After months of putting it off, I jumped in and slapped two motors on to my mill.
I've already identified that the XY mechanisms on my mill aren't going to be up to the task (they have excessive backlash in both the bearing mount & the nuts).
Therefore, it's not worth spending too much time on the installation, as I'll need to redo it when I upgrade the mechanisms. I still hadn't done a "real world test" on my DIY servos & controller, and was keen to see the mill's table move.
Enter the angle grinder, 2 short pieces of RHS and some hose clamps...
So, what did I learn?
Keyboard: The wireless flexible keyboard I got is great. Chuck it where you need it.
Current Draw: It's not unusual in my 1:1 setup to see the motors draw 10A @ 12V. Hopefully this should drop when we switch to 36V. w
H-bridge Temperature: The H-bridge chips got hot. Real hot. I couldn't keep my finger on the heat sink, hot. Since pairs of H-bridges share heat sinks, I swapped the Y axis onto a different pair than the X axis. Then they both got hot... How hot? Not that hot: 57°C. I put a small fan near and let it continue to run: 32°C (ambient was 25°C). Not neccessary, but a larger heat sink or small fan would keep it cool.
PID Tuning: The inertia & friction of the table's screws changed the tuning requirements quite dramatically.
Encoder Inputs: Since I only used 2 of 4 servo channels on my controller, the other 2 encoder inputs were left floating. Phantom transitions on these lines fire interrupts and unnecessarily consume controller time.
Limit Switches: This was a simple test, and no limit switches were installed. Luckily, the flexible coupling slipped when it attempted to go beyond the table's travel. Limit switches are a must.
DIY Flexible couplings: OK, small length of hose with hose clamps. While there is some twist in the soft hose I used, when you consider the 0.2mm of existing screw backlash (@ 3mm/rev) equals 24°, the <10° of hose twist & <6° of servo error is quite acceptable (for now).
The Z axis hasn't had anything done yet, but that's OK. Baby steps. Although it would be easier, I don't want to automate the quill since it's got a lot of play in its rack & pinion setup. I should get moving on the ball screw upgrade and automate the column.
Even with only the X & Y axes done, the machine is transformed. I'm happy to perform any required Z movement manually for the time being.
All in all... I'm pleased, and it's quite exciting (chips will fly soon).