Hi all,
I decided to try making a full bowl on my OneFinity using the rotary, and here’s what I got working.
I started with a chunk of oak I had lying around and drew a bowl in Autodesk Fusion to match those dimensions. I glued a 3/4" block of poplar onto the oak, and screwed the faceplate from the OneFinity rotary to the poplar.
To hollow the inside of the bowl, I started with a fixture from 2 pieces of scrap MDF. The first piece has a center hole so I can reliably center it, and 3 pins created using the double-sided carving technique from V-Carve to register the 2 pieces together. It also has 2 recesses for bolts that you’ll see later:
The second piece registers to this one, and has a 1.25" square cut out to hold the rotary chuck:
This gives me a way to set the fixture (the center hole fits a .25" bit), and clamp the rotary plate to the table. The base of my glue chuck has 2 recesses for holding bolts, so the chuck gets bolted to the top fixture plate:
(this is taken after it’s been carved, buy you can see how it could be bolted to the top fixture for hollowing)
From here, I can hollow out the bowl as a standard pocket - I used a 3/8" bowl bit so I had something with enough reach.
After you cut out the center, move the piece to the rotary to carve the outside of the bowl. I used V-Carve to import the STL from Fusion, and carved the outside of the bowl from there. I used V-Carve’s rotary widgets to round the blank and to carve the texture with a v-bit:
For a test run, it worked pretty well! I’m making a couple of adjustments as I plan to do this again. I left too much stock at the bottom of the bowl; I need to carve a little deeper. The V-bit also left a bunch of fuzzies on the oak; I need to do 2 passes here to reduce that tear-out instead of ripping through it in a single pass.
I raised the entire CNC by placing 4 pieces of MDF (3 inches) under each foot, then resurfaced the spoilboard to get enough clearance for this work. That means for some things I have to put another sacrificial piece on top of the spoilboard to lift things up, but I’m planning a vacuum holddown that will do that anyway, so that’s OK.
Coming up with a way to bolt the blank in its chuck to the spoilboard was the trickiest part. Bolting the faceplate down to the fixture worked really well, much better than trying to hold the whole thing by the faceplate square alone.
I’ll post an update once I’ve tested and finished round 2. Then I’ll try some real wood!