What is the maximum height of the work material that I can place on the work bed?

The total travel distance for the Z axis is 5.5″. However, you need to keep in mind that some of that height will be used up by the systemheld tool that you place on the machine.  For example, the HF500 spindle and collet stick below the tool holder by about 1.2″  This would reduce the total material height to 4.3″  From that you need to account for the length of the tool as well.