Strange joint behaviour with active contact set...

[Anonymous]

I'm making a fairly simple model after a photo of a wooden original, and just to learn Fusion 360 I decided to try to implement the locking features in the cad model. The final two lock stages look like this:

With a finger nail, remove the locking wedge, allowing the lid to be moved (movement controlled by the Pin and Slot joint as well as a Contact Set rule including teh lid, the box and the wedge.)

The strange thing is, when the Contact Set rule is in force, every time I try to swing the lid away from the box, the pin moves back towards the "locked" position, making the lid catch on the "locking feature" to the right in the second picture... When the lid is perfectly centered, the pin has full range of motion along the slot. 

Supressing the Contact Slot rule makes the pin stray out of the slot when opening the box:

I'm sure it's a silly beginner's error, I only have a few hours of Fusion 360 experience, and a day or two of Inventor Fusion before that...

And: for those who wonder about what strange box this is, it's a straight razor box! It's a puzzle box, that was meant to (hopefully) be complicated enough to keep the sharp tool away from curious kids. There are a few more layers of interlocking bits and pieces, but I've not added them yet.

/John

[James.Youmatz · Accepted solution]

Hi @Anonymous,

Welcome to the Fusion 360 Community!

This is a really awesome design, I like it a lot! I think I found the issue with the contact sets. When I first got your file, I noticed that everything was locked in place. I think this had to do with the tab that was all the way up (as well as a combination of a few other things). My first step was to enable the design history. I do this so that I can create a snapshot in time of the position of the fully aligned box (you will notice in the screencast below I forget to do this at first and go back and do this after. It is denoted as an orange symbol in the timeline and are one of the two options that pop up in my ribbon when I move any piece, the other option being to revert back to the last snapshot). Once it is all aligned and set up, I demonstrate what the issue is. The pin and slot joint has its joint origin set up with the slot of the lid. This means when it rotates, it can rotate off center and causes contact (which I demonstrate at one point). I then delete the pin and slot joint (making sure the box is fully aligned) and create an as-built joint. I then select the rotation position to be with respect to the pin so that the pivot point does not move with the lid and then everything seems to operate as it should! Once I'm done demonstrating the animation, I then hit revert so all the pieces can go back together nicely (as you will now be unable to put the fingernail slider back into position by moving it with contact sets enabled). Check out the screencast below and let me know if you have any questions!

[Anonymous]

Thanks! The As Built joint is a new one to me, I will try it out! I'll watch the screencast and give you a shout if there is something that I can't get to work.

Regarding the design, the box was given to me by a carpenter back in my childhood (mid 70s! Am I really that hideously old?? ;D ).

As the box is very dried up and warped, I thought I might make a new one, material still undecided. 

Take care James, and once again thank you!

/John