Aaaaaaaaaand we’re back. This week was CNC machining. I initially decided to make a landscape, but unfortunately there were some issues with VCarve on the OEDK computer attached to the Shapeoko. Everything was updated and fixed quickly, but given the length of the cut (~2 hours), the inevitability that something will go wrong, and my desire to sleep, I pivoted. Quick takeaways for making landscapes:
- I used map2stl.com to pick a custom area. The .stl download was incredibly detailed, so I imported the model into Fusion and reduced the number of faces to smooth things over. (You could also tweak the sampling rate on the website, which determines detail)
- Fusion imports .stl files as a mesh body. This is fine for editing, but once you toss that into VCarve the software gets confused. In Fusion, repair the mesh (remove any holes) then convert it into a solid body first
capture from map2stl; you can see the detailed .stl in the bottom right
.stl simplified in Fusion
imported into vcarve
The realization that I wouldn’t be able to make the landscape (after planing, staining, rigging, and prepping the wood the day prior) was another tally on the week’s misfortune. I needed to pivot.
I had been thinking about a gift I could give to my close friend who is graduating, as I’m visiting them this coming weekend for a smaller graduation ceremony before commencement. They’re pretty into tarot, so I selected the seventh major arcana card, the chariot. From what I could find, it symbolizes overcoming obstacles and victory through determination. This felt pretty apt, both for graduation and picking an entirely new project with 3 days to finish.
I found a really cool expressionist rendition of this card online by Jeffrey Thompson. I simplified the design a little to make it easier to CNC, converted this to an .svg (thank you, Adobe Creative Cloud subscription I forgot to cancel), and opened it up in Carbide Create.
I selected the 1/8″ and 1/16″ endmills for the majority of the work. Pretty much everything used pocket cuts; I used a contour cut with the 1/32″ endmill only to refine the smallest details of the lettering, like the insides of the A and O in “CHARIOT” and the separation between letters. Since the 1/16″ and 1/32″ endmills are tiny (read: inefficient), I limited the areas they’d work within to cut down on time. To do this, I drew bounding boxes with the box and offset drawing tools (highlighted in orange in the pictures below), then selected these for pocket cuts.
toolpaths for this piece!
bounding boxes I drew for the 1/16″ and 1/32″ pocket cuts
toolpath simulation
piece with the working area cut out (note margins left for Shapeoko clamps); this piece was 1/4″ too narrow, which is why the cleared area isn’t centered 😖
I didn’t want the final piece to be 3/4″ thick. There weren’t any lab assistants available to help me get into the woodshop and plane a plank of wood down (being at the OEDK during normal working hours would have fixed this), so I used the 1/4″ endmill in the Shapeoko to cut down the working area of the wood to 0.375″. I only cut out the area of what I needed (instead of the entire piece), since it was faster and didn’t require working around clamps on the X-carve bed.
Then I transferred my piece to the Nomad (I’d eventually need a 1/32″ endmill for the fine lettering). To be able to re-zero the origin with the BitZero, I kept the outer edges of the original 3/4″ plank. I knew I wanted the final piece to have contrast between the raised and recessed areas, so it’s at this point I should have stained the wood. I did not do that.
wedged a clamp under my piece in the Nomad to prevent wiggle during the pocket cuts. (adjusted with bubble level in my pen)
Moving ahead, I cut out the first piece. I had no issues (RARE for CNC work). Once the cut was done, I saw the VII was thicker than I’d intended. I added a contour cut for those letters as well, realizing only after the fact I did not change the contour setting to be outside/right, leaving these letters super skinny. I fixed that in the toolpaths for the next piece.
The last step was cutting the piece out. Here, I realized the tiny margins I left on either side were very much not helpful. If I were to cut out the piece in the Nomad, it would remove the wood that was touching the clamps and erode away what was actually secured, leaving my piece floating. So I did one last transfer to the Shapeoko and cut everything out. I had to finish this cut on the bandsaw, since the bit did not go all the way through. Then I did everything all again for piece #2🕺🏽
I wanted to use one of the pieces as a stamp to make custom cards for my other graduating friends. My roommate pointed out that for this, the lettering should be flipped laterally. While waiting for the second piece to be faced down to 0.375″, I made reverse lettering stamps.
lettering reversed; words condensed to save space
post bandsaw. Left side of the V (up top) snapped, so I shaved down the other letters to match
finishing edges, removing whiskers with razor
Once the second piece was complete, I moved to finishing. The flat endmills leave a ton of whiskers, and I wasn’t sure if the amount of sanding required would break off the finer details. So instead I ran over each edge with a fresh razor blade, which was effective though tedious. Then I sanded everything up to 220 grit, going light on the top surfaces since I was wary of breaking the delicate parts (the V on the first piece had already snapped).
Finally: staining. Wood stain is super runny, so I knew this would be difficult — brushing it over the top of the surface would leave a high chance for the stain to bleed everywhere and touch the recessed areas. I decided to dip the pieces in wood stain face-down.
dipping face-down in some stain
I practiced dipping on the reversed letters first (IT WORKED 😀 )
dabbing off the the excess (proof of stamp!)
This worked out better than expected. While staining the first piece, I found that even after wiping off excess stain the tiny bit that remained would pool in recessed areas, especially near the thinner cuts. So for the second piece, I dipped it for less time (~30s instead of ~3 min), then left both face-down after removing the excess to prevent leftover stain from being wicked down by the wood fibers. While this happened, I also stained the sides and back.
Following this, any stain that accidentally made it to the recessed parts did not actually seep far into the wood, so I just scraped it off with a razor. After this, I wanted to apply a finishing coat to seal everything, but you’re supposed to let stain fully dry before sealing. Since it was T-10 hours to submission, I turned in the pieces as is, and plan to finish them after grading.
Here’s how the final pieces turned out!
turned in on the class table
proof of clean workspace 🫡
I had fun with this homework, despite the mid project crisis (which I think was mostly induced by having lost my Rice ID at the same time). The most time intensive part was set up, since I was switching between machines and needed to re-zero each time, and swap between four different bits AND the dowel for zeroing on top of this. In terms of difficulty, this project had many more points of failure than others (toolpath creation, clamping, zeroing correctly, tool changes, all which can catastrophically mess it up and require a restart), but did not seem much harder in a technical aspect. I also thought it would be much more difficult to book the CNCs for when I needed, but they were pretty available.
Here’s my cost analysis for this project (not including the initial pieces I prepped for the landscape):
It ended up totaling to $822.65, with the largest costs being machine time and hardware used (ie: the low profile Carbide 3D clamp).
Cost links (in order):
*For McMaster links, can reference the end mill catalog here and Ctrl+F the part #s (https://www.mcmaster.com/catalog/131/2879) without requiring sign in
