
#1
Jul2004, 12:03 PM

P: 1

I have a tool that is used in CNC metal cutting machines. This tool rotates and we have a machine that calculates the amount of immbalance. The known values are, rpm, amount of imbalance (gmm), diameter.
I'm trying to find a formula that calculates the centrifugal force that is generated from the known values above. 



#2
Jul2004, 01:23 PM

P: 525

when you say "imbalance," in what manner or orientation is the object not balanced? If you can provide a little more detail, I can help.




#3
Jul2104, 05:15 AM

Sci Advisor
P: 1,341

What units are gmm ? What's "imbalance" (pressure, force) ?
For the force in general you have: Force = Mass * (Velocity)^2 / Radius = Mass * (rpm / 60) * Radius But, you'll have to be more specific  do you want the force as a radius function at some partial radius for the tool lenght, or a moment around an axis or something ? 



#4
Jul2604, 11:09 PM

P: 25

Centrifugal Force Formulas
Affinity Laws for Centrifugal Applications:
Flow1/Flow2 = RPM1/RPM2 Pres1/Pres2 = (RPM1)2/(RPM2)2 BHP1/BHP2 = (RPM1)3/(RPM2)3 For Pumps: BHP= (CFM x PSF)/(33000 x Efficiency of Fan) BHP= (CFM x PIW)/(6344 x Efficiency of Fan) BHP= (CFM x PSI)/(229 x Efficiency of Fan) Head in Feet= 2.31 PSIG Where: BHP = Brake Horsepower GPM = Gallons per Minute FT = Feet PSI = Pounds per Square Inch PSIG = Pounds per Square Inch Gravity PSF = Pounds per Square Foot PIW = Inches of Water Gauge Specific Gravity of Water = 1.0 I pulled that from a website... it deals with liquids, however hope u can adapt it for your uses.. hope it helps 



#5
Oct1508, 09:13 AM

P: 1

Hi jhetfield. You've probably solved this long ago but, I just saw it and thought I'd answer. Your question is perfectly legitimate. As I understand it, your toolholder balancer shows the tool has an unbalance. This unbalance is measured in gmm (grams at a 1mm radius). First, lets convert your unbalance in gmm to ozin (ounceinches). To do this, multiply your gmm value by 0.00139 (gmm x 0.00139 = ozin). A quick approximation (pretty close) of the force generated would be:
F = 1.67U(n/1000)^2 F = force in lbs. U = unbalance in ozin n = speed in rpm. By the way, not that it really matters but, "imbalance" exists in your checkbook, "unbalance" exists in your rotor. The ISO changed this terminology a few years back. Hope this helps. 


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