Knowledge handover: Nina Frei, maintenance

Date: 2026-10-19
Type: Meeting notes
Attendees: Nina Frei, Lukas Brunner, Thomas Huber
Tags: #line-3-retrofit

Nina Frei leaves Bergwerk Präzision AG on 30.11.2026 after 17 years. This session captured what she knows that is not written down anywhere else.

How to calibrate the Line 3 spindles

1. Warm the spindle up for 15 minutes at 6'000 rpm. Cold readings always look too good.
2. Clamp the reference mandrel from the blue case, not the grey one; the grey one is bent.
3. Measure the runout at the tip with the dial gauge. Target: 2 µm or less. Above 4 µm, check the tool holder before you blame the bearing.
4. Measure vibration at 6'000, 9'000 and 12'000 rpm. Above 2.8 mm/s at any speed, plan a bearing check within a week.
5. Write all readings into the maintenance log, with the spindle hours.

Things only Nina knew

• Spindle 4 always reads 0.3 mm/s higher than the others; that is the mounting, not wear.
• The Aarmatic service hotline is slow; call their technician Marco Bianchi directly. His number is on page 2 of the maintenance binder.
• The coolant filter on Line 3 clogs every 6 weeks in summer. The new filter from the retrofit should fix this.

Decision: Lukas Brunner takes over maintenance planning for all lines from 01.12.2026.
Decision: Spindle checks on Line 3 happen every month and after every crash, using Nina's five steps: warm-up, reference mandrel, runout, vibration, log.

• Action: @Nina Frei record a short video of the calibration with the reference mandrel (due 2026-11-20)
• Action: @Lukas Brunner shadow Nina Frei during the bearing swap in the retrofit window (due 2026-11-13)
• Action: @Thomas Huber add the monthly spindle check to the maintenance plan (due 2026-11-27)