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What should have been a simple assembly constraint...


HCb

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Hi, All, I'm back at trying to design a project in Inventor and I have a problem. I just started using 2015 and it's got the "new" Joint functionality which has caused me some trouble.

 

I built a homemade screen printing press 3+ years ago. I want to build a new one which is better. I thought I'd use Inventor to design it as I need to get better with Inventor and a project is good motivation to spend some screen time with it. I want a linkage setup which will allow the screen to rotate up and move back but not pivot the screen to 45 degrees or more. So, I'm trying to model some linkages which are not symmetrical.

 

I'm having problems limiting the rotation of the linkages I've drawn. I tried using Joint but it wants to make the faces of the parts mate. What I've done is to draw a base unit just to have a Grounded part. I put some ears on it to function as the anchor for pivot points on the lower linkages. I created a Work Plane centered between the two ears and one between the two linkages then Constrained them to one another to center the linkage assembly to the base. In real life, if I built this as it is shown, I would put a steel rod or all-thread through the ears and linkages. I tried a Joint there but, like I mentioned, it tries to make the faces touch which I don't want and which violates the centering done via the Work Planes and throws an error. I could do a Gap between the faces but I don't want that because 1) I can't Measure it and 2) it's not very dynamic in case I change some other dimensions. I could not create a Joint from the hole's center to an Axis between the ears on the base.

 

I thought Joint, with it's Angular Limits might be nice but no joy. So, I moved to Constraints. I tried Angle on the Assembly tab of Constraints then I tried both the Directed and Undirected angles. Directed might work except that it doesn't allow Minimum and Maximum. Undirected allows the Minimum and Maximum but when I set the Minimum to 0 degrees and the Maximum to 30 degrees (between the lower linkage top face and the base piece's top face) I can move the linkage from +30 degrees to -30 degrees. ??? I've played with it for over an hour, trying different things, searching online, and reading through my 2012 Mastering book by Curtis Waguespack and I'm just not getting this solved. I'm sure it's me and it's probably some basically stupid thing I'm doing.

 

Can someone please point me in the right direction?

 

Thank you.

 

--HC

 

LinkageTest.zip

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  • 1 month later...

I don't know if this is what you are trying to accomplish, but if you right click on your Rotational:2 constraint select Drive, set the start and end to whatever your needs are, for example Start -135° End -90°. That is how I've always managed rotational limits and gives you something to use during the animation environment for videos. You can also simply edit this joint and under the limits tab these amounts will limit your movement in the assembly view.

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