dlgabry wrote:I've got to add this toy to my wishlist! Couple of questions.....
Was this done on bare wood, or was some sort of coating applied first?
The laser picture looks like there's a microswitch operated by the stud on the Z carriage?
I'm curous about the circuit you used to modulate the laser.
I think you said the feed rate you used was 40IPM?
The wood is unfinished birch cabinet grade plywood.
The electrical components were bought from RadioShack. Selectable 300ma power supply from 1.5,3,4.5,6,7.5,9 and 12VDC. A LM317T adjustable voltage regulator circuit. Schematic of circuit is on the package of the chip. This will give you variable voltage based on input voltage, but will not go down to zero volts, therefore you have to put a 5V 7805 on the output so it will give you 0-5V or lower based on your input.
Potentiometer is attached to Z axis through a 2 disk Huco slip clutch to keep over travel of Z axis from damaging potentiometer. The stud is to keep the board I made from rotating and has rubber between the stud and the board to allow for any slight wobbling of the potentiometer shaft. With this board, it works great on a laser that has Analog or TTL 0-5V Modulation that works properly, it needs an input voltage of 7.5VDC from the power supply which will give you 0-4.8VDC on the output. You move the Z axis to focus the laser off the material. I found that a black anodized surface works best for that because it does not reflect the beam and does not burn the surface while your adjusting the Z axis. I use the analog voltage meter to calibrate Z0.0" You just loosen the slip clutch and rotate the potentiometer until it just reads 0 Volts and then tighten the slip clutch back up.
I made a new profile in Mach for the laser. You have the go into motor tuning setup and change the Steps Per for the Z axis so the volts on the meter will go from 0-4.8V with the Z axis moving from Z0. to Z-.005". This movement is not enough to bring the laser out of focus. G-Code from PhotoVcarve then will vary the power from 0 to full power and give you shading and I used a Z retract of +.002" to insure the laser goes off completely when it retracts. When I get that laser back, I still need to refine the settings some more to get the image to come out perfect. Feed rates are a big factor with the power of the laser also. I found that 40-50IPM works best with my 1W-1.7W lasers. If you want it darker, slow the feed rate down, but of course it takes longer.
The problem I had with the analog modulation on the 1W laser was with no voltage to the connections, the laser would come on. I found that if I touched the the positive and negative wire together, the laser would go off. I started with a 5V SPDT relay so when Z went into negative, the laser would come on and when it would go positive on Z, it would go off. It worked, but the problem with a relay is the drop in voltage is not the same as the drop out voltage, therefore it was effecting the resolution of the lasered image. A diode across the positive and negative of the relay coil helped collapse the coil voltage quicker, but it was not enough. The relay package states it's good for 10,000,000 cycles, but I switched it on on/off 88,525 times in the last image I posted alone, so I needed something more reliable and switches on/off as close as possible to the same voltage. I then made a new board with a Triac to do the switching. It switched on/off within .0002" of Z movement instead of the .001” I was getting with the relay. The gate on the Triac needs 3V maximum voltage to switch, so changing my power supply to 6V and readjusting the motor tuning steps, I got 2.5V at a negative .0015” on Z.
Giving a value of .015” of cut depth and a retract of Z+.0015” in PhotoVcarve and making all white of a black and white image transparent, will generate a code that makes the cut deptch Z-.0015” where black is and will retract to Z+.0015” where white is. No special PP is used either.
jimwill2 wrote:Very impressive! Thanks for sharing details with us.
Thanks for the compliment Jim. It took some time to figure all this out and allot of help from my son.
I made this one today just for fun.
Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver