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The process of balancing the “cartridge” on the Core Balancer Primary (DBST-10)

Categories: Turbocharger repair

There is always a technological imbalance after the cartridge assembly. Even with very careful assembly according to the marks. It is caused by gaps between the parts, unevenness of the bearing, washer and compressor wheel. Besides, the nut is never screwed in the threads equally 2 times. To fix this core imbalance, as well as to perform auxiliary and control operations, use an additional balancing stand DBST-10.

The stand is a resonance-type equipment having a soft torsional suspension. This allows to determine with high accuracy (0.4 g*mm/kg) the position and value of imbalance. In addition, the low rotational speed and the fact that the bench has an oil system. It allows the “cartridge” to be checked in a safe environment.

The oil station of the bench allows to imitate the working conditions of the turbocharger, makes it possible to test the “cartridge” for oil leakage. Also, both to control the quality of assembly, and to running-in of parts of the “cartridge” to each other. That excludes the risk of parts to be damaged by overheating.

The balancing process consists of the following operations:

  • preparatory;
  • setting up the stand;
  • setting up the balancing system;
  • determining and correcting the imbalance.

Preparatory operation

The preparatory operation begins with the selection of tooling and adapters to install the “cartridge” on the stand. Then all the contact surfaces of the “cartridge”, including the adapters, are cleaned and wiped with a dry clean rag. Then a “contrast mark” is put on the impeller of the “turbine wheel”.

Adapter for DBST-10
Turbocharger Core Balancing Machine DBST-10

Setting up the stand

To set up the stand please install a “cartridge” in the stand, connecting it to the oil system and setting the position of the air nozzle and RPM marker. In addition, it is necessary to adjust the compressed air supply to set the necessary speed of the turbocharger shaft.

Setting up balancing system

In order to set up the balancing system, you must first enter the primary information. This includes the radii of the first and second correction planes, the specific unbalance of the rotor and the rotor mass. With this information and the calculation functions, it is easy to determine the weight of the “test weights” required to calibrate the balancing system and to calculate the permissible unbalance for each correction plane.

The balancing system is calibrated in three steps:

  1. Start “without reference weights”
  2. Start “with test weights in the first correction plane
  3. Start “with test weights in the second correction plane

After all three launches, the “computing unit” of the test bench can (based on the information collected from the sensors) use complex mathematical algorithms to determine the location and magnitude of unbalance in two planes simultaneously.

The process of balancing the “cartridge”

Balancing operation

A characteristic feature of the balancing operation is that unbalance is corrected in only one plane of correction, although both planes are used for adjustment.

This is important: imbalance occurs because the compressor wheel nut slightly changes its angular position during the assembly of the “cartridge”. So that means that to balance, it is only necessary to correct the imbalance in the correction plane on the nut side. In this case, if the machine will determine a sharp increase in imbalance on the second plane (and there should be no imbalance, because after the first balancing it was eliminated). It will speak of any serious violations occurred during assembly. In this case, the turbocharger is disassembled and checked all over again.

Unbalance correction is performed by removing material from the surface of the “compressor wheel nut” and is considered complete when the unbalanced mass is less than the permissible residual unbalance. The material is removed with a hand-held drilling machine or a hand-operated scraper. As a rule, the unbalance in the first plane remains within the tolerance. In summary, that’s how we fix core imbalance.