Dynamic Simulation Joint Preview meaning- and how to get it

[sschneiderXHH8R]

Hi.  I have an assembly comprised of smooth vertical tracks, ground, a lifting frame and a roughly rectangular component to be lifted by the lifting frame.

The dynamic simulation joints are working about half the time.  In the joints that work correctly, I get a "preview origin" when I hover over the joint in the browser.  I have attached a snip of what I'm seeing.

I've tried reordering the components within the Joint command (switching component 1 and 2), contact sets on/off and choosing different faces on the components that may engage with the other.

Thanks in advance.

[JDMather]

I don't understand the question.

What version of Inventor are you using?

Can you Attach your assembly here?

[sschneiderXHH8R]

Hi!

I am running Inventor 2018. The issue is within the Dynamic Simulation
environment; the two parts (connected by a revolution mate within this
assembly) are supposed to engage with the posts on either side of the
Stoplog Lower Tier. Instead, they pass through and interact with the
Ground.

As far as I can recall and tell from the browser, the joints were made in
the same manner. The 3D contact joints involving the Ground display this
"preview origin" when I hover over them in the browser-
[image: image.png]
-that leads me to believe that the joints were constructed differently. In
case it matters, the Stoplog Lower Tier was drawn in AutoCAD 3D, then
exported into a single part with a single body solid.

Thanks,
Steve Schneider

[JDMather]

Based on your image I would use a 2D Contact Joint rather than a 3D Contact Joint.

[sschneiderXHH8R]

I'd tried that earlier- I assumed that for simplicity's sake we could assume the Pick Frame slid perfectly aligned with the center YZ plane.

The joints appeared to apply just fine, but when I hit play on the simulation player I got the message "Contact is no longer in XZ plane of the parent frame of joint '2D Contact:3 (Hook assy;1, Stoplog Lower Tier:1)'".

[JDMather]

---

@sschneiderXHH8R wrote:

"Contact is no longer in XZ plane of the parent frame of joint '2D Contact:3 (Hook assy;1, Stoplog Lower Tier:1)'".

---

Sounds like an easy problem to fix.

[sschneiderXHH8R]

I'd love to hear what that solution is. Judging by the 2D Contact
animation, the joint is intended for parts that are in constant contact and
all contact is within a single plane. This assembly essentially has
contact in only the one plane, but two mobile parts (Hook assy and Pick
frame) start off separate from the Grounded part and make contact during
the simulation.

The 2D Contact tool doesn't require the definition of any planes. I'd like
some graphical representation of what the error is describing so I am able
to fix it, something similar to Sketch Doctor.

I have tried adding spatial joints between both mobile parts and the
grounded part, and the result was the same.

Thanks,
Steve

[JDMather]

You have not provided any actionable information - not even a screen capture of the existing Joints browser.

I frequently (almost always, hmmm probably always?) use 2D contact for components that are not in constant contact (to detect and end of DoF between components).

[JDMather]

---

@sschneiderXHH8R wrote:
...I have tried adding spatial joints between both mobile parts a....

---

A mobile part does not need a Spatial Joint - it already had DoF mobility.

A spatial joint adds 6 DoF - in other words unrestricted freedom to move anywhere in space until (defined) contact.

Bouncing ball or projectile are good examples.

[sschneiderXHH8R]

I'd attached the assembly and each of the part files to the reply of message 3 in this thread, but apparently they did not go through.  I will try again, and also include a snip of the current status of the simulation, including the contact points.  The software knows that the two parts involved in the joint are interacting- it's simply not acting on it.

[sschneiderXHH8R]

More parts

[JDMather]

Whenever Attaching files you should verify that they did in fact get attached.

You cannot attach files by email reply - must use the web forum.

The easiest way to attach an assembly (with all parts) is to go to Files>Save As>Pack and Go from the top level assembly and this collects all files into a folder. Select the option to zip the folder or check that all is in the folder and then right click and select Send to Compressed (zipped) Folder. Attach the resulting *.zip file here.

[sschneiderXHH8R]

Assembly PackNGo compressed zip file attached.  Adding that to my list of Inventor skills...

[JDMather]

Why is Stoplog Lower Tier grounded?

Isn't the Design Intent to pick it up with the Hook assy?

(We can make the hooks go down and latch on with that grounded, but seems to me that logically you want to pick it up.)

[sschneiderXHH8R]

While this is my first project involving Dynamic Simulation, it's not my first crack at this.  In the "real" assembly, that's exactly what I am trying to do.  In this "baby step" assembly, I'm just trying to get the parts to all play nice together.  There are additional components like a rod between the protrusion in the center of the shaft and the small bracket near the center of the frame that is used to manipulate the hook assembly.  Its relationship is tricky, as it behaves similar a piston with no pivot in a slot instead of a hole.  I haven't tried the Jack Joint, but that's the closest thing I would compare it to.

[JDMather]

Have fun (see Attached).

I would have liked to give better description of steps - but I have to get other work completed.

[sschneiderXHH8R]

Holy cow.

Thanks for your interest and your help!  I'll unpack everything you've done and see if I can recreate it!

Steve

[JDMather]

I walked away from the problem for a few minutes and realized my mistake.

I had set to instantaneous motion on picking up the load and Inventor returned error.

I set a fudge to overcome this error.

In the Rev1 attached I set a smooth Harmonic motion and now I don't need the fudge.

[sschneiderXHH8R]

Thanks for your help with this- I just have a few quick questions.

1- How did you impart motion to the assembly?  I had thought there would be an External Load applied, 0 at first so gravity could pull the frame down, then positive (Y) in excess of the weight of the frame and stoplog once the hooks engaged.  I don't see anything in the browser, and I think I've been through all the subtabs in the Dynamic Simulation environment.

2- I noticed that the Stoplog's home position was .1" above the ground.  I set it to 0 and the simulation ran fine.  Was there a reason it was set to .1"?

3- The contacts that I'd had in the assembly when I sent it to you were not, as far as I can tell, significantly different from the ones you sent back.  The origins of your 2D contacts look "clean" in that there appears to be agreement in their right-hand-rules, if such a thing matters.  But if it does matter, I don't see any method of tweaking the origins of the 2D Contacts.

[JDMather]

Fifteen weeks of classroom instruction in 20 minutes - turn on your sound.

Oops, wait a bit for the video to compile and I will be back...