Visible 3Bot Assembly

3-Gantry-completeThe Visible 3Bot — a 3-gantry Visible Robot

This assembly guide for the 3-gantry Visible Robot relies heavily on the Visible Robot Assembly guide. Rather than repeat that text here, most of the assembly instructions will be found in that guide so that document is key. Consider this guide an addendum.


The Visible 3Bot can be built from the ground up with all three gantries, or it can be built by changing the base frame to accept two additional Y-axis drives (‘Y1’ and ‘Y2’) and then adding two gantries to an already-built Visible Robot.

Differences to the Base Frame

The base frame is most obviously different in that it uses three motors, three leadscrews and three leadnuts, instead of the one of each used by the Visible Robot. There are other differences.

Due to the extra space required to mount two motors at the “far-end”—the side opposite to where the ‘Y’ motor is mounted on the Visible Robot, the trapezoidal stiffening rods are placed at a more acute angle than on the one-gantry machine. This requires a different angle for their containment in the base-corners, hence, the base-corners are different parts than the base-corners used on the Visible Robot. At the far-end, instead of the two parts—the y_far_end and the y_far_end_nut_seat—used to capture both the leadscrew and the trapezoidal rods, there are five parts—two 3bot_trap_rod_captures, two 3bot_far_end_nut_seats, and the 3bot_y_leadscrew_capture part. At the near-end, we add two more parts, the 3bot_y_leadscrew_capture parts.

Thumbnails (design screenshots) of these new parts are shown in the bill-of-materials—BOM_Visible-Robot_3-Gantry.

To avoid further complicating a document that already accommodates a number of options, I’ll simply refer to the Step Number in the Visible Robot Assembly document in this guide.

To make it easier to refer to the two documents, I’ll use the same headings between the two. For example: dealing with the assembly of the base frame in the Visible Robot assembly doc is called: “Assembling the Base Frame.” I’ll use that same title, here, and refer to the Step Numbers within that section of the Visible Robot Assembly doc where something different needs to be done to assemble the Visible 3Bot.

Assembling the Base Frame

The Visible 3Bot base frame replaces the following parts of the similarly named parts of the Visible Robot.

Printed parts

base_corner_3b_00_top                   // Ymin / Xmin

base_corner_3b_00_bottom            //     “           “

base_corner_3b_01_top                  // Ymin / Xmax

base_corner_3b_01_bottom            //     “           “

base_corner_3b_10_top                  // Ymax / Xmin

base_corner_3b_10_bottom            //     “           “

base_corner_3b_11_top                  // Ymax / Xmax w/oblong hole

base_corner_3b_11_bottom            //     “           “            “          “

y_nema23_motor_mount (3)          // NEMA17 part can be substituted

nema_17_to_23_motor_mount (3) // used with NEMA17 motors on ‘Y’ axis

y_gantry_drive (3)                         // ‘Y’ anti-backlash nut mount

3bot_y_leadscrew_capture (3)

3bot_trap_rod_capture (2)

3bot_y_far_end_nut_seat (2)         // seat for frame-stiffening nuts

leveling_dial (4)                             // manual bed-level adjustments

leveling_dial_static (4)                   //       “          “               “

Precision parts

12mm x 800mm shafts (2)             // Y-axis

12mm linear bearings (12)             // could also be considered gantry parts

¼” – .250 (lead) x 30” (760mm) leadscrew (3) // Y-axis drive

¼” – .250 (lead) anti-backlash nut (3) // “ “

5mm x ¼” flexible coupler (3) // used with NEMA17 motor


¼” x ¼” flexible coupler (3)           // used with NEMA23 motor

Electrical parts

NEMA23 motor (3)                        // NEMA17 motor can be substituted

Ymax microswitch (3)                    // endstop

Ymin microswitch (3)                    // “


31½” x 17½” x 5/16” (800mm x 445mm x 8mm) glass plate

Threaded-rod (t-rod)

5/16” x 21 ½” (545mm) t-rods (4) // near-end and far end-pieces

5/16” x 33” (840mm) t-rods (2) // trapezoidal bracing

Fasteners – If doing a metric assembly with 8mm t-rod, substitute 8mm parts

for the 5/16” bolts and nuts and 7mm parts for the ¼” -20 hex bolts/nuts

of the leveling dials. If you’re using a NEMA17 motor, you’ll use 4 extra

M3 x 12 screws in place of the M4 x 16 screws and locknuts used for the

NEMA23 motor.

