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- Jul 28, 2017
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This is a story about something I encountered during a milling job on my Sieg SX2 mill.
The issue of climb milling can be tricky. I once encountered something I call "deferred climb milling" while milling a slot in a steel plate. I had the plate installed so the depth of the slot was in the Z axis, so Z was fixed and I was moving X and Y. So the side of the end mill was doing the cutting. The procedure was: after finishing one pass on Y, move Y back so the next pass would be a conventional milling operation. Step X over by the DOC my mill/EM could handle, then do another pass. Here's the deal. If I had moved X while the end mill was in contact with the work, that would have been a climb milling step, so there was some backlash in X waiting to be yanked forward by the cutting forces. So when I brought the end mill into the work to start the next cut, the backlash IN X came into action, increasing the DOC enough that the end mill grabbed the work and stalled the motor in an instant. Fast enough that it unscrewed the collet nut holding the end mill!! What did I do wrong? I failed to lock the X axis. I'm fortunate the end mill didn't break, or throw the work across the room.
Since that time I have tweaked/modified my mill to reduce the backlash in X and Y, enough to permit light climb milling in steel -- but I still make sure to lock all the undriven axes when I'm milling, Mill. Unlock. Step. Lock. Repeat....
The issue of climb milling can be tricky. I once encountered something I call "deferred climb milling" while milling a slot in a steel plate. I had the plate installed so the depth of the slot was in the Z axis, so Z was fixed and I was moving X and Y. So the side of the end mill was doing the cutting. The procedure was: after finishing one pass on Y, move Y back so the next pass would be a conventional milling operation. Step X over by the DOC my mill/EM could handle, then do another pass. Here's the deal. If I had moved X while the end mill was in contact with the work, that would have been a climb milling step, so there was some backlash in X waiting to be yanked forward by the cutting forces. So when I brought the end mill into the work to start the next cut, the backlash IN X came into action, increasing the DOC enough that the end mill grabbed the work and stalled the motor in an instant. Fast enough that it unscrewed the collet nut holding the end mill!! What did I do wrong? I failed to lock the X axis. I'm fortunate the end mill didn't break, or throw the work across the room.
Since that time I have tweaked/modified my mill to reduce the backlash in X and Y, enough to permit light climb milling in steel -- but I still make sure to lock all the undriven axes when I'm milling, Mill. Unlock. Step. Lock. Repeat....