DIG

1) The cabine is made of sheet steel because it is   strong.

2) Arm and Feather  is made of steel because it is strong.

3) Spoon is made of welded steel because it is strong, too.

The cabine is mounted on a spinning crown.
The arm is conected to the feather.
The arm is attached to the bucket cylinder.
The spoon is suspended from the arm.

The purpose of the cabine is to manipulate the machine.
The purpose of the feather is to guide the arm.
The purpose of the spoon is to dig.
The purpose of the  arm is to guide the spoon.