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Step 4.4: Level 2: Sketch-Loops and Extrusions in Parts

Contents

Solids in a Part

1.	Add a Sketch-Loop in the Part-Editor

2.	Add a Profile in the Mechanism-Editor

3.	Select the Profile and Extrusion

4.	Use the Extrusion dialog-box in the Mechanism-Editor

5.	Add one more Profile, use the SAME sketch-loop

6.	Add more Sketch-Loops to the Part

7.	Add a Hole to cut through Extrusions

1: Add a Sketch-Loop to a Part in the Part Editor

GA-Rocker-1

I have prepared this simple model. I have added a:

1.	Line to the Base-Part

New Part

3.	Pin-Joint between a Point in the Line in the Base-Part and a Point at the Origin of the new Part

4.	Motion-Dimension FB

The kinematic-chain is kinematically-defined - the Part-Outlines are green. The Part is a Rocker.

GA-PE-1

STEP 1:

Start the Part-Editor to edit the Part.

•	Double-click the Part-Outline.

The Part is in the same orientation in the Part-Editor as it is in the Mechanism-Editor.

You can use the View toolbar > View Align tool to rotate the Part so that its X-axis is horizontal.

I usually do not do 'View Align'.

GA-PE-LinesArcs1

STEP 2:

Use the Part-Editor to add a 3 Lines and 3 Arcs

For the purposes of this tutorial ONLY , do NOT merge the points as you add the sketch-elements.

It is always faster to use the Merge-and-Hover technique as you add the sketch-elements.

In this case, the image shows that the Arcs and Lines are not merged.

GA-PE-LinesArcs1-Merging

STEP 3:

Click Geometry toolbar > Merge-Points tool

You need to:

1.	Click the two Points you want to merge

Make sure Point 1 is red when you click the Point 2

2.	Click the graphic-area to complete the command

Merge-Point is not a persistent command

Do the Merge-Point command six times to merge two Points size times.

GA-ME-LinesArcs1-Merged

STEP 4:

Close the Part-Editor when the Sketch-Loop is complete.

•	In the Mechanism-Editor, the colour of the sketch-loop matches the colour of the Part-Outline in the Mechanism-Editor –

This means the sketch-loop will be blue if the Part is not kinematically-defined, and green if it is kinematically-defined.

In this case the Part-Outline is green. Therefore, the sketch-elements in the Part are also green.

2: Add a Profile in the Mechanism Editor

GA-ME-AddProfile1

In the Mechanism-Editor, select the Add Profile command.

STEP 1:

Add menu > Mechanism sub-menu > Solids sub-menu > Add Profile.
- or -
Solid Toolbar > Add Profile icon

In the graphic-area, select a Line or Arc that in the sketch-loop.

CM-ME-AddProfile1

STEP 2:

Make sure the sketch-element is in the Command-Manager

MechDesigner will add the Profile only if the sketch-loop is 'valid'. That is, Points at the ends of the sketch-element are merged.

Message in Feedback Area for 'Invalid Sketch-Loop'

If the sketch-loop is not 'valid', MechDesigner does not add the sketch-element to the selection-box in the Command-Manager.

In this case, see left for the message is in the Message Window.

CM-ME-AddProfile-1

STEP 3:

Click OK in the Command-Manager
- or -
Right-Click in the graphic-area as a short-cut.

The colours of the sketch-elements are now Pink [default colour]. Why? You actually see the Profile element from the Front-View. The Profile element is in front of the sketch-elements . The Profile hides the sketch-elements.

You will not see the sketch-elements when the view is the Front View.

GA-ModelEditor-Solid

STEP 4:

Look in the Model name-tab.

Spin the model, if necessary, to see the Extrusion that fills the gap between the Profile contours.

[Use the left-right & up-down arrow-keys on your keyboard to spin the model].

GA-MechEditor-ProfileCont-1

STEP 5:

Click the Mechanism-Editor, and spin the View with the Arrow keys on your keyboard.

Bug: if when you use your keyboard arrow-keys and the Mechanism-Editor tab changes to the Model-Editor name-tab, then:

1.	Click the Mechanism-Editor tab

2.	Click somewhere in the Selection-Window

3.	Use the arrow -keys again to spin the view.

You can see one of the two Profile contours.

There are always two Profile contours – the Primary Contour and Secondary Contours.

The Primary Contour and the Sketch-loop are at the same position. MechDesigner may show the sketch-elements in preference to the Profile.

How do you edit the Profile contours? See 'next part to this step in this tutorial'.

GA-MechEditor-ProfileCont-1

STEP 1:

Click the Profile.

