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Author Topic: My first attempts at laser engraving.  (Read 91499 times)

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Re: My first attempts at laser engraving.
« Reply #100 on: July 05, 2009, 04:59:26 AM »
Thanks Tweakie and Guy,

I appreciate you both for your wiliness to give an honest opinion. Guy, that was a funny comment about being insane. HA The answer is yes! (in a good way, me thinks) The only thing I know about a “Laser” is that I’m impressed with the engraving applications and I could use one for my wood projects. I’m with you regarding getting the most for your money but unless someone offers up a different option that is kind of easy like this one; I will go ahead and give it a try. I will definitely wait to see if you or anyone else has a recommendation to consider. I know that this is an experimental type of deal. If I’m wrong about this being kind of an easy setup, please speak up. Guy, you mentioned having control via the CNC machine and this unit does come with a driver circuit board that works with Mach3 so I was think’n that this would work. What system do you use? It sounds like you use a more powerful system.

Tweakie, I had no idea that a heat sink and fan would probably be needed. I will figure that out before I do anything. I was excited to finally see someone actually having success doing this. The add on “Laser” seems to be perfect for my engraving needs and maybe I will be able to cut with it as advertized but I won’t get my hopes up on that.

The point about burning on the edges is something that I had heard of. A printing company has a nice 30K! system and he explained that he uses wood that has a coating on it and this eliminates the issue. In general, I would not use this type of pretreated wood but I would like to find out if there is a coating that could be used. The burned edges in some engraving applications could give a branding iron type effect maybe.

Any other comments will certainly be appreciated.

Thanks Again!
Bill
« Last Edit: July 05, 2009, 05:02:02 AM by BJenkins »
Re: My first attempts at laser engraving.
« Reply #101 on: July 05, 2009, 05:58:16 AM »
1/ I do not use a laser system at home, yet. I have used many laser systems.

2/ diode lasers "seem" like a cool idea, until you realise the drawbacks...

3/ diode laser like soft start and soft stop or they die very fast, CO2 lasers can go on/off at 10kHz or more no problemo

4/ diode lasers need low voltage and high current, CO2 lasers need high voltage and low current, lot cheaper...

5/ diode lasers above milliwatts aren't spot / single small round beam type diodes any more, they are usually bar / wide flat beam type diodes, suddenly the whole optics thing gets far more complex.

6/ diode lasers generally don't produce pukka IR which is what you really need to cut and engrave, diode lasers are FANTASTIC for use in creating light shows.

================

I've seen with my own eyes 18 watt CO2 lasers vastly outperform 50 watt diode fibre lasers on wood / plastics / leather marking and cutting, not just in quality, not just in speed, but also in ease of use... but then the fibre laser was bought to engrave part numbers and branding on to small precision metal parts, and that job it did EXTREMELY well.

Tweakie has in reality gone about as far as you can with the low power laser diodes, rip apart an old CD or DVD burner if you want to play on the cheap, but it will tell you nothing useful about high power laser diodes or high power CO2 lasers.

CO2 lasers are basically just a glass tube with an anode at one end and a cathode at the other, and a mixture of gases inside which are excited by the high voltage (15-25 kV) much like a neon tube or flourescent tube... they really are as non complex as that.

the big difference between a neon tube and a laser tube is the mirrors and lenses, interestingly made of semiconductors for IR wavelengths, plus the tube is die straight, plus it may have an outer sheath that is water cooled.

the CO2 laser PSU is not just a neon transformer HT source, you can connect a potentiometer up to it, or a CNC machine output, and get on/off and PWM control of power, so your XY machine moves at a constant mm/sec and the laser simply goes on/off and various power levels to get the desired effect...

unlike the diode laser the tube CO2 laser can do this on/off PWM thing at many kilohertz with no ill effects.

to CUT as opposed to ENGRAVE you need (should have with engrave too really) a combined focus lens and air jet, so the vapourised material is blown away, you need to match feed rates / laser power / PWM duty cycle well to cut or engrave cleanly, with a CO2 laser PSU capable of multi-kilohertz response this is a piece of piss, 50mm/min @ 50% PWM gives the same delivered power per mm2 of work as 100mm/min @ 100% PWM, but on a given wood each may well burn to a different colour, hello "grayscale" - don't even dream about doing this with a diode / fibre laser.

Fixed laser tube and flying optics adds hugely to the build cost, those optics have to be spot on at both ends of the table X and Y travel, then more complication for Z focus... if you can mount the tube on the Z things get vastly simpler and cheaper.

health and safety and other legal stuff also adds vastly to the cost, HEPA air filters and sealed negative pressure cabinets and so on and so forth all start costing lots of money very quickly indeed... in my shed I don't need any of that stuff, I have a brain, and I'm not selling it as a turnkey commercial product.

-----------------------------

in science fiction the defence against a laser is a mirror, and basically it is right, anything that is "shiny" to THE FREQUENCY AT WHICH THE LASER DELIVERS THE BULK OF ITS POWER will not cut or mark at all well, an IR CO2 laser works best all round because not many things are "shiny" to IR, far more stuff is "shiny" to visible light..

Tweakies lower power diode laser will simply bounce off a glass mirror, but turn it the other way round and it will slowly burn through the silver coating on the rear of the mirror, then paint it black and you have a nice fancy mirror.

As anyone with a greenhouse or who drives knows, UV goes through glass and IR doesn't, so it is a LOT easier to engrave glass with an IR CO2 laser than with a visible light laser, the visible light laser will usually melt and crack the glass before it engraves, the CO2 will engrave on a mere fraction of the power the diode laser uses, and the flipside of power is feed speed, if a is 100 times as effective as b then a uses 100 times the feed speed.

