Scratching my 50 y/o head once again after I thought I had figured it out.
I need to CNC several parts from 1/4 inch 6061 aluminum. After days of experimentation and a bunch of broken bits, I thought I got it (with help from folks on this forum)
My ProBotix Nebula table router (which I know perfectly well is not a metalworking CNC) was churning out parts cleanly one after another.
Then, on part #8 it all went haywire. Same gcode, same exact sheet of aluminum, same everyhing! But the part started with a bad vibration and a broken bit.
OK, replaced the bit (same model: Yonoco 1/8inch single flute carbide spiral O-cut) - same problem. Chip weld, terrible vibration sound, HEAPS of cotton-candy-like shavings as the bit gets deeper. None of which was observed before.
What's going on, any clues?!
I cant think of any variable that has changed between the parts. I've heard somewhere that bearings on routers go bad, could that be it? The router has worked for 10 hours combined - max at the lowest RPM.
A little background, I used to use DWP611 router, but it had the minimum RPM of 16,000. I had to push it too fast to have an acceptable chipload, but then the machine was not rigid enough to handle it. So, I adapted Makita, which has the minimum RPM of 10,000 ... Still high for aluminum on my CNC, but it was working very well until now, and I was happy.
Taking 0.5mm deep passes at 500 mm/min speed, conventional milling (again, it worked beautifully for many sessions ... and now suddenly this).