Start with the real issue
If your calibration results change every time, the problem is rarely the machine alone.
Most of the time, it’s a combination of small issues that don’t look obvious.
1. Setup is not consistent
Even small changes matter:
- Fixture position
- Ball orientation
- Probe angle
If your setup is slightly different each time, your results will never match.
2. Temperature is changing more than you think
People often say “room temperature is stable”.
In reality:
- Machine warms up
- Airflow changes
- Operator movement affects local temperature
This affects both the machine and the calibration artifact.
3. Probe condition is ignored
Common issue:
- Probe not recalibrated
- Stylus slightly bent
- Wear over time
Even small probe errors can shift results noticeably.
4. Measurement strategy is not consistent
If you change:
- Number of points
- Distribution
- Measurement speed
You are effectively running a different test.
5. Data filtering differences
Some software filters outliers automatically. Some don’t.
So:
- Same measurement
- Different processing
→ Different results
What engineers usually check
Instead of chasing perfect numbers, focus on:
👉 Is the trend stable?
👉 Do errors repeat in the same direction?
That tells you more than a single “good result”.
Final thought
Repeatability is not about doing one measurement well.
It’s about doing the same measurement the same way every time.