PLEASE HELP WITH A JOINT VERSUS A CONSTRAINT QUESTION

[Anonymous]

i'm tearing my hair out. can you please tell me where i can go to find out how to use the constraint or joint commands to have several bodies rotate or revolve around a steel pin. Think of wooden slats lain side by side, then a pin driven through the ends, from left to right, like several hinges side by side in a row, but connected with a single pin. I want all the slats to be separately modeled, but I want all of them to move at one time. When I string the slats together with the pin, then constrain the top faces to join them together, the entire assembly moves, including the pin, and what I want is for the slats alone to move up or down, and the pin to be stationary. If i do no constrains, the slats move independently, but the second i put any kind of constrain on them to cause them all to move at the same time, the entire assembly moves. not just the slats. you probably don't answer specific questions about software usage, but can you PLEASE send somewhere to find this answer? I spent two hours yesterday trying to do this

[jtylerbc · Accepted solution]

Of course, since you didn't post files (or pictures), we're all going to be guessing a bit here.  But here is what I think is going on, based just on your written description.

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@Anonymous wrote:

When I string the slats together with the pin, then constrain the top faces to join them together, the entire assembly moves, including the pin, and what I want is for the slats alone to move up or down, and the pin to be stationary.

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It sounds as though the constraints you are putting between the components are probably reasonable, but you haven't actually defined the pin (or anything else) as stationary yet.  Once you have the pin's location defined, then the whole system will start to behave more like what you want, instead of just dragging around together.  Ground the pin, or constrain it to the assembly origin. 

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@Anonymous wrote:

you probably don't answer specific questions about software usage, but can you PLEASE send somewhere to find this answer? I spent two hours yesterday trying to do this

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Although Autodesk employees do post here, this is mainly a forum of users helping each other out.  So answering specific questions about usage is exactly what we do here.  You're in the right place.

[johnsonshiue]

Hi Dennis,

Inventor Assembly Constraints and Joints are similar. Joints are like combo constraints. They help you reduce DOF much more quickly than constraints, since constraints offer DOF reduction on a more atomic basis.

Another major difference between Constraints and Joints is the ability to accept construction geometry. Joints only allow you to pick body geometry, while Constraints allow you to pick pretty much any kind of geometry (sketch, work geometry, body geometry and so on).

Lastly, you can automate constraining process using iMate to certain degree. But, Joints are pretty much manual only.

Please share the Inventor files. Forum experts can take a look and help provide further guidance.

Many thanks!

[Anonymous]

I am familiar with the differences.  I had a specific problem that I needed resolved....How to perform the task I related in my question?

[johnsonshiue]

Hi! Please share the files here or send them (zipped) directly to me. It is very hard to understand the issue without seeing the files.

Many thanks!

[rhasell]

Without any images or files, I am guessing you are missing at least one Grounded component.

[TheCADWhisperer]

Are you a student?

Is this a school assignment?

Can you Attach image.  Yes? No?

Can you Attach Inventor assembly? Yes? No?

[Anonymous]

you were absolutely right.  it was as easy as grounding the pin.  you have no idea how grateful i am to you.  part of the problem of learning things on your own -- and not having the patience to sit through endless hours of classes lol -- is holes in the learning process.  thank you so much for your answer.  as for posting photos and inventor files, this is my first time posting on this site, and my first time being here, this problem being the reason...lol...so i didnt know about posting photos or inventor files or how it was done.  as a hobby i fool around with inventor, mostly while designing furniture.  lately i have been designing futons, and i had been designing one that folded out like a fold out couch.  the slats for the seat are arranged so that when you unfold them outward, the backrest of the futon becomes the feet of the bottom of the bed.  like opening a book, the futon opens, and every other slat on the seat lifts up and unfolds from the seat, with the posts at the head of the futon becoming the feet.  i am not sure if it is a unique idea, but i have never seen it.  i'll be glad to share it with you when i am finished with it...Dennis