Help! Chatter using 3 flute finisher on Aluminium Part

[m_morgan]

I'm trying to finish a part with pocket walls 25mm(1") tall by 2mm (0.080") thick using waterlining, and a 3 flute mitsubishi carbide endmill. I'm taking 0.5mm (0.020") off the wall, and stepping down in 3mm increments.

 

Currently the speed and feed is S25000rpm F10000mm/min (400imp) and it's chattering like mad as it gets toward the middle (least supported) sections of the wall.

 

Help! I was hoping to reduce chatter, not make more of it!

[jeff]

What diameter endmill are you using?

have you tried slowing down the rpm and taking it full depth maybe 2 finish passes.

[m_morgan]

Sorry, using a 10mm (0.4") tool with a 3mm (0.120") corner rad.

 

Haven't tried anything bar slowing the spindle speed down. Thought about a full depth cut, but worried that it might increase the chatter.

[ToolMan184]

According to my math it should be about 13,000 RPM and about 135 IPM with what you are using now (.020" x .118" depth)

[Tim Johnson]

Are you roughing out the pocket before the finish cut? If you are try making the finish cut on every depth of cut. That almost always works for me.

[Chris Rizzo]

Is it a high helix cutter? Using the shortest possible length? just some ideas

[MLS]

Speeds and feeds are fine unless your hitting corners hard then might bump down the feed a bit.

 

Three things.

 

One.

Biggest thing. Use a sharp to .03 R cutter to melt down to the fillet then come back in and cut the fillet staying off the wall .001 to .002 The radius on the cutter adds a huge amount of pressure.

 

Two.

Leave more excess on the wall. .100 inch approx and take a semi-finish(+.02) cut, then finish THEN take a step down.(.100 max on that DIA cutter) OR Leave the same excess (.100) and take a max .06 step down and go straight to finish( you can even increase the feed if you do this).

 

Three

Shorter is better. Solid relieved shank carbide with a short LOC is best.

 

You should be able to cut a wall twice as tall and half the thickness like this without chatter assuming the machine is up to it.

[doyleg]

MLS #2 will work. that is what i do when we have thin walls. leave more material. it needs the extra material to reduce chatter.

[doyleg]

MLS #2 will work. that is what i do when we have thin walls. leave more material. it needs the extra material to reduce chatter.

[bhayden10]

I just finished a 4" x 6" box with .08 walls 3" deep. I have an old mazak, with 7000 max but ran a YG extended .375 dia eml. at 6400 @55 ipm .125 stepdown and finished the inside and outside at the same time with no chatter issues. Slow by your standards but it worked.

[Roger Peterson]

That big corner radius is causing a lot of problems. Next time maybe look at roughing and finishing as you move down the pocket, or at least leave more material for the finish pass to take off (this means less pressure on the wall as well stiffens the wall up).

 

JM2C

[m_morgan]

Brilliant guys! Will do a bit of re-programming using a square finishing cutter, and come back in to put the rad on last.

 

Semi-finish then finish also sounds like a reasonable idea.

 

Lots of testing to do now, but I'll let you all know how it goes!

 

Thank you very much for all your help guys!