PDA

View Full Version : Laser Engraving and Christmas Presents...



Dragons_fire
11-28-2010, 01:07 PM
Heres a few pics of my latest project. Ive been making lots of pens for presents and a lot of the guys i work with suggested i do this.

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1000996.jpg

Its made out of parts i had laying around, other than the laser which was ordered from DX for under $30. The steppers are 12v 36oz/in unipolars and run off of drivers i made from L297 and ULN2308 chips. The timing pulleys, belt and the rails the laser slides on were salvaged from old printers and scanners, and the rest is made from 3/4" UHMW.

The cicruit for the laser is still just breadboarded, i will hopefully get it made today.

Im using EMC2 on a spare desktop i had laying around, i would like to run it off my laptop, but it has too much latency. Im using Engrave-11.py for engraving the text, and dxf2gcode for my graphics.

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1000994.jpg

I've been too scared to try it on a real pen yet, just because it doesnt always burn everything 100% yet. So far i have just cut up some 3/8" dowel to practice on. On the one that says "Merry Christmas", i can only write at approximately .125in/min. The Dragons Fire one was written around 1.5in/min just because it is slightly darker.

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1000995.jpg

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1000993.jpg

Dragons_fire
11-28-2010, 01:23 PM
Heres the fish I did on the back of the Dragons Fire one..

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1000997.jpg

And some details about the "pen" holder. The longer piece of aluminum on the right side, has a cone shaped piece of silicone and the smaller one on the left has a small cone shaped piece. the left side is spring loaded, so all i have to do is push the pen in that side, line up the other side and let go.

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1000998.jpg

Dragons_fire
11-28-2010, 01:37 PM
I drilled through the side of the aluminum "briefcase" that i put it all in, and mounted the parallel connector and 2 banana plugs. The whole thing runs off the PS in the desktop, so i put 12v in through the banana jacks.

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1010002.jpg

The boards inside the case are:

The top one is kind of like a breakout board, it takes my 12v in, and outputs 12v, 5v and ground on the three terminal strips. Then the bottom two boards are my stepper drivers.

http://i163.photobucket.com/albums/t305/dragons_fire_photo/CNC%20Laser/P1010001.jpg

The darlington chips get to about 45 degrees C after running for an hour, and the steppers warm up too while running. I put the fan in the top to blow cool air down onto the electronics, then it exits the electronics enclosure through small holes that are aimed right at the steppers.

danlb
11-28-2010, 02:24 PM
I am VERY ipmressed. Nicely done in all respects.

The only thing setting it apart from some commercial models I've seen are the yellow DANGER stickers.

Dan

Evan
11-28-2010, 02:50 PM
Outstanding! I love the entire concept! Super simple, light weight and portable. The only thing I see that needs to be addressed is the heat sinking of the laser head. Change that block of plastic to a block of finned aluminum or the laser is going to bite the dust. Make the laser head a close fit and install with some heat sink grease and a small setscrew. Also, the lens focusing adjuster is always loose on those so give the threads a couple of wraps of teflon pumbing tape.

For best results use fine grain hardwoods. Softwoods burn too easily and unpredictably and coarse grain woods like oak burn at different rates across the growth rings.

The focus is critical. You can tell when it is correct because the spot turns from red to incandescent white as it burns when it is well focused.

kf2qd
11-28-2010, 03:00 PM
How about giving some more details on that laser. Could think of a few other things that might be possible, and that sounds plenty affordable.

How many watts, what kind of power supply???

Thanks -

kf2qd
11-28-2010, 03:13 PM
I found the item on Deal Extreme - But they can't ship to the USA because the FDA needs to protect us from our own stupidity...

Have to see if I could find a way to ship it to Mexico...

Evan
11-28-2010, 03:17 PM
It is 200 milliwatts and runs on 6 volts DC. It cannot be imported to the US or Australia. Canada has no regulations on the import of lasers of any type that emit visble radiation below one half watt.

IT IS NOT EYE SAFE. Even specular reflections have the potential to cause eye damage. Diffuse reflection won't at this power level but don't take any chances. An LCD autodark welding helmet is 100% protection.

http://www.dealextreme.com/details.dx/sku.11315

The problem with trying to drop ship to Mexico is that they won't take your money if it bills to a US address.

Dragons_fire
11-28-2010, 03:29 PM
Thanks for the comments. The laser is a 200mW red laser from Deal Extreme. I think its a different model than Evan is using, but its almost the same.

As to Evans suggestions, im out of 317 chips, so right now the laser is running at 5v off of a 7805, it doesnt seem to heat up at all, even after running for hours. I also took the weak little spring out of the focuser and but in one thats about 10 times as stiff. It stays in focus really well now.

I have been using an autodark welding mask while playing with it, and i use an OA #5 welding mask while trying to focus because it blocks enough light i can really see the dot it makes.

Most of the pens i make are hardwoods, and i have played with some little pieces of bloodwood, mahogany, Padauk and Purpleheart. The purpleheart and Bloodwood burn really quickly. Im guessing its because the wood is a darker colour, and they have so much oil in them that the oil burns easier.

I have the laser in series with a 470ohm resistor, and that gives me a really faint little dot i can use for lining up the laser with the start point. It then uses a darlington to bypass the resistor when the laser is supposed to be on. I just use the Z-axis direction to turn the laser on and off, and i made my code with just a couple thou of z axis movement. This works good, because especially with lighter wood, the laser needs to sit a little longer to start burning, then when it does, the speeds can increase.

Dragons_fire
11-28-2010, 03:33 PM
I also meant to add that I usually close the lid of the case when its running, just to stop the reflections. I had it open in the dark one evening, and the whole room sparkled from the reflections off the pen. They were also clear coated before burning, and as the pen turns its like having a disco ball with a red light!! ;)

Dragons_fire
02-07-2011, 12:30 PM
bringing back my old thread...

I added the 317 regulator yesterday and cranked the laser up to slightly over 6v. Before it was running at 5v off of a 7805, and i could burn light coloured woods at around 7mm/min, and sometimes it would skip small spots. Now i can get the same amount of burn without skipping at a feed of around 75mm/min.

So onto a question. Im just having a brain fart and i cant figure this out.

When I built the machine, it thinks that the pen rotation is just a linear movement. I was using 10mm (3/8") dowels to represent pens so i told the machine that one rotation is 31.4mm.

If i throw a 25mm (1") dowel in there, the circumfrence is 78.5mm. If i leave the program the same, are my engravings going to come out 2.5 times bigger? Im fairly sure thats right, i just keep getting confused and cant figure it out.

TGTool
02-07-2011, 12:47 PM
Yes, the program will rotate the part the same angular amount so the circumferential distance will just be multiplied by the difference in Radius.

Dragons_fire
02-07-2011, 12:51 PM
Yes, the program will rotate the part the same angular amount so the circumferential distance will just be multiplied by the difference in Radius.

Is it the difference in radius or diameter?

macona
02-07-2011, 04:21 PM
Circumference.

If you use a friction drive you wont have this problem it drives the surface of the item so no matter what the diameter the engraving will be the same size. Like the one in this youtube video:

http://www.youtube.com/v/WbPJ7eSyfxc

Easy to make, both wheels are driven with a timing belt. I have even marked cigarettes with one. If you need a little more wight metal washers at the ends work nice.

-Jerry

justanengineer
02-08-2011, 12:07 AM
Very nice job. It has me thinking I really need to do a CNC project.