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Laser Etching Trickery

Clear acrylic etching on a blue laser: if you have an LED laser you were probably told that the only acrylic to use is orange or green opaque.

I do not have the space necessary to add a full size CO2 laser but cutting and etching with lasers is fun. So I started my lasing journey with J-Techs 7w LED laser. These lasers generate a 405nM beam and can engrave in wood or cut thin (really thin) material. The nice thing is that they attach directly to my CNC head so they don’t require an entire machine to be added.

If your noticed, the bracket holding the JTech is transparent blue. That’s because at some point the original bracket broke so I was able to reproduce it from a STL that the founder of Jtech was kind to send me so I could print it at home. This is a closeup:

At some point I decided to invest in a more powerful laser, still sticking to LED and a form factor which attaches to my CNC head. This time I went for PLH3D-15W by Opt Lasers, a company in Poland whos service and support are excellent!

As I quickly learned, you can not etch clear acrylic with only 15w laser and definitely not blue LED laser. However there is a trick I learned and would like to pass along to you:

Why clear acrylic doesn’t etch easily

Transparent acrylic or light colored acrylic simply passes the laser beam right through. Only opaque and dark acrylic such as black colored, will absorb the energy at the surface just enough to etch it. Of course you need to dial in the power and speed settings (and this depends on the color, laser power and your feed speed so don’t try to copy someone else’s recipe).

However… if you place transparent acrylic on a reflective material such as metal then you can rely on the very high heat at the point of contact between the metal and acrylic.The heat transfer through aluminum is what does the etching. The rest is about calibrating the % power to use and I use a grey calibration wheel for that. I found that spraying the sheet of metal with grey or event dark color (eg black) spray - will do the trick. Just lay the acrylic on top and let the heat begin. Just remember you are etching the bottom (underside) of your acrylic so you will want to reverse your text or images in your software. This is my setup: i took a flat aluminum sheet, spray painted it with a grey spray paint coat and laid the acrylic on top. I focused my laser on the aluminum sheet not the top of the acrylic because that’s where I want the heat to focus.

Here is the result after placing the acrylic in a base. By the way this is a pre-cut shape to fit a base. Both of which are available on Amazon:

Ask me if you have any questions.

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