5. solid modeling - ceet.niu.edu creo, the initial orientation of the sketch plane and its reference...

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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.

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Sketch Window

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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)

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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

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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).

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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.

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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

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Tools > Relation > enter the relation as shown below > Ok

Relations

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• Turn on/off the display in Graphics Toolbar.

To Control the Dimensions

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• To Modify the Number of Decimal Places in Dimensions, click

Parameters tab and change it (see below).

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• 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

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In this example, the bottom horizontal dimension is to be replaced by another

new horizontal dimension.

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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

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Creating Geometry in Sketcher

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Tangent to Three Entities

Spline

Use Edge / Edge Offset

Coordinate System

Axis Point

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Text

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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

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Dragging

Any geometry can be dragged to change the shape.

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To move a line, click select the line and then drag.

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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.

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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

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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

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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

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Divide

Edit > Trim > Divide > Click the entity at the locations where you want to

divide.

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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

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Trim Entities to a Bounding Entity

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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

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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.

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Example 1

Create the following model by using various sketcher menus and

constraints.

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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)

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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.

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Example 2

Create the following model using the half sections in the sketcher.

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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

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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.

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Example 3

Create the extended part that uses part of the outline of the existing part

on the right.

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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”.

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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.

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Dimension

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Example 4

Create the part below by using Offset Edge.

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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

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Dimension

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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

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Edit > Copy

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Edit > Scale and Rotate