Pattern features + pattern on closed path?

[t_tackenbergS9X6F]

Hi! Hoping someone can help me with this problem I am experiencing (f3d file attached). I have created an elliptical tray, with a single rib in it. The rib was made using an extrude and a fillet. I'd like to pattern the rib, going around the tray. My thought was to do a pattern on path, using the outside edge of the tray (or the ellipse in the initial sketch) as the path. When I select either one of the features for the pattern, it works:

As soon as I add the second feature to the selection, things go awry and it tries to pattern the whole body:

I've had some better result when making the rib as a separate body and patterning that, but it seems to me this should work with a feature pattern as well? I have the same problem when selecting rectangular or circular pattern...

Secondary question: Is there a way to pattern the rib all the way around the path and neatly divide the steps (like in circular pattern)? I've had some "success" by using the measure option in the length field, but somehow always need to set the quantity to N+1 and will result in a duplicate body at the start position. It also seems to differ which path I am selecting if this will work. 

I guess my question comes down to: What is the best way to pattern this rib around my tray? Any help is appreciated!

 

[kacper.suchomski · Accepted solution]

Hi

I can easily prepare it using the face pattern.

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@t_tackenbergS9X6F wrote:

Secondary question: Is there a way to pattern the rib all the way around the path and neatly divide the steps (like in circular pattern)? I've had some "success" by using the measure option in the length field, but somehow always need to set the quantity to N+1 and will result in a duplicate body at the start position. It also seems to differ which path I am selecting if this will work. 

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This is very logical behavior. A path has a beginning and an end. A loop is a special case, but all the rules and behaviors still apply.
Therefore, if you set the full length of a loop, you'll get two occurrences - at the beginning and end of the loop.

The solution is simple math.
You try to measure the loop and multiply the result by (n-1)/n.
You can do this using absolute values ​​or by parameterizing it to automatically change the spacing value when the number of occurrences changes.

[t_tackenbergS9X6F]

Amazing, thank you so much for your help! I think I was getting too bogged down in trying to find a feature to click, to just think of solving it with some math...

Do you have any idea why the feature pattern doesn't work? Face pattern is good alternative, but I am just trying to understand when to use which.

[kacper.suchomski]

This is an unusual situation because two factors have converged.

1. The face of the copied element is also the face of the fixed element.
2. Furthermore, repeating fillets in a pattern is almost always a bad idea.

[t_tackenbergS9X6F]

Oh I just noticed, when doing the pattern with faces, you also don't have the problem of creating the extra body. So you can set it to extent, use measure and just accept to use N+1 for the quantity and get the desired result (less elegant, but it works).

I'm running into the next question now; can we make the measured length a parameter? So that the pattern will still function correctly when we change the size of the tray? Or if change the shape to round?

[g-andresen]

Hi,

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@t_tackenbergS9X6F  schrieb:

… can we make the measured length a parameter?

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No, loop lenght is measured and inserted using copy & paste.

As far as I know, the circumferences of ellipses can only be calculated approximately, depending on their shape (elongated or more rounded).

Try searching for the Ramanujan approximation.

Günther

[kacper.suchomski]

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@t_tackenbergS9X6F wrote:

Oh I just noticed, when doing the pattern with faces, you also don't have the problem of creating the extra body. So you can set it to extent, use measure and just accept to use N+1 for the quantity and get the desired result (less elegant, but it works).

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This isn't a problem in any scenario, because in the end you still need to use the Combine command to combine all the bodies in the component, so the target geometry will match no matter how many bodies or faces you end up with during the process.

[t_tackenbergS9X6F]

I ran into another problem with this same part: i have changed the dimensions of the first sketch, so the ellips is now a circle. When I try to adjust  the settings for the pattern on path, the measure tool now returns the diameter, instead of the arc length. I think I should be able to multiply by Pi to get the circumference, but when I type this, I don't get a result (see screenshot, f3d also attached). Is there a way to get the circumference from the measure tool? Does anyone know why multiplying with Pi doesn't work?

 N.B. I just noticed I can make it work by using spacing instead of extent and using the formula ( d * PI ) / N. But still wondering why it will not work when using the extent and d * PI...