Hello again,
Today I’m trying to finish the box that contains the electronics of the OX CNC.
I already have a box that I made from layers of MDF So right now it looks like this:
It’s not the prettiest box right now. I didn’t have the proper clamps when I did them, so the MDF moved a little, but I will redo the MDF layers when I have some time.
I want to have a translucent cover, it’s fun to show off a little bit. So i went to my local renovation center and they had some poly-carbonate with a price mistake on it (yes!). I was actually looking for acrylic but the poly was cheaper, thicker and as we will see later much harder.
Poly-carbonate is way harder than acrylic, I’ve never used that material before so I’m not really sure what the feed/plunge rate to use. Determining these settings are very random when you are trying new materials
Fortunately, I found out the other day that Othermachine, who sells a small milling machine that has almost the same RPM limits as my current spindle, has a lot of suggested rates on their site for their machine. This how I base my feed rates for now.
I’m repeating myself, but man! Polycarbonate is a hard material, make sure your belts are tight. Othermachine suggest these rates:
Tool: 1/8″ flat end mill
Feed rate: 23.622 in/min (360 mm/min)
Plunge rate: 1.81 in/min (46 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.010″ (0.25 mm)
Compare this to normal acrylic with the same tool:
Tool: 1/8″ flat end mill
Feed rate: 59 in/min (1500 mm/min)
Plunge rate: 1.81 in/min (46 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.005″ (0.13 mm)
Even at these speeds I had some skipping… I had to lower the feedrate to 250 mm/min… Now that could be the results of many things… When it happened I checked all my excentrics and my belts… I had to retighten everything again (and contemplate if the belts are secure enough with the tiny little screws at each end of the rails, I’ll probably need to change that) and the second time it went through. It could also be the result of me using some cheap ass stepper drivers that overheat (these… I will change in the near future).
In the mean time, here’s the result:
You can see the “scar” of the skipping on the right side of the piece.
Here’s the Fusion 360 file for the whole box: http://a360.co/2cWySSP
This is the kind of material you need to experiment with. I will update this article when I have done more tests.
Now… what else can we do with this material? How about an illuminated LED name tag to annoy my colleagues?
Disclaimer: I’m not very good at writing articles, this is why I force myself to do it a bit more these days. If you have questions please fell free to ask in the comments I will answer every questions. Thanks for understanding.
