Assignment
- Mill something "large" (from plywood with dimensions 500 x 400 x 15 mm, using cylindrical end mills of 4 or 6 mm)
- Create a model and develop a CNC machining program (ideally using Fusion360 Design & Manufacturing)
- Use 2D operations (so-called 2.5D machining) such as:
- Contour - cutting horizontal perimeters using an end mill
- Bore - drilling holes using an end mill
- Face - leveling flat surfaces using an end mill (typically with maximum diameter)
- Trace - passing any mill along an edge or drawn curve
- 2D chamfer - beveling horizontal edges using a V-tip mill
- Spot drill - pre-drilling holes using a center drill
- We will be using wood end mills (1-2 flutes) with diameters of 4, 6, 8, and 12mm, an engraving and edge mill with a 90-degree angle, and a center drill with a 90-degree angle
Design
For this week, I decided to make a much better looking tissue box for out living room. Not only the design annoys me to the very core, but the fucntionality of it sub par as well, the tissue that is supposed to be sticking out always to be easily accessible falls back inside. So that is also something I would like to fix.
For the design I used Fusion 360, and I started with a simple box. I then added a small cutout for the tissues to stick out of.
Pro Tip
When you have the general shape of the model you want to create. In my case the pieces of the box that could lay flat. Do a test arrangement to see if it fits within your allocated material.)
Fusion 360 model
CAM
For the CAM I used Fusion 360 as well, it is accessible in the manufacture tab in the top left tab menu. Created a new setup, didnt select a machine and then entered the allocated stock dimensions. I also placed the origin in the bottom left corner of the model and stock.
I used the following tools:
- 4mm end mill
- 6mm end mill
- 90 degree V-tip mill for chamfers and for "engravings"
used the following operations in sequence:
- Adaptive clearing - this is a 2D operation that clears out the material in the recessed sections. I used a 6mm end mill for this operation where applicable. I also enabled 1mm of radial stock to leave because I later planned to make contours with the 4mm drill.
- 2D pocket - this is a 2D operation that clears out the material in the recessed remaining sections and in the hole for the tissues. I used a 4mm end mill for this operation. No need for leaving out the stock this time.
- 2D Contour - this is a 2D operation that I used to sharpen the edges of the box. I used a 4mm end mill for this operation. I disabled stock to leave to get the wanted model shape.
- 2D Chamfer - this is a 2D operation that creates a chamfer on all the upper-most edges exposed by the previous operations. I used a 90 degree V-tip mill for this operation.(and forgot to chamfer the hole for tissues)
- Trace - this is the operation I used to "engrave" the sketches (10mm-offset-edges of the recessed parts of the model) 1mm deep into the recesses with the V-tip mill again.
- 2D Contour - Finally, I used this operation to cut out the box from the stock. I used the 4mm for this operation as the 6mm would not fit.
Pro Tip
Always simulate and look at every operation and how it interracts with the stock. This way you can see if the toolpath is correct and if the tool is not going to hit anything it should not. This is especially important when using adaptive clearing, because the toolpath can overshoot quite a lot.
After I was happy with the toolpaths, I sent the file to Krištof.
Cutting
The cutting was done by the machine and its overseer, selfless Krištof Pucejdl, operating it till 3 AM. I oversaw the cutting of my box, which basically consited of me telling him what to select for the chamfering and engraving operations. Tool changing was done automatically, by a vacuum-based system on the machine. Very cool.
After the cutting was done, I immidiately started with the post-processing.
Pro Tip
Always check the toolpath and the stock before cutting. This way you can avoid overshoots and other mishaps. I had a few overshoots on the box, which were caused by the adaptive clearing operation. The toolpath for the specific machine was not the same as in my CAM.
Post-processing
After the cutting was done, I took the pieces out of the machine and started with the post-processing. First, I used a sandpaper sponge to smooth out the edges and remove any burrs. After that, I started filing down the fingers I had on the pieces of the box to make them fit into each other. We later discovered that the mill used a 3mm end mill, so the fingers were too big (about 2mm difference). I used a file to make them fit. I also used a file to smooth out the edges of the box and make it look nicer.
Assembly and finishing touches
- First, I assembled the box and made sure everything fit. Kept filing everything fit.
- Then, I used a wood glue to glue the pieces together. I used Herkules proffesional I had at home
- I used a nails hammered into the bottom fingers to hold the box together while the glue dried overnight.
- After the glue dried, I used a sandpaper sponge to smooth out the edges and remove any burrs. Especially on the recesses.
- I added small wooden pins with grooves (so called: "carpentry nails" in Czech) to the lid piece, drilling holes for them and then gluing them in, to make it allign with the bottom and also make it stay in place
- Finally, I used a transparent wood paint to finish the box. I used a classic paintbrush to apply it and then let it dry overnight.
Conclusion
I am very happy with the result. The box looks much better than the previous one and it is also much more functional. I learned a lot about the CNC milling process and grew to adore (machine-assisted) wood-working/carpentry.
Next time, I am tripple checking the sizes of the mills and also the CAM program so that no overshoots ("wood bite-offs") or other mishaps have a chance to happen.