Help with Transition & Directed Angle Constraints

[jeanchile]

Hello All,

I am trying to generate a quick "proof-of-concept" model for an idea I had to replace our current gravity hinges with something easier and cheaper to fabricate. It involves cutting a pipe so that is spins around a pin but because of the way the pipe is cut there is a positive stop in the closed position and you can open the hinge about 270 degrees.

In my mind, a simple transition constraint and a directed angle would provide me the motion I needed but I can't seem to get it to work. The hinge over rotates depending upon the angle value and I'm wondering if you kind people have some input on how I can accomplish this. This is what it looks like:

Any ideas? Thanks in advance for any help with this!

[Curtis_Waguespack]

Hi  jeanchile,

I didn't have the chance to look at your files, but I think you might find that using an Angle constraint with a Constraint Limit, will work better than the angle constraint and transition constraint.

http://www.cadalyst.com/cad/inventor/take-inventor-assembly-constraints-max-%E2%80%94-and-min-13626

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[jeanchile]

Thanks for the response Curtis (as always). I had already planned on using constraint limits to define the open angle of the hinge. What I am struggling with is how to get the top part of the hinge to follow the bottom part (i.e. how do I get the top part of the hinge to rotate and move vertically up) as it would have to do in the real world in order to rotate.

[cwhetten]

The transitional constraint is necessary to get the top half of the hinge to move up as it rotates.  But Curtis is right about the constraint limits.  You will want a combination of transitional constraint and an angle constraint with limits.

I tried this, and for some reason, limits aren't available for the directed angle type constraint (the limit options were all grayed out when I tried it).  Also, the Undirected Angle type constraint only allows limits from -180 to 180 degrees.

If you want angle limits from 0 to 270 degrees, you will have to use the Explicit Reference Vector type constraint.

It seems to work pretty well, although depending on how far you drag it, it can jump to invalid positions (like 360 degrees, since this also equals 0 degrees and doesn't violate the transitional constraint).  So, it's not perfect, but it might be enough for what you need.

I don't have version 2013, so I can't post a useful file for you.  But, hopefully this description will be of help.

Cameron Whetten
Inventor 2014

[jeanchile]

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@cwhetten wrote:

If you want angle limits from 0 to 270 degrees, you will have to use the Explicit Reference Vector type constraint.

It seems to work pretty well, although depending on how far you drag it, it can jump to invalid positions (like 360 degrees, since this also equals 0 degrees and doesn't violate the transitional constraint).  So, it's not perfect, but it might be enough for what you need.

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Thank you but this is exactly what I tried and was hoping for better results. If I'm not careful I can end up with transposed degrees, the hinge moving downward instead of upward, etc

I am specifically looking for some way to make this work exactly like it would in the "real world".

Thank you for the quick responses though!

[Curtis_Waguespack]

Hi  jeanchile,

I'm in the same boat as cwhetten concerning Inventor versions, and I'm not in front of Inventor at the moment, but can you use an angle constaint with a limit and a mate constraint between a vertex (green dot) and a face (red face), so that the vertex will translate along the face as the angle changes?

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[jeanchile]

Thanks Curtis, but there is either something I am missing or I'm not able to create a mate of that type. I cannot select the vertex, unless I create a work point on the part, and no matter what I do, I cannot select the helical face of the pipe. Got any other ideas I can try sir?

[jeanchile]

Anyone else have any ideas? It seems no matter what combination of constraints and contact sets I use I still can't get this to work as expected without the thing flipping around and/or getting stuck.

I get the feeling I am approaching this the wrong way.

[Curtis_Waguespack]

Hi jeanchile,

Can you post your IPTs as STEP files for me? I might be able to look at this later, but will be on an older system that only has an older version of Inventor installed at the moment.

Thanks,
Curtis
http://inventortrenches.blogspot.com

[jeanchile]

Wow! Thank you for doing this. What I am hoping to obtain when I am done is a fully working safety gate with this hinge articulating exactly as it should in the real world that I can present and show to others.

[Curtis_Waguespack]

Hi jeanchile,

I took a brief look at this, and was able to get a an acceptable solution by adding some fillets and driving the Angle Constraint. I think you might be able to add Constraint Limits to this, but I was looking at this in and old version of Inventor 2010 which does not have Constraint Limits. Attached are the files.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[GSE_Dan_A · Accepted solution]

I took a different approach.  With the post assembly in the downward position, the length of the assembly is 5 inches.  With the assembly in the fully open position (270 degrees), the assembly length is 5.9375in.  Therefore, I created two workplanes (1 5 inches from the bottom and 1 5.9375 inches from the bottom). I then mated the top face of the Upper Post to the 5 inch workplane and set a limit of Max = 0in Min = -0.9375in.  This allows the upper post to spin up until it reaches max height (angle between faces = 270 degrees).  I can attach parts or screen shots if you would like.

[jeanchile]

Thanks for your help with this Curtis. You spend a lot of time crafting your responses in order to help with people on this forum and it is awesome! We all appreciate it immensely and your presence here is a gift.

However... this was crap and didn't help me at all .

This proposed method, although a clever option I certainly hadn't thought of, still ends up with a solution where the hinge behaves erratically when you drag it around from open to closed.

That being said.....

[jeanchile]

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@GSE_Dan_A wrote:

I took a different approach......

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THIS was the out-of-the-box type of thing I was hoping for. I skipped making the extra work planes because I didn't need them (I just used the top and bottoms of the hinge pipes with the known offset dimensions) but using this method it works like a charm.

Very well done! Thank you.

[Curtis_Waguespack]

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@jeanchile wrote:

  ... this was crap and didn't help me at all .

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Indeed, I was relieved to see GSE_Dan_A's reply as well. 

[GSE_Dan_A]

And here I was thinking that my approach was strange!! Just happy to contribute back to the community!