A 50 watt diode / fibre laser is absolutely great if all you ever want to do is mark / etch metal all day long, it is basically ********* all use for cutting out material into patterns, cutting gaskets, engraving glass, or anything else.

---------------------------------

In closing

cheap CO2 laser tubes have a bad rep for "short life", eg 1,500 hours or so, you get a LOT more hours running it from a pukka DC laser power source than you do from a neon sign transformer, which costs nearly as much anyway, plus, 1,500 hours is 30 hours a week for a year, if you use it 5 hours a week it is six years, and don't forget diode laser life is not that much longer, and literally and absolutely killed the instant you use anything other than an ideal power source, it's like being given a random light bulb, the difference between "bright" and "blown" is fractional, but a tungsten filament light bulb is about a thousand times more forgiving than a laser diode... you could get (all other things being equal) 750/800 mW out of a bog standard DVD writer diode for several hours, maybe tens of hours, and save 455 bucks over that ebay thing, which is TOTALLY lacking in all the essential info (looks like a surplus Coherent unit though)

but tubes are fairly cheap and easy to swap out, just like changing a flourescent tube in many respects.

CO2 lasers are also very well understood, which means it is easy and cheap to take adequate safety precautions, unlike diode / fibre lasers you can actually watch a CO2 laser below about 50 watts work via a sheet of thick glass / acrylic and safety goggles

CO2 lasers are mass produced, and the only game in town when it comes to producing a genuine beam at any decent levels of power, with no extra peripherals required.

CO2 lasers have essentially infinitely adjustable power output, diode lasers do not, more like an arc lamp, and CO2 lasers can be turned on and off in 1 thousandth of a second, diode lasers can not, you're talking multiples of tenths of a second to ramp up and down.

HTH etc

Offline Tweakie.CNC

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Re: My first attempts at laser engraving.
« Reply #102 on: July 05, 2009, 08:38:41 AM »
Hi everybody,

More for information only, as I have already posted the picture on another thread, but these little gaskets were cut with a 150 mW diode laser.
The crankcase was scanned (on my printer/scanner) and the image converted to vector and then to GCode. The gaskets produced are a perfect fit and probably a good example of what can be achieved.

Tweakie.
PEACE
Re: My first attempts at laser engraving.
« Reply #103 on: July 05, 2009, 09:00:50 AM »
That is impressive! Especially considering that you don’t have much money in your system and that a cheap China Laser is $1500US plus.

How long does it take to cut something like the gasket?

Thanks,
Bill

Offline Tweakie.CNC

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Re: My first attempts at laser engraving.
« Reply #104 on: July 05, 2009, 10:46:12 AM »
Hi Bill,

As far as I can remember the feedrate was set at 30 mm/minute so total time would have been around 15 minutes per gasket. OK it is very slow but then I have all the time that God has decided to allow me.

Tweakie.
PEACE
Re: My first attempts at laser engraving.
« Reply #105 on: July 05, 2009, 11:40:55 AM »
Thanks Tweakie,

Slow, yes but you have found another way to use your CNC. I'm starting to understand. I can see that this little add on is not really going to satisfy someone who needs a laser for anything more than making a few slow but precise parts or engravings. I can also see that the durability issue needs to be considered before purchasing a $455 experiment like I'm considering. It would be nice to own an Epilog Zing 60W but I bet the price is over $8000US. Just guessing. I'm not sure I really want to know. HA! I did some other researching/dreaming to see what the small Laser Engravers cost and I found some $1500 China EBay "deals". I'm not too sure about those.

I wonder if the 1W unit would be much faster? I do my 2D CAD work using BobCadCam and I generate my GCode from there. I can import .BMP images which I have played around with. I read that you do some editing to remove Z movement from the GCode and I guess that is something else I need to consider. The engraving I would like to do is on the same size and quality as your Daisy Azimuth but much more detailed and I would like to cut a few small parts that are .0625 in thickness but my router will do that. I also wonder about programing the start and stop that I assume is required. I think I have too many questions to ask at this point but all of this information has been extremely helpful.

I'm still think'n and learn'n.

Bill

Offline Tweakie.CNC

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Re: My first attempts at laser engraving.
« Reply #106 on: July 06, 2009, 02:34:30 AM »
Hi Bill,

Initially I did edit out the Z moves but have now found that there is advantage to leaving the code 'as is'. I now disable the Z axis movement and make use of the Z code, by altering the Z Axis DRO scale factor to set the required dwell time.

Guy is, of course, quite right - If you want to do serious work then you need a serious laser and as we already know, nothing in the world of CNC comes cheap.

Tweakie.
PEACE

Offline Chris.Botha

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Re: My first attempts at laser engraving.
« Reply #107 on: July 07, 2009, 12:07:47 AM »
here are my first results tweakie. been pretty sick and had family issues so bit delayed. th "tick" marks  are from bad pathing. brought Z down in a ramping move by mistake. will retest later.


Offline Tweakie.CNC

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Re: My first attempts at laser engraving.
« Reply #108 on: July 07, 2009, 01:33:08 AM »
Brilliant.

Tweakie.
PEACE

Offline Chris.Botha

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Re: My first attempts at laser engraving.
« Reply #109 on: July 07, 2009, 05:21:42 AM »
thanks. building my own bluray laser now. hoping to get sustained 400mw from it. been on the laser forums a bit :)