Introduction: Aluminum Lego Tree
I wanted to make a 2.5" tree.
A guy I know announced that he was going to assemble a treescape collaboration project and raffle it off for charity. His local animal shelter floods frequently and is raising funds to help move, so he decided to do this to help. The treescape would be a collection of maker donated trees mounted on a board, with zero restrictions on materials tools or techniques used. Do whatever you want, just keep it under 2.5".
One of my specialties is carving 3d models on the cnc, so I started by searching for a model of a tree. When I saw a model of a Lego tree, I knew I had to make one. I quickly discarded the idea of using wood, as the elements of the model were too fragile. Thankfully aluminum can be milled with normal woodworking tools, so the plan was to carve it from a solid block of aluminum. Besides, who wouldn't want an aluminum Lego tree?
Aluminum 1.5" square bar 3.6" long
1/4" endmill with 1.5" reach
1/8" endmill with 1" reach
1/16" endmill with 1" reach
Cutting fluid (I used WD-40)
Bandsaw or hacksaw
Patience... lots of it
Step 1: Fusion the Model
I started by importing the Lego tree model into Fusion360 as a mesh. I scaled it to 2.5" tall, and converted the mesh to a body. Next I modeled a simple cylinder up through the trunk as a support post, and added a thin rectangular box to each end to represent the extra stock and to keep the part supported and aligned perfectly for a double-sided carve setup.
Step 2: Model a Fixture
I created a sketch on the XY plane and drew rectangles that fit around the end blocks. I added circles to each corner (dogbone) to compensate for the fact that a round endmill can't reach an inside corner. I extruded the shapes down, and added a thin floor to connect them (it was also required for the pocket path). This is the final model of the fixture, and it will hold a block of aluminum 1.5x1.5x3.6 with zero offset so that it is held firmly in place.
Step 3: Program and Carve the Fixture
I created a Setup for the fixture, and used the bottom left corner of the aluminum block as the origin.
For the physical fixture, I screwed an offcut from a 2x4 to the cnc.
A pocket toolpath with a 1/4" endmill hogged out most of the pocket. I used a second pocket path with rest machining to clean out the rounded corners with a 1/8" endmill.
The aluminum block fit perfectly!
Step 4: Front Setup and Toolpaths
I used the same bottom left corner of the block for a new Setup. The Setup model included the tree, the center support bar, and the two end blocks.
I used a 3d Pocket Clearing toolpath with a long 1/8" endmill to clear most of the material down to the center line. With a stepdown of .02" and a speed of 25ipm this was about a two hour carve. I had to sit there and babysit the whole time, adding a tiny shot of WD-40 every couple minutes to keep it lubricated.
To get the details between the tines, I used a 3d adaptive path with a long 1/16" endmill. Even with the rest machining, because of the .01" stepdown and the 10ipm speed this was a three hour run.
Step 5: Back Setup and Toolpaths
For the back side Setup, I rotated the model 180° and chose the new bottom left corner for the origin.
The roughing toolpath with the 1/8" endmill and the detail path with the 1/16" endmill were copy/pasted into the new Setup as everything else was the same as the front.
Step 6: Carving. and More Carving
I described the two Setups and four toolpaths above, here are some shots of the process.
With each side taking about five hours, it took me four nights to complete. I will say that after those 10 hours, I never want to smell WD-40 again. Yuck!
Step 7: Cleanup
After pulling it off the cnc and getting a couple of photos, I used the bandsaw to cut the support bar off the top and bottom. On the top I cut it as close as I could, but on the bottom I left 1/2" below the base to act as the root. It is supposed to stick into a treescape, so the extra support is perfect. I used a metal file to grind off the rest of the top support and round it off.
Step 8: Finished Tree
And.... the tree is done! I was thrilled with the way it turned out!
It is unfortunate that I managed to create a Lego that would be even more painful to step on! 😉
Let's hope that never happens!
Step 9: In the Treescape
The treescape was a huge success, and over $2200 was raised for the shelter!
You can see the result of allowing makers to do whatever they want. There are a wide variety of wood, metal, clay, and leather trees and they are all impressive!
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