The “working envelope” is the volume of space a machine can reach with whatever attachment, called an “end-effector”—a 3D-printing extruder nozzle, for example—that’s being used.
The 3D-printable files for the Visible Robot provide a large working envelope, but which depends on end-effector selection, Z-axis shaft height, and leveling arrangement selected.
With slightly longer or shorter gantry shafts and rods, of say +/- 50mm (2”), the machine can be build to give a taller, but less stiff work area, or a shorter, stiffer working envelope (better for CNC-type work).
If your goal is to 3D-print tall objects, obviously the taller gantry configuration is appealing. However, it comes at a cost. That cost is stiffness, which can translate to a more visible “wobble” as the machine accelerates and decelerates. Think about the parts you’ll be working on and their sizes. The “stock” dimensions are a compromise to give both good stiffness and a decent working envelope—but you can easily choose to go taller or shorter.
The configuration of the machine the Visible Robot Assembly document addresses is with 500mm X-axis shafts, 800mm Y-axis shafts, 300mm gantry shafts and Z-axis shafts ( ~20” x 31.5” x 11.75” x 11.75”). The bed is an 8mm (5/16”) glass plate, resting on four manually-operated leveling dials. The Z-axis motor is top-mounted.
Using the Original X-Z axis carriage, the maximum working envelope (top of glass bed to bottom of ‘X’ carriage) is 370 x 600 x 205mm (14.5” x 23.5” x 8”) with leveling dials, and 370 x 600 x 225mm (14.5” x 23.5” x 8.75”), without.
With an E3D V6 hotend and Finix Extruder mounted and with leveling dials, in 3D printing configuration, this is reduced to, 370 x 600 x 85mm (14.5” x 23.5” x 3.75”).
With the Alternate X-Z axis, this configuration yields a maximum X, Y, Z working envelope of 370 x 600 x 225mm (14.5” x 23.5” x 8.75”) with leveling dials, and 370 x 600 x 255mm (13.75” x 23” x 10”), without.
An attached E3D V6 hotend and Finix Extruder, with leveling dials reduces this to, 370 x 600 x 120mm (14.5” x 23.5” x 4.75”). Without leveling dials, ‘Z’ axis travel is 145mm (5.75”).
NOTE: While the leveling dials are shown mounted to the tops of the base_corners in the documentation, you might also mount them underneath the corners to increase your working envelope and still have the ability to level the machine. (There are recesses for the leveling bolts on both top and bottom parts to the base-corners).