Assembly Split 

The Assembly Split command splits parts rapidly and very productively. You could actually split each part in the Part Design workbench, but the Assembly Split command is more  productive since it requires only one interaction. This task shows you how to split a product including four parts. You can split three of these parts by using a surface.
Open an assembly. Ensure the design mode is on.
1.   Click Split .
2.  Select the splitting surface, that is Loft.1.

The dialog box that appears displays the names as well as the paths of the parts that may be affected by the split action.
  The assembly feature's name now appears in the top left corner of the dialog box. If desired, you can edit this name.

3.  The frame 'Affected parts' is exclusively reserved for the parts you wish to use. For the purposes of our scenario, you are going to split Bulkhead A.1, Bulkhead A.2 and Bulkhead B. Note that Bulkhead A.2 and Bulkhead A.1 are two instances of Bulkhead A.

Move the parts to the list 'Affected parts". To do so, select Bulkhead A.1 and click the  button. 
4. Repeat the operation for the other two parts. Alternatively, double-click each part.

The other three buttons let you move the names of the parts from one list to another too:

  moves all selected parts to the list 'Affected parts'
  moves all selected parts to the list 'Parts possibly affected'
  moves the selected part to the list 'Parts possibly affected'

The Split Definition dialog box that has appeared, indicates the splitting element.

5. Arrows in the geometry indicate the portion of parts that are kept. If the arrows point in the wrong direction, click them to reverse the direction.
6. Check the option Highlight affected parts to clearly identify the parts to split.

7.  Click OK to confirm.

The parts are split. Material has been removed from Bulkhead A.1, Bulkhead A.2 and Bulkhead B. Conversely, Bulkhead C is intact.

A new entity 'Assembly Features' appears in the specification tree. It contains the assembly split referred to as 'Assembly Split.1" and the name of affected parts.

Moreover, this feature has generated a split feature in Bulkhead B and two split features in  Bulkhead A.1 and Bulkhead A.2, these parts being instances of a same original part. An arrow symbol identifies these splits in the tree, meaning that a link exists between Assembly Split.1and them.

Editing an Assembly Split
To edit an assembly split, double-click 'Assembly Split.X' entity then you can either:
  modify the list of the parts you wish to split
  change the splitting surface
  redefine the portions of material to keep

If you need to cut the link between a generated split and Assembly Split.X, just use the Isolate contextual command. Obtain a 'traditional' split feature as if you have designed it in Part Design and you can edit it in Part Design.
 

Reusing Part Design Splits
  To increase your productivity, you can create Assembly splits from existing Part Design splits, or more precisely by reusing the specifications you entered for designing Part Design splits. To do so, just proceed as follows:
  1.   Click the Split icon .
  2.  Select the Part Design split of interest.
  3.  Both the Split Definition and the Assembly Features Definition dialog boxes display. You then just need to specify the parts to split. 

The assembly split inherits the specifications as displayed in the Part Design Split Definition dialog box. You can edit these specifications at any time. Editing an Assembly feature created in this way does not affect the specifications used for the Part Design feature.
 

Reusing Assembly Design Splits
  The application also lets you reuse Assembly Splits specifications to accelerate the design process. In this case, you just need to select the existing assembly split, click the Assembly Split icon and then select a face. Only the Assembly Features Definition dialog box appears to let you determine the parts of interest.