Laser questions for Viktor

Unfortunately I have not been able to find the two posts I'm about to refer to. I'm not even sure it I saw then in the forums or on blog posts somewhere. However, somewhere I read about Viktor using a laser welder to weld a nut to something, I can't remember what exactly. Also, I read somewhere about Viktor playing with liquid glass and using a laser with a fiber optic cable to set the liquid glass.

I'm hoping Viktor or something else can tell us about the laser welding rig and the laser used to set the liquid glass, especially if they are self build. Details about the power supplies and lasers used would be greatly appreciated.

I have been fascinated by lasers forever; however, in my old age I have become more cautious of experimenting with things that could permanently hurt me. I would love to make a laser cutter to cut balsa wood, but I'm not sure how powerful of a Laser LED I will need or enough about electronics to design the power supply.

Any information will be greatly appreciated,

Jeremy

I don't think that cutting balsa with a diode laser is possible at all.

Afair Viktor had some CO2 Laser... I can't remember really.

'sid

Hi Jeremy,

... in the past i used and built different Lasers:

20 years ago i started at home with a 'naked' CO2-glasstube-laser with 1,5Watt output-power (price ~1000 Deutschmarks) and a 1,5kV DC power-supply for cutting thin sheets of paper, plastic and some other materials by feeding the ray with moving mirrors and focussing the beam with a Germanium-lens. This was only good for thin sheets (<1mm) of good absorbing (or dark coloured) paper, plastik, fabric and leather ...

Some years later, in 1993-1995 i revived this sytem for a laserplotter with a sealed 5Watt-CO2-Laser (~3000 Deutschmarks) embedded in a self-developed 2D-plotter for marking signs and cutting labels and stickers - worked good, but the mother-company had had some trouble so the R&D was the first area to shut down ...

In 2003 i had the possibility to make some testing and developing with a turnkey 20Watt disc-laser (~30000 Euros) with a spot of 10 microns - a very fine but expensive 'toy' for micro-fabrication ...

In 2006-2007 i used and optimized two welding-lasers from Estonia - one with 3kW/puls (e.g. 30Watt CW), 70 microns spotsize and the other with 500mJ/puls (e.g. 3Watt CW) and 10 microns spot-size. The market-prices should be around 30000 Euros.

Then in 2007 i developed a micro-welding system with a fiber-coupled diode-laser with 8Watt output-power and focus-diameter of 0,1mm. Costs: for the laser-diode ~350 Euros, ~300 Euros for the powersupply and some ten Euros for the stabilisation and PWM-electronics.

Actually i have a fiber-coupled 1Watt-diode-laser with 0,06mm spot at home, so i'm planning some experiments with sheet-cutting and micro-laser-curing or -sintering.

The experiments with water-glass were around paste-extruding at room-temp for building ceramic objects. If i can cure or finish them better with the laser, is an open question ...

Viktor

I had not read this thread [forums.reprap.org] until just now, it answer a few of the questions I had. Now I know what power and type of lasers used.

Jeremy

Thank you Viktor this information will be helpful. However, what I'm gathering is my idea of a cheap home built laser cutter for balsa is a little beyond my means at the moment. But prices will come down as the technologies become more prominent.

Jeremy

I have been doing more reading, and it is starting to appear that a 35W CO2 laser is totally doable. The cost of the tubes have come down *a lot* from the last time I looking into building one.

However, I'm coming up sort on information regarding a power supply. It appears as most people are using a neon sign transforming that is rectified to DC. While I'm sure this will power the laser, I'm looking for a more controllable laser output. I did find a rather complicated power supply in the Electronic Gadgets for the Evil Genius book. It is both voltage and current limiting, and includes the 10 second delay required for Bureau of Radio and Health compliance. However, I'm not genius enough to understand all of the complexities of the schematic in order to add computer control.

