Well putting this together for a test today. Using their numbers of 18000rpm and 60ipm I get huge deflection warnings, 300%+ over the desired number. This is also for slotting so that may be the issue.
Okay so playing with the numbers, stickout is a huge component of deflection, I had that at around 1-1/8" but I don’t need that much exposed, the full depth is nominally 3/4" and the cutting threads are 13/16" (.8125") so I’ll put the number at .9 and just eyeball it during setup to just above the stop of the cutting threads.
Awesome so that immediately dropped my deflection warning in half to 168%. Let’s see how various adjustments can help it.
- Increasing RPMS 10% to 19800 brings it to 152%
- Decreasing feedrate 10% brings it to 151%
- Decreasing cut depth 10% brings it to 151%
So those are all about even, a 10% adjustment to a relevant number produces a roughly equivalent 10% drop. Because my final product is me cutting out a hexagon the machine is reversing both axes fully across only a 2" area, so I suspect maintaining the ipm listed would be difficult for the shapeoko. To account for machine stiffness problems I feel I want to pull back a bit on the cut depth. So I’ll try dropping feedrate to 50ipm and cut depth to .1".
Okay not bad, that got me down to 112% of the recommended roughing deflection. I’d probably be okay at this point, these are all just estimates anyways. But I also want to make sure I’m getting good cycle times so I’m going to go back to the first number I punched in, the stickout. I can easily calibrate stickout by positioning the machine next to the wood I’m going to cut, putting the bit loose in the collet, and then using the jog controller to lower the collect carefully until it’s just above the workpiece. I can mark the bit with sharpie or just try to tighten the collet in place enough to hold the bit, then lift it and finish tightening it. So let’s go back and lower our stickout to 0.85", should probably be less than that using the above method but a little margin for error seems good.
Okay there we go, 94% deflection so right where I want to be. The estimated chipload is .0014" which is right around manufacturer specs of .0016". So that works for slotting, finally I’ll reduce the radial engagement to see how pocketing should go.
Essentially the machine maxes out at my imposed limit of 100ipm before I get any deflection warning.