Geometry Basics

1
Geometry Basics

• Importing, Creating, and Modifying Geometry for
  Meshing

2
Geometry Primitive Creation

• Many analytic geometrytypes may be created in
  CUBIT
• Useful when creatinggeometry from scratch,and
  in decomposition

3
Create Button

• Geometry Primitives are accessed with the Create
  button
• Seven primitive types are currently available

For command line syntax
CUBITgt help create
4
Geometry Booleans

• Geometry Booleans define the shape of a Body
  based on overlapping regions
• Subtract
• Remove regions of overlap
• Intersect
• Delete all except regions of overlap
• Unite
• Combine all regions

5
Subtract

• Removes regions that overlap

Before
After
CUBITgt subtract body 2 from 1
6
Intersect

• Removes regions that dont overlap

Before
After
CUBITgt intersect body 1 2
7
Unite

• Combines all regions into one Body

Before
After
CUBITgt unite body 1 2
8
Importing Geometry

• Previously created geometry may be imported from
  CAD files
• ACIS
• STEP
• IGES
• Geometry translators may be used to import
  unsupported CAD formats
• pro2acis

9
Importing Geometry
2
3
1
Select thefile format
Select the geometry file
Click theImport button
CUBITgt import acis filename.sat
10
Webcutting

• Webcutting slices 1 Body into 2 Bodies
• Many methods to determine where to make the slice
• Plane
• Cylinder
• Extended Surface
• Intersection with Tool Body

For command line syntax
CUBITgt help webcut
11
WebcutImplicit Surface Definition
Coordinate plane
Plane from vertices
Result
Cylindrical surface
Plane normal to curve
12
Webcutting with Plane
1
3
4
5
2
Plane command
Select Bodies and plane orientation
Click Apply or Preview
Volume menu
Webcut menu
13
Webcutting with Cylinder
5
1
4
2
3
Click Apply or Preview
Volume menu
Webcut menu
Select Bodies and define cylinder
Select Cylinder Radius
14
Webcut withPlane Normal to Curve
4
Select Bodies
5
Select normal Curve
6
Select Vertex from which to measure
7
Select offset along curve
8
Click Apply or Preview
3
Select Plane Nrml to Curve (vertex)
2
1
Click Webcut
Click Volume
15
Exercise 3

• Partitioning a Piston

16
Partition a Piston
Partition the piston into 4 quarters. Delete all
but one quarter.
Steps
1)
Import piston.stp
Split the geometry in half
2)
Split the geometry in half again
3)
Delete all but 1 body
4)
Save as qtr_piston.sat
5)
17
Step 1 - Import the geometry file
2
Select piston.stp
1
18
Step 2 - Webcut (Partition) the geometry
Leave the word all
Cutting plane Preview
Execute the Preview command and view the graphics
window
1
2
3
Volume menu
Plane command
Webcut menu
19
Step 2 continued - Webcut (Partition) the geometry
1
Execute the Cut command by pressing Apply
Two separate and unconnected bodies
20
Step 3 - Webcut (Partition) the geometry
1
Change cutting plane to be Normal to the Z Axis
21
Step 3 continued - Webcut (Partition) the
geometry again
1
Preview the cutting plane Execute the Cut
command by pressing Apply
2
Cutting plane Preview
Four separate and unconnected bodies
22
Step 4 - Delete unneeded bodies
1
2
3
Change from Webcut menu to Delete menu
Pick the bodies from the graphics window
Execute the command by pressing Apply