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Lofting Around a Corner
In this month’s exercise, we’re going to quickly
create a lofted shape that sweeps around a corner.
I’ve illustrated our goal to the right.
The trick to creating this part is to use a Path
Curve to control the sweep of the loft around the
corner.
We’ll start with a new file in View 1. (The Top
View.)
Use the ROUNDED RECTANGLE BY WIDTH HEIGHT
Icon and create a rectangle with 0.5 inch corner radii. Use the
MidCtr Anchor Option. Type 3 for the Width and Height and
using the Keyin Option place it at the origin of the file.
Now, switch to View 5 (The Right View.) and click on the
CIRCLE BY DIAMETER Icon.
Type 2 for the Diameter and using the Keyin Option hit the
ENTER Key to indicate 0 for the XC Value. Now, type –3
for YC and 4 for ZC.
Switch to View 2. (The Front View.)
Click on the RECTANGLE BY CORNERS Icon.
Use the Keyin Option first and hit the ENTER Key three
times to place the first corner at the origin.
Then, use the CtrMid Option and click on the circle that you made previously. (It looks
like a vertical line in this view since you are looking at it on edge.)
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Switch to the Isometric View and your screen
should look like this: (I’ve used a different
construction color for the rectangle to add
clarity to the illustration.)
Now, click on the FILLET WITH TRIM Icon and create a
2.75 radius fillet at the lower, left corner of the rectangle you
just made. (Note: In some versions of KeyCreator you will
get an annoying message that warns you that the entities are
not in a plane and that a Nurbs Spline can be created. You
can avoid this by not passing your cursor over any part of the
rounded rectangle as you pick the vertical edge of the
rectangle.)
Your screen should look like this:
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Next, click on the CHAIN TO SPLINE Icon.
Select the two short line segments and the fillet
indicated by arrows in the illustration below.
Depending on the configuration settings in your
system, you may or may not get a message
prompting you to delete the original entities.
For purposes of this exercise you can delete or save the original entities. (Note: The
configuration setting is in TOOLS/OPTIONS/ENTITIES near the bottom of the sheet.)
Now, click on the LOFT Icon.
A Dialog Box appears.
Select the Curve/Edge Option.
Then, select the entire rounded
rectangle that you created in
the first step. Hit the ENTER
Key.
The Dialog Box appears again. With the Curve/Edge Option still selected, click on the
OK Button. This time select the circle and hit the ENTER Key.
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The Dialog Box appears again. This time, click on the DONE
Button.
A second Dialog Box appears.
By default, the first three Options should be checked.
Just click on the OK Button.
You will now get a lofted solid that looks
like this:
Now this is not what we want. I had you
do this to illustrate why we needed to
construct the path spline that we are going
to use to fix the problem.
You can click once on the UNDO Icon to revert to the construction
curves.
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Click again on the LOFT Icon.
Using the Curve/Edge Option select again the two profiles just
like you did before.
This time, when the Dialog Box appears after you select
the circle, do NOT click on the DONE Button. Instead,
click on the Path/Curve Option.
Select the spline that you created from the two lines and
fillet. (Note: The Path Curve must be a single entity. That’s
why we took the time to convert the three entities into the
spline.) Hit the ENTER Key.
When the Dialog Box reappears, click on the
DONE Button.
When the second Dialog Box appears, click on
the OK Button.
Your lofted solid now looks like what we want.
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You can now click on the SHELL Icon.
A Dialog Box appears.
Type 0.05 for the shell thickness and hit the
ENTER Key.
Select the two end faces of the lofted
solid and hit the ENTER key.
Your completed part will look like this:
This part is supplied for download as
“LoftAroundCorner01” with this lesson.
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