1. Stages for the SSW translation system for PACMAN
Accuracy verification of the CERN metrology lab

2. Introduction
Accurate translation stages required for Stretched Wire magnetic measurement systems
2 XY mounts on granite directly ordered from company (PImiCos, DE)
At delivery accuracy verification performed on the Leitz Infinity 3D measuring machine

3. Stages specifications
Property
Value
Travel Range (horizontal/vertical)
50 mm
Encoder Type
Linear
Repeatability of displacement
≤ 0.05µm
Bidirectional repeatability
≤ 0.1 µm
Min. incremental motion
≤ 0.05 µm
Accuracy over 50 mm
< 1 µm
Origin repeatability
< 0.05 µm
Pitch/Yaw
+/- 15 µrad
Orthogonality of the XZ stages
< 15 µrad
Straightness/Flatness
+/- 0.5 µm

4. Setup at the CERN metrology lab
5 kg load
Probe fixed at 50 mm from the surface of the table
Coordinate system plane YZ defined according the maximum stroke positions

5. Absolute accuracy tolerance
Measurement performed at 50 mm from the table surface:
Absolute XY position allowed error (RMS):
Accuracy 1 um
Pitch/yaw
0.75
Orthogonality
Straightness/Flatness
0.5
Total
1.5
Leitz absolute error
0.35
Total maximum allowed error
±1.9

6. Main absolute measurement positions

7. Results over full stroke (50 mm)

8. Range used in PACMAN
- Real displacement range during PACMAN use: ± 3 mm in vertical and horizontal from centre - Re-measurement of the critical area on the Leitz machine

9. Conclusion - Stages out of specification:
Absolute positionning errors on full 50 mm stroke still up to 2.8 um (max. admissible error ±1.9 um)
Straightness/flatness (X and Y enveloppe) of V-axis = 1.3 um (max. spec. ±0.5 um)
Orthogonality stage B = urad (specified ≤ 15 urad)
No time for sending the stages back to manufacturer
±10 mm limited measuring area for use with PACMAN within tolerance (±1.9 um)
Less criticial for axis finding with the vibrating wire method with best fit
Alternative solution: send back the stages and use SSW5 stages instead but need of checking overall dimensions for integration on the Leitz PACMAN setup