Now we need to cut out the cavity that the spring will be attached to on the bottom of the head model.



For this I use the 123D Design web app to create an assembly of two cylinders that we will use as the cut out piece. Essentially its a cylinder with a diameter of 2cm and height of 1cm. Then I assemble another cylinder on top of that (centered) with a diameter of 1 cm and height of 1 cm (See sketch).

I won't detail how to do this within 123D Design, its pretty intuitive. I attached the cutout model to this step for convenience and here is a link to the model as well:



http://www.123dapp.com/smb-123D_Design/bobblehead-cutout/1650663



This cutout piece is made with scale in mind (which is important for when we 3D print it, so we'll use this cutout piece as reference to scale the head model to.





Back in Meshmixer...

1. Click "File...Import", then choose "Append" in the dialog that pops up to add it to the MeshMixer workspace as a new separate object.

2. If asked, click "Yes" to shift position.



The cutout piece is imported and is at the scale we want the bobblehead to print. We'll want to scale and position the head and make sure not to scale the cutout piece. You can switch between the active object by clicking on the object (head or cutout) OR, show the objects browser to select them there.



3. (optional) Click "View Objects Browser" See that you can select one or the other to make it active.

4. Rotate the cutout piece rightside up by using the Transform too. Click "T", then use the rotation manipulator and the snapping angles to snap it 90 degrees, with the small cylinder on top. Then click "Accept" in the upper left corner.

5. Next, make the head object active by clicking on it (or use the Object Browser).

6. Scale the head up and move it into place, so the cutout is poking just through the bottom. Use "Transform" here again. The middle white box in the manipulator will scale the object.

(Note: I had to make the bottom of the cylinder assembly cutout extend on the bottom to properly pop out the bottom of the head. To do this, select the bottom faces with Select mode, then Transform them downwards.



ALAS, now make the cut!!



7. Select, in order while pressing Shift to multiselect, the head model, then select the cutout piece (easiest to do this in the Objects Browser while pressing Shift to multiselect).

8. From the Edit bucket on the left panel, choose "Boolean Difference"

9. The model will temporarily change color so you can inspect the cut. Lastly click "Accept" to finish the operation and the texture returns.





