Stacking planes precisely Problem: when many planes are stacked on top of each other, errors in the thickness of the individual planes will add up Note: we encountered this problem when we wanted to build a precise field cage for a TPC-like chamber Solution: Establish a precise reference for each plane. Press each plane indiviually with some elastic element against this reference 20.02.2014 1 Ulrich Landgraf Donnerstag, 20. Februar 2014
Stacking planes precisely 6 5 4 3 2 1 Bolt to press precision spacers together D D upper panel Precision spacer � 0,010 A Position of lower surface of the upper panel is defined by upper surface of lower spacer lower panel C C O-‑ring A Upper surface of spacer has to be higher than lower plane by at least the planarity of the lower panel B B Scale: 5:1 Quantity: 1 General Tolerances Form Tolerances Edge Dimensions Surface DIN ISO -‑ -‑ DIN 6784 DIN 7167 DIN 7168-‑m 1302 -‑ -‑ Name Date Spacing Planes Drawn 11.02.2014 U. Landgraf A A Checked Standard ATLAS-‑NSW-‑Micromegas 1 /1 Physikalisches Institut DEMO Universit � t Freiburg A3 Hermann-‑Herder-‑Str. 3 State Changes Date Name File Name: D:\ATLAS Data\Micromegas\Mechanics\Spacing_Planes.idw 6 5 4 3 2 1 20.02.2014 2 Ulrich Landgraf Donnerstag, 20. Februar 2014
Stacking planes precisely Remarks: • The elastic elements must not be O-rings, also several spring washer types can be used: • Also if there are small gaps between the planes the assembly can be gas tight: taken from Simrit catalog Compression Ratio Tolerance for tightness is 25% The compression ratio is the ratio between compression Compression ratio is typically expressed as a percentage. squeeze and the uncompressed O-ring cross-section. of diameter, i.e. 750 µ m for Calculation Recommended Value an O-ring with Compression Squeeze Piston- or Rod-Type Seal OD = 3 mm Compression Ratio (%) = x 100 Minimum: 5% Target: 20% Maximum: 30% CS Compression Squeeze Face-Type Seal CS H Minimum: 10% Target: 25% Maximum: 35% • If applied in many places around the frame this can even flatten a bent plane - provided the elastic force of the O-rings exceeds the one of the plane! 20.02.2014 3 Ulrich Landgraf Donnerstag, 20. Februar 2014
Current FE board model imported Full 3D-model of the FE board from board designers imported: Can check now for problems easily! 20.02.2014 4 Ulrich Landgraf Donnerstag, 20. Februar 2014
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