I’m telling you … no one is more impressed than me, that the drill (with a ball head carbide cutter) actually ran and didn’t tear the assembly to pieces. But it did run, and it did run as planned.
The original software I had put together was using the accelstepper software, that I wanted to create a slow start/stop to the mandrel turning which would allow the simulation of sine waves. However, I couldn’t get the logic worked out correctly, so I ripped out the accelStepper, and just used the Adafruit motor shield library and put in my own routines. The end result is near perfect control over the mandrel rotation positioning.
The basic mechanics are pretty much worked out. We have some fine tuning to do yet. For instance, the screw we are using to secure the tail end of the mandrel just seems too flimsy. We are going to replace it with a bearing mounted in the end cover. The bearing center will slide on over the end of the mandrel, securing it into place, no screw required. I also will be looking for a way to secure the drill motor to the unit, with some form of acousitc insulation. I don’t need the carriage assembly to act like a resonator for the motor – things are loud enough as is.
Currently the unit looks like this:
Here is an image of the first attempts using the first software. You can see how the mandrel “twist” wanders all over the place. I don’t know what I was doing wrong, but since I couldn’t get on top of it, I dropped back a step and used just the straight motorshield library – and figure I will have to ask the arduino to do some calculations to approximate the curvature at the amplitude top and bottom to look like a sine wave.
I also experimented with using the serial console to the arduino as the input device, and loaded 3 configurations into the EEPROM to handle the sine, right and left spiral configurations. I have to run a 2nd program to update the EEPROM data when I change the preprogrammed patterns, but that shouldn’t be too bad. What I do need to have as adjustments for each turning is the demarcation of start and stop (the linear length), how fast the mandrel twists, and how deep the cutter head is set for. Those seem to be the parameters I want to fool around with the most.
I plan on next wiring up the PowerSwitch Tail II to the unit, to have the arduino start and stop the drill motor. I don’t have too, but I have the the switch, and really like the idea of driving it this way :). I also need to rejigger the motor shield to remove the pins (and wiring) I had in place for the start and end position switches that have been removed. In doing that cleanup I can drop out the battery shield I was using, and take it back to the arduino, motorshield and the display/button shield.