In this video we will talk about combine harvesters.

The process of balancing rotors on combine harvesters is no different from balancing any other rotors.
For example fans, crushers, mulchers, augers, rotary machines, rotor motors, separators, couplings, spindles of CNC machines, hammer mills, centrifuges, flail mowers, sharpening stones.

But each machine has its own nuance that you need to be aware of and pay attention to before balancing.

If it is a rotary combine, the main rotor can be balanced.
In keyboard harvesters, you can balance the threshing drum, the beater.

The most common problems occur when balancing straw chopper rotors.
Sometimes it takes 1 hour to balance a combine chopper if it is in good condition, sometimes the process takes all day or even longer if repairs are needed.

Aside from bearing wear, the most frequent problems arise from the weak construction of the chopper body, which becomes covered with imperceptible cracks due to the strong vibration during operation.
The cracks can be quite inconspicuous and can be hidden anywhere.
The stiffness of the structure becomes insufficient, resonance phenomena occur.
Stable vibration amplitude and phase readings cannot be obtained because of the deformations of the housing.
Similar problems arise due to the loosening of bolt connections.

Remove any loose or dangling parts. For example the straw spreader, or weld them to the straw shredder body.

Bearings. Before balancing, I recommend replacing the bearings with new ones.
Quite often when mounting new bearings one makes the mistake of over-tightening them.
As a result the rotor rotates with noticeable force, the bearings get hot, and there is vibration.
When tightening the nut check the rotation of the rotor. It should rotate freely with no force.

Inspect the old weights before balancing. It is very likely that the nut has worn down and the weight should be removed because it may come out during running.

Check the blades, they may be jammed and not straightened by centrifugal force.
The worst thing is when they do it intermittently.

Check the idler pulleys.
Remove the belts and check the bearings for backlash.
Replace the bearings if necessary.

Rollers that are at or near the same RPM as the shredder can be a source of interference when measuring vibration levels.

To identify such problems, vibration can be measured for several minutes in the vibration meter mode.
If the roller has an imbalance of its own, you will notice a wave-like change in the vibration reading when you measure the vibration in the vibrometer mode.

The vibration of the roller will be the same as that of the shredder rotor, causing resonance and increasing the vibration, then it will be in antiphase and decreasing the vibration level.

Check the curvature of the shaft with a dial gauge. Self-aligning bearings may compensate for some of the curvature and misalignment of the shaft.

If the vibration level is high, balance in two or three steps.
First, balance the rotor at a low speed.
Then do the balancing procedure again at medium speed and then at operating speed.
Perform the balancing procedure from the beginning each time.
Avoid resonant frequencies.

Install corrective weights of half the weight shown by the software.
This is due to the non-linearity of the oscillating system.

Use washers of various sizes as corrective weights, which are placed on special perforated discs located on the edges of the rotor.
If such discs are not available, it is possible to install the weights on the bolts that fasten the knives.
In this case, select in the program the blade coordinate system and enter the number of rows of knives.
Usually there are four rows.