laser divergence and machine size

Discussions on optics for laser cutter/engravers

laser divergence and machine size

Postby educa » Thu Jul 12, 2012 9:01 pm

Hi,

I am almost ready to buy my laser tube, but my machine travel is larger then buildlog model.
My machineable distance is around 1,2 x 0,6 meter (4'x2')

I would like to buy a 80watt industrial reci tube.

Because the machine is bigger, the laser beam will at farthest have to travel around 7 foot distance.

Would that be possible? Won't my laser beam become too big before hitting my lens because of beam divergence?

Does anyone have any hints about beam size and divergence ?

Would this be possible at all? Is a 80watt tube better then a 40watt tube in such a case?

Kind regards,

Bart
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Re: laser divergence and machine size

Postby bdring » Thu Jul 12, 2012 9:39 pm

Bart
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Re: laser divergence and machine size

Postby educa » Thu Jul 12, 2012 9:55 pm

Bart,

My name really is also Bart. I know your calculator page, but that page needs beam diameters and divergence. That are details which I don't know about the reci tube. Thats why I was looking for more information about this.

Do you know about beam diameter and divergence of certain laser tubes and what might be realistic to expect?
My mirrors are 25mm dia. My znse lens is 18 or 19mm dia and I use the pro laser mount where the hole where the laserbeam enters is 14mm diameter.

Any help/hints please?
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Re: laser divergence and machine size

Postby bdring » Thu Jul 12, 2012 10:43 pm

I did this page as I was learning about laser a long time ago.

http://www.buildlog.net/cnc_laser/cnc_b ... search.htm
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Re: laser divergence and machine size

Postby educa » Fri Jul 13, 2012 7:40 am

The aperture of 5.5 and divergence of 2.5 I found there, have these numbers proven to be correct or are they only guessinh at that stage?
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Re: laser divergence and machine size

Postby bdring » Fri Jul 13, 2012 12:12 pm

That was pretty close to what I measured on my first standard 40W tube. Longer tubes should have a lower divergence.
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Re: laser divergence and machine size

Postby educa » Fri Jul 13, 2012 4:21 pm

Thanks for this information Bart.

You know, I would like to go with a 80 watt tube because my machine is big enough to house it + more cutting power is always nice if you can afford it.


At first 40 watt tubes look a lot cheaper and they are in numbers, but if a 40watt lasts 1000 to 1500 hours and a 80watt 8000 hours, then the difference gets a lot smaller of course.


My machine is able to handle plates upto 1220x610 mm with a resolution of 0.02mm per step (around 1270 steps per inch) in both X and Y.

The mirrors are not the big problem since these are 25mm diameter, where 23mm is usable of them.

The big problematic point is where the laser enters the pro laser mount. That laserhead has a hole of 14mm where the beam enters. After that there is again a 25mm (23mm usable) mirror so thats big enough and also the lens is between 18 and 20mm (forgot to measure. I bought it at cncoletech on ebay to be high quality znse lens 50.8mm FL. Anyway, even 18mm would do)


The longest path my beam would have to travel is 2.35 meter.

If I enter in your calculator an aperture of 5.5mm and divergence of 2.5mrad, then the spot size at 2.35m is 11.375mm which is still 2.625mm smaller then the hole in the laserhead.



So... thats why I was looking for real data about these tubes.


I think I found out that the 80watt industrial tubes sold by cncoletech are in fact RECI W2 tubes, so I mailed reci for info and hope to get it (I even wonder why they don't put this on their website, because it is in fact an important spec)

Now I'll lookup a few buildlogs for people with more then 40 watt laser and bigger build size then the 2.x laser to see if they might have some specs.

Kind regards,

Bart

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Re: laser divergence and machine size

Postby peter_ » Fri Jul 13, 2012 4:57 pm

I wish you the best of luck, and I'd love to hear more about your project.

I've been working on building a machine with a 1m x 1m travel as a hobby project for the past year. About a month of it was spent actually building the machine, and the rest of the time has been spend fiddling with it, replacing rail systems, etc, to get a flat beam path over the entire 2m travel. So far the Makerslide I used was the closest, but iirc (it's been a while) there was some wobble and a little skew, and I didn't have an appreciation of where it was coming from. I was using the 2.x parts, and the cheap chinese mirror/lens mounts.

best of luck!
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Re: laser divergence and machine size

Postby educa » Fri Jul 13, 2012 5:14 pm

I do have a buildlog at viewtopic.php?f=16&t=968

Until now it looks like the system is pretty ok and even the beam alignment is very OK. I tested with a very focussed red laser pointer (focussed to infinity, so pretty good focus but of course not perfect)

I managed to get the laser dot perfectly in center on all mirrors on all possible locations on the machine, so I guess my alignment will be spot on.

IF the laser beam passes that 14mm (which is big) hole then it should work perfectly. (I hope)


Kind regards,
Bart
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Re: laser divergence and machine size

Postby TLHarrell » Fri Jul 13, 2012 6:31 pm

If the rest of your beam path is 25mm, why not open up the hole in the laser head to 25mm or a lot closer to that than 14mm?
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