This is an adjustable assembly which is controlled from the Expressions Editor of the assembly with a series of angular constraints with high and low values. The main part is “excav_assy. The components are the tracks, the cab, (arm1) the big arm, (arm 2) the small arm, the bucket and the piston_base and piston_ext . I’ve continued my convention of naming all of the parts of a small assembly with a similar prefix. This helps with organization and keeps the parts listed in the same place to make loading the assembly easier.
To make the excavator components move, make the assembly the work part then open the expressions editor and pull up the Named Expressions list. The expressions that control the parts are named, followed by the upper and lower limit indicted by an (l) or (h) after the shortened name.
The control expressions are, cabangle, bigarm, smarm (small arm), and bucket. The tracks are Fixed with a constraint and shouldn’t move.
Download part files below