What is the hierarchy of Extrusions?

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What is the hierarchy of Extrusions?

The Parent to Child hierarchy is as follows


There are a number of elements that must 'co-exist' to create Extrusions for Solid Modeling. It is helpful to understand the:

Commands that you need to use

Actions that MechDesigner adds to the model for you.

Command 1 :

Add sketch-elements to Lines, Cad-Lines, Arcs, Circles to define the shape of a sketch-loop

- or -

Add Polyline to a 2D-Cam or a Gear-Pair

MechDesigner :


...are recognized by MechDesigner when sketch-elements are added as a sketch-loop

Command 2 :

Add Profile:

Select a sketch-element that one sketch-element in a sketch-loop

MechDesigner :


... are added with a Add-Profile

Command 3 :

Add Holes: Through Extrusions


1.We do not show a sketch-loop as an element in the Geometry-Tree

2.We do not show the sketch-elements in the Geometric-Tree. Click a constraint to see the sketch-element in the Selection-Window.

3.Auto-Profiles and Profiles have slightly different properties:

You can delete a Profile. The sketch-loop stays in the Part-Editor.

You cannot delete an Auto-Profile with the delete key or command.

To remove an Auto-Profile you must:

For the Complete Mechanism: De-select the Auto-Profiles

- or -

For individual Auto-Profiles: Use the Add / Remove Auto-Profile

The sketch-loop is also deleted.

See Tutorial 4

See also How to add sketch-loops



A Sketch-Loop is series of sketch-elementsRed-14-1b, joined end-to-end, or a Circle, added to a Part.

The Sketch-Loop cannot have branches - 'T-bars'

The Sketch-Loop cannot cross itself - 'Figure-of-Eights'.

Sketch-Elements and Sketch-Loops do NOT show in the Assembly-Tree.

To add a Profile, select a Sketch-LoopRed-14-1b, to define the shape - called the contour - of the Profile

The Profile is two contours: the Primary ContourRed-14-2 and the Secondary ContourRed-14-3.

The Profile contours are offset from each other, they can only be offset along the Z-axis of the Part; the Secondary Contour is always at a more positive Z-axis value (it is in-front of the Primary Contour when viewed from the 'Front' view).

The ExtrusionRed-14-4 simply fills the space between the Primary and Secondary Contours of the Profile.

Extrusions have a few more properties: visibility, density, color, opacity, etc.

The location of the Profile contours are edited with the Extrusion dialog-box.

You can sketch many Sketch-Loops in each Part - hence Add many Profile and Extrusions

You can supply many Profiles from one Sketch-Loop - each with different offsets

You can use a sketch-loop to cut a hole through an Extrusion