SNK HPS120B Spindle Repair

The SNK HPS120B is a massive 5-axis CNC machining center.  It comes fitted with this grease lubricated and stator driven spindle capable of running up to 12,000 RPM.

CHALLENGE

Our customer sent in this SNK HPS120B spindle stating that the spindle was noisy.  When it arrived at Northland Tool we noted that the spindle was noisy when spun by hand.  During disassembly, we found that the rotor was extremely difficult to remove and there was damage between the rotor ID and journal.

Damage on jounal under rotor

After completing the breakdown, we recorded that the front quad set of bearings had been heavily contaminated with oil.  The drawbar pulled low force and was extremely noisy when actuated. The bellevilles appeared to have been binding on the drawbar.  We then performed a full dimensional evaluation where we found a few issues.  First, the ID tooling taper was in poor condition and failed our air gauging tests. The taper also had high runout.  Second, the front bearing journal shoulder had slightly high runout.  No other dimensional deviations were noted during this repair.

SOLUTION

The following actions were performed on this SNK HPS120B spindle:

• Clean, inspect overall dimensions
• Replace bearings, bolts, o-rings, bellevilles, and grippers
• Grind, plate, grind (GPG) the rotor journal
• GPG the 50 ID tooling taper
• Kiss grind the rotor ID and front bearing shoulder

RESULT

After reassembly of all components and adjusting bearing preload, we put the spindle through a rigorous break-in and testing procedure to make sure it passes our final quality inspection. See below for the passing test reports:

Bearing Vibration Analysis Spectrum:

This spindle passed our final quality inspection and was returned to our customer with a 1-year warranty.