5/16” nuts (14)                              // base_corners, far-end, motor-mount

5/16” star-washers (14)                 //         “                  “                “

5/16” locknuts (12)                       //         “                  “

M4 x 16 screws (12)                     // NEMA23 motor

M4 locknuts (12)                          //         “             “

M3 x 25 screws (8)                       // base_corners

¼”- 20 x 3/4” hex bolt (4)             // leveling_dial

¼”- 20 nut (4)                               //           “

M3 x 10 screws (4)                      //            “

M3 x 16 screws (8)                      //            “

Other parts

.177 cal (4.5mm) BBs (~60)        // leveling_dial

Tools needed & recommended – same as used in Visible_Robot_Assembly


Follow the steps in the Visible_Robot_Assembly document, with these exceptions.

Replace Step #1 of the Visible_Robot_Assembly with this: “Put two of the 5/16” t-rods, one after the other, through the tunnels in the 3bot_y_leadscrew_capture, then the y_nema23_motor_mount, and finally, through the other 3bot_y_leadscrew_capture.”

Replace Step #2 with this: “Pass a star-washer along the t-rod you’ve determined to be the top-most t-rod and then thread a 5/16” nut following the washer up against the roughly-centered motor mount and 3bot_y_leadscrew_capture part. Do the same for the other side.”

Replace Step #5 with this: “Repeat steps 1, 3 and 4 with the other two (far-end) t-rods, using the respective combination of 3bot_trap_rod_capture, y_nema23_motor_mount, 3bot_y_leadscrew_capture, y_nema23_motor_mount, and 3bot_trap_rod_capture parts instead of the y_nema23_motor_mount. (The y_far_end is tightened onto threaded rod using an M3 screw, rather than the pair of nuts with washers).”

Replace Step #9 with this: “Slide the end of one of the trapezoidal-stiffening t-rods into the hole for it on either base_corner_00 or base_corner_01. Push the t-rod into the base corner until there’s enough room to fit the other end of the t-rod into its hole in the 3bot_trap_rod_capture part. But don’t fit the other end yet.”

Replace Step #12 with this: “Do the same with the pair of t-rods with the far-end 3bot_trap_rod_capture parts, using base_corner_10 and base_corner_11. The flat plate for mounting the 3bot_far_end_nut_seat should be on the outside, with the tunnels that will receive the trapezoidal-stiffening t-rods facing inside.”

Continue with the steps in the Visible_Robot_Assembly document until you come to Step #17. Skip this step if you have previously assembled one or more gantries, and continue with Step #18. Otherwise, you can choose to either repeat Step #17 for each of the gantries you will mount or move on to the sections entitled “Assembling the (Original) X-Z Axis Carriage” or “Alternate_X_Z_Carriage” (your choice of X-Z carriage assemblies) and “Assembling the Gantry,” then come back here when your gantries are assembled.

NOTE: The “Alternate_X_Z_Carriage” document is a separate document from “Visible_Robot_Assembly.”

TIP: If you decide to move on to assemble the X-Z carriages and gantries, you might want to temporarily put together the far-end of the frame by doing Steps #19 and #20 (You’ll have to undo these steps when you come back, but there’s less danger of breakage if you tie them together in the meantime).

Repeat Step #18 in the Visible_Robot_Assembly guide for each of the gantries until they are all mounted.

From here to completion, the 3Bot assembly is the same as that of the Visible Robot. Proceed from Step #19 to the end of the Visible Robot Assembly guide,