WAM™ Wrist – Cable Maintenance Guide [email protected]
www.barrett.com
© 2008 Barrett Technology®, Inc.
Document: D1004, Version: AG.00
Page 4 of 13
Unlike the 4-DOF WAM, the Phase leads for the Wrist motors should NOT be unplugged when cabling. The Wrist should be
mounted in a vertical orientation (tool end facing up). If a Barrett Hand was purchased, the Wrist can be secured in the Lexan
stand. Without the Lexan stand, the Wrist should be left on the WAM Arm itself with the elbow joint propped up and taped
securely to orient the Wrist vertically.
Make sure that the Wrist is either mounted on the 4-DOF arm (with power OFF) or that the Wrist Safety
Termination (Figure 2) is plugged into the bottom of the Wrist.
This will protect the motor controllers (Pucks) from
electrical damage as the motors are turned manually during the cabling process.
Figure 2: Wrist Maintenance Kit
2.2 Terminology
Anchor
– location on the pulleys or pinions that the cable
terminations are inserted into for retention and tensioning.
Anchor-Separator
– A raised section of the pinion which
creates a separate groove for the termination anchor and which
only allows the cable to cross at one of two places, where it
flattens out.
Cable
– a “wire rope” typically made from very fine strands of
stainless steel. The tensile strength and stiffness is very high in a
stranded cable yet it maintains flexibility in bending.
Cable circuit
– the cables and cable paths through a
transmission from input (motor) to output.
Clutch Housing
– the upper portion of the black motor shafts. It
has a groove in the top of it that engages the autotensioner
mechanism and can used to push against with the push-pull
hook during manual tensioning.
Clutch Lock
– the circular aluminum piece directly above the
Clutch Housing, which contains holes to place the Wrist
Cross
wrap
– when spanning the distance between two parallel
transmission elements (pinions or pulleys) the drive cable
crosses the plane that contains the axes of both elements. This
wrap results in the elements rotating in opposite directions
when cabled.
M5/M6-Side
– directions often used in this text to identify an
item. The motor number indicates the motor (or side of the
wrist containing the motor) the component is closest to Tension
Tool in while tensioning the Wrist.
Open wrap
– when spanning the distance between two
parallel transmission elements (pinions or pulleys) the drive
cable does not cross the plane that contains the axes of both
elements. This wrap results in both elements rotating in the
same direction.
Pinion
– the smaller-diameter, higher-speed cylinder in a pair of
cabled transmission elements.
Pre-tension
– cable tension, internal to a cable circuit, which is
present even when the drive has no external loading. Pre-
tension is added to eliminate backlash (in this case, cable slack)
in the transmission even with commanded torques.
Pulley
– the larger-diameter, slower-speed cylinder in a pair of
cabled transmission elements.
Stages
– as with gear trains, cable circuits can be composed of
several transmission stages, each contributing its part to the
final transmission ratio. Stage-1 is from the motor to the first
pulley, Stage-2 is from the pinion attached to the first pulley to
the second pulley, and Stage-3 is from the pinion attached to the
second pulley to the differential.
Tensioner
– the mechanism in a cabled transmission, which
applies and maintains pre-tension in the drive cables. Barrett’s
patented single-point tensioner uses split motor pinions that
counter-rotate via an integrated one-way clutch to pre-tension
entire cable circuits.
Termination
–a brass sphere swaged or crimped onto the end of
a cable, which serves as a point to hold onto the cable.
Upper & Lower
– directions used in this text to identify
different sections of pinions and pulleys. Upper refers to the
section of the pinion/pulley above the split (closer to the tool
end of the Wrist), lower refers to the section below the split
(closer to the base of the wrist).
Wrist Safety
Termination
