# Anchor point in swept surface - Catia

#### k.udhay

##### New member
What is the exact use of anchor point(s) in catia swept surface using two guide curves option? Believe me, there is no good answer by anyone in internet including google.
Apart from a geometrical way of defining (like normal to tangent of continuously changing radius blah blah ), a good example showing clearly the significance of anchor point(s) is highly appreciated. As far as I see, many have asked this questions in different places (forums, youtube, blogs etc.) and gone unanswered. Hence the answers given here will be definitely helpful for many beginners like me. Thanks.

#### MrCATIA

##### Super Moderator
Anchor Points are used to position the profile to the Guide Curve, when sweeping a surface.

In the situation where two Guide Curves are used, two Anchor Points can be used to position the profile, which allows the Profile to be stretched and rotated as it is swept along the surface length. Most of the time, the Profile curve is drawn explicitly in position to the Guide Curves, which eliminates the need to use Anchor Points. But sometimes the Profile is defined away from the Guide Curves, so the Anchor Points must be used to define where the Profile will be swept.

There's a more detailed description with pictures in the CATIA Online Help

#### k.udhay

##### New member
Thanks, Mr. Catia. Can you pl. give a simple example showing exact difference with and without anchor points?

#### MrCATIA

##### Super Moderator
OK - I'll try to go thru a little example that will hopefully explain how to use Anchor Points with a Swept Surface.

Let's start with this little example below: we have a support bracket and we need to add two gaskets on the upper curved surfaces. Both of these surfaces are complex with varying angled slope, and varying widths. I've drawn the profile of the gasket in red.

Example 1:

To begin, I have very carefully drawn a sketch of the profile of my gasket. I have constrained the profile with two bottom corner points coincident with the edges of the surface.

By constraining the sketch to the exact location, we don't need to use Anchor Points. We can make the Swept Surface by just choosing the Profile sketch and the two Guide curves.

Clicking OK, we can see the resulting surface. If we zoom-in, we can see how the surface has twisted and stretched in order to sweep the surface with the two corner points following the Guide curves.

Due to space limitations, this will be continued on the next post.....

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#### MrCATIA

##### Super Moderator
continuting on.....

Example 2:

We could do the same Swept Surface a little easier if we use Anchor Points! I've drawn a new sketch of the profile, but this time I just drew it out in space with no relationship to the Guide curves. (If I had a Catalog of profiles, I could have easily copied the sketch from there)

This time, we can make the Swept Surface just like we did earlier, but we will choose the Two Points option, and we will select the two bottom vertex points in our sketch. Make sure the points are selected in order, with the first Anchor point aligning with the first Guide, and the second Anchor with the second Guide

Clicking OK, we get the Swept Surface. The same (or similar) to the first example, but this time with using the much simpler profile sketch.

Hopefully, this shows how Anchor Points can be used to position the profile relative to the Guides.

a final example will be in the next post.....

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#### MrCATIA

##### Super Moderator
Example 3: using Anchor Points with a Swept Surface

Now we want to add another gasket on the right side of the support. Instead of drawing another sketch just like the first one, we can just use the first sketch again!

Just like before, we can select our profile, and the two Guide Curves. To maintain the same dimensions as the profile, choose the option Point And Direction. The first Anchor Point will position the profile with the first Guide curve. Select a line in the Profile Sketch which will rotate the profile in the direction of the second Guide curve.

And here is our Swept Surface. Zoom-in to see that this surface twisted to follow the Guides, but it kept the same size.

If the surface is flipped around, the Anchor Direction is probably pointing the wrong way. To fix this, double-click on the surface to edit it. Choose the Position Profile option on the very bottom of the menu, and clide the option to invert the profile extremities.

I hope these little examples have helped you understand how to use Anchor Points.

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#### k.udhay

##### New member
Thank you, Mr. Catia. You truly deserve the name.

Doubt 1: When I pick anchor point (vertex 10 of sketch 6), where is it located in the guide curve. I mean it can be assumed by catia that the anchor point is at the beginning or middle of end of guide curve. How is this controlled?

Doubt 2: The sketch to be swept (sketch 6) is oriented with guide curve so that the anchoring edge becomes perpendicular to the guide curve. Is what I understand correct?

Thanks a ton!

#### MrCATIA

##### Super Moderator
Doubt 1: When I pick anchor point (vertex 10 of sketch 6), where is it located in the guide curve. I mean it can be assumed by catia that the anchor point is at the beginning or middle of end of guide curve. How is this controlled?
The Anchor point is calculated based on it's position to the Guide curve within the sketch plane. It will be swept from the beginning to the end to make the surface.

Doubt 2: The sketch to be swept (sketch 6) is oriented with guide curve so that the anchoring edge becomes perpendicular to the guide curve. Is what I understand correct?
Each section of the surface is oriented based on the spine.

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Thanks a lot!

#### trexhunter

##### New member
this thread is amazing. thank you MrCATIA!

for someone looking for hints on anchor direction(two guide curves-point& direction anchoring type) like me,
try catia documents again. the explanation of the document is horrible and made me confused. i think others will have same problem.

go the documents(Creating Swept Surfaces Using an Explicit Profile) and lookup for the part "If the profile is manually positioned..". you'll see the concept of anchor points more clear with this baseball field shaped profile.
for anchor direction, keep other configurations but choose straight edges of the shape as anchor direction. try other dirctions on ZY plane then you'll see how anchor direction works.

#### anurag.sethi

##### New member
Thanks , it really helped me a lot

Thnks mr catia..i will really appreciate you