The biggest issue with powder coat is that you typically need a conductive base for application (i.e. metals), seemingly limiting its use. I refused to believe that I could only powder coat certain things, and therefore wanted to do all I could to push powder coating technology into new arenas.
Additionally, I had done some work before on lasering ceramic tiles. I ended up really liking the effect of having a shiny glazed surface right next to a gritty textured, bare sintered tile. However, I really wanted there to be some way to increase the depth of this effect - was there any way to add more colors?
I decided to combine both the ideas to use a laser as both an etching instrument and a powder coat mask creating instrument. Additionally, I ended up figuring out a way to get enough conductivity on a ceramic tile to apply powder coat evenly to a non-conductive surface! The end result? Some sweet Legend of Zelda themed tiles (that I ended up turning into coasters for now).
Step 1: Find Thee Some Tiles!
Don't want to use the tiles I did? No problem. Here's some tips for picking a nice tile that looks cool when you are done lasering it:
- Really light colors or really dark colors look a lot better than neutral colors. Remember that the underlying ceramic will be a gray color which only becomes noticeable if the color of the tile ceramic stands out against the color of the tile.
- Shiny tiles don't work so well. My guess is that you get some reflection of the laser, and you get more "etching" than cutting of the underlying material.
- If you need these to fit into something, don't trust the sizes of tiles to be perfect. The size of the tile is pretty much always overstated...you know how those marketing people work. The 4" x 4" tiles that I purchased were about 3.6" x 3.6". So, if you need your tile to fit something, buy 1 first, before you plan a magnificent Legend of Zelda fresco around tiles that are the incorrect size :).
Step 2: Make Thee a Jig!
First, grab some scrap wood, and stack your tile on top of it. Cut a rectangle out of it that is a little bigger than your tile. Even if you think your wood is already the correct size, I'd recommend cutting the sides with a chop saw or something so you 100% know that every edge in your piece is completely straight. If the edges on the jig aren't straight, then when you line up your tile in the laser, your tile won't be straight, and your final image will be crooked. Then, if you are at all like me, you'll start crying.
Edges straight? Check. Next step, get another piece of scrap wood. Slide your tile to a corner of the rectangular piece of wood you just cut out. Place the second scrap flush to the tile and the rectangular piece of wood. Mark with a pencil the height of the tile + rectangular wood combination. Cut here (with a chop saw or band saw). Cut this piece in two maintaining the measured height so you'll have a piece for 2 sides of your rectangle base. These pieces will act as "barricades" on the edge of your jig that you can use to place the tile in the same spot every time. Since this jig will be going under a laser, its important that the height of these barricade pieces is about the same height as the focus plane of your laser. Much higher than that, and the laser head will plow into the piece, most likely damaging your laser and killing your piece.
Now, all you need to do is grab some wood glue, and glue everything together! Hold it in place with a few clamps, and come back in a few hours to have your jig framework completed.
Step 3: Make Thine Jig Setup in Photoshop
Now that you know what your jig looks like, where home is, and what your tile size is, you'll need to duplicate that setup in photoshop or some other graphics program. In photoshop, I made my "image size" the size of the jig setup. I used guides (View > New Guide) to set the boundaries for where the "printable" edges of the tile would be. Because my tiles rounded near the corners, I set the maximum image size to 3" x 3" on my tile even though the tile size was ~3.6" x 3.6".
After this is setup, its very simple to plop whatever images you need right into your e-jig.
Step 4: Design Thy Image to Be Lasered
Tips for deigning an image to be lasered:
- Each path with the laser should be on a separate layer. In my images, I have a total of 3 layers for each image. One layer is the laser "raster" channel, where the laser will etch away the glaze on the tile to reveal the underlying ceramic.
- The second layer is a "vector" channel, where the laser will cut through a mask.
- The third layer actually doesn't get cut on the laser at all, but I like to include it to give me some reference for the other 2 layers (so yes, this isn't required either).
- I did everything in raster in photoshop, then used the "trace bitmap" feature in Corel Draw to convert the vector channel layer into vector paths. IMO, design is a lot easier if you are just working in 1 program.
- I didn't care too much about color when I was doing this - I figured I'd convert it all to black and white at the end, but used various colors at this step just to easily associate one layer with a color.
Step 5: Lazor Thy Raster Layer!
Drop the tile in your jig, place it into your laser, and set up the home position to match the dot on your jig. Then, print, print, print!
