Laser mod kit?

MeanderBolt
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Laser mod kit?

Post by MeanderBolt » Sat Nov 30, 2013 10:49 pm

Has anyone seen or used one of these kits from JTech Photonics? While 1.7W is not a 40W CO2, it seems to do well with many soft (and usually dark) materials. I think I would want to find a way to cool it better though.
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twforeman
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Re: Laser mod kit?

Post by twforeman » Sun Dec 01, 2013 3:37 am

That looks like a neat kit, but alas in addition to being $225 it is also out of stock.
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orangezero
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Re: Laser mod kit?

Post by orangezero » Mon Dec 02, 2013 7:02 pm

I've been thinking of getting one setup for my delta printer or my cnc (whenever that gets done). These are some parts I'm interested in.

Lasers:
http://www.ebay.com/itm/Nichia-NDB7875- ... 2a215900d7 $99
http://www.ebay.com/itm/2W-445nm-M140-B ... 27ca04078a $68

Current regulator: (edit: unsure if this is appropriate)
http://www.ebay.com/itm/Blue-LED-DC-Ste ... 565e20423b

You'd also need a heatsink for the laser, and a power supply of some sort, as well as a way to mount. A lot of the DIY 2w laser discussion involves batteries and portability, which would be less of a concern here. You'd hate to have a battery run out in mid-etch.

I didn't realize these ~2w blue lasers could cut through 1/8in balsa. My idea was to use it exclusively for etching into acrylic or wood, or perhaps a few other things.

CAUTION, as most know, this would be highly dangerous to your eyesight unless a lot of caution and safety was built in. You'd almost need some type of case that would keep a stray laser beam from bouncing around and getting in your eye (and I've seen no shapeoko's that could). I'd be hesitant to have a setup with just goggles (although duplication isn't a bad idea).

In any case, I'd be interested if anyone had any suggestions. I'm curious about the current regulator I listed, as it has voltage and amp control. Others go higher, but limiting it to 2A is probably a good idea. I'm just not sure how accurate or robust they are. I have little experience with lasers, but have done a few projects with higher powered LEDs (xp-g, xp-g2, nichia 90+cri) which have the same constant current issues.

MeanderBolt
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Re: Laser mod kit?

Post by MeanderBolt » Sat Jan 11, 2014 4:57 am

Today my ADD pulled me back towards the laser thing again and I found a couple really good threads on the Laserpointer forums. The long and short of it is... for cutting in a precise way, 405nm is the way to go. You will see a nasty Coke vs. Pepsi argument about 405nm vs 455nm (visible light) diodes. The take away is that the 455 while more powerful in total output, can not 1. get small enough to cut in a usable way. It is not a round beam like the 405nm lasers. So while 455nm will cut, it will not be precise, and the kerf will be an odd shape as they put out an almost line like beam. I short line, but not condensed into a nice tight spot.

The 405nm lasers can be focused to a very tight beam ( less than 0.1mm) and can cut through many lightweight materials. You will not be cutting through any boards or metals with this set up.

If you have a healthy respect for lasers, you could also enter into the 975nm area (IR) and get much higher powers,and small diameter beams. But the danger goes up as you can not see the laser light. By the time you realize you shot your eye out, it would be to late to do anything about it, meaning... you are forever blind.

It was demonstrated that you can do PCBs with it which is an interest for me. Instead of milling your isolation areas, Y\you paint a copper board with black spray and burn off the isolation which is then the area that gets removed by a chemical etchant.

Clearly, if we had our druthers, we'd head straight for a 60W CO2 laser, but I just spent all my money on a Shapeoko. 8-)
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halfnormal
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Re: Laser mod kit?

Post by halfnormal » Mon Jan 13, 2014 3:37 am

I have talked to the folks over at Laser-Bot and their product seems like a nice all in one package. Searching ebay and reading forums, it is really hit and miss with rolling your own. I will be ordering one of their kits in a few weeks when I return from vacation. I will be detailing the build log here. This will be just to play with as I really want to purchase a 40 watt CO2 unit. There are a lot of cheap Chinese units now available for around $600.00 and there is a board available to have it run alternate cam packages. Now only if I could start a kickstarter for my CNC/LASER Cutter/3Dprinter all in one unit!

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Re: Laser mod kit?

Post by MeanderBolt » Mon Jan 13, 2014 6:55 pm

Searching ebay and reading forums, it is really hit and miss with rolling your own.
Yeah, this is why I just gave the condensed version. The above was squeezed out of too many pages of arguments between the folks who just care about silly bright lasers and the folks who understood what the guy was trying to do. You might want to ask the Laser-Bot guys what the how close you can get the laser to the cutting area and keep the focus tight. Also ask about the shape of the beam. I had read a lot on their sight and they were using the 445nm lasers. This may make a oblong beam which is not what you want. I was looking at them too until I read the bit about the 405 / 445 shape thing. I am still reading. I can not do much anyhow until my S2 gets here, set up, tested...

BTW,
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halfnormal
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Re: Laser mod kit?

