I didn’t realise until today that you can’t flip a work plane’s normal in an Inventor Assembly. So using a single parameter to drive a mate constraint simultaneously, on multiple parts can prove problematic. We’ve recently been designing a rotary dining table, by turning the whole table the table sections slide out opening up a gap between them to insert another leaf. We wanted to animate that movement so we could check it worked and behaved desirably prior to commencing production.As it happens we’ve struggled in a number of ways to get Inventor to play ball with the constraints and even found some odd bugs along the way. However, I found quite a nice way to overcome this particular issue in Inventor today and thought it would make a cool blog post.
When you create work planes in a part to create sketches or help model features, you can right click on it and flip the normal. Well you can’t with a work plane created in an Assembly, which frustrated me for a few minutes today. At first I thought about creating the work planes in the parts themselves which wouldn’t have worked, then I thought about creating an empty reference part containing back to back, mirrored work planes. However, the 2nd option was a tab messy.
Listening in Maths lessons help!
I started to think about how I could link some parameters together to inverse the value but maintain a relationship so they could be driven simultaneously in the kinematic simulation. Then I remembered something, I didn’t have to create a new formula based user parameter. I could use exactly the same one when creating the constraint, but multiply it by negative one to invert the parameter just for constraints i needed.
If you use the drive constraint tool in Inventor, it will only drive a single constraint at a time and it doesn’t modify the parameter value. So instead I took advantage of Inventor iLogic forms. They’re so simple to use! If you haven’t checked them out yet, you really should. Drag & Drop parameters, layouts and controls then if you need to tie some of those controls to iLogic rules all in a matter of minutes. Ideal I say.
In our case we were using a few transitional constraints which were quite tricky to drag around with a mouse, using an iLogic form slider bar made sure the components moved in the direction they should.