The Laser module attachment

A project log for The Omni multi-machine

Laser cuts, routes, plots, engraves and makes vinyl stencils and more for makers ,crafters and builders.

castvee8castvee8 04/10/2019 at 19:503 Comments

I always liked the idea of laser cutting but the cost even as low as it has gotton was still not in my reach. I was cruising the ebay pages of laser products and started seeing laser engravers-thsy are basic woodburning type beasts that make really nice engravers but lack the power to actually cut. I first bought a 2 watt version and was going to settle for the engraver as an attachment but after using it to make some cool wood etches I wanted more power. I found a 7.5 watt version for around 45$ and bit the bullet and got it. I couldn't help but notice that this version would actually cut thin materials and really engraved well also. Again I ordered the next step up a ten watt version. This thing was pretty amazing for the cost and I quickly experimented to find its limitations. It is shown in the prototype photo.

Here is the 2 watt version:

It does etch/engrave just fine but will only cut very thin stuff-and not all that well.

If you just want to engrave-this is cheap and perfect. The final version of the machine will be able to accept the 15 watt version. I am underfunded right now and just can't afford it. all of my data and photos will reflect the ten watt version.

In order to save my table from laser damage I simply found a material that the laser could not cut through and did not burn well to make a smelly mess. under the material to be cut I place a small 3 D printed frame shown here:

This elevated the workpiece away from the table and allows space for the laser to pierce and safely absorb the beam without problems.

 In the final version machine the table will have a laser safe shield to protect  the user from laser energy. The shield will also function as a router shield from chips, etc.

useful tips on these laser modules:

Be careful when you hook up and test these things. The light will cook your eyes, your skin and anything,even across the room. You need a backstop, and some eyewear that is laser rated.

When you are purchasing the laser module of your power choice::

Buy from a reputable dealer with perfect feedback and good customer ratings. Many of the power ratings are NOT as advertised. The higher the wattage the more fudging they tend to do. My first ten watt laser module was only tested at 7.4 watts. I balked greatly and got another. The ten watt one measures at 11.2 watt.

So many China dealers are fudging the ratings on these modules. Beware.


salec wrote 04/11/2019 at 16:23 point

The laser power meters I've worked with (for fiber optic telecomunnications) were actually measuring thermal power of an absolutely black body (a hollow sphere or box light trap / absorber). I don't know the details of the construction, or method they used to measure the thermal power, so I can only guess.

In a pinch, calorimetric method could be used: make a light trap and dip it into a vessel of known amount (mass) of water (but keep the trap entry hole above the water surface). Note the water temperature, start the chronometer and measure the time until until thermometer shows rise of temperature of one notch, while irradiating the trap. The power should be found as:

P = m * C * (T2-T1) / t,

where m is the mass of the water, C is specific heat capacity of water, T2 is higher temperature, T1 is starting temperature, and t is time it took to heat up from T1 to T2.

This is simpler to calculate if you use Si units, but the formula above is universal, just mind the conversion of units.

Note that there are systematic errors which can creep in: natural cooling off of the water to surroundings, or water heating up from the ambiental heat, and neither the heat capacity of the absorber itself, nor the escaped/re-emitted light is taken into account. But I expect the results to be in ballpark. If you take larger amount of water, thermally isolated wessel and do it in a room with constant temperature, experiment/measurement will have greater resolution (the time will be longer).

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castvee8 wrote 04/11/2019 at 12:54 point

I borrow a laser power meter from someone. I am thinking of making a pierce test chart from this to give ballpark estimates and posting here for those who do not have access to such equipment. This test could use a common material such as stacked paper? or something everyone would have. It won't give such precise results but may be helpful. In many cases it is blatantly obvious once you have a good one to compare it to. Now that I have several in all power ranges a simplified test might be somewhat useful.

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Tom Nardi wrote 04/11/2019 at 04:00 point

Out of curiosity, how are you measuring actual laser power? I'm putting together a diode laser engraver/cutter myself, and have been looking at 7+ watt modules. Would be nice to have some way to verify what I actually receive.

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