When you click a Profile contour in the graphic-area, two elements show in the Selection-Window.

•

Profile

•

Extrusion

Selection-Window

STEP 2A:

Right-click the Extrusion element in the Selection-Window.
Click 'Edit' from the contextual-menu,

The Extrusion dialog-box opens.

Assembly-Tree

STEP 2B:

- or -
Right-Click the Extrusion element in the Assembly-Tree, and
Click Edit Element in the menu

The Extrusion dialog-box opens.

Dialog-13.2-Extrusion-ExParameters

Dialog-13.2-Extrusion-Colour

Dialog-13.2-Extrusion-Mass

Extrusion Parameters

Three parameters control the location, relative to the Mechanism-Plane, of the Primary and Secondary Contours of the Profile.

Extrusion Depth specifies the distance to the Secondary-Contour from the Primary-Contour. This is always a positive value. The Secondary Contour is always 'in-front' of the Primary Contour.

Extrusion Offset moves the Primary Contour along the Z-Axis of the Part.

Part Offset moves the Primary Contours of ALL the Extrusions in a Part.

The other parameters edit the Properties of the Extrusion.

Show or Hide Extrusion, Extrusion Colour, Change Transparency, Graphic Quality

Material Density

MechDesigner calculates the Mass and Inertia from the Density, Profile Contour, and the Extrusion Depth parameters.

GA-ExtrusionDepth10

1.	Extrusion Depth:

•	When you edit the Extrusion Depth, only the Secondary Contour moves along the Z-axis.

In the image to the left:

•	Extrusion Depth is 10mm.

•	The Primary Contour is coincident with the sketch-loop. The sketch-loop may show in the graphic-area over the Profile.

GA-ExtrusionDepth30

STEP 1:

Edit the Extrusion Depth.

•	I have edited the Extrusion Depth to 30mm with the spin-box tool. The Spin-Increment is 10, so it took two clicks!

•	The Secondary Contour moves away from the Primary Contour. The Primary Contour does not move when you edit the Extrusion Depth.

Note: If the model is very large, the Extrusion Depth parameter can take a few seconds to update.

GA-ExtrusionOffset-10

2.	Extrusion Offset and Part Offset

•	There is only one Extrusion in this model. Therefore, comparison between Extrusion Offset and Part Offset is not immediately clear.

•	MechDesigner adds the Extrusion Offset and Part Offset. They calculate where the Primary contour is relative to the Mechanism-Plane. These values are Positive or Negative.

•	The Secondary contour always moves with the Primary contour.

STEP 2:

Edit the Extrusion Offset.

•	The Extrusion Offset is -10mm.

•	The Primary Contour moves from the Mechanism-Plane in a negative direction by 10mm.

•	The image to the left shows the new positions of the Primary and Secondary contours.

GA-PartOffset-30

3.	Part Offset:

•	A Part may have more than one Extrusion and it may be convenient to move all of the Extrusions together.

•	The Part Offset applies to all Extrusions in a Part

•	Add the Part Offset to the Extrusion Offset to equal the total offset of the Primary contour from the Mechanism-Plane.

STEP 3:

Edit the Part Offset

•	The Part Offset is 30mm

•	Add the Part Offset to the Extrusion Offset. The total offset is (-10+30) = 20mm from the Mechanism-Plane.

STEP 1:

Toggle IN Visibility toolbar >'Show Model Element in Mechanism'

GA-ExtrusionOffset-20

STEP 2:

First, edit the Extrusion again.

Remember, to Edit an Extrusion:

1.	Click the Profile in the graphic-area

2.	Right-click the Extrusion in the Selection-Window

3.	Click 'Edit element' in the contextual-menu

Enter these values in the Extrusion dialog-box:

•	Extrusion Depth = 10

•	Extrusion Offset = 20

•	Part Offset = 0

GA-AddProfile-00

STEP 3:

Add a new Profile

CM-ME-AddProfile1

1.	In the Mechanism-Editor,

Use the in the Solids Toolbar

2.	In the graphic-area, select a Line or Arc from the same sketch-loop.

3.	Click OK in the Command-Manager.

GA-AddProfile-01

STEP 4:

Edit the new Extrusion.

1.	Click on the Profile in the graphic-area

2.	Right-Click the Extrusion in the Selection-Window

3.	Click 'Edit'

Enter these values:

•	Extrusion Depth = 10

•	Extrusion Offset = -30

•	Part Offset = 0

GA-AddProfile-01-EndView

STEP 5:

Look at the two extrusions with the 'Right View'

•	In the Mechanism-Editor, use the View > From Right menu option.

