Introduction: Laser Engraved Christmas Ornament
Last year my brother suggested it would be cool to keep a piece of a Christmas tree and use it to make an ornament that could be used the following year. This was my first attempt at that idea. I made five ornaments and gave them to my roommates as gifts. The ornaments are disks cut from the base of last year's tree, which I then engraved a photo into using a laser cutter.
a piece of the trunk of a Christmas tree
image editing software
Step 1: Keep a Piece of Your Tree
My brother suggested this last year, so when I threw away my tree I cut off the base and kept it. I cut it off with a hand saw, which I found exhausting. The tree was a noble fir.
I knew the ornaments would each be about a 1/4 inch and I would make at least six of them (one for each person in the house plus a spare or a practice piece). The rest of the length was used to hold the piece while cutting the disks. While cutting I wished that I had kept a large piece to give me more to work with.
Step 2: Cut the Wood Into Disks
I cut the tree into disks that I would then engrave with a laser cutter. I used a vertical bandsaw since that's all I had access to. It really wasn't ideal, since the straightness of the cut depended on my ability to hold the piece steady while cutting it. Also the bandsaw wasn't in great shape and had a kink in the blade, causing a sort of stripe pattern to be cut into the wood.
Also I didn't have a lot of wood to hold onto, and wished I had kept a larger piece. Alternatively it would help to attach the piece securely to something to keep it steady. I held it with a C clamp, which was far from ideal.
Step 3: Sand the Disks
You don't have to do this if you cut it with a circular saw, or any saw that makes nice smooth cuts. Since the saw I used made very uneven cuts, I sanded the pieces with 80 grit sandpaper.
Step 4: Prepare the Image
I knew exactly which image I wanted to use- a photo of my roommates and me at our holiday party last year. Unlike when cutting with a laser cutter, in which case the part needs to feature paths the laser can traverse, with engraving it doesn't need paths.
I made a version that was high contrast consisting of only black and white, and a grayscale version. I ended up using the grayscale version, but in the end the ornaments looks like they were high contrast anyway. It appears that for grayscale images the laser's intensity is adjusted based on the grayscale value, but that just results in different depths of the cut into the wood. The visibility of the image appears to come not from the depth of the cut but from the wood being scorched by the laser, and the intensity did not result in an appreciable difference in the color of the wood. Perhaps if I played around with it more it could have gotten a slightly better result, but I'm still very happy with how they turned out.
Its also interesting that the rings in the tree also influenced the depth of the cuts. The parts of the rings that are densest were not cut as deeply as the less dense regions. I didn't mind because it looked cool and the image is still visible.
I also added "2015" above the image, since I'm hoping to do this every year, and I want to be able to tell which ones are from which year.
Step 5: Laser Engraving
For a laser, I went to a local makerspace in Los Angeles called The Build Shop, which I highly recommend. The laser I used was a 100W CO2 laser made by Universal Laser Systems. The Build Shop opens all files in Adobe Illustrator to send them to the laser cutter. Since I don't have a copy of Adobe Illustrator I edited my files in Gimp and saved them as PDFs.
Before cutting, the woman helping me laid down sheets of paper and created a file with 3 inch diameter circles. By cutting the circles into the paper, it created targets that could be used to place the wooden disks right where the laser would etch the images.
In the past when using a laser cutter there was a step to set the bed of the laser cutter at a height that would ensure the laser beam was focused at the midplane of whatever is being cut. For this however the woman helping me didn't set the height, and all the disks were of slightly different thicknesses. I was delighted to find out that evidently for laser engraving, the height of the laser bed is not as critical as it is when cutting.
The whole process is pretty fast. For five ornaments that are each about 3 inches in diameter, the whole thing took about 10 minutes. The laser head moves so fast that it's just a blur in my photos. As an aside, the exposure time of that photo is 1/24 seconds, and that streak of light in the third photo appears to be about 2.5 inches long, so I'm guessing the laser head is travelling nearly 60 inches per second. I can't believe it's that fast.
Step 6: Add a String to Hang It
To give the ornaments something to hang from, I drilled a hole for a piece of string and tied two loops. The laser cutter could have made the hole, but I didn't have time while at the shop. I used twine since I had some lying around, and because the color and texture go well with wood. I tied a loop through the hole in the ornament and then tied a loop of twine through the first loop so that the string it hangs from is in the same plane as the ornament. This helps it hang more nicely than if it was hanging from a loop that was oriented 90 degrees to the wood disk.
After that, I wrapped them up and gave them to my roommates at this year's party. I'm really pleased with how they came out, and I'm looking forward to doing this again next year.