I have a PCNC 1100 that I use in my Fabrication shop for various internal work.... don't really advertise or "hire out" with it (because I am not proficient with it).
A friend was in a bind, and needed some tools made to press some bearings.... He needs two circles cut from 0.5" thick aluminum... one circle 7.1 inches and one circle 7.4 inches.... sounded easy enough...... I ordered the material online (8" x 8" squares)..... I ordered twice as much as needed so that I could screw up.
.... I struggled with feed and speed for a while.... finally I dialed it way back to what I thought was a safe setup... just so I could get it done..... (broke a few end mills)......
In the end, I was using a .25" end mill.... running at 3" per minute, taking a 0.05" bite..... this worked well until I got down to about 0.35" ~ 0.4" deep... the end mill started "loading" up on me.... the flutes would fill up (packed) with aluminum.... the first couple of times this happened I didn't get shut down in time and the end mill broke.... eventually I got to where I could here the motor slow down, and stop it before it broke....
I am theorizing that the reason that it was loading up, was that I was so deep in the cut, with both metal against both sides of the cut.... can someone please give me some pointers of how I should have set this up?
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By the way.... I did actually get the 7.1" completed..... I was so close to getting it.... I was cut through 0.45" of the 0.5" .... only 0.05" to go.... but it finally got to where I could only move about 1" and was loaded up..... and each time I would load up, I had to hit the e-stop..... that seemed to make my x and y co-ordinates lose steps (cause when I would re-start, the cut would be ever so slightly off).
So, I took the 8" x 8" out of the vise.... and "broke" the outside off (leaving me a circle that had rough edges on the top .07" or so... and a few other rough spots....... then I chucked it up in my 4th axis (mounted horizontal).... brough the end mill to the edge of the material...and turned the 4th axis... was able to clean it up pretty nicely.
- One thought I have for the 7.4" piece is a bit off the wall..... I have a cnc plasma table, and I was thinking of cutting it a bit oversize say 7.6" circle... then chuck that in my 4th axis and spin it down to the prescribed 7.4" ..... I know that it not the correct way to do it... but the experience tonight had me ready to pull my hair out.....
Look forward to suggestions and advice.