7. Computer Controlled Machining
This week it is all about CNC (= Computer Numerical Control)!
For this topic we dive deeper into how to design your pieces and how to operate the machine.
Points to talk about: used software, end mills, machine, design, setup,... cnc process, finishing of the pieces, assembly and test.
This is the type of machine that we will be using this week: RaptorX-SL - Series.
2D design
For this assignment, we have a big sheet of Plywood. Dimensions of this sheet are: 2440mm x 1220mm x 15mm or 10mm.
I had a couple of ideas for this assignment: a Work From Home standing desk, a fun rocking chair for a toddler, a birdfeeder that i designed a couple of years ago, a chair/stool with a shape based on an animal.
I choose for the chair/ stool shaped like a fish :) and based on a chair designed by Marc Newson.
I used Rhino to design the shape. The shape it pretty straighforward: a fish shape with 4 holes repeated 14 times with wooden "washers" in between.
workflows for CNC production
Export the file to Rhino 6 and import it in Rhino on the desktop computer. This computer has Rhinocam.
This is the software we need, to create the file that the cnc can read and where we set up the design and the necessary positions for the screws.
With this software you can set up all the parameters.
To make the workflow easier, it is better to create differet layers to define the different cuts and settings.
I used the layers: screws, inside cut, outside cut and pocketing.
To win some time and avoid big loss of material, it is important to organize the sheet as good as possible. The spacing between the parts needs to be big enough for the mill to pass in both directions.
In the layer Inside cut, i added everything where the mills needs to cut on the inside of the line. This is in my design the part of the inside of the stool. I also added the wooden washers in this space because this is a lost part of the cut.
In the layer of outside cut, i added the big shape of the stool. Here the mill cuts on the outside of the line. The washers are also cut on the outside of the line.
in the layer Pocketing, i added the holes where the rope or rebar goes through. This is also on the inside of the washer.
CNC production
Let the fun begin :)
Use safety glasses before cutting!
- 1. Downloading the file onto the desktop computer that is connected with the cnc.
- 2. Putting the wooden sheet onto the cnc platform.
- 3. Changing the mill with the one we choose. In this case a 6mm.
- 4. Setting the origins: first the X and Y and then the Z.
- 5. Start the first cycle: screws! In this cycle, the machine mills the designated holes for the screws.
- 6. Screw the sheet onto the sacrificial board. Make sure that you screw the screws first in for 2/3, get out and screw them back in for 100%. Doing it this way makes sure that the sheet is fully flat onto the sacrifivcial board.
- 7. Start the second milling cycle: Pocketing.
- 8. Start the third milling cycle: inside cut. This is the part inside of the fish. Inside cut means that the machine mills on the inside of the line.
- 9. Fix the problem: unfortunatly as you can see in the second picture, the inside shape was only connected to the sheet with bridges. These bridges were not strong enough and broke because the milling of the machine is to strong. To fix this problem i used screws to fix all the pieces to the sacrificial board.
- 10. Relaunch the machine. (i had to press the emergency stop button when i saw the bridges break. To continue with the process, i had to create a new file where i only kept what had to be milled. Thi sfile is the Second Try file :p)
- 11. The machine is ready after 1.30h of cutting (problems included)
- 12. Cleaning the surface with the vacuum to have a clear view of the milled pieces before taking them off (unscrewing) of the sacrificial board.
- 13. Taking the pieces out of the wooden sheet. To do this, i had to break the bridges between the pieces. I used a hammer and a chisel
- 14. Take everything from the machine and leave it clean and organized behind.
- 15. Time to sand the pieces.
- 16. Time to assemble!! woohoo
- 17. Take some nice pictures of the end result
- 18. Be happy with the result :p
Pictures and videos from the process
Here you can see some pictures of the process and below some videos.
These are the tools i used to break the bridges.
Here you can see the problem with the bridges.
here is a video where the cnc is preparing the screw holes.
Final product
There was no toddler available for the picture so my dog can give you an idea of size :p.
