Laser cutter / engraver

[yngndrw]

Yes you are probably right.

Peltiers have a maximum differential temperature (Delta T.) which means that they can have upto a difference of usually 50C between the hot side and the cold side. This delta T is usually only obtained when there is no "load". (I.e. It is pumping no heat.) However as the amount of heat pumped rises versus the cooling power of the peltier, the delta T is decreased.

In this application, seems as the output power of the laser would probably be limited by factors other than the temperature, delta T probably doesn't need to be anywhere near the specification of the peltier. I think an 80Watt peltier running at around 10-20Watts would be more than enough. This would increase efficiency and should still be able to get sub-zero temperature, allowing the laser diodes to be pushed. The fact that the "hot side" of the peltier is going to be water cooled, would mean that the delta T is pushed to it's full potential.

Can anybody explain to me the limiting factors of a laser diode, as well as how long a 112D Sony DRU-190S laser diode could live when pushed to 500mW with this kind of cooling ?

Also does anybody know what current would be required to run one of these lasers at around 500mW ? I don't have a LPM and I don't intend on spending that much money for one.

Thanks.

 

[yngndrw]

I just noticed that stonetek.org is selling Sony SLD1239JL laser diodes. How do these compare to the 112D laser diodes in terms of how much they can be pushed.

The datasheet says 180mW at 40% duty cycle. I wonder how much it can be pushed with cooling. The same / more than the 112D's ? If so it would be much easier for me to buy those. I could also buy the safety goggles from there while I'm at it.

When can I post links btw ? I havn't found any information on the restriction of this forum.

Edit: Just looked up about the SLD1239JL laser diode on this forum and it seems about 150mW with air cooling is the max of them.
Woop said earlier that the 115D laser diode can hit around 270mW. I will have another search but incase I cannot find it, is the 112D the same ?

Edit2: Just found, the 112D is the same as the 115D. Guess I'll be digging my own laser diode out of a drive then. :c
Could anybody measure the laser diode out of a 112D / 115D for me please, all dimensions and in mm. Thanks !

Edit3: Just found out that the Sony DRU-190S laser diode is better than the 112D / 115D. (Well the same but easier to remove.)
Could anybody get me dimensions for this instead please ?

 

[Photon_Pharmer]

what could I expect the life of the laser diodes to be ?

I think that the only way to know is with experimentation. You should be prepared to go through a few diodes on your quest.

My advice would be to go with one diode >1watt infrared. Just find the power level you need to do the job. You can easily spend all your creative energy trying to combine multiple beams and wavelengths, plumbing cooling lines,... and never get to the actual CNC mechanics. Check out the laser shows that folks are building, getting those things dialed in is pure black magic.

 

[Schrecken_Licht]

How thick is the rubber you want to cut? If you're talking like wetsuit thickness, I think you'll need well more than 500mw or even a watt. I know my 20 watt CO2 laser could do it, in fact focused it will cut thru fiberglass cloth like a hot knife thru styrofoam. That would be more than plenty to engrave (well, depends on what you're engraving on....) and probably ideal to cut fabrics and materials.

I don't know what you're budget is, but you can get a ready-made CO2 laser or build one yourself, though it would be a good bit more costly than a diode laser. There's also at least one person on these boards who can build these lasers. But there is one thing to consider - with CO2 lasers you need special optics - which can be very expensive, though you can find good ones for sale cheaper, like on Ebay.

 

[yngndrw]

Photon_Pharmer: I hear you with that. Why do you say infrared instead of say, red ? I'd like a coloured laser so I can turn it down and align it "by eye". Though if infrared lasers are cheaper per watt, I'd be willing to give up that. I will have a look around, but they seem expensive.

Schrecken_Licht: The neoprene thickness is upto 1cm. The engraving is into plasic (Clear) and maybe even aluminium. (Silver) I understand that these are far from ideal colours though.

Regarding CO2 laser tubes:
I wanted to go the solid-state route for two reasons. Size / weight as the machine was ment to be quite small and also I wanted a "moving laser" machine, so the laser can't be too fragile. Also the cost of the CO2 lasers, along with the cutting gas to clear the smoke from the lense was too much. Then again, I've only seen a 100Watt CO2 laser on Ebay.

For the lenses, I think I've seen CO2 laser lenses for around £22 which is acceptable. I suppose I could make my own CO2 laser tube, but I'd have no idea about how to dimension it. On the other hand, I can get small amounts of CO2 with no problems - I used to work at a paintballing site and although they mainly use compressed air, they do have some CO2.

Might be nice to build one of around 5Watts. Should be pretty small.

Are there any links so *detailed* guides on building CO2 laser tubes ? I've not seen a detailed one yet.

Thanks.

Edit: Just found a guide and I never realised that the CO2 has to be constantly replaced. I don't think I can afford to get a bottle of CO2.

Edit2: Just asked a company for a quote on a 1Watt 670nm laser diode. If it isn't too much I might go for that. What do you think about 1Watt ? Enough or not ? If not what kind of power do you think I'd need ?

 

[Photon_Pharmer]

Why ir? Get on ebay, you'll find ir diodes up to 100watts. 1-3watt usually can be had for under $75.

 

[yngndrw]

Ah, I've been looking on the UK Ebay and saw nothing. Just a shame that the shipping is a bit high sometimes.

What power rating should I be looking out for ? 1Watt ? More ?

Cheers.

 

[Photon_Pharmer]

http://cgi.ebay.com/Laser-Diode-1-2...oryZ7287QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
I see these available all the time. They are often used to "pump" solid state lasers. I don't know what power level you will need. I've seen video of an ir CNC cutter on here somewhere, there should be component specs for it.

 

[yngndrw]

Alright then I'll have a look for that thread.
Cheers.

