Prusa Enclosure Enhancement - Concrete Slab integrated in LACK table

General idea
Placing a 40x40x4 concrete slab under your 3D-printer significantly reduces noise/vibration transferred to the enclosure.

Placing the slab on top of the LACK table causes reduced height needed for the printer PRUSA MK3S+ with MMU2S.

In this upgrade a concrete slab is integrated into the LACK table of thEnclosure V2.
Noise and vibrations significantly reduced by this approach.
The assembly also leaves the option to integreate a 140x140 fan (PWM) under the table for controlled enclosure ventilation.

Materials:
   1x concrete slab 40cm x 40cm x 4cm
   8x round felt pads, glueable face, diameter ~25mm, height ~5mm
   1x LACK table (or bottom LACK table of LACK enclosure V2)
   4x M3x12 hexagon socket head screws
   1x Multi purpose glue (e.g. UHU Allzweckkleber)

Tools:
   1x cardboard cutter
   1x straight cutting guide 
   1x hexagon spanner
   1x 8mm wood drill + portable electric drill

Steps of Assembly:

 1) Print parts:
   4x FixingCorner_v00  (PETG as recommended material)
   4x Clamp_v00             (PETG as recommended material)
   1x FanFixation_top_v00
   1x FanFixation_center_v00
   1x FanFixation_bottom_v00 (modify center part as grid in slicer)
   1x FanInletCuttingTool_v01

2) Concrete-slab-holder assembly
   - assemble the parts 4xFixingCorner_v00   and 4xClamp_v00 
     (slide in a Clamp_v00 in between two FixingCorner_v00 to connect the parts)

3) Tabletop upper cardboard cutout for concrete-slab holder
    - on the upper cardboard of the tabletop (table surface) make a centered 415mm x 415mm 
      square cut out.
      Use the cardboard cutter and the straight cutting guide for precise cutting.
    - after removing the upper tabletop cardboard (square) cutout,
     cut the vertical support structure along the edges of the new cutout
    - remove the vertical thin honecomb cardboard support structure from the 
      cutout region.
   - do not remove the support structure under the remaining upper cardboard

4) Tabletop lower cardboard cutout for fan fixation
   - mark the center of the lower tabletop cardboard
   - drill a 8mm hole in the center
   - put the pin of the tool FanInletCuttingTool_v01 through the hole
   - turning the tool and guiding the cardboard cutter blade with the slot in the tool, 
     you can make a clean circular cutout in the lower cardboard of the tabletop
   - after comleting the circular cutout, place part FanFixation_center_v00 over
      the cutout, properly align the circular center and orientation and then
     mark the 4 holes for the fan fixation screw domes with a pen on the cardboard
   - drill 4 holes for the screw domes at the markings
   - fit the part FanFixation_top_v00 into the prepared cutout, screw domes facing down

5) Assembly of FanFixation_top_v00 
   - fit the part FanFixation_top_v00 into the prepared cutout, screw domes facing down
   - apply glue to the surface of FanFixation_top_v00 that touches the cardboard
   - glue FanFixation_top_v00 into the prepared cutout
   - wait for the glue to build up good adhesion
 

6) Assembly of concrete-slab-holder
   - push the pre-assembled concrete-slab-holder into the cutout from the top
 

7) Preparation of the concrete-slab
   - turn the concrete slab upside down
   - place (glue) two stacked felt pads in each corner of the concrete-slab (bottom side)

   - place the felt pads ~25mm from the edges

   - turn back the slab into normal position

8) Concrete-slab placement
   - place the concrete-slab rotated by 45° on the tabletop

   - put your hand through the FanFixation cutout on the bottom of the tabletop and
     slightly lift up the slab
   - rotate the slab by 45° + keep supporting from below
   - carefully lower the slab into the slab-holder until the felt-pads touch the bottom
     (the slab needs to be supported from underneath the table, as the sides will almost
      completely be hidden in the slab-holder and you will not be able to hold it this way)

   - adjust the spacing of the slab to the side walls
     (the slab must not touch the slab-holder side walls as to avoid unwanted direct
      noise transmission)
 

9) Assembly of the FanFixation
   - place FanFixation_center_v00 and FanFixation_bottom_v00 under the tabletop
     and secure the parts with the four M3x12 hexagon socket head screws

   - Option Fan: Using M3x35 screws; a 140x140 fan (PWM controlled) can be mounted
     between the parts FanFixation_center_v00 and FanFixation_bottom_v00 to allow 
     controlled ventilation of the enclosure.
     (The control electronics is not covered in this documentation and might follow later.)

10) (Re-)assembly of LACK enclosure V2 
   - (re-)assemble your LACK enclosure V2
 

   - place 3D-printer on concrete slab
   - enjoy the silence ;-)