Machining aluminum high doc low radial

J

Jacob653

Plastic

Joined

Jan 8, 2021

• Apr 28, 2021

• #1

hello,

I'm running into some problems with chatter and getting a really bad finish on my parts. I'm using a 3"LOC .25 Dia carbide ball end mill 3 flute. It stickouts from the tool holder flange by 9".I have to use a heatshrink style holder that has a heatshrink extension to reach the bottom of the pocket. I'm trying to do a side profile with it at the bottom of a pocket. The stepover i have set right now is .01 radial engagement with 2.5" doc. Wanting to know what others would try and set their speeds and feeds.

Thank you if i don't reply back.


After testing. So far i just slowed it down all the way to 200 rpm and a ipm of .6. and it came out good enough. Thank you everybody for the suggestions.

 

Last edited: Apr 29, 2021

B

Booze Daily

Titanium

Joined

Sep 18, 2015

Location

Ohio

• Apr 28, 2021

• #2

Really effin’ slow. Like maybe 800-1000 rpm 4-5 ipm.

 

V

vmipacman

Cast Iron

Joined

Nov 21, 2014

Location

Virginia, USA

• Apr 28, 2021

• #3

You weren’t kidding about long stickout.

Be careful of excessive run out.

I wouldn’t run that over 2500 rpm. Prob would end up like 2k. Take small step downs like .02”. I don’t think you will be able to finish the wall very deep. Maybe finish .25” of the wall height at a time. Light shallow passes at a slow rpm. Going to take a while.
No way will you be able to side mill 2.5”. With light passes and no chatter, even many step downs won’t show much in the finish and the radius of your ball will mask most of that anyway.

 

plastikdreams

Diamond

Joined

May 31, 2011

Location

upstate nj

• Apr 28, 2021

• #4

Yeah that's a slow and steady cut...If you can ramp down to keep engagement both radially and axially I think that would be your best bet...and leave a few thou for a spring pass.

 

D Nelson

Stainless

Joined

Jan 7, 2015

Location

Missouri Ida

• Apr 28, 2021

• #5

Needs to be a undercut Endmill to keep side load down
Don


Sent from my iPhone using Tapatalk Pro

 

Mtndew

Diamond

Joined

Jun 7, 2012

Location

Michigan

• Apr 29, 2021

• #6

Jacob653 said:

hello,

I'm running into some problems with chatter and getting a really bad finish on my parts. I'm using a 3"LOC .25 Dia carbide ball end mill 3 flute.

Click to expand...

With that amount of stickout for that size end mill, I'd look for more flutes.
More flutes = stronger end mill.

Find an end mill with 5-6 flutes and decrease your stepover by 50% or more.

 

mhajicek

Diamond

Joined

May 11, 2017

Location

Maple Grove, MN, USA

• Apr 29, 2021

• #7

Yep. Deflection goes up with I believe the third power of stickout for the same sideload. Any little bit you can shorten that tool or increase its diameter will help, in addition to what's been said already. Relieved cutter making shallower passes (1/2" LOC?) will increase rigidity and reduce sideload.

 

Mike1974

Diamond

Joined

Nov 5, 2014

Location

Tampa area

• Apr 29, 2021

• #8

I'm surprised you haven't broken it yet with 3" LOC!!

https://www.mscdirect.com/product/details/61726394

 

zero_divide

Stainless

Joined

Feb 2, 2012

Location

Toronto

• Apr 29, 2021

• #9

Can you use a tapered Endmill?
It is very rare someone REALLY needs to use a long ballnose with straight walls.

I would suggest
0. Try to see if a tapered tool can be used.
1. switching to a bullnose with a small radius. Maybe .03r
2. Use a necked tool with small LOC.

I didn't even know they make 10" long 1/4" ballnoses

EDIT: another thing I would suggest:
At certain WOC, the axial force (and thus deflection) will be close to zero. Depends on a lot of factors like tool design, helix angle etc. You would need to make some test cuts to find the sweet spot.