This assignment was a great experience in learning how CNC machines work, as well as an exercise in patience. I got to troubleshoot quite a bit, whether it was adding in small pieces of wood / cardboard to the spaces between the wood block and the clamps on the Nomad, ensuring use of the proper version of CarbideCreate, or recalibrating the zero position for the drill after probe failures.
First, I downloaded an svg image of an orca from the Noun Project (owned by the user pramana), and imported it into CarbideCreate v6.
Image of the toolpaths for the orca.
I set the toolpaths to include two pockets of differing depths to show the fins and differing colorations on the orca. Initially, these pockets were quite deep (the human eye perceives depth at a much better resolution than I thought!) and I changed them to be shallower by a factor of more than 10 for my second print after a conversation with Dr. Wettergreen.
It initially took around 27 minutes with the 0.15 inch and 0.05 inch pockets, but I made them 0.05 inch and 0.005 inch (which in hindsight is effectively nothing), respectively, for the second cut. This shortened the cut time to 13 minutes.
I then added a contour toolpath to actually cut the orca out of the wood block. Importantly, I learned that you should measure the thickness of the wood after clamping it on the Shapeoko, because there can be significant wood compression that would cause the drill to go deeper than intended, possibly damaging the metal base of the machine.
Experimented with different orientations to determine what wood orienation was easiest to clamp. Ultimately, I still went with the vertical orientation for the cut.
Clamping the wood block on the Shapeoko machine. The depth distortion can be significant here, so re-measuring is important.
Drilling begins on the Shapeoko
Progress on the Shapeoko machine. This was for the first cut, which had deep pockets and took nearly 30 minutes.
Orca 1, fresh out of the machine. The pockets are very deep.
I used the Shapeoko Pro for the first cut, then the Nomad for the second one. I had some trouble doing my second cut on the Nomad — first, the wood kept slipping out of the clamps near the end of the cut. I used pieces of scrap wood and cardboard to keep the wood in place, which made it work. Unfortunately, the wood piece I used for that cut was too thick (over an inch and a half), which made it impossible for the drill to fully cut through the piece. I have kept this piece and may use the band saw to fully extract it once I complete my training for that tool.
Modifying the pocket depth to be smaller.
Cutting on the Nomad 3. Clamping was difficult but using small pieces of scrap wood helped stabilize it.
A failed cut on the Nomad 3– the wood got out of the clamps about 80% into the print, and re-aligning it / redoing the file to just cut the contour was unsuccessful. I ended up doing the cut one final time and it worked.
Last cut. This time the pockets are much shallower, which makes it look more aesthetic (at least to me).
I used wood stain to post-process my orca cuts.
After choosing a thinner piece of wood, I was able to get a nice cut. I then hand sanded both these pieces, noting that the first one was a bit harder to sand because of the deeper pockets on the front of the piece. Finally, I used a walnut color wood stain to finish my pieces. The second piece took a bit longer to stain, because the smaller pockets made it slightly more difficult to cover all of the protruding borders of the piece (around the orca’s eye and such).
Final orcas!
Clean workspace after finishing (vacuumed all the CNC area, used a dustpan and broom)
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | Wood | $0.0237/cubic inch | Homedepot.com | 2pcs (0.75 x 4 x 6 inches) |
$0.86 |
| Wood stain (walnut) | $14.97/qt | Amazon | 0.05 cup | $0.19 | |
| Labor | Prototyping Engineer | $36 / hour | ZipRecruiter.com | 6 hr | $216 |
| Overhead | CNC machine renting (Nomad 3 and Shapeoko Pro) | $50/hr | https://manor-mill.com/machinerentals | 3 hr | $150 |
| Post-processing tools (Sandpaper and brushes) | $12.68/20 pcs of 9×11 320 grit paper Brush $1.87 |
Amazon Homedepot.com |
⅛ sheet 1 |
$0.08
$1.87 |
|
| Design | Engineering and Development | $25.75 / hour | ZipRecruiter.com | 1 hr | $25.75 |
| TOTAL | $394.75 |
The bulk of the costs come from machine rental and prototyping fees.
