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WAM™ Wrist – Cable Maintenance Guide support@barrett.com 

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 

Summary of Contents for WAM Wrist

Page 1: ...WAM Wrist Cable Maintenance Guide Barrett Technology Inc Document D1004 Version AG 00 ...

Page 2: ...2 2 TERMINOLOGY 4 2 3 CABLES AND CABLING ORDER 6 3 CABLING THE DIFFERENTIAL 6 4 M5 STAGE 3 9 5 M6 STAGE 3 10 6 M5 AND M6 STAGES 1 AND 2 11 6 1 TOOLS AND TIPS 11 6 2 M5 M6 STAGE 1 PREINSTALLATION 11 6 3 M5 M6 STAGE 2 11 6 4 M5 AND M6 STAGE 1 12 6 5 PRE TENSIONING M5 M6 CIRCUIT 12 7 AUTOTENSIONING 13 Barrett Technology Inc 625 Mount Auburn Street Cambridge MA 02138 U S A US 617 252 9000 This manual ...

Page 3: ... 1 For First Time Cablers Re cabling the Wrist is generally easier if the user is familiar with cabling other mechanisms such as the WAM Arm If the user is cabling the Wrist for the first time she should read this entire section on wrist cabling especially Section 6 5 on pre tensioning input circuits and section 1 of the WAM Arm cabling manual before beginning to cable the Wrist Make sure that pro...

Page 4: ...s 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 span...

Page 5: ...ing the number of turns Throughout this manual there are instructions to wind a cable around a pinion or pulley a certain number of turns It is important to understand exactly how the number of turns are counted Always start at the anchor brass termination of the cable as the zero point and end where the cable comes off of the pulley In the example picture below the lower cable is wound around the...

Page 6: ...ength between terminations mm B1216 WristCable Differential Level1 1 1 97 2 B1217 WristCable Differential Level2 1 1 107 2 B1218 WristCable Differential Level3 1 1 132 2 B1219 WristCable Differential Level4 1 1 152 2 B3477 WristCable Stage1 4 2 860 5 B3478 WristCable Stage2 4 2 610 5 B3479 WristCable Stage3 4 2 560 5 3 Cabling the Differential The differential circuits are shown in Figure 5 They c...

Page 7: ... the Level 2 horizontal pulley anchor Rotate the bottom 3rd stage pulley counter clockwise approximately turn The cable should now be threaded through the small gap between the Level 2 horizontal and vertical pulleys Remove the brass termination from the horizontal pulley and leave both ends of the cable unconnected 4 Get a Level 1 cable B1216 and insert one end of the cable into the vertical anch...

Page 8: ...ecessary and insert the free end of the Level 3 cable into the anchor on the horizontal pulley and rotate back to tighten 12 Rotate J6 slightly in the negative direction while keeping tension on the Level 3 cable so that the Level 4 horizontal termination is visible and accessible Insert one termination of the Level 4 cable B1219 into the anchor in the horizontal step Wrap the cable around approxi...

Page 9: ...ble B3479 to the lower anchor in the lower 3rd stage pulley Wrap the cable up the pulley 3 times using tape to hold each wrap as necessary This cable will transition above the first cable so it must wrap between the wraps of the first see color enhanced Figure 10 7 Cross over to the pinion using a cross wrap Attach the free end of the cable to the anchor in the top of the pinion and rotate the top...

Page 10: ...le is tight 5 Immobilize the bottom of the pinion with tape to prevent cable unwinding see Figure 14 6 Attach one end of another 3rd stage cable B3479 to the lower anchor in the upper 3rd stage pulley Wrap the cable up the pulley 3 5 times using tape to hold each wrap as necessary This cable will transition above the first cable so it must wrap between the wraps of the first see color enhanced Fig...

Page 11: ... B3478 Attach one end to the top anchor of the 2nd stage pulley 2 Wrap the cable around the pulley 1 75 2 times using tape to hold the wraps 3 Transition over to the 2nd stage pinion using an open wrap Attach the free end of the cable to the bottom anchor of the pinion Slowly and evenly wind on the cable by rotating the pinion until the cable is tight after approximately of a turn the cable should...

Page 12: ...utch Housing which houses the one way clutch and rotate the Clutch Housing to take up the slack Guide the cable carefully to ensure that the cable winds on smoothly and evenly Rotate the Clutch Housing until the cable is tight It is normal that the Clutch Housing may be a bit difficult to rotate The stage should now look like Figure 21 7 Remove all tape except for the tape across the stage 3 pinio...

Page 13: ...nt themselves but not necessarily in the proper arrangement Once the cables have been repositioned as shown in Figure 22 retension again by inserting the Wrist Tension Tool into the clutch lock to keep the motor shaft from turning and pushing on the clutch housing with the push pull hook Repeat the process of running the wrist through its range of motion and re tensioning until all the stage 1 and...

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