Post by halfnormal » Tue Jan 14, 2014 3:27 am

I really doubt I will see a big difference in the ability to burn and cut with a 2 watt LASER regardless of the beam shape. The adage you get what you pay for is true here. That is why I mentioned the future purchase of a CO2 LASER. $200.00 is cheap to find out if I will really need/use a higher wattage LASER. The best part is that they are a USA company and support will be an email or phone call away.

Nigel K Tolley
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Re: Laser mod kit?

Post by Nigel K Tolley » Sat Feb 08, 2014 7:32 pm

Hi all,

You can modify a line projecting beam into a spot fairly easily, by using a shaping lens. A cylindrical rod will focus a line down to a spot, but it is quite a tricky thing to do, and it will likely diverge very rapidly after the focal point.

The reason you can cut with just 2W of power with these diodes is because the shorter wavelength lets you focus them down to a sharper point than you can with a CO2 or other IR laser. (Of course, CO2 goes to much higher power!) The "sharpness" of the focal point is strongly dependent on the wavelength. The shorter the wavelength the smaller the dot can be, all else being equal. Since the best spotsize is basically the wavelength / 6, using blue light which is under half the wavelength of IR will give a much higher power cutting spot at the same focal distance.

Anyway, the arguments about which wavelength is safer for your eyes is a wrong one. At powers above one watt, you are going to be blinded by even a specular reflection. A reflection where a high percentage of the beam hit you in the eye? It would likely blind you for life faster than you could blink. I've stared into 12mW beams at 670nm, and that's about as bright as is handleable. Green (540nm) at ~43mW is painfully bright just scattering off an object and around a room. 1000mW in blue? Blindness.

The big advantage about using IR is that you can safely see what is being cut by using a plastic that is opaque to IR that transmits the visible light. Polycarbonate is a great one to choose. Using blue? Well, you could buy some really dark tinted glass or plastic (Make sure it is tinted all the way through, not a surface coating!!) that blocks the blue, so you can see the green and red parts of the spectrum, but for cost reasons that's going to be best as a pair of goggles. The safest (and cheapest) way would be to use a closed box with no windows and a beam interlock, then put a cheap webcam inside so you can see the cutting action. Open the box, the beam cuts out before the seal is broken.

I've got a plan to buy a couple of these Shapeoko 2 bots, and I'll be helping to load a 30 or 40W IR CO2 tube into one, and some mirrors, and the whole lot will be inside a polycarbonate box. The other plan is to fit a plasma cutter to one fitted with NEMA2x motors rather than the NEMA17s.

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Re: Laser mod kit?

Post by cvoinescu » Sat Feb 08, 2014 9:19 pm

Nigel K Tolley wrote:blue light which is under half the wavelength of IR
You mean about 25 times smaller. Carbon dioxide lasers have a wavelength of 10,600 nm, compared to, say, 473 nm for a blue laser pointer or 405 nm for a Blu-ray laser diode.
Nigel K Tolley wrote:Anyway, the arguments about which wavelength is safer for your eyes is a wrong one. At powers above one watt, you are going to be blinded by even a specular reflection.
One could argue that carbon dioxide lasers are inherently much less dangerous to the eye than near-IR, visible and ultraviolet lasers. While some sensible precautions are still needed, the cornea is opaque at carbon dioxide laser frequencies; the only kind of damage they can cause is thermal. Carbon dioxide lasers have a wide beam (on the order of 10 mm diameter for a 40 W unit) that's focused to a small spot by a lens (usually with a 25 to 100 mm focal distance); anywhere significantly outside this distance, the beam is too spread out to cause damage. Even commercial laser cutters have ventilation slits that would not prevent 100% of reflections from getting out of the enclosure; this would be extremely dangerous for even a small blue diode laser, but it's harmless for a carbon dioxide laser a hundred times more powerful. The bright visible and ultraviolet light caused by the extreme heat at the cutting spot is actually more dangerous to the eye than the laser radiation itself.

Note that the above is about carbon dioxide lasers at 10,600 nm, not IR diode lasers, which are an order of magnitude shorter wavelength -- those are still very dangerous. And I don't mean to say that carbon dioxide lasers are "safe", just that they're not as frightfully dangerous as near-IR and visible lasers.
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Nigel K Tolley
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Re: Laser mod kit?

Post by Nigel K Tolley » Sat Feb 08, 2014 10:42 pm

You are absolutely right.

I was thinking of IR as starting at around 900nm though, so blue is about half that, rather than the longer IR of a CO2 tube.

It's difficult since CO2 is IR and a hacked diode out a DVD drive is also IR, but one is, as you say, miles away in terms of optical properties from the other.

Spot wise wise, comparing apples to apples, you can't run a CO2 laser through a set of diode optics because it simply won't go through it, as the glass is optically clear, but 10.6um IR is totally blocked. Also, the power would frag it after a few tenths of a second, doing to them what the beam should be doing to the target material!

But yes, I concur with your 25x smaller spot size, going from CO2 wavelength IR to blue.

Edit to add: Has anyone made a Shapeoko kit into a (CO2) laser cutter yet?

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