Extruding 2D Objects into 3D Solids

• Lesson 2.1 focuses on creating solids from 2D objects
• Solid modeling and editing methods transform 2D objects into 3D solids and surfaces

Activity 2.1

• Requires analysis of 2D wireframe figures to determine which commands were used

EXTRUDE [EXT]

• It creates a 3D solid or surface by extending a 2D or 3D curve
• Extrusions can extend in the Z direction, be set to taper, or follow a path
• Open or closed objects can be extruded to create 3D surfaces or solids

Extrusion Steps

• Open the PRACTICE1.DWG drawing file
• Use the EXT command
• The default settings are a wire frame density of ISOLINES=4, and a closed profiles creation mode set to Solid
• Select objects to extrude, or use the [MOde] option and refer to Figure 103
• Available mode options include Solid and Surface
• Specify the height of the extrusion, or use [Direction/Path/Taper angle/Expression]: 1
• Extrude also applies to Figures 104 and 105

Key Prompts

• Face and edge subobjects are selectable by pressing Ctrl while selecting
• Mode controls whether the extruded object becomes a solid or a surface
• Surfaces can be NURBS surfaces or procedural surfaces, depending on the SURFACEMODELINGMODE system variable

Height of Extrusion

• Selected objects are extruded along the positive or negative Z axis
• The direction is relative to the UCS (User Coordinate System) at the time of creation or based on the original UCS for multiple selections
• The position of the UCS affects the placement of the extrusion

Extruding Horizontally

• Rotate the UCS by 90 degrees using the UCS command X-Axis rotate
• Draw a circle at coordinates 1,1 with a radius of 0.5
• Extrude the circle at a height of -2

Direction

• Specifies the extrusion's length and direction using two specific points
• The direction cannot be parallel to the plane of the sweep curve created by the extrusion

Path

• Specifies the extrusion path based on a selected object
• The path moves to the centroid of the profile, then the profile of the selected object extrudes along the chosen path to create solids or surfaces

Extrusion Path Steps

• Open a new drawing template in ACAD
• Create an ARC with a starting point of -3,8.5, an ending point of -3,2.5, and a radius of 3
• Create LINE1 with a starting point of -6,2.5 and a length of 6
• Create LINE2 with a starting point of -5,7.5 and a length of 3
• Create three RECTANGLES with measurements of 1x1, based on Figure 114
• Offset all RECTANGLES to a distance of 0.25 inward
• Rotate Rectangle1, Rectangle2, and Rectangle3 by 90 degrees using the green or red orbit of the 3Drotate command
• Move Rectangle1 to the Arc, Rectangle2 to Line2, and Rectangle3 to Line1
• Command: EXTRUDE
• Current wire frame density: ISOLINES=4, Closed profiles creation mode = Solid
• Select the rectangle to extrude or click Rectangle1
• Select the extrusion path
• Perform the processes for the other rectangles

Taper Angle

• Specifies the taper angle for the extrusion
• Positive angles taper inward, and negative angles taper outward
• Default angle is 0, creating a 2D object perpendicular to its 2D plane
• Selected objects and loops are tapered the same
• Angle of taper: Specifies the taper angle between -90 and +90 degrees
• Specify two points: Defines the taper angle based on two specified points

Extrusion with Taper Angle Steps

• Create two 1x1 rectangles: Rectangle1 at corner 0,0 and Rectangle2 at corner 3,0
• Command: EXTRUDE
• Current wire frame density: ISOLINES=4, Closed profiles creation mode = Solid
• Select objects to extrude
• Specify height of extrusion
• Specify angle of taper for extrusion <15>: 15
• Specify height of extrusion <1.0000>: 1
• Repeat for Rectangle2, setting the taper angle to -15

Do It Yourself Extrusion

• Create a circle at the center of 0.5,0.5,1 with a radius of 0.15
• Extrude the circle with a taper angle of 1 at the height of 4
• Create a sphere at the center of 0.5,0.5,5 with a radius of 0.5

PRESSPULL [PRESSPULL]

• Dynamically modifies objects by extrusion and offset
• Provides visual feedback while moving the cursor after selecting a 2D object, closed boundary, or 3D solid face
• The press or pull behavior depends on the type of object selected to create extrusions and offsets
• Results in the creation of a 3D solid metal
• Presspull retains the 2D object and creates an extruded solid object
• Add or subtract pulled objects

Presspull Steps

• Create a 4x3 rectangle (first corner at 0,0; other corner at 4,3)
• Create four circles with a radius of 0.25, centered at 0.5,0.5; 3.5,0.5; 3.5,2.5; and 0.5x3.5
• Create a circle with a radius of 0.5 at the center point 2,1.5
• Command: Presspull, then select the object or bounded area
• Specify an extrusion height or [Multiple]: 1

