topic Re: Learning how to apply rotational pivots and linking objects to move with the pivot points in Fusion Design, Validate & Document Forum

Learning how to apply rotational pivots and linking objects to move with the pivot points

tomHKD9J — Fri, 09 Jul 2021 08:56:45 GMT

Hello @jhackney1972 ,

I am working on my project and am having trouble adding parts with rotational pivots. I am including the file and hopefully you can see what I am trying to accomplish. It is far from done however I am hoping I can link the objects so I can simulate and study what it is doing and then make adjustments to get the desired results. I have watched several videos, including the one you did with the timing gears, pertaining to motion and pivots and they are not translating to what I am trying to accomplish completely, I am definitely missing something. Any help would be greatly appreciated.

Thank ups ion advance,

-Tom

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

davebYYPCU — Fri, 09 Jul 2021 10:59:00 GMT

Your last joint brings the assembly to an alignment lock, the way you have set it up at the moment.

Removing the joint limit here (circled) removes the lock so that the joint can and does complete,

but

If you want to have any further movement (I believe you do)

This is now all locked up and can't move with these 4 Revolve Joints, changing any one to Cylindrical will fix it, because this one is the one out of alignment.

Might help....

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

tomHKD9J — Fri, 09 Jul 2021 11:27:29 GMT

I am working on making it a parallelogram and will report back.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

davebYYPCU — Fri, 09 Jul 2021 11:36:40 GMT

Nah, the parallelogram thing was first thoughts, not required, but if you wish.

I can not find how this elbow got misaligned, it's pair is ok, and all is in alignment in itself.

Insert with mouse slippage or Capture position before the Joint? (deleted after the joint) are a possibility, but it should not have any influence, especially as it's pair is exactly right.

Might help....

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

tomHKD9J — Fri, 09 Jul 2021 12:49:32 GMT

I have set everything up as a parallelogram and moved the heights to where they are needed but it is still not connecting the control linkage. It keeps giving me an error for joint conflict and I am completely lost as to what it is referencing. It is getting closer though.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

jhackney1972 — Fri, 09 Jul 2021 14:31:35 GMT

@davebYYPCU has already mentioned the error and how to compensate for it. It does not matter which revolve joint you decide to apply it to, normal, but since you have a 0.0005" misalignment stack up error, one of the revolve joints must be replaced with a Cylindrical joint. Cylindrical joint, of course, had a linear degree of freedom that takes care of the misalignment. I would make it a habit in all 4 linkage models to make one joint a Cylindrical joint. Model is attached.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

TheCADWhisperer — Fri, 09 Jul 2021 14:33:05 GMT

First thing I notice is undefined sketches.

Then I start doing some measurements and find discrepancies.

I would expect to find multiple issues if I dug deeper due to undefined sketches.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

tomHKD9J — Fri, 09 Jul 2021 14:59:37 GMT

Can you elaborate on undefined? What I am not understanding is both of those components are the same part pulled from a single drawing, one is a copy of the other. It looks like I must have missed a step in doing something that would make them defined?

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

TheCADWhisperer — Fri, 09 Jul 2021 16:05:49 GMT

@tomHKD9J wrote:
It looks like I must have missed a step in doing something that would make them defined?

Forget everything else - this all goes back to the very foundation of your design - Sketch1.

Blue lines and white dots should keep you awake at nights.

You want black geometry (depending on your color scheme).

Watch this video on constraining sketches...

https://youtu.be/lS6PranD8Js

Examine the Attached file.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

tomHKD9J — Fri, 09 Jul 2021 15:26:52 GMT

Thank you once again. The cylindrical joint makes sense. I am still trying to figure out how the misalignment happened and looking at it it is really small however most of the components were created from the same drawing. I know we are talking .0004 of an inch but one part of is thinking this shouldn't happen at all but somehow it is. I will try to figure out where I made the mistake but once again, thank you for showing me the tools.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

tomHKD9J — Fri, 09 Jul 2021 15:52:07 GMT

Thank you! You couldn't have said a more truer statement as for as it keeping me up at night. 2 in a row in fact and somehow I missed the blue lines. Being this is a self learning thing, it is a crucial step I know I have heard but somehow have overlooked it. Thank you again for taking the time. I will go back and revisit things and in the future make sure the I am seeing a lot more of the black lines.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

TheCADWhisperer — Fri, 09 Jul 2021 16:09:47 GMT

When you are fully defining your sketches - use some logic based on assembly or manufacturing considerations. Don’t just keep slapping on dimensions till it turns black.

You want predictable behavior when (notice I didn’t say “if”) you make edits.

Re: Learning how to apply rotational pivots and linking objects to move with the pivot points

tomHKD9J — Fri, 09 Jul 2021 16:14:59 GMT

I have no idea how I missed your channel and videos. Thank you again for the information. I am going to go back through and redo this model using the techniques you showed so I can become more fluent. Constraints were troublesome to me because I would continually get warnings of a drawing being over constrained so I somehow thought they were not good. I still have much to learn.