Two-plane dynamically balancing

[bernardg]

Hello All,

We make dc motors... and for a new application, we need to assemble the blower wheel to our motor shaft and have them dynamically balanced.

The config will look something similar to this...

|-----------| ___
Motor----------------|___|
|-----------| shaft blower wheel

Our customer demands that we balance the blower wheels dynamically to a spec of 0.015 oz-in. The wheels has two planes where we have provision to add balancing clips to add mass to it. Those two planes are separated by 3.5 inches.

Hope that most of you have some kind of experience in working with a two-plane balancing machine. So, a couple of quick questions...
(i) In any standard balancer, what are the inputs that we have to feed into the equipment?
(ii) What is the the underlying mechanism behind the balancer? When we spin the wheel to the predetermined rpm, how does it measure the amount of imbalance at any quadrant of the wheel... and then traslate that value of imbalance into mass (grams)?

Thanks in advance for all your help.

BRG

 

[alexit]

Check out balancemaster.com or schenck-usa.com for machinery

The machine has a drive belt (very low mass, like reel-to-reel leader tape) and a pair of v-shaped cradles. These cradles float on very lightly damped chassis (air or spring, depending on capacity of machine.)
An optical tachometer detects angular position and part velocity using a mark you place on the part.

For two-plane balancing you have two displacement (or acceleration sensors if bigger parts) and measure the resultant displacement at each sensor. Knowing the angular position of max displacement, use known imbalances (tiny pieces of parafin is good) to change part imbalance and measure again. Now from change in measurement you know magnitude (oz) and angular location of needed part correction in each of the sensor planes.

The vendors will be much better in their explanation...

 

[bklauba]

You also could buy a balancing stand, and combine it with a good quality portable vibration analyzer. That way, once you get the motors assembled, you can use the analyzer to inspect the motors, for balancing and other dynamic character (bearings, lose assembly, lose iron, rubbing, etc.) Check out

http://www.thomasregisterdirectory....rs/vibration_analysis_services_0029215_1.html

for a list of manufacturers of vibration analysis gear.

BK

 

[desimontreal]

Probably location of the center of gravity of the whole thing relative to a location - pedestal.

You might also need to correct for tooling error by taking several reading before correcting for unbalance at two planes.
Usually, you index the part 180 degrees for the second reading to determine the tooling error and correct unbalance ... see shenck representative. They usually have a nice book that explains everything. Also good to know the required rpm to balance the part - you dont want to balance a part closed to its natural frequency - its a different game all together .

DM -- getting old and forgetting..