Pinkrab assembly

One arm is assembled from printed parts, 7 STS3215 servos, one servo board, and one camera. From the base to the fingertip, you alternate between a servo and the part that servo turns, and the servo ids are 1–7 starting from the base. The left and right arms are mirror images of each other, so the order is the same.

Left armRight arm

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1. 1Base

   Hold the base against the pegboard, push the bolts through from the front and tighten them with nuts at the back. The bolts pass the 8 mm base plate and the 5 mm panel, and the nuts seat on the remaining 7 mm. The two arms are 480 mm apart, and the top of the base is 180 mm above the desk.

   • M4×20 countersunk + M4 nut×4Base → pegboard
2. 2shoulder_pan servo (id 1)

   Fit a horn on each side of the servo and fix only the top horn with its centre screw. Put the servo in the base servo mount and fix it with 2 screws at the top and 2 at the bottom, then set the mount on the base and fix it at both sides.

   • M3×6×1Top horn, centre
   • M2×6×4Servo → base
   • M2×6×2base servo mount fixing
3. 3Servo board

   Fix the Seeed XIAO bus servo board to the driver mount with 4 screws, then slide the driver mount in from the side into the slot between the base and the servo holder. The screw heads sink into the mount, so attach the board before sliding it in.

   • M2.5×4driver mount fixing
4. 4Shoulder

   Set the shoulder on the top and bottom horns of the id 1 servo and fix each horn with 4 screws. The shoulder servo mount comes attached to the shoulder.

   • M3×6×8shoulder → horn
5. 5shoulder_lift servo (id 2)

   Fit the horns and fix the top horn, then put the servo in the shoulder servo mount and fix it.

   • M3×6×1Top horn, centre
   • M2×6×2Servo → shoulder servo mount
   • M2×6×2Servo → shoulder
6. 6Upper arm

   Fix the upper arm (upper_arm) to the horns on both sides of the id 2 servo.

   • M3×6×8upper arm → horn
7. 7elbow_flex servo (id 3)

   Fit the horns and fix the top horn, then put the servo in the servo seat at the end of the upper arm and fix it.

   • M3×6×1Top horn, centre
   • M2×6×4Servo → upper arm
8. 8Forearm

   Fix the wrist_yaw_bracket that becomes the forearm to the horns on both sides of the id 3 servo.

   • M3×6×8wrist yaw bracket → horn
9. 9wrist_flex servo (id 4)

   Fit the horns and fix the top horn, then put the servo in the servo seat of the forearm and fix it.

   • M3×6×1Top horn, centre
   • M2×6×4Servo → wrist yaw bracket
10. 10wrist_yaw bracket

    Fix the second wrist_yaw_bracket to the horns on both sides of the id 4 servo.

    • M3×6×8wrist yaw bracket → horn
11. 11wrist_yaw servo (id 5)

    Fit the horns and fix the top horn, then put the servo in the servo seat of the bracket and fix it.

    • M3×6×1Top horn, centre
    • M2×6×4Servo → wrist yaw bracket
12. 12Wrist

    Fix the wrist to the horns on both sides of the id 5 servo.

    • M3×6×8wrist → horn
13. 13wrist_roll servo (id 6)

    This servo gets only one horn, on the top, fixed with its centre screw. Put the servo in the servo seat of the wrist and fix it with the 2 front screws, with the horn facing outward, where the claw goes.

    • M3×6×1Top horn, centre
    • M2×6×2wrist fixing
14. 14claw

    Set the claw base against the horn of the id 6 servo and tighten 4 screws from the servo seat inside the claw. The next step's servo covers this seat, so tighten the screws first.

    • M3×6×4claw → horn
15. 15Camera nuts

    Push an M3 hex nut into each of the 2 nut slots on the inside of the claw's side face. The servo of the next step closes the slots, so put the nuts in before the servo. These nuts take the M3×10 bolts that hold the camera bracket.

    • M3 hex nut×2claw nut slot
16. 16gripper servo (id 7)

    Fit the horns and fix the top horn, then put the servo in the servo seat of the claw and fix it with 2 screws on each side.

    • M3×6×1Top horn, centre
    • M2×6×4Servo → claw
17. 17jaw

    Fix the jaw to the horn of the id 7 servo with a horn screw. The screw-head seats are on both faces of the jaw. Turn the jaw by hand and check that it closes against the claw.

    • M2.5×8jaw → horn
18. 18Camera

    Remove the four corner screws of the AR0234 camera module and fix the module to the camera bracket with 4 M2 screws long enough to pass the front wall of the bracket. Fix the bracket to the side face of the claw with 2 bolts, which go into the nuts placed inside the claw earlier.

    • M3×10×2camera bracket fixing
    • M2×4Camera module → bracket
19. 19Cables

    Connect the servos with servo cables in order from the base to the fingertip, and connect the first servo to the servo board. Power the servo board with 12 V, and connect the board and the camera to the host by USB. The servo ids are written one by one in the setup step after assembly.

• Servo ids are set after assembly, in Setup, by connecting the servos one at a time.

Screws

The count is the sum of the screws used in each step.

Screw	One Pinkrab arm	Pair (2)
M4×20 countersunk + M4 nut	4	8
M3×6	51	102
M2×6	28	56
M2.5	12	24
M3 hex nut	2	4
M3×10	2	4
M2	4	8