Remove the two Allen bolts pos 8 which hold the black steel disc pos 6 and remove the disc.
Now you can unscrew the timing belt pulley, it might be hard to get the pulley off as was the case on one of the three pulleys on my DM1007.
It is the fit in combination with the thread causing the issue.
Careful tapping with a Nylon hammer on the (disasembled) ball screw shaft end while holding the timing belt pulley and turning the pulley bit by bit might help to get it off.
Hereby the dimensions I have taken from such a pulley.
Strange enough one of the three pulleys on my machine had a Ø10.1 hole on one of the pulleys.
Ream the pulley before re-assembling so the fit will be okay.