Does anyone know of an available power supply schematic that will allow the power output and pulse length to be controlled by a computer/mcu? Or a more appropriate forum to ask in? While this is the reprap forum, it seems people here have broad subject expertise and are pleasantly helpful.

Thanks in advance,

Jeremy

> The cost of the tubes have come down *a lot* from the last time I looking into
>building one.

How much was it, and how much is now?

Honestly, it probably more an issue of availability and my own value of money. I have been able to find Sealed CO2 laser tubes from various sources on the net for around $300 - $400. Given my current financial situation, that falls into the "doable" category. 10 years ago when I looked into doing his, information was harder to come by. I had instructions to build my own flowing gas tube, but the gasses where hard to get where I lived. And to be honest, back then $300 - $400 seemed like a lot of money.

So, I'm not really sure if things are cheaper, or with the evolution of the internet and myself, if information is just easier to get and my pocket is deeper.

Jeremy

I've been doing a bit of testing with the Sinterstation I use and I'm quite surprised by the results.

I'm managing to sinter powdered nylon (albeit quite lightly) at around 3 Watts of laser power without problem. I imagine this could be brought down to 2 Watt. 12-15 watt is more normal for this machine. At 2 Watt, the result may be somewhat of a "green" part, but its quite encouraging that its possible to get the material to melt and adhere at such low (relatively) laser powers.

The biggest challenge for a homemade machine to replicate this is to keep the bed temperature stable. Of course, the relatively slow speed of our laser positioning system (cartesian bot vs galvo's) taking a long time to complete a single scan will also work against keeping consistent bed temperatures.

That said, reprap's community has already produced some fantastic ideas, and I don't doubt that if a design became viable, it would only be a matter of time before a more viable material that isn't quite as fussy as Nylon is found. Whereby we could use lower and less strict temperatures and lower laser powers.

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it would only be a matter of time before a more viable material that isn't quite as fussy as Nylon is found

Nylon is mechanically pretty sound, which I guess is why it is used. Its melting point is pretty high though (at least compared to the stuff we usually use) so I imagine that using a powder form of any of reprap's more common materials would make things much easier.

What is the formula to calculate the percentage of mirror transmission in laser cavity if one of the mirror is fully reflectivity 99.99 percent and another one is how much?

Thoughts on sintering plastic powders (Nylon)

If your powder bed was pre heated with warmed air to say 40 Deg C then a low power laser head is just that more doable.

Working on the principle that the bed is already a number of degrees warmer than ambient means the laser power is'nt expended warming up the sinterings that little bit.

I guess reducing the temperature difference from sintering area to non sintering area reduces the rate at which the heat leaks away (Thermo Dynamics) as well.

Raising the bed temp above ambient also makes it that much more easy to keep it at a fixed temp as you would only ever have to heat it.

40 Degrees C is about the temperature of a hot bath.

Would it be doable to heat it further ????

Thoughts for what they are worth.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Bonjour

I have a little question:
I want etching with a laser the photoresit of PCP
What is the wavelenght an the power for make this ?
I want use a diode laser with lens and mirror on table XY.

I have make a test with galvanometric head at 1064 nm and it 100% OK

But there is only a little bug: the price of this system and i am amateur.

Thanks

Thierry

Hi Thierry,

for normal photoresist you need higher energies with 1064nm or a CO2-laser with 10600nm ... with a black coating instead of the normally transparent photoresist you can use diodelasers with 500mW and higher ...

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Viktor
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Hi Viktor,

I habe 2 dealers of PCB, the color of the first is dark green and teh second is dark blue ( blue nigtt ).
What is the best color?

OK for the CO2 but i dont want use. I have use in industry, big power...

Is it important to use 1064 nm ?

For the diode it ok for me.

Many thanks

Thierry

... i would try with dark blue - the more 'distance' to the laser-wavelength, the better.

My 1Watt-diode has 808nm, the 5Watt-diodes 975nm and the fiberlaser 1070nm ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]