I have multiple printers on 2 tabletops with no wall to support for some kind of shelves, I needed good filament storing solution (for 100spools), so I designed this RACK that you can directly feed printers from. I put INSERTS for VERTCAL POLES  into holes for cable grommet on the tabletop, screwed the nut from top and fixed it to backwall with M6 screws. Then I put drainage pipes into inserts and attached ARMS to them with M6 screws, then put a pair of PIPES through ARM holes. Filaments used for printing are resting on ROLLERS.

Printing Parts of the RACK consist of TABLETOP INSERT and NUT for vertical pipe, ARMS for horizontal pipes, and SPOOL ROLLERS feeding 3d Printer/s. 

It does not require to be near a wall and can be easily expanded. Can hold 15 standard (20x7) spools per level on standard 150cm table, easily fitting 3 or more levels per tabletop 40+ spools. Extremely convenient to see and manage filaments this way, changing and feeding printers from the RACK is fast and easy.

You can change parameters in f360 model for vertical and horizontal pipe diameter to adapt to pipes available to you, parts will adjust accordingly, also change location and diameter of table holes. For stability you might need to change/adapt TABLETOP INSERT to fix it to the side or back wall below your table. One ARM consists of 2 identical sides, ROLLERs as well.

Note: do not overload the rack if the vertical poles are not stiff enough.

HARDWARE

For 1 tabletop you need:

2 Vertical PIPES (in my case drainage pipe DN50x3mm 200cm).

2 Horizontal PIPES per level (in my case 25mm metal pipe 150cm).

M6x30 Screws, washers, nuts (4 per level) for ARMS and 2 M6x40 for insert fixing below the table.

M3x18 Screws, nuts (4 per spool) for 1 set of rollers.

608 Bearings ( 8mm x 22mm x 7mm) 4 per spool.

Fillament:

use PETG or ABS, I print with 30-50% infill and at least 4 walls.