Plunge Roughing

[Pearcey]

I have a large volume of aluminum to rough out and am considering using the plunge rough to try and avoid the block from twisting due to stress.

 

Does anybody have any comments on plunge roughing or any other technique that is less stress relieving to the aluminum.

 

Regards

Ken Pearce

[BernieT]

I don't think it matters much the way the aluminum is machined, if there are stresses in it, it will warp. If possible, run a test part to see if this mat'l is stable. Also consider stress relieving your raw stock and stress relieving it again after roughing. (I estimate about 275 Deg F for an hour or two)

 

Good luck, BerTau

[Matt C]

Please note the following conditions that must be met when doing such:

 

Through the spindle coolant (will not work with out this one)

Done in a horizontal application starting at the bottom of the work piece and moving upwards which allows for better chip evacuation.

Use no bigger than a 2.5 dia plunger (unless you have more than a 50 HP machine)

70% tool engagement when steeping over.

 

I have done this several times and have had success with it. Try running it at around 1500 SFM and at around .0065 per rev on the feed. I know this sounds slow but chip evacuation is emperative and if you go any faster than that you will load up the tool. As for the stress if it is anything other that 7050 you will probably be alright.

 

Good Luck

Matt C

[David S]

Don't forget to recheck your TOOL LENGTH OFFSET after your Plunge Roughing. It might change. This operation might not be faster, but it is very X-Y stable (safer).

 

quote:

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Does anybody have any comments on plunge roughing or any other technique that is less stress relieving to the aluminum.

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The stress comes from the material you are cutting, not the way you are cutting. Try take the stress out before you cut. Or buy a stable material. Ask Material Supply Dealer. They will give you a "Data Sheet" about the materials they are selling.

 

Good Luck!

 

[ 07-19-2002, 11:49 AM: Message edited by: David S ]

[Jack Mitchell]

I'm sorry guy's, I disagree!

The stress and distortion that will likely occur is from the clamping of the material rather than the cutting abuse.

 

As memory serves me, the quickest method of removing a volumn of material is by drilling. You could slot drill with say a 1" two flute or even a four flute - yet you still have to contend with the ribbon build-up on the cutter.

 

The approach is sound - spot then drill aggresively, then machine the profile accordingly.

 

Try clamping the vice or strap clamps using only your tongue - I'm serious here.

 

Regards, Jack

[McRae]

Jack,

 

I would like to refine your argument and indicate that the Stesses you are indicating will be released after the material has been unclamped. I suspect that the root question is to do with cutting material skin and relieving the residual stresses from the material condition and the effect that the plunge roughing would have on this.

 

The answer to this is - you tell us if it distorts! The only way to know is to do it!

 

Again Jack's point stands that if you distort the part while clamping - remember that it will release when you let off the pressure and so good luck trying to machine a quality part...

[TheePres]

Residual Stress Management - 7050 Alum

[David S]

Oh, one more thing I forgot to mention: Heat is your biggest enemy (if every thing else is right). A lot of coolant, sharp tool and slower speed are what you need for your low stress cutting. go ahead, try it. Good luck again!