Need laser information

I am looking to do some work on developing a laser sintering machine. I'm Ok on the mechanical side of things, but know very little about lasers. Can anyone help?

I need know the following:-

I want to use a laser diode (I want to buy one, not salvage one from a DVD) what specifications do I need to melt ABS powder. I would prefer a visible beam as I feel this is a safer option. I live in the UK are there online suppliers of this sort of thing? What wattage and wavelength would be suitable?

What driver circuits do I need to drive the laser?

Any safety hints other than the obvious not to stare in the lens. Can I get safety goggles for extra insurance.

Do I need to focus the diode through a lens and at what distance to the object.

Any help would be appreciated.

Hi Martin,

... read through the LaserCutter-Wiki and the related threads in the forum ...

You need powers above 1 Watt in a spot of maybe 0.1mm, or it's no real fun with sintering

Comercial pigtaled diodes are in prices from 200 to 500 Euros, 808nm is 'dark red' and weak visible ...

Like posted in the Wiki you can apply a visible pilot-laser (e.g. a pointer) in the IR-beam ...

The power-sourcing and controlling is shown with some simple electronics in the Wiki too ...

Best hint is a pigtailed diode from Lumics (around 300 Euros) ... or a recycled 5Watt-diodelaser from me (below 100 Euros)

Edited 1 time(s). Last edit at 03/24/2010 08:49AM by VDX.

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Viktor
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Thanks Viktor this is just what I need.

I did look through the forums, but its becoming so large that I missed this!

Perhaps I should have take the hint from "Laser" in the title!

I'll do a bit of reading up on the subject.

Martin

Edited 1 time(s). Last edit at 03/24/2010 02:34PM by martinprice2004.

Perhaps something like this would be a more cost effective and simple solution than lasers.

[www.orbi-tech.de]

... some years ago i tested with similar optical heads for soldering - the focus was the same with 3mm diameter, but the head and the special lamps with a really small emitting spot were extreme expensive - the head around 3000 Euros, a single lamp (with maybe 200 hours lifetime) around 300 Euros!

Tests with sintering plastic powder went really fine, i've melted glass-powder to solid glass too, so you can make funny things with this toys ... but with a comercial pigtailed diode-laser with 9Watts power and a proper DIY-driver you're in a range of 500 Euros and you can reduce the spot-size down to 0.1mm diameter, what's much more interesting though

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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]

It's been an idea of mine to use three (or more) weaker laser modules that coincide in one spot from different angles.

The gain in this setup that I chase is limiting the power to one specified coordinate . No one laser would be demolishing anything on it's own. And the setup as a whole, shouldn't be able to burn too deep.

As an added bonus, each individual laser module ought to be quite a bit more cheap. A possible drawback would be that the modules has to be placed a bit from the focal point to leave sufficient room for the modules next to each other.

Two lasers could be activated, elevating the temperature locally, while a third bring the working matter over the melting point by pulsing or continuous drive. As I understand, it helps from deforming if the whole working piece is kept a few degrees below melting point all the way. But I think the multiple laser setup could improve precision.

... with the sinking prices of high-power diodelasers a multi-laser setup won't be soeffective as a single laser with the same power as three or more combined.

With more lasers you have to focus every one precise on the same spot or you'll receive lower energy density because of a bigger resulting spot.

On the other side you can lower the energy of a single laser by power regulation or by PWM:

With a 5Watt-diode i can go down to 0.5Watts too ... the minimum threshold current is something like 0.4Amps what's equivalent to 0.4Watts.

With stronger lasers the threshold level (minimal laser-energy) is higher - so for example my 25Watt-diodes have a minimum-threshold of 0.7Watts ... below it will work as a simple IR-diode without lasering.

With PWM i can reduce the resulting power to nearly 0 even with max. current by defining the ON/OFF ratio so, that the ON-time is only some microseconds and the OFF-time some milliseconds, what's resulting in some microwatts effective energy on the spot ...

The idea of using two different focussed diodelasers is good - one with a wide focus heats the surface short below melting temp., another with a fine focus rises the temp. in the spot to melt or evaporate the material ...

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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]

To fabricate an artificial bone, the degradation rate of which is adjustable, porosity and pore size is controllable, and internal continuity is good, a device is developed with nano-sized hydroxyapatite as raw material, micron-sized spot of high-power laser as energy, and selective sintering as technology to fabricate three-dimensional porous. Its basic composition, design ideas, features and working principle are introduced. The feeding mechanical system, sintering system, and laser focusing system are described in detail. The motion precision and laser-spot control precision meet with the requirements with testing.

http://www.jklasers.com