SWEEP [SWEEP]

• Command for creating a 3D solid or surface by sweeping a 2D or 3D curve along a path
• Automatically aligns the sweep object to the object
• SURFACEMODELLINGMODE determines if SWEEP creates a procedural or NURBS surface

Sweep Steps

• Command: SWEEP
• Current wire frame density: ISOLINES=4, Closed profiles creation mode = Solid
• Select objects to sweep or [MOde]
• The Mode has closed profiles creation mode [SOlid/SUrface]
• Select the sweep path or [Alignment/Base point/Scale/Twist]
• Alignment will align the sweep object perpendicular to the path before sweep [Yes/No]<Yes> where Yes is the default value
• Specify the base point
• Enter the scale factor
• Twist allows banking or allows banking for a non-planar sweep path [Bank Expression]

Sweep Alignment

• Sweep Alignment YES: In this mode, a polyline and a hexagon are drawn
• Selects object and sweep path
• Aligns the sweep object perpendicular to the path before the sweep [Yes/No]<Yes>: Y
• Sweep Alignment NO: In this mode, only the initial sweeping point adheres to the angle where the object is placed to be swept
• A polygon is rotated 45 degrees
• Selects objects and sweep path
• Align the sweep object perpendicular to the path before sweep [Yes/No]<Yes>: N
• SWEEP Basepoint: Specifies a base point for the objects to be swept

Sweep Twist

• Sets a twist angle for the objects being swept
• The twist angle specifies the amount of rotation along the entire length of the sweep path

HELIX

• Creates a 2D spiral or 3D spring
• Open a new drawing ACAD.DWT
• Command: HELIX with Number of turns = 3.0000 Twist=CCW
• Specify the center point of base: 0,0
• Specify the base radius or [Diameter] <0.0000>: 1
• Specify the top radius or [Diameter] <0.0000>: 1
• Specify the helix height or [Axis endpoint/Turns/turn Height/tWist] <1.0000>: 2
• Save the drawing as a Helix

REVOLVE SURFACE [REVSURF]

• It Creates a mesh by revolving a profile about an axis
• Line, arc, circle, or 2D or 3D polyline objects may be selected for revolving in a circular path around an axis
• Steps to create revolve surface include entering command revsurf, selecting the object to revolve and the defining axis

Revolve Surface Properties

• A smoothness level selectable from Level 0 to Level 4

Revolve surface process

• Create a new drawing using an ACAD template
• Set the view to Front View
• Create objects to dimensions in figure 1
• Command: REVSURF
• Current wire frame density: SURFTAB1=6, SURFTAB2=6
• Select the object to revolve
• Select the object that defines the axis of revolution
• Specify the start angle and the included angle
• Change the properties smoothness to Level 4

REVOLVE [REV]

• It creates a 3D solid or surface by sweeping an object around an axis
• Open profiles can create surfaces, and closed profiles can create either a solid or a surface
• The Mode option controls whether a solid or surface is created
• When creating a surface, variable SURFACEMODELINGMODE controls if a procedural or NURBS surface is created

Revolve Path and Profile Curves

• Can be open or closed
• Can be planar or non-planar
• Can be solid and surfaces edges
• A single object to extrude multiple lines, convert them to a single object with the JOIN command
• A single region to extrude multiple regions, first convert them to a single object with the UNION command

Revolve Steps

Open a new drawing.

• Offsets the object
• Draw lines to enclose the objects
• Join all objects
• Use the REVOLVE command

FYI

• REVSURF creates an object in 3D mesh, while REVOLVE creates an object in 3D solid
• REVSURF surface is not smooth by default; applying smoothness level compresses its physical appearance
• REVOLVE preserves the object's appearance
• Instead of using REVSURF and REVOLVE, EXTRUDE PATH can be used

LOFT

• It creates a 3D solid or surface in the space between several cross sections
• Cross sections are specified to define the shape of the resulting solid or surface
• At least two cross sections must be specified
• Loft cross sections can be open or closed, planar or non-planar, and can also be edge subobjects
• Open cross sections create surfaces, and closed cross sections create solids or surfaces

Loft Steps

• Command: LOFT
• Current wire frame density: ISOLINES=4, Closed profiles creation mode = Solid
• Select cross sections in lofting order or [Point/Join multiple edges/MOde]: multiple clicks on the circles
• Select path profile and select the line
• Enter an option [Guides/Path/Cross sections only/Settings] <Cross sections only>: P