This post is a direct continuation of my Part 2 CNC machine build.
Metals. The strongest & most practical materials to use in high-stress or high-temperature engineering builds. Being able to design and manufacture parts with aluminum, steel, and more opens up the kind of projects you can make, and gives you even more freedom than before. For the last six or seven months, I’ve been grasping at a chance to feel this freedom. The freedom to mill aluminum.
Tolerances – Solved!
In the past, I talked about my sub-par machining skills. The parts I drilled holes into as well as the parts I tried to level & make perpendicular weren’t the best. This manifested itself into very, very sticky linear rail movement and locking up of the steppers when I’d try and move the axes. Because CNC machines have to be so accurate and take a ton of stress, they need very tight tolerances. This is something I struggle with. However, I found a solution.
In the above model, you can see I elongated the mounting holes in order to allow adjusting of the positioning on the fly. Whenever I was happy with the positioning, I could put a little thread locker on the bolts and screw them in. This would allow me to avoid having to re-design the entire thing with tighter tolerances and saved me a ton of time.
Software
For this CNC machine, I’m using an old 3018 CNC controller. I tuned this controller to the correct X-steps, Y-steps, and Z-steps for my machine, as well as changing a few other settings related to interfacing with the steppers. Then, I was ready to cut.
You can see I have the cut depth fairly low. This is because there’s a bit of a flaw with the CNC machine’s design – there’s a pretty big lever arm between the router tip & the stable part of the Y-axis carriage. Due to mechanical advantage, this causes the aluminum that the bit is trying to cut influence the router tip a significant amount. This means feedrate must be low, and cuts must be shallow in order for this machine to work well.
Cutting.
This was it. The moment of truth. I would finally see if six months of my life were spent in vain.
I could lie and say this was incredibly dramatic, but the truth is it took an hour and a half to cut the piece because I was being incredibly conservative with feedrate and cut depth. It was pretty anti-climactic, but it worked!
When cutting, I have to be there at all times. I have to make sure:
- The router doesn’t catch fire
- I continue adding oil to the aluminum to prevent high temperatures
- Vacuuming the aluminum scraps up
- Making sure there’s no other catastrophic failure that I’m unaware of
I learned a lot from this project. It taught me a lot about subtractive manufacturing & working with industrial level materials and pieces. Despite running into many issues, I enjoyed my time working on this machine.
