This guide describes how to replace the encoder disk on MiR Hook 250. The encoder is used to keep track of which angle the hook arm is positioned in. Over time, the encoder disk can wear out, and must be replaced. If the encoder disk appears fine, but the angle of the hook arm is inaccurate, you may just need to recalibrate the disk—see Calibrating the encoder disk.

Things you'll need

• T9, T10, and T25 Torx screwdrivers

• 2.5 mm and 4 mm Hex screwdrivers

• 0.4 mm torque wrench with a T9 Torx head

• Pliers (to cut cable ties)

• Cable ties

• Hook calibration parts from MiR

Before replacing the encoder disk

Step 1: Turn off the robot and disconnect the battery. To disconnect the battery, follow these steps:

1. Remove the rear cover by pressing the two white buttons and pulling off the cover. When removing the cover, un-click the two bottom corners first and then the two top corners.
   
   
2. Turn the Battery lock switch clockwise to release the Battery lever.
   
3. Pull the Battery lever down to disconnect the battery.
   
4. Turn the Battery lock switch counter-clockwise to lock the battery lever again.

Step 2: Unscrew the antennas from the front cover.

Step 3: Remove the center cover by unscrewing the four screws (two on each side) with a T25 Torx screwdriver and lifting the cover off.

Step 4: Remove the front and rear covers. The covers are held in place with magnets.

Step 5: Locate the cables near the encoder disk and cut the cable ties that hold the cables together using a set of pliers. Gently, pull the cable apart slightly so you can access the screws underneath.

Step 6: Cut the strips holding the cables together on the side of the hook. Be careful not to cut the cables.

Step 7: Remove the cable cover by unscrewing the two screws with a T25 Torx screwdriver.

Step 8: Lift the encoder read head. To do this, follow these steps:

1. Unscrew the two outer small screws with a T10 Torx screwdriver.
   

2. Loosen the two middle screws with the calibration parts.
   

3. Tighten the two small screws again.
   

This is necessary to lift the encoder read head, to make sure that it does not damage the new encoder disk when reapplied later.

Replacing the encoder disk

Step 1: Remove the encoder mounting plate by unscrewing the four screws using a 4 mm Hex screwdriver and remove the mounting plate.

Step 2: Remove the old encoder disk by unscrewing the six screws with a T9 Torx screwdriver and remove the disk.

Step 3: Insert the new encoder disk and screw in the six screws you just removed before with a T9 Torx screwdriver. Tighten the screws to 0.4 Nm. Ensure that the little hole in the disk is facing the front of the robot.

Step 4: Remount the encoder mounting plate by screwing in the four screws with a 4 mm Hex screwdriver. Tighten the screws to 1.0 Nm.

Step 5: Check the LED on the encoder. It has to be bright green. If it is red or yellow, you have to use the Hook calibration parts—see Calibrating the encoder disk.

• If it is green then try and rotate the Hook slowly to each of the outermost positions, stopping if the LED changes color.

• If it changes color, then you have to calibrate the encoder with the next steps or check the disk to see if it is broken.

• If it is green all the way, you can remount everything and you are done.

Calibrating the encoder disk

Step 1: Insert the two small calibration parts into the middle screws with the short part at the bottom.

Step 2: Add the top parts.

The middle calibration parts are to define the distance from the encoder disk and the outer parts are to keep the encoder firmly in place.

Step 3: Loosen the outermost screws as much as possible and then slowly tighten them again on each side until the LED turns green.

Step 4: Tighten the calibration parts until they reach the encoder. Make sure the LED stays green. Once the encoder is in place, tighten all the screws to ensure the encoder will not move. The encoder LED has to stay green.

Step 5: Rotate the hook to its outermost positions. If the LED turns red or yellow at any point, then you have to recalibrate from Step 1 or examine the disk for errors. If it stays green, then you are done.

Step 6: Remount the encoder mounting plate, and reorganize the cables with cable ties.

Step 7: Remount all the covers and the antennas.