5. Solid modeling - ceet.niu.edu Creo, the initial orientation of the sketch plane and its reference...
Transcript of 5. Solid modeling - ceet.niu.edu Creo, the initial orientation of the sketch plane and its reference...
KIM,ME,NIU
Sketcher
All feature creation begins with two-dimensional drawing in the
sketcher and then adding the third dimension in some way. The
sketcher has many menus to help create various types of
sketches.
The section of solid models must be closed without any loose
open ends and any overlapping with other curves. If there are
more than one outline, they must not intersect and all of them
must be closed.
Alternatively, the solid section can be made with open line
sketch and adding thickness by Thicken Sketch.
The section of surfaces (i.e., quilts) can be any way, open and
intersect.
KIM,ME,NIU
Sketch Window
KIM,ME,NIU
In Creo, the initial orientation of the sketch plane and its reference planes
is in 3D.
You can use Sketch View command in Graphics Toolbar to get the sketch
view rather than 3D.
The Initial Orientation of Sketch Plane (SP)
KIM,ME,NIU
When a geometry is sketched, the default dimensions (so called, weak
dimensions) are given.
The dimension can be changed by double clicking it and entering a new
value > CR.
Weak and Strong Dimensions
KIM,ME,NIU
Use Sketch View and then sketch with Line and Circle similar to below.
This shows default dimensions. Also, the sketch is shaded because the
sketch is closed (i.e., successful).
KIM,ME,NIU
1. Click and hold a dimension and move to a new position.
2. Double click a dimension and edit it and end it with CR. Repeat this for
all dimensions as shown below.
KIM,ME,NIU
Click Dimension > select the entity or entities with the left mouse button >
place the dimension at the desired position using the middle mouse
button.
To Create Dimensions
KIM,ME,NIU
KIM,ME,NIU
KIM,ME,NIU
KIM,ME,NIU
KIM,ME,NIU
Tools > Relation > enter the relation as shown below > Ok
Relations
KIM,ME,NIU
• Turn on/off the display in Graphics Toolbar.
To Control the Dimensions
KIM,ME,NIU
• To Modify the Number of Decimal Places in Dimensions, click
Parameters tab and change it (see below).
KIM,ME,NIU
• Replacing an existing
sketcher dimension with an
equivalent one that retains
the symbolic dimension
(sd#) of the original is useful
to preserve additional data
associated with the original
dimension (for example,
geometric tolerance symbol
or extra text added in
drawing mode). Click a
dimension > MRB > Replace
> create a new equivalent
dimension.
To Replace a Dimension
KIM,ME,NIU
In this example, the bottom horizontal dimension is to be replaced by another
new horizontal dimension.
KIM,ME,NIU
For linear dimensions, you can enter a negative dimension value. This
causes the geometry to reverse direction. In Sketcher, the negative sign
always appears next to the dimension. In Part mode, dimension values
always appear as positive.
Negative Dimensions
KIM,ME,NIU
Creating Geometry in Sketcher
KIM,ME,NIU
Tangent to Three Entities
Spline
Use Edge / Edge Offset
Coordinate System
Axis Point
KIM,ME,NIU
Text
KIM,ME,NIU
Manipulating Sketcher Geometry
Dragging
Dynamic Trim of Section Entities
Trim Entities to Each Other (Other Entities)
Divide Entities
Intersect Entities
Mirror Geometry
Dynamic Trimming and Possible Problems
KIM,ME,NIU
Dragging
Any geometry can be dragged to change the shape.
KIM,ME,NIU
To move a line, click select the line and then drag.
KIM,ME,NIU
Dynamic Trim of Section Entities
Edit > Trim > Delete Segment > click any segment to remove. When the
mouse is over a segment, it is highlighted ready to be selected.
KIM,ME,NIU
Trim Entities to Each Other (Other Entites)
Edit > Trim > Corner > click two entities (they do not have to intersect) on
the portion of the entity to keep
KIM,ME,NIU
Trim Entities by an Increment
Sketch > click Intent Manager (to turn off) > Geom Tools > Trim > Increm >
Enter the incremental length. A positive value lengthens an entity, and a
negative value shortens it. Note to use Untrim Last if needed
KIM,ME,NIU
Trim Entities to a Specific Length
Sketch > click Intent Manager (to turn off) > Geom Tools > Trim > Increm >
Enter the incremental length. A positive value lengthens an entity, and a
negative value shortens it. Note to use Untrim Last if needed
KIM,ME,NIU
Divide
Edit > Trim > Divide > Click the entity at the locations where you want to
divide.