Edit: It was very hard to find it when the forum only allows you to get 10 results per search. Ended up having to use google to search the site.

I found it though, it was the same project that was posted on CNC Zone, the one that linked me to here in the first place. The thread starter was Fred_DASP, seems as I cannot post links.
He was using a normal DVD writer laser, the red one. He was engraving into black plastic - Not enough power for my requirements I don't think.

I have however found a thread talking about 1Watt lasers and what can be done with them.
I think I'll be okay with either a 1Watt laser or a 2Watt laser. I have found a can-like 1Watt infrared laser diode for $80 shipped. A bit more than I wanted to spend but not too bad. What do you think ?

Edit2: I have found a nice 2Watt 808nm (Infrared) laser diode on Ebay and I may go for that.

I would like to select some safety glasses however. I have seen some on Ebay (Search for item number 150175930288), are these any good for this laser diode ? They say "808nm-850nm Diode Laser OD= 2", but I'm not so sure what OD is even after searching.

The laser diode says "Beam divergency(deg):12/40", why are there two numbers and what does this mean ? I expected just one number showing the angle from the axis the laser is pointed in.

Thanks.

Edit3: Started to design the laser head. I started by drawing the part that I cannot control, the laser diode it's self. It's in a generic TO-3 package.

Attached is a cute little render of it.

I'll do the rest of the laser head once I've had some time to think about how to do it.

Hmm, a small aside. I wonder if this laser will be able to engrave copper. I.e. Making PCBs with a 2Watt laser.

 

[Dark_Horse]

Sorry for the OT
Woop,

ok i take back what i said about the optics being useless, i just tried using the objective lens (the one mounted on a servo with magnets and coils) and it works really good, parallel beam width is less than 1mm... (awesome) i mounted it in an aixiz module

I think this is important, especially for those of us trying to find lenses that are coated for 405nM, this would mean the best ones to use are the ones that came with the diode, sounds good anyway :. I love the sound of a 1mm BR beam !
Which lense, from a PS3 sled, or a 115?

 

[Photon_Pharmer]

The safety glasses are a must, especially with the invisible wavelengths. These will allow you to focus your beam safely, and more effectively. OD=optical density, the negative logarithm of transmission. Someone posted a chart that shows the amount of light attenuated at each OD #. This forum had a crash a few weeks back, this may be leaving some gaps in your searchs.

 

[woop]

Sorry for the OT
Woop,

ok i take back what i said about the optics being useless, i just tried using the objective lens (the one mounted on a servo with magnets and coils) and it works really good, parallel beam width is less than 1mm... (awesome) i mounted it in an aixiz module

I think this is important, especially for those of us trying to find lenses that are coated for 405nM, this would mean the best ones to use are the ones that came with the diode, sounds good anyway :. I love the sound of a 1mm BR beam !
Which lense, from a PS3 sled, or a 115?

i used the objective lens out of a 115
the lens in the blueray is actually part frensel for a shorter focus point. so it leaves rings in the beam.
i think the 115 lens is also part frensel but the lines are only around the outside of the lens.
i don't think it would be much good for pointing, more for short distances.

 

[yngndrw]

I feel silly now, I searched for information about OD yet missed the stickie in the safety forum. I posted in that about them.

Regarding the laser head:
I have had a sleep and still not come up with an idea about how to hold the optics, however I have thought of the optics that I want.

A two lens system, one focuses the beam, the second makes it parallel. This system means that the first len's position isn't too important and the second can just be adjusted to align it all. However the alignment on the axis is very important for both lenses. (See attached.)

The bit that I'm un sure of is how to secure the lenses. In adition to that, I need to be able to adjust the second lens' position along the axis without the risk of it coming loose / unadjusted with vibrations. I also want it to keep aligned with the axis at all times. (I.e. Adjustment via one screw would be ideal, leaving the rest upto the machining accuracy.)

On another note, the stepper motors have arived and are quite cute. I will get designing some microstepping controllers soon.

I have also sketched out the laser diode holder and waterblock. There will be a 1MOhm resistor mounted to the bottom of the laser diode to stop static. This will sit in a small channel in the copper plate. This will unfortunatly loose some of the cooling effect, but it shouldn't cause a problem. On the positive side, it will mean that the laser diode will be indestructable as far as static goes. I will probably insulate the laser diode from the copper block with a mica washer.

I have also worked out how much I need to cool.
The laser diode takes 6.2Watts of power. 2Watts is emitted as light leaving the rest as heat. However, if I was to try and cut something that's highly reflective the 2Watts of light energy would bounce back up into the laser, resulting in 6.2Watts of heating.

Hence 8-10Watts of cooling should be more than enough.

 

[yngndrw]

Does anybody have any thought on how to secure the lenses above, to allow *easy* adjustment of the second lens without affecting the alignment ? I can't think of a solution for this.

Also, do you think this setup would be able to cut the copper off a PCB ? (Leaving the fiberglass underneath.)
Should I go for a focused beam, or a parallel beam ?

Thanks.

 

[woop]

if you have a ps3 sled, you could use the linear lens servo (stepper motor) out of that and put your concave lens on it.
someone would probably have a few they can sell you. maybe ask daedel

or you could have some sort of threaded barrel

 

[yngndrw]

Do you mean the servo motor that moves the whole sled ?

The motor driving the gold-coloured screw drive in this picture: www <dot> gzskydz <dot> com <slash> admin <slash> upload <slash> upload <slash> 20071013185452 <dot> jpg

The problem with using a threaded barrel is that I can't really adjust it while testing it (Easily) using that method. Maybe putting a nut on the end of the threaded lense holder would allow adjustment with a spanner ?

Thanks for the ideas.