“Make Something BIG” Week.
Assignments
Our tasks for this week are:
- Group assignment:
- Do your lab’s safety training
- Test runout, alignment, speeds, feeds, materials, and toolpaths for your machine
- Individual assignment: Make (design+mill+assemble) Something BIG (~meter-scale)
- EC: Don’t use glue/fasteners
Group Assignment
The group assignment for this week is documented on our group webpage.
As a group we completed the safety training and followed the workflow for using the CNC (fixturing stock, changing the tool, zeroing). This included preparing the CAM files using Rhino CAM to make a cut test array to compare how different parameters changed the resulting cuts. For our 15mm thick plywood test stock, we varied spindle speed (18000 vs 20000 RPM), feed rate (3000-5000), cut style (climb vs conventional), and Down Cut vs Up Cut endmill. We included bridges/tabs in the file to prevent the pieces from flying out during the protocol.
Individual Assignment
I struggled this week with having grand aspirations for a project (a chair that could transform into a ladder? the frame of a skin on frame boat? a giant heart made with a waffle pattern? a waffle-grid Womb chair? A bench that made use of a living hinge for the curvature of the back rest?) but not actually having a lot of time between work commitments.
In the end, I decided to just keep it simple, so I made a stool. And I love it!
Design
Time was ticking so in the end I took inspiration from a few flat pack stool designs I found online and designed my own stool in Fusion 360.
My stool has three pieces: a seat and two legs pieces. I used 15mm thick plywood. It’s press fit construction, and I didn’t account for any kerf in my design because I wanted the joints to be quite snug (and they were! It’s perfect, where I can get them to slide together but they don’t come apart). I opted to make pockets to connect the base to the seat rather than cutting all the way through, and made use of the Boolean/combine tool in Fusion360 to make the interlocking joints.
Flat Packing the parts for CNC milling
Next I positioned the parts on the “stock”:
Adding Dogbones
I found a Fusion360 plugin to add Dogbones to the pieces (this is necessary in CNC-milled parts due to the tool having a radius).
Once up and running, it was easy to select the edges where I needed to incorporate dogbones so my pieces would sit nicely together.
CAM
Although Fusion does have its own CAM workflow, I was running out of time, would have needed to watch a lot of tutorials to figure out how to do it, and our lab has experts in RhinoCAM. So I exported my flat-packed design as a DXFs and imported into Rhino where I could take advantage of the RhinoCAM workflow.
Here are the resulting three files:
- Screws
- Pocketing
- Profile
Cutting
I used a 6mm DownCut endmill tool for my 15mm thick plywood.
Once I ran the ‘Screws’ file and fixtured down my stock (and re-zeroed the Z, of course), I was ready to send my files to the machine.
Some quick filing/sanding to remove the residual material from the bridges:
Hero Shots!
Reflections
I’m quite pleased with the result, and I’ve been using it at the lab everyday! I like the height I designed it with and it helps me maintain good posture while I’m on my laptop.
Files
Fusion360 Design file for my stool | F3D file