Turbocharger shaft and wheel assembly

1. A method comprising:

co-axially locating a turbine wheel and a shaft in axial alignment with gravity wherein an axial force applicator assembly comprises a rotatable turbine wheel nose collet and a force applicator that applies an axially directed force aligned with gravity to a nose of the turbine wheel, wherein the turbine wheel transfers at least a portion of the force to the shaft, wherein a rotatable turbine wheel centering collet supports the turbine wheel and wherein a rotatable shaft collet supports the shaft;

rotating the rotatable shaft collet and the rotatable turbine wheel centering collet in unison via respective drive mechanisms wherein the rotatable turbine wheel nose collet rotates, via the turbine wheel, responsive to rotation of the rotatable turbine wheel centering collet by its drive mechanism;

energizing at least one laser beam; and

via the at least one laser beam, forming a weld between the turbine wheel and the shaft.

2. The method of claim 1 comprising, during the forming, adjusting the axially directed force applied to the turbine wheel.

3. The method of claim 1 wherein the force is less than approximately 100 N.

4. The method of claim 1 wherein the force is less than approximately 30 N.

5. The method of claim 1 comprising aiming the at least one laser beam at a joint between the turbine wheel and the shaft.

6. The method of claim 5 wherein the aiming aims the at least one laser beam to a greater percentage at the turbine wheel.

7. The method of claim 6 wherein the forming a weld comprises a weld that comprises a higher percentage of material of the turbine wheel than material of the shaft.

8. The method of claim 1 comprising applying a compliance force that compensates for material loss in the axial direction as associated with the forming a weld.

9. The method of claim 1 wherein a contact between the turbine wheel and the shaft exists at a single mating region.

10. The method of claim 1 further comprising analyzing quality of a weld by reflecting energy off the turbine wheel and the shaft and analyzing the energy.

11. The method of claim 10 wherein the energy comprises at least one of visible light energy, ultraviolet energy, infrared energy and near infrared energy.

12. The method of claim 1 further comprising forming a plasma and acquiring information from the plasma and analyzing the information as to a chemical characteristic.

13. The method of claim 1 comprising energizing two laser beams; via the two laser beams, forming two welds, each of the welds between the turbine wheel and the shaft; forming two plasmas via the two laser beams; acquiring information from the two plasmas; and analyzing the information.

14. The method of claim 13 comprising controlling at least one parameter responsive to the analyzing of the information.

15. The method of claim 1 comprising sensing information about a weld formed between the turbine wheel and the shaft, analyzing at least a portion of the information to determine quality of the weld and, based at least in part on the quality of the weld, accepting the weld or rejecting the weld.

16. A method comprising:

co-axially locating a turbine wheel and a shaft in axial alignment with gravity wherein an axial force applicator assembly comprises a rotatable turbine wheel nose collet and a force applicator that applies an axially directed force aligned with gravity to a nose of the turbine wheel, wherein the turbine wheel transfers at least a portion of the force to the shaft, wherein a rotatable turbine wheel centering collet supports the turbine wheel and wherein a rotatable shaft collet supports the shaft;

rotating the rotatable shaft collet and the rotatable turbine wheel centering collet in unison via respective drive mechanisms wherein the rotatable turbine wheel nose collet rotates, via the turbine wheel, responsive to rotation of the rotatable turbine wheel centering collet by its drive mechanism;

acquiring information associated with a joint formed between the turbine wheel and the shaft;

analyzing at least a portion of the information; and

based at least in part on the analyzing, adjusting at least one parameter associated with a welding process to weld the turbine wheel and the shaft.

17. The method of claim 16 wherein the acquiring information comprises probing with a contact probe or a non-contact probe.

18. The method of claim 16 wherein the analyzing comprises analyzing the joint with respect to one or more points of contact, one or more gaps or one or more points of contact and one or more gaps between the turbine wheel and the shaft.

19. The method of claim 16 wherein the analyzing comprises analyzing the joint with respect to one or more points of contact.