I finally learned why my tool paths were chattering on aluminum at the Cleveland trade show

So I was at the Midwest machining expo in Cleveland last month and this old timer from a tooling company watched me struggle with a demo part. He asked what speeds I was running and I told him 12,000 RPM with a standard 3 flute end mill. He just shook his head and said I was way too fast for that setup. Turns out I was getting harmonic chatter because the tool was flexing at that RPM range. He had me drop it to 8,500 and add a little more stepover and the finish came out glass smooth. I have been running aluminum the same way for 3 years and never even thought to slow down. Has anyone else had a random stranger at a show completely change their approach to a basic operation?

2 comments

2 Comments

rosebarnes29d ago

The 8500 RPM range is exactly where I landed after fighting with a 1/4 inch two flute in 6061 for a whole afternoon at a shop in Detroit. I was getting this terrible high pitched whine and a washboard surface that made no sense at 10k. A guy from a coolant company walked by and said my chipload was too thin at that speed, making the tool rub instead of cut, and he had me drop to 7500 with a deeper axial depth. That combo fixed everything on the spot and I felt like an idiot for not trying it sooner. It's wild how a five second conversation with someone who has seen it a hundred times can save you hours of head scratching.

robert_lopez6427d ago

@rosebarnes that chipload thing is exactly what I had to unlearn. I always thought faster RPM meant better finish in aluminum but it's the opposite once you get past a certain point. Did you ever try going even lower like 6500 or 7000 with a bigger stepover? I've been messing with that lately on some 7075 parts and it seems to cut down on tool wear too. The old guy at the show told me most guys run aluminum too hot and thin and it just makes the tool burn up for no good reason. That high pitched whine you mentioned is the tool telling you it hates what you're doing to it.