KIM,ME,NIU
Intersect Entities
Sketch > click Intent Manager (to turn off) > Geom Tools > Intersect > pick
the first and second entities near the intersection point > Yes (to delete
dimensions). The entities are split at the intersection point
KIM,ME,NIU
Trim Entities to a Bounding Entity
KIM,ME,NIU
Mirror Geometry
Mirror Sketcher geometry about a sketched centerline. Select an entity or
multiple entities to mirror > click or Edit > Mirror > select a center line
KIM,ME,NIU
Dynamic Trimming and Possible Problems
First use [Extrude > Sketch > pick the top datum plane for sketch plane >
click Sketch button]. Now, in the sketcher, sketch the rough half section
and a horizontal line as shown. Don’t worry about the dimensions right
now. Note that a straight horizontal line is used to trim the arcs.
KIM,ME,NIU
KIM,ME,NIU
KIM,ME,NIU
KIM,ME,NIU
KIM,ME,NIU
Example 1
Create the following model by using various sketcher menus and
constraints.
KIM,ME,NIU
Tangent and Trim
Hole and Copy (see the website, Edit Feature > Copy, for details):
Extrude > …
in the sketch mode draw circles and lines
Constraint > Tangent
Pick on one outer circle and then the line (make the line
tangent to circle)
Repeat this for all tangent lines
Constraint > Trim
select entities to trim (i.e., delete)
KIM,ME,NIU
Hole Dialog Window ABOUT THREADS
For second linear reference, pick
on the axis of the big hole and
then HP to specify the distance
from the axis along HP.
KIM,ME,NIU
Example 2
Create the following model using the half sections in the sketcher.
KIM,ME,NIU
Sketch/Mirror and Tangent
Extrude > Sketch the cylinder on HDP. For key hole, draw half the section in sketch mode and use Mirror menu Create center line Draw lines Change dimensions as needed Select lines to mirror [shift key down and selecting lines]
Click Mirror menu Pick on center line for mirroring
For protruded part to the right, draw half the section in sketch mode and use Mirror menu Create center line Draw lines Use constraint Tangent to make the line tangent to circle
Override default dimensions and change dimensions as needed
Select lines to mirror [shift key down and selecting lines]
Click Mirror menu Pick on center line for mirroring
KIM,ME,NIU
Dimension
Note that the angle dimension appearing in protruded part is not
active dimension, but reference dimension and must not be used to
define the shape.
KIM,ME,NIU
Example 3
Create the extended part that uses part of the outline of the existing part
on the right.
KIM,ME,NIU
Project
Create the object on the right-side with a spline and lines
Create two datum planes. First one at 30o angle to the front face of the right-side object thru the vertical edge at front*. The second one is created by offset from the previous at 60 distance
Create > Solid > Protrusion > Extrude > One Side
Select the second datum plane as sketch plane [do not flip arrow direction**] and top datum as top plane
Sketch > Project > Loop > select the front face of the object which is defined by the loop (you may rotate the object for viewing. Now you see projected sketch on the sketch plane)
Draw a vertical line and Trim
Sketch Done > Depth > Till Surface > select the front face of the original object
* Thru > Select Edge > Angle > Select Plane > Done > enter value
** keep default direction because we use “UpTo Surface”.
KIM,ME,NIU
Hint: if you make a mistake in sketching and want to redo some parts,
then use “quit > cancel” and then click the item in dialog you want to
redo.
KIM,ME,NIU
Dimension
KIM,ME,NIU
Example 4
Create the part below by using Offset Edge.
KIM,ME,NIU
Offset Edge
Extrude > … > construct the bottom block with a round.
Extrude > One Side > select the top surface as SP > select the front
face as bottom RP > close refs window
Sketch > Edge Offset > Chain > select the first line and the last line to
offset clockwise (Arc can offset up to its radius).
Type in the value (can be negative) for offset
OK
KIM,ME,NIU
Dimension
KIM,ME,NIU
Working with Sections
To Retrieve an Existing Section or Drawing
To Copy Imported Drawings into Sketcher
Edit > Copy
Edit > Scale and Rotate
To Exit Sketcher with an Incomplete Section
KIM,ME,NIU
Edit > Copy
KIM,ME,NIU
Edit > Scale and Rotate