If you are building the CNC foam cutter for RC wings, then you would probably need 10" max travel on the Y towers. If building a hot wire CNC foam cutter for props, crowns, moldings You would probably want to go with a 4' x 4' (X x Y) EPS Foam billets are usually 3' x 4' x 8' or 4' x 4' x 8' XPS foam comes in sheets of about 4' x 8' x (1" or 2" or 3" thick) If building a CNC foam cutter to cut Polyurethane foam - FORGET IT Polyurethane foam should not be cut with hot wire, but a blade or a saw There are CNC foam cutters for Polyurethane that work similar to a band saw But use a abrasive wire instead of a saw - click here for more information In this section we will build the two Y posts or towers (Y axis). The posts can be found at the fence section at Home Depot You can replace these posts by any other post as long as you are able to keep them from vibrating during the cut. Any vibration of the posts will result in vibrations on the wire resulting in "waves" or not smooth cut of the foam.
The following can be found in the drawer section, you will need two 16" drawer slides The Home Depot Catalog number for 24" slides made by Liberty 7-81266-18070-4
The above picture is of the 2"x4FT Post with foot - that's the Home Depot name
Cat num: 204-008
Home Depot num: 6-39426-48607-7