Inventor 2018 Joint Tool- Losing Angular Limits inside the assembly

[Anonymous]

I have an issue with a Fanuc robot assembly inside Inventor. I've setup the model up using joints for constraining the limits of the robot arm, but I find that it keeps losing the angular limits that I've placed on the rotational joint. I then put the limits back in only to later find out that they are missing again. I've seen a post from 2014 with someone having the same issue and the consensus was that it's too difficult to solve and so what it does is delete the limits. 

Anyone else have this issue more recently, or perhaps have some workarounds for this? Perhaps another way to accomplish the same thing? I've attached a zip file of the robot assm if anyone would want to look at it. 

[johnsonshiue]

Hi Richard,

I took a quick look at the assembly. It seems  that there are duplicate constraints. The angular constraint and mate from J1~J6 seem to conflict with joints. If I suppress these constraints, the joints will work. Is it what you are seeing? One thing you may consider is to turn on "Protect" for the joints (right-click on the joints -> Protect).

Many thanks!

[Anonymous]

Those extra constraints are there for the purpose of setting up different positional reps(i.e., zero position, flexible, etc.), but I didn't waste the time because the rotational joint won't keep the limits. If you suppress those constraints and play around with the rotational joints, the limits will eventually disappear. You're the same person who replied to the last thread about this in 2014 so I assume it's the same and that no improvements have been made to keep the limits intact? I can get the joints to work with limits for a little bit, then they fault out and there is no further limiting. I right click, edit the joint and find that the numbers I entered are gone. 

[johnsonshiue]

Hi Richard,

Indeed, there is no change in behavior in terms of the limit joints in this particular case.

Many thanks!

[Anonymous]

My recommendation is to delete all your joints and redo them with Constraints. Constraints work so much better in Positional Reps.

[Anonymous]

Thanks Doug, I'll try that instead. I just attended some Inventor training and they stressed using joints instead of constraints heavily. It's unfortunate that the joint tool isn't as strong as the constraint tool. Thanks for the info.