The vacuum for a large table is easily achieved with a shop vac.

So, the most challenging aspect of a large, custom made vacuum forming table is the need to have or build a large enough oven.

A pizza oven would work.

Or, you can build an oven — 

• it has to have a heat source (two domestic electric barbecues? two kitchen counter top electric griddles?, etc.
• It must be able to be opened quickly
• it's helpful for it to have peep holes so that you can observe the plastic while it's warming
• it has to have some sort of support inside to hold up the plastic frames

Despite the extra trouble, it is possible to get terrific and unusual results — check out what one 30"x30" table owner achieved: forgeofhephaestus.com

If building an oven is a little more “sweat equity” than you were planning on “spending” then perhaps a 24"x24", stand-alone commercial grade vacuum forming machine would work for you. See this company's website  —  www.vacugenic.com.  Their vacuum forming machine is more expensive than one of our vacuum forming tables, but it has its own heat and vacuum source.

Important: custom made tables are not returnable.