Help choosing a laser & optics

[2_many_hobbies]

Hello, I will start this off by saying I know nothing about laser or optics so this is all a wild adventure to me.

My wife wants to do highly detailed cards and things out of paper and heavy weighted paper so I suggested I put together a laser engraver after seeing a site where a guy used a laser from an old dvd-rw overpowered to cut paper.

Im not sure what power I will need but I have found THIS and though the title says 5W the description says 1W so Im not sure.

So we want a laser that is capable of cutting construction paper and maybe some vinyl so what power of laser do I need and what optics to focus it?

Or... Would I be better suited at making a knife based cutter?

I was thinking of making some pulse electronics so we could do engraving on the heavy weight paper if possible, but we couldn't on a knife based system

Thanks!

[zax15uk]

The diode is a 5W 808nm unit, but if used in a DPSS application (for a green laser) they optimistically state you'll achieve 1W output. In your application that isn't important as you would use the laser directly. If correctly focused it would be capable of cutting paper and possibly thin card stock.

A DVD-burner diode is typically a 200mW 635-650nm, which could be over powered to 250 or even 300mW in pulse mode with adequate cooling. It would also be capable (as you have seen) of cutting paper.

Just remember you'll need optics and safety shields (or glasses) to complete the machine, which a simple drag knife cutter won't.

A laser offers many advantages over the knife cutter, especially for intricate designs. Unless you just want to make the system yourself I would probably suggest you look at a low cost (yes, this means Chinese made) 40W CO2 system - the desktop units. These are available for under $1k shipped to your door and are safe and easy to operate.

If you want something simple, an alternative would be a product like the Cricut.

Zax.

[LaserImage]

Zax pretty much answered everything but I need to add one warning - don't cut vinyl with a laser. The byproduct of cutting vinyl is chlorine gas, when it mixes with the moisture in the air you get hydrochloric acid very nasty stuff! It will oxidize, very quickly, anything metal and it will also eat your lungs. If you really need to cut vinyl you need to stick to a drag knife plotter, unless you have a spare set of lungs that is...

Gary

[zax15uk]

Gary, yes - always a good idea to remind people that anything containing chlorine (like PVC) is a BAD idea. It combines with moisture in the air and your lungs to form hydrochloric acid, enough said!

I cut some plastic that I thought was safe, but as soon as I saw the tell-tale green smoke I turned the laser off but in a couple of seconds it had already caused screws and metal to corrode - very scary stuff.

Zax.

[2_many_hobbies]

Thanks for the heads up on the vinyl! That could have gone very badly... I didn't know PCV had chlorine in it but i'll defiantly remember green smoke is very bad.

Im wondering now after some reading that a 808nm laser wont have the penetrating power and would require more power to cut what a lower wavelength one would need. I have seen a few ~635nm 1W diodes would they be better suited to cutting card stock?

I want to 'cut' the card stock more than 'singe' my way through like I have seen the modified low power ones do.

[zax15uk]

Laser cutting paper/card involves burning the material away, but with sufficient power density and minimal contact time it can leave a clean edge (reduced charring).

In theory the 808nm should have a higher IR output compared to 635nm (which is a visible light output) but of course it depends if the diode has an IR filter and how good the lens is.

A CO2 laser at 10,600nm (10.6um) wavelength is in the far infrared range so has much more cutting power in comparison (for organic materials).

If you only intend to cut thin card stock, the lens can have a very small spot size (high power density). This will result in a shallow depth of field so only practical if you can maintain a flat surface relative to the laser.

Zax.

[2_many_hobbies]

Maintaining a level table is easy as im using an old Japanese positioning stage that is 0.002" flat and it is currently my multi use table (Pen, extruder, random tests)

I was under the impression that the cutting power is done by the amount of energy the material absorbs from the laser which is why I would have thought visible light would be better than IR is that incorrect?

Would this be suitable for my needs?
LASER / COOLER / OPTICS

All the other optics I found were for other wavelengths but they where all round, is this one meant more for par lasers or something?

[zax15uk]

Well you are correct, but why would you think visible light is absorbed better than the IR? If you are cutting white card stock for example most visible light energy is reflected and not absorbed. This is even more applicable as the material burns and produces smoke to further obscure the beam.

Those components look compatible but perhaps someone with more experience of DPSS lasers can comment. The lens is shaped to produce a circular spot which is obviously better for cutting applications, the laser output is elliptical on these units. The prices are certainly good, and if you can get a suitable PSU you'll have a working laser.

Zax.

[2_many_hobbies]

Theirs not alot of info on the ebay page, It looks like they are 3V and would probably draw 3-6A. Pen lasers are directly connected to the batteries and you can control the output power by varying the input current. Would the 3-5W ones be just like the little ones?

If so I can easily make my own driver. I feel bad asking so many easy questions, do you guys recommended any websites I could read up on DIY laser focusing and control?

[zax15uk]

The PSU needs to provide a stable voltage with current regulation. This is easy at low power (LM317/350 or L200 etc) but more difficult at 6A/15W.

Sam's Laser FAQ is an excellent resource: http://www.repairfaq.org/sam/lasersam.htm

Don't worry about asking too many questions, especially if you've searched the forum archives and haven't found an answer. It just means the answer will be there for the next inventor

Zax.

[zax15uk]

One thing I didn't mention that makes the PSU circuit even more interesting is that you probably want a pulse mode driver for optimum power while keeping thermal issues minimized. You might want to check that the rating is for CW (full on).

Zax.