chatter and vibration machining

B

brshannon1

Plastic

Joined

Jul 24, 2019

• Jul 24, 2019

• #1

I am machining a 34" diameter of 6061 alum on a 24" faceplate with 5.25" over hang all around the outside. It is .75" thick and bolted to the faceplate in 4 places. I am grooving the outer 4.5" (all over hang). Its not bad when I get close to the faceplate, but lots of chatter and vibration when I get towards the OD and as it gets thinner. I'm having trouble because its not fully supported I believe. what can i do to get rid of the chatter and vibration?

 

J

janvanruth

Titanium

Joined

Oct 27, 2013

Location

netherlands Asten

• Jul 24, 2019

• #2

slow it down?

 

C

CYLINDER MAN

Plastic

Joined

Oct 8, 2018

• Jul 24, 2019

• #3

smaller radius on cutter
slow speed and feed
is tool only out of holder as much as needed
heavy DOC sometimes

 

D

DDoug

Diamond

Joined

Oct 18, 2005

Location

NW Pa

• Jul 24, 2019

• #4

Loob ?

Tool nose radius ?

Maybe try a Die grinder mounted in toolpost ?

 

G

Gobo

Titanium

Joined

Jun 4, 2013

Location

Oregon, USA

• Jul 24, 2019

• #5

A positive rake tool will reduce you cutting pressure. Or try a narrower tool.

 

Conrad Hoffman

Diamond

Joined

May 10, 2009

Location

Canandaigua, NY, USA

• Jul 24, 2019

• #6

Gooseneck tool holder?
More on Spring tools

 

Mike1974

Diamond

Joined

Nov 5, 2014

Location

Tampa area

• Jul 24, 2019

• #7

Conrad Hoffman said:

Gooseneck tool holder?
More on Spring tools

Click to expand...

Interesting, never seen one before. Seems to me it would increase chatter as it could 'give' then dig in, then give, then spring/dig in etc..?

 

Conrad Hoffman

Diamond

Joined

May 10, 2009

Location

Canandaigua, NY, USA

• Jul 24, 2019

• #8

No, the clever thing is how they arrange the flex point. Normally, a tool digs in a bit and moves towards the work, digging in more. Imagine the tool post bending in a bit towards the work under load. Then material gets removed, it releases and you have chatter. With the flex point in the right place, and being a bit more compliant than the compound/tool holder, the tool will tend to move away when it tries to dig in, thus, little or no chatter. Supposedly very good for threading and parting off, though I've never tried one. I actually have the loop from a commercial one, but no holder to mount it. Need to make something to try it.

 

Thunderjet

Stainless

Joined

Jun 24, 2019

• Jul 24, 2019

• #9

Slow it down.
Smaller radius on the tool.
Light d.o.c.
higher feed rate.
Watch the tool height closely.
Try WD40 as a cutting oil. (Cheap, works great on Al. Leaves a great finish to boot.)

 

R

richard newman

Titanium

Joined

Jul 28, 2006

Location

rochester, ny

• Jul 24, 2019

• #10

Does your part ring if you tap it on the overhang? If so might want to try to damp it in some way to avoid resonance. I've used something "gooey" stuck on the back of the overhang with double face tape.

 

D

DMF_TomB

Diamond

Joined

Dec 13, 2008

Location

Rochester, NY, USA

• Jul 25, 2019

• #11

brshannon1 said:

I am machining a 34" diameter of 6061 alum on a 24" faceplate with 5.25" over hang all around the outside. It is .75" thick and bolted to the faceplate in 4 places. I am grooving the outer 4.5" (all over hang). Its not bad when I get close to the faceplate, but lots of chatter and vibration when I get towards the OD and as it gets thinner. I'm having trouble because its not fully supported I believe. what can i do to get rid of the chatter and vibration?

Click to expand...

.
.
use a roughing and finish pass. say groove .300" wide use a .250 or .188 grooving tool and make side by side passes (short tool stickout) leaving .010 on sides and bottom of groove. remove bulk of material
.
then when taking finish pass the cutting forces are less.

 

A

atex57

Stainless

Joined

Sep 6, 2006

Location

SW Wisconsin

• Jul 25, 2019

• #12

Run the spindle in reverse and turn the tool upside down.

Ed.

 

D

DMF_TomB

Diamond

Joined

Dec 13, 2008

Location

Rochester, NY, USA

• Jul 25, 2019

• #13

its like machining anything. you take it all in one pass you going to get more vibration and a rougher finish that if you take a separate roughing and finish passes
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most who machine a keyway for example find its better to rough it out the majority of stock then just take light finish passes for a tighter tolerance and better finish. groove on lathe is same
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on a lathe if turning 10" od down to 9.0000 you going to take it all in one pass ? or rough it out and then take a light finish pass