when running the code and that is why I only generating the Z-.0015" and Z+.0015" motion to turn my laser on and off. If you make your depth of cuts considerably deeper, it will get real jerky when running your code. My 1W laser does instantly burn the birch plywood and basswood, but may not on harder woods. I have not tried any other wood yet, so I do not know. I'm sure it would require a more powerful laser, or running a considerably slower feedrate.

There are several ways to pulse a laser, either analog or TTL, with the output pins from Mach, special code, but this just worked best for me, on my machine, with my laser using the PhotoVcarve software and how it generates the G-Code.

I did another picture yesterday that Tweakie lasered with his C02 laser and and in my opinion, the detail looks just as good as his without going through the complications on code generation for pulsing the laser in Mach. I'm now getting better results by how I'm processing the image in Corel PhotoPaint before bringing into the PhotoVcarve software.

Jeff
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby dlgabry » Sat Mar 24, 2012 12:52 pm

This one was done with the analog control circuit and offset disk above on a color image 3" tall. I set the disk so that the laser was just beginning to turn on at a depth of zero. It doesn't make much of a mark at lesser depths, so it seems that I need to set a deeper start depth to get better results.
Tool is defined as a 30 degree/side engraving tool with a .010" flat tip, max depth was set at .015", and .010" stepover. The laser has a cooling fan, but its temperature was around 80 degrees for the darkest part of the image.
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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby JJWMACHINECO » Sun Mar 25, 2012 1:17 am

Dave, it looks like your getting there.

What I did when I was using the analog modulated laser is I made a new profile for Mach just for the laser and I played around with the steps in the motor tuning so when PhotoVcarve generated a code with let's say your total cut depth is .015" your Z axis would move from Z0.00" 0 volts to the modulation (zero laser power) to Z-.015" would be 5 volts to the modulation (full laser power). I also used V-bit as my tool instead of the engraving bit like i'm using with the black and white images. Try making a new tool for the laser as a V-bit at .125" dia. at a 120 degree included angle running at 40 IPM feed and max of your Z axis on your plunge rate. Use .01" step over and 100% increase in the contrast and change your steps for the Z axis motor to full power at a cut depth of .015" or what ever travel to get your full 5 volts from your Photointerupter for the modulation.

Your setup is more responsive then what I started out with, so you will just have to play around with your settings, but that should get you close. Also, just like any photo you may have made into a Lithophane or rotary bit engraving, you stll may have to edit the image like lightening or darkening, contrast, sharpen, ect. before bringing it into PhotoVcarve.

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Re: Can PhotoVcarve be used to Laser engrave on a CNC Router????

Postby dlgabry » Sun Mar 25, 2012 12:52 pm

Thanks for the info, Jeff! Yes, there's a lot of playtime going on right now until I get the settings right. I'll try your suggestions this morning. I'm really happy with this laser - no noise, no tear-out, no staining, no sanding & no waiting till everyone's awake in the mornings. It's way more powerful than I thought as my first attempts just toasted the whole picture black and about 1/32" deep.

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