User manual
Barrett Technology, Inc.
BA4-310 System User Manual Version 1.1
40
5.5 Differential Input (J2 & J3, M1 & M2)
NOTE: It is assumed in the following instructions that the differential output is already
properly cabled.
The cabling for these two circuits is identical, so references to motor axis 1 will be valid for
axis 2 as well. The motor axes will be cabled one at a time. Each drives one input pulley of the
cabled differential.
IMPORTANT: All references to clockwise/counter-clockwise and left/right assume the user is
facing the tombstone-shaped vertical support on the side of the differential being cabled.
For identification purposes the 2
nd
-stage cable whose loop-end is terminated closest to the
vertical supports will be called the outboard cable and the other 2
nd
-stage cable, terminated
closest to the first arm link, will be called the inboard cable.
The pulley/pinions for each circuit of the differential are identified as left and right, again,
assuming the user is facing the vertical support for the circuit she is cabling.
5.5.1 2
nd
Stage
[ ] 1.
Pull the plastic shoulder covers off the torso of the arm (they are held in place via
Velcro surfaces underneath)
[ ] 2.
Remove the metal shoulder wiring guard outside the tombstone-shaped vertical support
by loosening the 4 button head screws with a 1/16” hex wrench and sliding the guard up
and out.
[ ] 3.
Optional
- Remove the Joint 2 stops for improved 2
nd
-stage cable access. Be careful
any time after removing these stops to move the links very slowly and carefully into
place. Never leave the arm in a vertical position, where it could fall without a joint stop
in place.
To remove a Joint 2 stop, first pull out its rubber insert. Next, use a 3/16”hex wrench to
remove the two ¼”-20 socket cap screws under the insert. Once the screws are
removed, pull the stops radially away from the robot.
[ ] 4.
Choose a side of the differential to cable. Rotate the second and third joints (i.e. the
pitch and roll of the differential) so that 2
nd
-stage pulley is rotated
fully
counter-
clockwise. The teardrop-shaped slots on the input pulley (for terminating a cable loop)
should be facing upwards. Note that the actual position of the arm is slightly different
depending on which side of the differential the user is cabling.
The arm is to remain
in this position throughout the 2
nd
and 1
st
-stage cabling.
[ ] 5.
Form the two 2
nd
-stage cables (2286mm & 2032mm) into U-shapes without
permanently bending the cables (
i.e.
do not kink the cable bend). The loose ends of each
cable should be uneven by approximately 35mm.