Porous supports and vacuum hold down device using said supports

A vacuum hold down device comprising:

• a table comprising a perforated plate, the perforated plate having a bottom side connected to a vacuum system for producing reduced pressure on the bottom side, and
• a porous support removably positioned on a top side of the perforated plate of the table, wherein the porous support comprises a perforated tray and a blade penetrable porous structure, the perforated tray including a top side, a bottom side, and a plurality of traversing holes extending therebetween, the perforated tray further including side walls and a plurality of outer reliefs, the side walls extending upwardly from opposite ends of the top side of the perforated tray to form an integral, substantially rigid structure having a substantially U-shaped cross section, and the plurality of outer reliefs distributed on the bottom side of the tray and between the traversing holes, wherein the blade penetrable porous structure is fixed on the top side of the perforated tray between the side walls,
• wherein the outer reliefs create a space between the top side of the perforated plate of the table and the bottom side and side walls of the perforated tray, whereby an airflow generated by the reduced pressure of the vacuum system will pass through the blade penetrable porous structure, through the perforated tray, through the space, and through the perforated plate, and
• wherein the porous support as a unit is removable from and replaceable on the perforated plate.