machining through breaking end mills

[woffler]

I have a part that i am cutting with A carbide 1/8 dia. end mill 2 flute 3/4 loc through 5/8 6061 alum. Problem is no matter how i hold it if on a tool plate or in a vise .I am breaking end mills on the final pass may cut out two or three and then one will cock and bind and snap goes the wiesel .Any one have an idea how to elimanate this problem? Thanks

[jalessi]

Woffler,

What is your DOC, spindle speed and feed rate?

Jeff...

[woffler]

Spindle speed 1750 feed rate 3ipm doc .15

[jalessi]

Woffler,

I neglected to ask what step over you are using?

Your spindle speed seems very slow for what you are cutting.

Jeff...

[jalessi]

Your depth of cut is three times to much by the way, try 1/3 the diameter of your tool.

[diggityds]

CRANK THE SPINDLE UP TOO MORE THEN 3000, GO EASIER ON THE DOC MAYBE .020, SPEED UP THE IPM BETWEEN 15 OR 30, AND FLOOD THE LITTLE SUCKER COOLANT IS IMPORTANT. IN GENERAL KEEP THE CHIPS SMALL ON TINY FLUTED END MILLS

[jalessi]

http://www.datrondynamics.com/pressroom/RPM004.pdf

[diecutter]

I think woffler is saying that on the final pass the PART will move and jamb the cutter against the aluminum plate just as it seperates from the plate.

If this is the case you need to add bridges to hold the part, or secure it in another way before the full profile is cut. If the part has a hole in the design, you can machine all the parts except for the final pass, then pause and run a bolt through each hole and then make the final separation cut. I'm sure others will chime in with more methods.

[woffler]

Thanks to everyone for responding The speed is limited to 1970 rpm and you are right it is on the last cut that it jams aginst the plate .I will boost rpm all the way up and i am looking for a faster motor to get my spindle speed up geared head mill .I am using full flood cooling i will will reduce my depth of cut and make more passes there are no holes to anchor the part .The part looks like a long shaft with a hook on one end only .125 wide and 4.0 long lots of room for vibration on final bottom pass .

[jalessi]

Woffler,

Post a picture of the part, maybe someone will have a solution.

Jeff...

[davereagan]

A picture would be priceless. I strongly suspect the slot is closing up and pinching the endmill on the final cut.

[LeeWay]

On my steel sheet parts, I leave tabs or just a little foil under the cut. IOW, leave out the very last breakthrough pass. I then just bust them out with a bandsaw. It does need a little deburring afterward, but don't have any movement of the fixtured part.