Parametric Polygon

[Anonymous]

I am unable to define the number of sides of a polygon as a parameter.

I have created a parameter called "NumberOfSides" and changed it's units to 'ul' and have given it 10 as the value.

While creating the polygon, I am able to invoke the parameter from the list parameters drop down list.

But when I go into the parameters list and change the number, the polygon isn't updating itself.

I am able to parametrically change the dimensions of the polygon but not the number of sides of the polygon.

Any advice anyone??

[CCarreiras]

HI!

Place here the part...

[JDMather]

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@Anonymous wrote:

I am able to parametrically change the dimensions of the polygon but not the number of sides of the polygon.

Any advice anyone??

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What you are attempting is essentially a sketch pattern.

It is almost always preferable to do a feature or body pattern rather than a sketch pattern as this technique will reliably and predictably update with changes of parameter.

Model a "pie piece" feature and pattern it instead of sketch.

What version of Inventor are you using?  I can Attach an example if you can't figure it out.

[johnsonshiue]

Hi! Indeed, like JD and Carlos mentioned here, Inventor 2D Sketch does not have a command creating parameter-driven polygon. Changing number of sides changes topology of the profile, which can lead to downstream feature failures, since the downstream features may not know how to deal with the added sides.

Do you mind sharing a use case that you need to change number of sides of a polygon?

Many thanks!

[Anonymous]

@johnsonshiue: I was actually just fooling around in inventor trying to create octagonal spectacle frames like the ones a villain in an old james bond movie uses. I tried to change the parameter 'no of sides' to see how to look would change.

It isn't important but I would surely like to know how to accomplish that.

@JDMather:

I am using Inventor 2018 and I am not using sketch pattern. I am using polygon. I have had some previous experiences with coincident constraints missing while using sketch pattern and sketch mirror options and since then, I have learnt my lesson and rarely use them.

In case I have to, i draw whatever I need on a sketch plane, offset that plane by 0 mm and create a new sketch on the new plane and project the previous sketch geometry onto the new sketch. No more open loop nonsense.

I tried using a parameter "n" and creating a pie piece and doing it. It works but it seems to be quite a bit of a faff really! Create a pie piece(do the necessary pen and paper work first), circular pattern it, combine the pieces into 1 solid body.

I really think missing the option to keep polygon sides as a parameter/dimension is an oversight.

@johnsonshiue Since you are an Autodesk Corp. member, please see if you can fix this issue in future releases.

Coz I can think of many areas where changing number of polygon sides to make models auto update would be useful(wheel hub design, hexagonal/octagonal mesh design, knob design, anything where you wanna see how changing the number of sides affects the look of the model.).

[SBix26]

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@Anonymous wrote:

Create a pie piece(do the necessary pen and paper work first), circular pattern it, combine the pieces into 1 solid body.

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No pen and paper work necessary, no combining pieces necessary!  Let Inventor do the calculations for you (= 360° / n); patterning a feature merges into an existing solid body unless you deliberately specify otherwise.  See attached for an example using a slightly different shape (Inventor 2018 format).

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Sam B
Inventor Pro 2019.3 | Windows 7 SP1
LinkedIn

[johnsonshiue]

Hi! I agree with you that it will be great to have the ability as are many other great ideas on Inventor Ideas forum. It all comes down to the use case and its frequency.

Certainly, it will be a powerful workflow to change the sides of polygon by a parameter. However, you have to keep in mind that a polygon is not just a bunch of lines. These lines may have constraint and dimensional relationship with other lines. The faces created by the polygon may have other features. Unless the polygon sketch is standalone by itself, changing number of sides will lead to failures. This is why it is not that common to change the side of polygon.

JD's feature patterning suggestion is correct. It is because by patterning the features, it take into account the downstream features, not just the polygon sketch itself.

I am not a developer so I cannot give you a precise estimate of how much efforts are required to fulfill the request. I personally do not believe it would be a big project. However, it is not the most frequently used workflow in my opinion.

Many thanks!

[JDMather]

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@Anonymous wrote:

@JDMather:

I am using Inventor 2018 and I am not using sketch pattern. I am using polygon. ...

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I wrote, "...essentially a sketch pattern."  Obviously an experienced user should understand that you are using the polygon sketch tool - you even showed a screen capture image.  When you change the number of sides of a polygon - what are you doing?  Essentially you are changing a pattern.