Welcome to my instructable!
Today I would like to present you with a new concept of "Reverse Engraving" by showing you how I made this Illuminated Wooden Clock Photo Frame! Well, it's new to me and I haven't seen it used by anyone before so I had to come up with a name for it :)
What I used:
- one of these images for the design
clock mechanism from ebay
- two part epoxy resin
- some scrap hardwood
This is how it works:
- Engrave your design on the back of the board
- Fill it with epoxy resin
- After it hardens flip it over, and
- Plane the other side until your design appears
Let's get right into it!
Step 1: Engrave the Design on the Back of the Board
Carve out the area where the epoxy will be and engrave your design.
Important thing here is to engrave it deep enough, that the cutter goes almost all the way through the stock (the material being cut). I used software called Vcarve to make the design and generate the toolpaths and it has a neat feature that shows the maximum depth of cut of every toolpath (picture 1).
If the software you are using doesn't have that feature, you can just check the the generated g-code to see what is the highest value for Z (this may not be too easy as the file may have several thousands lines of code), or just engrave it on a scrap piece of wood first and see roughly how deep it goes.
In my case, the depth of cut was 2.9mm, so I just zeroed the tool on the cutting bed and raised it up by 2.9mm and zeroed it again.
As you can see on the 4th picture, I should have set the safe Z a bit higher to avoid making the cuts between the clock digits etc. No big deal though, none of that will be visible once it's assembled.
Also please remember that the design will be mirrored when its flipped, so account for that whilst creating it.
I also spray painted the inside white to help deflect the light from the wood.
Step 2: Pour the Epoxy Resin and Add the LED's
You could also add the LED's later, after the epoxy hardens by drilling the holes in it and sticking the LED's in.
Alternatively you can use LED strips and stick the to the back cover - this could help diffuse the light a bit better.
Step 3: Flip Over the Stock and Plane the Other Side
In this case, I planed it down by 2.9 mm - this was the maximum depth the cutter reached to engrave the design.
If you don't know how deep your cutter went, just plane it a bit at a time, until the design looks right (I suggest 0.3 mm increments).
Once that's done, flip it over again and cut out your frame (if applicable). I aligned it with the X axis of my router by moving the cutter along one of the edges that were cut earlier and adjusting the position of the stock until they were perfectly in line (pictures 4&5). For more info on this, check out my other instructables:
After I cut out the frame I also carved out the slot for the photo and 2mm acrylic glass but I must have forgot to take pictures of that. Because the wood was so thin I actually ended up going all the way through it, into the epoxy and damaging several LED's. So to stop the light from partially illuminating the photo, I painted the slot white and replace the damaged LED's.
Step 4: Wire Up Your LED's
This will vary depending on whether you used led's or Led strips and on what power supply you plan to use.
You will need to add resistors if you used LED's.
If you used a 12v LED strip, just use a 12v power supply.
Here is a great website to help you biuld your LED array:
Step 5: Add a Back Cover With a Stand and Oil/Varnish Everything
I cut my stand with a bandsaw, sanded it smooth and screwed it in to the back cover.
Add some kind of finish to all of the parts. I used wood oil - it really helps the grain show up.
Step 6: Final Thoughts
This was an experiment really, I had no idea how it would turn out. For this project I used bits of scrap hardwood that I had laying around and joined them together (I haven't done the best job ever - on one of the pictures you can see a light gap between the two halves). Also it didn't help that the wood I had was so thin (about 15 mm). I couldn't carve out too much room for the epoxy as I had to carve out a 2 mm slot for the photo and an acrylic glass on the reverse. Later I thought that I should have just made the photo backlit as well.
Finally, I was hoping the light would be diffused a little more as you can still see the hotspots.
All in all, I think the clock frame turned out OK, but what I really wanted to show you in this instructable was the concept of "Reverse Engraving", which worked out great.
It can be applied to other projects, backlit signs etc. where the letters are cut using an endmill instead of a V-bit.
Thanks for reading all this, I hope you found it interesting and learned something new today!