To give a little bit of guidance on how hard you're actually going to have to hit glaze in order to vaporize it, here are the settings that I ended up using:
Machine: 60W Epilog Helix
# of Passes: 1
Looking at the above numbers, as you may be guessing, this is not a fast process. To do a rather complicated cut through a 3" x 3" image, it took the laser an average of about 17 minutes. So, plan accordingly. Whether that be for food, or bathrooms, or whiskey or whatever.
Step 6: Mask Thine Tiles!
But wait! Before you go grab that blue painters tape out of your closet, don't forget that powder coating takes place in an oven at about 400-450F. At that temperature, pretty much every tape that exists either burns or melts. Lame. Oh wait...except one: Kapton! Kapton is that gold film that was used on the outside of the lunar lander and is super heat resistant, and nearly impervious to radiation. Cool! Better yet, its decomposition products are only carbon monoxide and carbon dioxide, thus making it totally safe in lasers - no equipment damage, no gassing out the room.
The biggest downer to kapton is cost. I haven't been able to find a supplier that sells a small amount of the stuff (if you know of one, I'm all ears!), so you end up having to buy the stuff in 36 yard increments. Ouch. I ended up ordering 1" wide, 2mil thick kapton tape from Uline for this project at a cost of $54...double ouch! Granted it will last me for awhile though. Also, although I ordered the 2mil stuff (I was concerned about handling and stability), I think if I had to order it again, I'd only get 1mil...which would knock the price down to $31. The film is really tough, so 2mil is pretty overkill.
After you have the tape, simply cover the top of your tile in it, making sure to keep it away from the jigged edges, and overlap the tape a bit where you need to.
Step 7: Lazor Thine Tape Layer!
Machine: 45W Epilog Helix (yes, this is correct even though the other laser was a 60W. I did this over 2 days on 2 different lasers).
Frequency: 5000 Hz
Note: I think even these mild settings were a little overkill for what I was doing. I'd recommend others try backing off on the power a little bit to see if even better cuts could be achieved.
In the end, your parts should look a lot like the below. The black lines are where the kapton tape has been cut, and can be removed.
Step 8: Remove Thy Kapton Tape to Form a Mask, Prep for Powder Coat
A couple of other hints from a guy that has done a lot of mask stuff:
- Keep a pair of scissors handy. When a piece of mask gets too big to manage, cut it off!
- You'll have the most problems trying to keep small pieces of mask from coming off with the big mask. Pay a lot of attention to the small bits when you are removing sections of the mask.
- Some of the laser cuts may be right where you have 2 pieces of tape overlapping...make sure both of them come off (particularly if there is only a little sliver).
- Patience is not only a virtue, but also really useful during this step. Slower is easier.
Step 9: Powder Coat Thine Tiles!
Powder coating is awesome for a lot of reasons, but the trickiest part is trying to figure out how you are going to make something conduct enough electricity to deposit a thin layer of polymer/dye mix on it. For these particular tiles, here's how I solved that problem:
First, I set up a steel oven grate and attached my powder coating grounding cable directly to it. On top of the oven grate, I added a piece of waxed paper to keep powder coat from sticking to the grate itself. Finally on top of the wax paper, I placed my tiles. For those familiar with the process, I did not do any pre-treatment of the tile whatsoever - no cleaning, no degassing. I then loaded by powder gun with a copper vein powder from Columbia Coatings, and got to spraying using a 10,000V bias. The cost of 1 lb. of the powder? about $15. The amount I used for this project? Maybe 1/10th of a pound. This is the other reason why powder coat rocks - there is so little material usage, and its so cheap!
In the end, I had a beautiful even coating on top of my tiles!
I then carefully moved the tiles from the oven grate and wax paper, and baked them in a convection toaster oven at 400F for ~15 minutes (manufacturers recommended settings). Be careful not to knock any powder coat off during the moving process - at this point there isn't any force keeping the powder stuck to the surface other than some residual electrical charge!
Step 10: Remove Thy Remaining Mask!
To remove the masks, I again used a bunch of dental picks, but only because the surface was hot. At this point, the powder coated layer won't be coming off without a lot of effort, so you can be a little abusive to it if needed.
Step 11: Enjoy Thy Final Product!
Also, you could theoretically make a many more colored structure by adding lots of additional masks, and more layers of powder coating as a really fun extension (I'll be trying this shortly :) ). Powder coat comes in a lot of different transparent colors which could produce a crazy effect on top of ceramics as well. What may thy future hold with powder coated ceramics?!