Passive mechanical damping and stiffness enhancement
====================================================

Constrained layer damping (CLD)
-------------------------------

Carbon fiber CLD (structural)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- Carbon fiber plates bonded to steel plates
- Applied only to load-bearing steel plates with high modal strain
- Explicit locations:
  
  - spindle tower plates (both sides)
  - optional X-carriage side plates
- Purpose:
  
  - increase structural damping
  - suppress bending modes
- Not intended to significantly increase stiffness
- Carbon fiber plates not used as mounting surfaces

3M damping tape (non-structural)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- Viscoelastic damping tape applied to thin sheet metal
- Explicit locations:
  
  - enclosure inner sheet-metal panels
  - thin covers and noise-radiating panels
- Purpose:
  
  - suppress panel ringing
  - reduce airborne noise
- Explicitly not applied to:
  
  - precision interfaces
  - rails
  - force-loop components

Epoxy granite (EG)
------------------

- Epoxy-based mineral composite used as internal damping filler
- Composition:
  
  - epoxy resin
  - low-cost mineral aggregates
- Filling strategy:
  
  - perimeter fill preferred
  - hollow core retained to reduce mass
- Explicit locations:

  - X-carriage box-section beams: yes
  - Y-axis rail support beams: optional, evaluative
- Purpose:

  - structural damping
  - acoustic attenuation
- Stiffness contribution considered negligible

Elastomeric isolation (PU)
--------------------------

- Thin polyurethane layer introduced at selected interfaces
- Explicit location:

  - between spindle housing and spindle mounting plate
- Purpose:

  - isolate high-frequency vibration
  - reduce noise transmission
- PU layer:

  - preloaded by bolting
  - not part of stiffness or compliance tuning
- Not used at:

  - linear guide interfaces
  - force-loop structural joints