topic Re: Inventor Studio - Animate Constraint problem with multiple subAssemblies in Inventor Forum

Inventor Studio - Animate Constraint problem with multiple subAssemblies

jim — Tue, 09 Apr 2019 16:35:49 GMT

I have an assembly which has two piston subassemblies in it. These are both the same .asm. In the top assembly, I want to first actuate one piston and then the other. Each piston has a rod, sleeve mate which controls how far the piston is extended and limits the stroke.

If I attempt to animate Insert1 on the second piston, I get an error saying that the constraint is used and the previous track must be deleted.

I have attached a zip with some sample parts in it. This is a simplified model since the pistons are missing their clevis and trunion mounts (this adds hinge points and makes providing external constraints difficult - basically they have to be driven by the rod/sleeve insert); but they exhibit the same problem. My Autodesk reseller tech support has not been able to find a solution to the problem. It seems like it shouldn't be an issue since the constraints are obviously not the same. I am using Inventor 2018.

Screencast - https://autode.sk/2D7NjNW

Jim

Re: Inventor Studio - Animate Constraint problem with multiple subAssemblies

Lewis.Young — Wed, 10 Apr 2019 09:26:00 GMT

Hello,

Sadly I'm on Inv 2017 so i can't open the files, however i have two possible workarounds.

1. In the sub-assembly (PistonAssy), set the insert contraint to have minimum and maximum limits (The stroke distance you want it to travel in the animation, eg. 0mm to 100mm). The piston should now move freely within a range.

Now go back into the main assembly, right click each of the sub-assemblies and make them "Flexible". Now you can constrain a face on each piston individually from within the main assembly, allowing you to animate each constraint without affecting the other.

2. The second option is to take the moving parts out of the sub assembly and bring them into the main assembly, so you have two separate sets of components. Then you can constrain them individually.

Let me know how you get on. If i'm not explaining myself properly i'd be happy to make a screencast.

Lewis Young
Windows 7 x64 - 32GB Ram
Intel Xeon E5-1620 v2 @ 3.70GHz
nVidia Quadro M2000 - 4GB
Inventor Professional 2017.3
Vault Basic 2017
3ds Max 2018

Re: Inventor Studio - Animate Constraint problem with multiple subAssemblies

jim — Wed, 17 Apr 2019 14:39:03 GMT

Hi Lewis, If I make the assemblies flexible, the constraints can't be within the sub-assembly - they would have to be sub-assembly to main assembly, correct? This might work, the complication is that in the actual model the piston is linked by joints to other components so the parts that cause the motion don't stay in line with anything in the main assembly. ( the piston tips as it retracts, so the only "accurate" constraint is between the piston and piston sleeve of the sum assembly) I seem to be getting that this is a "bug" with Studio since it can't tell the difference between constraints with the same name in different parts. Jim

Re: Inventor Studio - Animate Constraint problem with multiple subAssemblies

swalton — Wed, 17 Apr 2019 15:01:37 GMT

I am following this a bit late.

As I understand it:

Your hydraulic cylinder sub assembly had a constraint that controls the stroke length
Your parent assembly has 2 or more instances of that cylinder.
You want each instance to be animated, but with a different stroke length.

Is that correct?

If so, using the flexible option is a good choice. Without using it, Inventor will make each cylinder the same length.

I usually make 3 position reps in a hydraulic cylinder:

Fully Retracted

Fully Extended

Flexible, where the stroke length constraint is free to vary between the retracted and extended length, similar to @Lewis.Young suggestion.

When I place that cylinder in an assembly, I select one of the 3 position reps, based on my design need. Most often, I use some set of upper level assembly constraints to locate the component that is moved by the cylinder. In that case, I select the Flexible position rep in each cylinder, and then set each on to Flexible with the right mouse button menu. Done correctly, this allows me to move the driven components in the upper level assembly without worrying about the constraints in each hydraulic cylinder.

Re: Inventor Studio - Animate Constraint problem with multiple subAssemblies

jim — Wed, 17 Apr 2019 17:20:11 GMT

I created 3 Position representations. Retracted, Extended, and Flexible (plus Master)

In retracted and extended I overrode the PistonDistance Constraint with the max and min values.

If I make the piston subAssembly flexible, Then selecting either Retracted or Extended doesn't move the piston. If I don't make the subAssembly flexible the model blows up because the rod and clevis joints on the piston can't move.

Do I now need to make demote the piston to its own subassembly leaving the rod and clevis joints flexible in the top assembly. Then if I want to use the "Retracted" "Extended" positions - I need to remove the flexibility from the piston and select one of those positions? Why does it seem like if the subAssembly is flexible, the position location representations aren't acted on? Do I need separate actual constraints for the set positions instead of just changing the value?

Re: Inventor Studio - Animate Constraint problem with multiple subAssemblies

johnsonshiue — Wed, 17 Apr 2019 22:37:38 GMT

Hi! Please share an example here so forum experts can take a look.

Many thanks!