8. Computer-Controlled Machining¶
This week, we need to design and fabricate a big thing! I’m thinking about making a chair! The first thing that came to my mind what’s the dimensions and angles of this chair? Is it suitable for school Fablab limitation space? I struggled at the beginning. But, I guess there is a standard or recommended dimensions/angles for the folding chairs. I searched online for the folding chair pinsterest and I found a lot of resources providing that data! I am insteresting in Desile Folding Chair $335
Learn to use large-scale CNC machines (CNC: Computer Numerical Control) this week.
Commonly used CNC machining materials¶
Group assignment¶
Test runout, alignment, speeds, feeds, and toolpaths for your machine.
Individual assignment: use CNC make a folding chair and tool box¶
The individual assignment requirements for this week are ‘MAKE SOMETHING BIG’
Design¶
Draw three parts in Fusion 360: stand, sitting plate and back plate. Because the thickness of the material is still uncertain, it is necessary to set the thickness of all parts as adjustable parameters: create a custom parameter in Modify-Parameter, and then use the parameters that have been set. When drawing graphics and stretching in sketch, use the set parameters as the sitting plate holes diameter (Thickness x 1.4).
The thing is relatively big. To be on the safe side, I first did a simulation with fusion360.
Profile Toolpaths¶
I need select the suitable outside or inside profile when cut out a part. Profile toolpaths will change theposition of kerf and the dimensions of the part.
CNC Milling¶
Now it’s real. This is a 0690 CNC machine made in China. First trial material use 12mm OSB. Second trial material use 18mm OSB.
Export the NC file From Fusion360¶
Import the NC file into CNC
Feed rate¶
Chip load: ~ 0.001-0.010” = feed rate (inches per minute) / (RPM x number of flutes)
Cut depth: ~ tool diameter
Step-over: ~ tool diameter/2
Video of machine cutting¶
Assembly¶
You only need carefully to drill the pin hole with 5mm drill.
There are only three parts, so there is no difficulty in installing it.
You can fold it for storage and open it with one hand.
Bouns Assignment Tools Box¶
It is my first time use dog bone on woodwork design. It is not difficult to use this technique.
I will remind the dog bone skill for press-fit joint in my further design. I add the dog bone on each conners.
OSB is easy to milling and assembly but it will absort water. Therefore the project will keep long time, it is important to coat a varnish onto wood as surface finishing.
It is a funny week for me to experience CNC woodwork, before this week I only use the hand tool and electric hand tool to make workwook.
Here is the file (folding_chair.cdr) (folding_chair.f3d) (tool_box.f3d) for folding chair and tool box.