June 2018 Doc
Hi, Connor!
Document to track progress / changes on Bessie
Today we completed the coolant loop. There was pre mixed coolant (7.5%) in the reservoir but new coolant mixture has been purchased and is in the yellow chemical cabinet. We used a small water feature pump which has very low head. I would say the flow is adequate for the milling we were doing in aluminium with a 3mm end mill. If we find we need more flow there is a larger pump that has 3m head and 3000litre / hour flow. There is a mesh in the drain and an inline filter on the gravity return back to the reservoir.
As of right now the coolant pump is turned on manually. There are additional outputs available on the Mach3 controller board and we want to use a 220v relay to turn on / off the coolant using Mach3 / Gcode. Coming Soon...
RPM set in Gcode does not represent actual RPM. The spindle RPM is considerably faster than the RPM you set. We spent some time setting explicit speeds by issuing the gcode
S10000 M3
And then used the laser RPM gauge to measure the actual speed. Results are here. The differential is not a constant. It increases linearly with RPM and behaves strangely below about 4k rpm. Someone with better knowledge of variable speed drives may be able to correct this but for now the proposed solution is to use the fusion 360 post processor to fix the gcode. i.e when the user wants 21000 rpm we will write 13000 to the gcode. We can also tweak the post processor to limit the max rpm to 24000 which is the max rpm of the spindle.
Edit: There is an auto-zero probe that requires setup. Intermittent behaviour was observed resulting in the the Z-Axis continuing after making contact (BAD!).