topic Re: Questions on angle constraints and driven dimensions in Inventor Forum

Questions on angle constraints and driven dimensions

Anonymous — Fri, 03 Feb 2017 10:23:16 GMT

My journey from being a Creo user to becoming accustomed to Inventor continues.

Today I'm trying to figure out how to define dimensions in a sophisticated and rational way. At first I was thinking I should go for a Geneva mechanism (see link for description of the geometry), but that might be a bit too large of a piece to swallow, so I'm starting off with making a nice pentagon (see below).

What I have here are five lines that are joined at their ends. Together they form a pentagon. However, the angles between the lines are uneven, which isn't very nice. I wish the angles to be equal to each other, so that my pentagon is nice and symmetric. The angles have the names d0-d4, where d0 is at about 2 o' clock in the screenshot and d4 is at 12 o' clock. The angle value of D4 is within parantheses, because it must be a driven value since the angles must add up to 360 degrees.

How do I make all angles equal to each other?

(making the lengths of the lines equal would make a nice pentagon, but that would be cheating)

If I would have been using creo, I would just have taken the "equal" constraint and clicked the angles in a random order and they'd eventuall all end up at 72 108 degrees. For some reason, this is not how things are done in Inventor.

Questions:

1) Is there a simple way to click my way to constraining the angles so that they are equal to each other?

2) Is there some way to just write a rule that d0=d1=d2=d3=d4 ?

Thank you

Re: Questions on angle constraints and driven dimensions

Rob67ert — Fri, 03 Feb 2017 10:15:59 GMT

Hi,
if you add the second angle dimension, you can point it (by click on the dimension) to the first one to be the same.

Re: Questions on angle constraints and driven dimensions

Anonymous — Fri, 03 Feb 2017 10:29:51 GMT

Very nice! Thank you!

I'm still curious about if there is any way to write d0=d1=d2=d3.

Re: Questions on angle constraints and driven dimensions

Rob67ert — Fri, 03 Feb 2017 10:37:51 GMT

That could be done with iLogic.
Add a rule and type:

d0=d1=d2=d3

InventorVb.DocumentUpdate()

Save rule and run it.

Re: Questions on angle constraints and driven dimensions

Anonymous — Fri, 03 Feb 2017 10:53:49 GMT

Well... I first wrote just d0=d1=d2=d3=d4 and hit update up in the left corner. This made all the angles change, but in a way that makes no sense at all to me. I then included your second line "InventorVb.DocumentUpdate()", right clicked the rule and clicked "Run Rule". That didn't change anything and I can't click update.

What am I doing wrong?

Re: Questions on angle constraints and driven dimensions

Rob67ert — Fri, 03 Feb 2017 11:06:43 GMT

My mistake 🙂
make is d4=d3=d2=d1=d0
Now the look at d0
If you use d0=d1 you will give d0 the value of d1

Re: Questions on angle constraints and driven dimensions

Anonymous — Fri, 03 Feb 2017 12:04:52 GMT

I could not make it work, with the method you describe. What eventually worked for me was doing it like this.

The angles are named d2,d3,d4,d5,d6. The rule is

d3=d2
d4=d2
d5=d2
d6=d2

Then I set d2 to 108 degrees.

HOWEVER, it would be more impressive if Inventor would understand by itself that, if all the angles are equal, then 108 is the only solution. Either I'm doing it wrong, or Inventor does not do this. Luckily, this is just a theoretical exercise, since I am fully capable of calculating the angles by myself :).

Any further input would be appreciated.

Re: Questions on angle constraints and driven dimensions

YannickEnrico — Fri, 03 Feb 2017 12:06:10 GMT

You can also use the EQUAL constraint on all five lines and make do with one reference and two others - Just point the two others to the reference 🙂

Re: Questions on angle constraints and driven dimensions

Rob67ert — Fri, 03 Feb 2017 12:07:29 GMT

In this case you can also draw a polygon 🙂

Re: Questions on angle constraints and driven dimensions

TheCADWhisperer — Fri, 03 Feb 2017 12:41:14 GMT

@Anonymous wrote:

My journey from being a Creo user to becoming accustomed to Inventor continues.

Coming from Creo, you might not be aware of ....

or if you are used to more clicks per operation....