•	Note: To make the Extrusions symmetrical to the Mechanism-Plane: the Extrusion Offset of the Extrusion 'behind' the Mechanism-Plane must compensate by the Extrusion Depth (Part Offsets is zero). Experiment!

•	The Extrusion Depths are 10.

•	The Extrusion Offsets are 20 and -30

STEP 1:

Edit the Part in the Part-Editor

Double-click the Part-Outline, or a sketch-element, in the Part.

GA-Sketch-LoopConstriants

STEP 2:

Add dimensions and constraints to the sketch so the sketch-elements become black

I have added:

•	Tangent constraints between the Arcs and Lines

•	Coincident constraints between the centre of the bottom two Arcs and the ends of the CAD-Line

•	Coincident constraint between top Arc and the vertical Y-axis

•	Equal constraints to the Arcs

•	Dimensioned the Arc and the distance to the centre of the top Arc

•	Re-dimensioned the length of the CAD-Line

GA-ProfileContours

STEP 3:

Review the Profiles

Click the 'Show Model in Mechanism' tool to hide the Extrusions

You can see that the Profile contours and the Extrusions have also updated to the new shape of the sketch-loop.

[For some reason, the Profile contours are 'White' in this image - they are usually Pink].

GA-Sketch-LoopConstriant-Holes

STEP 4:

Add New Sketch-Elements

Here, I have added three Circles to the sketch.

The Circles are:

•	equal in size

•	coincident with centre-Point of the Arc.

A Circle is the most basic shape of a sketch-loop.

GA-ProfileandPins

STEP 5:

Add three new Profiles with the three Circles

Do the commands three more times.

AS BEFORE: Select Add Profile, select the Sketch-loop (the Circle), and click OK in the Command-Manager.

ALTERNATIVELY, try this new technique!

1.	Hover above the sketch-loop so it becomes red – DO NOT click it

2.	Right-Click

3.	Click Add Profile from the contextual sensitive icon palette

4.	Right-click to complete the command. (This is a keyboard shortcut for OK in the Command-Manager).

GA-sketchElements-Loops and Pins

STEP 5:

Edit the Three Extrusions

Here, we want the three Circles to be 'posts' between the two plates.

Edit each Extrusion, and enter these values in the Extrusion dialog-box

•	Extrusion Depth = 80

•	Extrusion Offset = -40

•	Part Offset = 0

•	Extrusion Colour – here all a light grey.

7: Add Holes

STEP 1:

Edit the Part in the Part-Editor

Double-click the Part-Outline, or a sketch-element in the Part.

GA-ProfileandHole

STEP 2:

Add a Sketch-Loop that you want to be the same shape as the Hole:

•	See the new Sketch to the left

•	The sketch-loop that is the shape of the hole is 'inside' the sketch-loop used for the Profile.

•	Close the Part-Editor.

CM-AddHole-1

STEP 3:

Add a Hole to each side 'plate'

Use the in the Solids toolbar.

In the Command-Manager:

•	Click a sketch-element on the sketch-loop intended to be the shape of the hole [an 'Arc' has the label 'Circle'].

•	Click the Profile with the Extrusion through which you want to cut the hole.

•

Click OK

Do Steps 1-3 again for the other Extrusion

GA-ProfileandHole-1

STEP 4:

View Holes through Extrusions

I have used the Display Filter to 'hide' Points.

With the 'Show Model in Mechanism' Toggled OFF, it is possible to see:

Sketch-loops [green] for the:

•	Primary Shape, the three Posts, and the Hole

Profiles [white - but default colour is Pink]

•	2 for the main shape, three for the posts, and the

Hole Element [also white, usually Maroon

GA-ProfileandHole-MechEd

STEP 5:

Show / Hide Model in Mechanism

With the 'Show Model in Mechanism' Toggle ON it is possible to see:

Extrusions:

•	2 Blue 'Plates' made from the one primary sketch-loop

•	3 Grey Posts/Pegs made from Circle sketch-loops

•	2 Holes derived from one sketch-loop

GA-MoEd-Part

STEP 6:

Click the Model name-tab to review the model in the Model-Editor

MechDesigner uses six lights to improve the display of the model.

STEP 7:

Right-click the Model element that is at the top of the Model Assembly-Tree.

The Model dialog-box opens.

Click the Lighting tab

Also, see: Visibility toolbar > Solids Display tool to view in the Mechanism-Editors:

'Solids with wire-edges', as 'Wire-edges only' or as 'Solids only, without wire-edges'.

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd