Walnut Groot - Cnc Carved From 5 Sides

I developed an easy system to carve 3d models from four sides on a hobby cnc. Using this system I carved Walnut Groot! And because I'm a bit extra, I carved the top of his head and explain how I reached the 5th side.

• Any hobby grade cnc (no rotary required!!)
• Fusion360
• 3" long 1/4" endmill
• 1/16" ballnose bit
• Block of wood 2.75"x2.75"x5.25"

Grab any model from Thingiverse with high levels of detail. Import the model into Fusion360 as a mesh.

Create a sketch on the X,Y plane, and draw a 2.75" square. Make sure the model is centered, and scaled to barely fit inside the square. Extrude the square down 1.25" to create the base. Next extrude the square up until it covers the top of the model, so we know how tall the stock needs to be.

The block of wood to use for the stock needs to be EXACTLY 2.75"x2.75", and approximately 5.25" tall (depending on the model). I cut the chunk out slightly large with the bandsaw, then used the table saw to trim it to the exact size.

A registration block is anything fixed to the cnc bed that forces your workpiece to sit in a precise position. To ensure that my block locks the corner of our stock at the precise X and Y zero of the cnc, I will use the software to cut a slot exactly 2.75" across.

In Fusion, I created the block around the base of the model laying down. Then I defined the origin as the bottom corner of the base (<-- super important point here!), and set up a pocket toolpath to carve it out.

On the cnc, I screwed down a chunk of 2x4. After running the toolpath, the walnut stock fits perfectly and will be in the exact same position regardless of which side is facing up.

Usually a registration block is all you need before you start. But... I'm going to be using an extra long 1/4" endmill for deep carves, the stock is 2 3/4" tall, and I'm working on top of a 3/4" spoilboard. The cnc just hasn't got the clearance for that, but it's not too far off.

Soooo... how about we just cut out the spoilboard where the block sits, and regain that 3/4" of clearance? Hey, why not?

I used the base and the stock (top of the block) as models, and created a pocket toolpath inside those edges. With the heights set to start at the stock bottom and carve down to stock bottom minus .7" it was happy to carve out that piece of the spoilboard for me.

Awesome! So let's get Groot out of this block. Now the only way to get to Groot is to carve him from all four sides. How we gonna do that? Great question! Pay attention, this is how we make the secret sauce!

We're going to create 4 new setups and rotate the orientation of the model 90 degrees each time.

Setup 1, with the right side of his face facing up. The bottom left corner of the base is the origin. It gets carved, obviously, from the top down.

For setup 2, rotate the model 90 degrees counter clockwise. Pick a vertical edge for Z and the new bottom left corner for origin, and carve the left side of his face.

Setup 3, rotate the model 90 degrees again. Pick a vertical edge for z, the new bottom left corner for origin, and carve his left shoulder.

Setup 4, rotate the model 90 degrees again. Pick new z line and bottom left corner for origin, and carve his right shoulder.

Because the X,Y, and Z NEVER CHANGE on the cnc, and the stock is ALWAYS in the EXACT place the carves will meet flawlessly around the model. That's the trick!

Ok a couple quick details... 

Each Setup uses the 3d mesh and the base for the model. We don't want it to touch the base, so it needs to know that it's there.

In each Setup I created a 3d adaptive toolpath with a 1/4" endmill:

• The machining boundary is set to the top of the stock block, and to only tool inside the boundary.
• Rest machining is checked, with "setup stock" as source for the first side, and "from previous operation" for the other three sides.
• The toolpath model is only the 3d mesh as we don't want it to touch the base.
• Carving height is from stock top to model bottom plus .75"
• Optimal load is .1" rough stepdown .05" and fine stepdown .005"
• Stock to leave is .02", because this is the roughing pass and we'll be carving in the details later.

Ok! With 4 Setups setup, and a roughing toolpath for each, we're ready for some 4-sided carving!

Workholding is about making sure that your stock stays exactly where you need it while carving. There are a handful of ways this can be done. You could use clamps to keep it stable in the registration block if you wanted. I chose to drill two 3" screws through the registration block and into the model base. It does leave 8 holes in the bottom of your model base, but hey who cares it's the bottom. Just set a depth flag on your drill bit so you don't poke out the top of the base.

Run the four roughing paths, turning the stock 90° counter-clockwise between each.

Ok let's give him details! I went back through each of the four Setups, and added another 3d adaptive toolpath for a 1/16" taper ballnose bit.

The Geometry is the same, Heights go down to model bottom plus 1.2"

Optimal load is only .01", uncheck Stock to leave, and turn on Smoothing.

Once we have four finishing toolpaths, we're ready!

Rotate our model back to the first position, and fire off the finishing pass.

As before, rotate the model 90° between each path.

After carving the details on all four sides, we're done! Or are we?

We have a model that looks great from all four sides. However, there are some areas on the top that it couldn't get to from the sides. So, let's see if we can carve it from the top too!

The first obvious problem is clearance height. It was a problem with the model laying down, and it's almost twice as tall. Well up isn't an option, so I'm going to go down. I'm already through the spoilboard, so it's time to cut a small square out of the cnc base which is just a sheet of 3/4" mdf.

Back in Fusion, and we're going to start with the model in carving position.

I made a sketch on the underside of the base, which is the same plane as the top of the base board.

I made a big rectangle to represent an area of the base board, and a 2.75" square exactly 2.5" up from the origin.

Then extruded the board down 3/4" leaving the square as a hole.

I made a new Setup using the model base for the origin and the baseboard as the model.

In that Setup I made a 2d pocket toolpath for the 1/4" endmill.

The square hole is the pocket selection, Heights from stock top to stock bottom, and multiple depths.

Ok, fire that off! And now I have a square hole in my cnc!

I now have enough clearance to hit the top of his head, and I have him placed digitally so I know exactly where he is.

Where is that? Exactly 2.5" back from the origin and 1.85" down, after measuring with a caliper from the origin surface down to the tabletop below.

Ok, so lets lie to the robot and just make it work. We cannot touch the physical origin, or we lose our accuracy.

This is easier than it sounds. We need an origin point 1.85" above the bottom of the base.

Ok, so I extruded the bottom of the base up 1.85". The top of the base is now vertically aligned with the origin.

Next I extruded the wall back by 2.5".

And now this new digital corner is in the same place as the origin in relation to the model.

I made a new Setup, using the new corner as the origin.

I created a 3d adaptive toolpath for the tapered ballnose bit.

Rest machining from previous steps, Heights from the model top to the model top minus 1", and the same settings as the other detail paths.

I used blue tape and ca glue to anchor him to the tabletop below. Might as well, I clearly left my sanity behind before I started this project.

Hey don't stop with one, this works with most detailed models! Most of them won't need to be carved from the top, unless they are indented like Groot. Albert's hair needed some top-down detail, but the dragon and Frank didn't.