Anti Vibration Boring Bar material and dampening fluid details needed 1

[ting-tong]

Hi friends
I am on a way to manufacture my own anti vibration boring bar to be used in VTL; Diameter 50 mm length 350 mm. I am not sure which material to choose either D2 or H13 steel. Also would like to receive information about the viscous fluid to be poured inside the boring bar to dampen the vibration.
Would be grateful if some one shares your knowledge and experience to help me build the boring bar.

KR

 

[mfgenggear]

You have capability to machine carbide?

 

[GregLocock]

Leaving aside the weird question as to why you'd machine the shaft of a boring bar out of tool steel, the choice of fluid is not a one size fits all proposal. Perhaps the simplest would be grease, or the cutting fluid from your machine. Other alternatives would be oil of some weight to be determined experimentally. Crucial variables would be the operating temperature and the frequency of vibration, which would depend in part on the stiffness of your toolpost.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Strong]

I understand vibration damping, but not this application. Why consider a liquid in the boring bar as offering significant damping?

Walt

 

[GregLocock]

The bar is not full of liquid. The sloshing action, at high speed, and I suppose shear forces at the boundary, tend to damp the chatter. Liquid damping has the advantage that it is not particularly highly tuned and is self cooling.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[EdStainless]

Stiff boar bars are either Mo alloy or tungsten carbide.
The fluid in them is just coolant that is pumped down the (often at high pressure) to cool the cutting surface and clear debris.

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P.E. Metallurgy

 

[hydtools]

See Sandvik:

Today`s innovative, patented systems of dampened tooling is seen globally as state-of-the-art technology. Although very distant compared to the original concept at the outset, tool-dampening can still be said to be based on the principle of a heavy mass, supported by specially designed rubber springs in a special fluid. It is the result of R&D into the nature of dynamic vibrations, and decades of experience from solving tool-reach applications. It has resulted in that Sandvik Coromant Silent Tools have moved dampened tooling on from problem solving to means of productivity boosting.

For more information please visit

http://www.sandvik.coromant.com/zh-cn/products/silent_tools/Pages/default.aspx

Ted

 

[Tmoose]

Is a new design anticipating a problem?

Or, is this an effort to reduce a setup that is known to chatter?

Since the modulus of elasticity of most steels is pretty close to the same, I would not expect a boring bar made from D2 to perform much better than on made of H13 regardless of heat treatment.

Nor would I expect several ounces of any liquid stored in a cavity in the boring bar to do much damping.

My old 2nd edition of Harris' Shock and Vibration Handbook (McGraw-Hill Handbooks) has a 20 page chapter(40) on machine tool vibration.
Pages 7 to 12 discuss chatter and other machine instabilities. A few kinds of dynamic absorbers are discussed. Auxiliary mass absorbers (damped and undamped) and

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impact dampers are discussed.
The separate chapter (6) on the "use of auxiliary mass dampers" has a section on boring bar dampers. A metal slug (auxilliary mass) fitted with small clearance in a bored hole towards the end of the boring bar can be useful. The clearance varies depending whether air or oil is used for damping.

A thoughtfully engineered boring bar clamped in a wimpy tool post will not perform to expectations.

As is sometimes the case when dealing with resonance, stiffening //or// softening can provide useful improvements.