Nuts and Volts - December 2008

PERSONAL ROBOTICS

■ FIGURE 7. Magazines used to raise rear support off work surface to allow clearance for hex nuts. Keeps unit stable for several assembly steps.

make it easier to install the threaded rods which tension the frame ends and hold the base together. The magazines provide clearance for the nuts on the end of the threaded rods. The holes that these threaded rods go into are surrounded by a slightly cone shaped recess which helps to guide the rods into and through the appropriate holes.

The precision-ground shafts are put into the gray bushings and the end tubes are put in place. The bushing plates that later connect to the gantry base are added next. (Make sure you install these the right way around as it is tedious to turn them around later.) Finally, the other frame end plate is added and held in place with washers and nuts added loosely (Figure 8).

At this point, the frame can be put flat on the work surface and the gantry is loosely bolted to the gantry bushing plates. Alignment of the unit takes place at this point (before the lead screws are added). By moving the gantry and Z axis assembly back and forth with a finger while carefully snugging up the existing bolts, you can tell if things are in alignment by how easily things slide on the Thomson shafts. Once you have the alignment feeling right, you can tighten the bolts about a half turn past finger tight.

Now that we have the table done, it’s time to add the lead screws that the motors will use to control the motions. There are several washers and locking collars which were in small, well labeled bags

(Figure 9). It is important to put these parts on in the correct order. (Note: The Z axis assembly already has its rods and lead screw installed, so we are only dealing with the X and Y axis here.) Once the lead screws are installed, I again turned them by hand to make sure there was no binding anywhere across the range of motion for both the X and Y axes.

■ FIGURE 8. Front support attached to tension rods (inside silver tubes)

via acorn nuts and washers.

blue motor goes on the Z axis and the yellow motors go on the X and Y axes. Someone was thinking ahead when they thought of color-coding the motors! A quick tip: Before mounting the motors, you may want to consider grinding a flat on the shafts. This will allow the coupler set-screws to make a better seat.

AND NOW, FOR SOME ELECTRONICS!

At this point, the complete $599 FireBall V90 CNC router is assembled. It’s now time to move on to the electronics package. In the standard motor package, the

■ FIGURE 9. Starting at top center and going clockwise: table supports, tool holder, Z axis assembly, hookup wire, fuses, fuse holders, power cord, lead screw bearings and clamps, and assorted bags of hardware.