Mori Seiki NH4000 DCG Spindle Repair

Our customer indicated to us that this Mori Seiki NH4000 DCG horizontal machining center had experienced a spindle crash. This global leader in the manufacturing of firearms has a large population of this machine model. They work closely with us in maintaining these spindles, sharing information and providing OEM parts, which we are unfortunately prohibited from obtaining directly.

CHALLENGE

As is so often the case, the oil mist lubricated front bearing set was contaminated with a thick brown sludge. We noted that the tooling taper and coolant plunger assemblies had been damaged in the crash. We assumed that this was also true of the tool gripper fingers (collet), as they were not present in the spindle incoming. Our customer did however provide a new set of OEM grippers and Bellevilles. We have found that unlike the majority of makes and models we rebuild, this particular Mori Seiki spindle model requires a set of OEM Bellevilles to supply the correct tool retention force. Our full dimensional evaluation of the bearing journals, shoulders, and housing bores did not reveal any other significant deviations.

SOLUTION

We performed a kiss grind of the tooling taper ID and face, and rebuilt the spindle with new ceramic hybrid bearings, o-rings, and assembly screws. We used the customer-supplied OEM parts to rebuild the drawbar assembly. Our customer has a practice of replacing the OEM coolant plunger assemblies themselves after the spindle is returned to them.

RESULT

After reassembly of all components, adjusting bearing preload, and undergoing break-in and testing procedures, this spindle passed our final quality inspection before being returned to our customer with a 1-year warranty.