Figured out a way to stop chatter on thin wall aluminum parts

Been fighting chatter for months on these 1/8 inch aluminum brackets we run every week. Last Tuesday I tried dropping my RPM from 8000 to 4500 and bumped up the feed rate by about 30%. Used a single flute end mill instead of my usual 2 flute and the finish came out glass smooth. Anyone else found weird combos like this that work better than the book says?

3 comments

3 Comments

parkera2223d ago

Hold on, are you sure that wasn't just a coincidence? I tried the exact same thing last year on some 6061 brackets and it made my chatter way worse. The lower RPM let the tool rub instead of cut and I actually got built-up edge that ruined three parts before I noticed. A single flute at that feed rate also left a weird washboard pattern on the wall for me. Maybe your machine is just really rigid or something, but the textbooks usually warn against that setup for a reason.

mila_flores823d ago

Wait, did you check if your spindle bearings were getting hot before you ran that setup? Because I've seen that exact washboard pattern happen when the tool is deflecting from inconsistent chip load, not just from wrong speeds and feeds. The single flute thing works good on thin wall stuff but only if your machine can hold the RPM steady under load otherwise it's a mess. What kind of holder were you using and did you measure the actual runout on the tool? I had a buddy who blamed the same type of pattern on his feeds but it turned out his collet was 0.003 off and that was the real problem the whole time.

gavinlopez18d ago

Man, that's rough. It's really frustrating when you're trying to dial something in and it just fights you the whole way. I've been in that same spot more times than I can count, where everything looks fine on paper but the machine says nope. @mila_flores8 might be onto something with the runout thing, my experience has been that even a tiny bit of deflection can make a washboard pattern pop up out of nowhere. It's weird how something like a collet being a few thousandths off can feel like a completely different issue. I'd definitely check that holder with an indicator if you haven't already, just to rule it out. Ruling out the simple stuff first saves a lot of headache down the line, in my experience.