Hey @Ben_Delarre just wondering if you had a chance to reconfigure and try again?
@Brandon_Satterfield got the new spoilboard on last night. But by the time I did that it was too late to run some cuts. Will give it a shot tonight though!
Somewhat success!
Cut was much better this time, a small amount of chatter but definitely reduced and nothing like the massive resonance I had before. Although it might not have been a fair test since somehow my Z0 was a little high and I didn’t actually cut all the way through the alu.
This had a very weird effect though, check this out:
The bottom of the sheet was embossed into the plywood. Not by much, maybe 0.05mm. This to me indicates that the bit is pressing down into the metal rather than cutting it. Could this be the contributing to the crazy resonance?
Included a bunch of other photos in the album, forgive the exterior finish on this part, I forgot to reverse the outside profile cut so I left a mirror finish on the sheet, woops!
The inside profile though you can see is pretty nice. From the videos you can definitely hear a little chatter in a couple of places, not exactly sure why that is, it seems to always be in roughly the same places. Maybe a slight misalignment somewhere?
I also think that I’m not getting enough air out of my 60W air pump as chip clearance deeper in the outside profile cut is not great, though oddly is better on the inner profile.
Anyway, this clearly is an improvement, so there’s definitely a flex issue going on at that extreme depth. Tomorrow night I’ll do another few tests. I want to change that inner profile to a pocket so I can do a full depth finish pass for accuracy of the hole (its a bit off still - any advice on full depth passes?). And I’ll get my Z height right so I definitely cut through on that last pass. If all goes well though I might finally be able to move forward with my project.
To me looking at the finish, you are recutting chips and rubbing. What’s your endmill diameter, flute count, RPM, and feedrate?
The finish on the sheet is much nicer as good as the finish on the inside profile. I should have done the outside profile in conventional rather than climb to get that finish on the part instead. Pretty much mirror quality, can see the arc segments in the finish.
Endmill is 4mm, single flute 15000rpm at 600mm/min with 0.5mm DOC.
Definitely is a little rubbing and recutting going on, but it’s all being left on the bad side of the cut. Getting a bit more air might help with the recutting, the pump I have is barely putting out that much.
I am so confused!
This time I did a full pocket operation with a 0.2mm finish cut on each pass. Worked wonderfully, barely any chatter at all until right at the end, then in the same goddamn places (top right and bottom left) I get this little chatter and it cuts through to the MDF. Not as bad as when it was a profile cut but still enough to put the cut out of round.
You can see in the video that it actually completes the final pass quite cleanly, no chatter at all until it touches the outside wall. Is it just that the ‘finish’ pass isn’t deep enough into the wall so its chattering off of it?
I am going to try another with a 20% stepover on the finish pass and see if that helps, the pass right now is 0.2mm so just 5% so maybe thats the problem, not enough tooth engagement on the final pass so its rubbing on the alu instead of cutting it?
Glad your moving forward brother. Up that DOC to .6. The thin metal on bottom is fine, just means the cut stopped right before penetrating all the way, gets thin and moves out of the way. I’ll get this at times on large sheets when auto level fails me.
I hope with the upped DOC you’ll get rid of that ringing, your not chattering as much butch she’s still saying “more”, you could also go faster on travel, or slower on RPM. Chatter is a wild thing, intuitively people want to go slower or grab less. It’s a sign that the polar opposite needs to happen.
This pocket was at 0.6DOC 700 feed, 20 plunge with a 0.2mm finish stepover.
I’m going to go do it again at 0.7DOC, 700feed, 20 plunge, 1mm finish stepover. Tempted to push it to 800feed but it sounds quite good at this speed no?
For sure shoulda way better brother! Nice thing about this, once you and the machine shake hands on Al you’ll have it forever.
Did it again:
Settings: 0.7DOC, 750mm/min, 20 plunge, 40% stepover, Climb cut, 15000rpm, 4mm bit.
Finish quality is astounding, mirror-like…but my hole is not round because of that crazy chatter which happens on the last perimeter around the pocket on the last pass only.
Anyone got any ideas we haven’t already tried?