Intro: Negative Laser Etched Metal
Needing a prototype done for a shaft encoder, Steveastrouk asked me to experiment with removal of paint on stainless steel using our laser cutter.
If successful the void in the paint could then be used to electrochemically etch the holes in the shaft encoder.
While not an instructable that's immediately accessible to a lot of people, hopefully you'll find the end result attractive and some of the instructions on prepping and painting metal useful. This instructable will hopefully serve as an introduction to several projects I'd like to publish over the next month.
Since shaft encoders are a bit boring, I also etched a graphic by HiddenPower, gmjhowe's logo and the hackaday logo to see how solid images looked as well as to give me a more interesting title image. I think they turned out great!
Step 1: Tools & Materials
- laser cutter
- bead blaster (optional, bead blaster not sand blaster since it's finer)
- something to cut the metal with (bandsaw, hacksaw, tin snips, guilotine)
- stainless steel sheet (I used 0.6mm)
- Plasti-Kote Woodstove Black
- acetone (or other cleaner/degreaser... IPA, Flash, Limonene)
- emery paper (if you don't have a bead blaster)
Sorry, there's no picture of all the tools in one place, getting the bead blaster, laser cutter and all the other bits in one place would be impossible! Instead, here is a picture of PKM, gmjhowe, Kiteman and Lemonie crowded around our laser cutter.
Step 2: Surface Preparation
Surface preparation is key here.
To get the paint to stick as well as possible, the metal should be clean with all grease removed from it. The surface also needs to be roughed up to give the paint more to stick to.
I first bead blasted all the sheets of metal I wanted to play with. This is to rough them up as described above, but also to remove all the crud and some of the grease. Don't have a bead blaster? No problem, some very fine grit emery paper should do the job just as well but take you a little longer.
To remove any remaining grease I squirted a tissue with acetone and wiped the sides to be painted, being careful to only hold the edges after cleaning. A kitchen cleaner like Flash would also suffice, as would IPA (isopropyl alcohol NOT india pale ale).
Step 3: Painting
Next it’s into an oven to warm the parts. The paint sticks better and gives a nicer coating if the metal is preheated.
Once warmed to your liking, spray the sheets in a well ventilated area.
Having sprayed them the parts can go back into the oven to dry. Drying takes about 2 hours in an oven and it helps to keep the dust off them while they're still wet. Alternatively leave them in a dust free place for 10 hours or until they're dry.
Step 4: Laser Etching
Once fully dry the painted stainless can be etched. I used a high power (98/100) , a high etch speed (300/400) and a step size of 0.1mm per scan. These worked better than the original settings I used since the thinner sheets of metal warped when I ran it at a lower speed.
The shaft encoder was designed in a CAD program called Alibre then exported into the program that came with our laser cutter as a .dxf file. This one took 2 minutes to run.
The logos I etched were imported as jpegs and the program sorts out the rest. They took slightly longer to etch since there was a larger area of paint to remove, 4 or 5 minutes.
Step 5: Results!
And here are some shots of the finished etched sheets.
Got a laser cutter and give it a go? Please post some pictures in the comments, it'd be great to see it done in some other colours, or perhaps layers of colours!