topic Re: Assembly constraints in Fusion Design, Validate & Document Forum

Assembly constraints

ashinbrot — Tue, 08 Apr 2025 18:49:29 GMT

I'm trying to wrap my head around the way Fusion can be used to create assemblies. I get that everything (at least planar and cylindrical, which are the vast majority of what I need) depend upon snaps. Snaps are a little inconvenient in that you need mating points or corners or some detail like that (which means datum planes are useless for assemblies, don't get me started) but my specific question is this: Why when setting up a cylindrical constraint am I offered the option of rotating my component but that rotation doesn't mean anything; that is, after the constraint is applied the component is not locked to the selected rotation angle? Makes no sense to me to offer me a constraint that isn't worth anything after it is applied.

Re: Assembly constraints

jhackney1972 — Tue, 08 Apr 2025 19:21:08 GMT

The ability to adjust the "initial" position of the two Joint components is available for all Joint types not just Cylindrical. Plus it is very possible that you may want to adjust the initial relationship of your two components WITHOUT having to set a Joint Limits or Drive Joint into the desired position.

Re: Assembly constraints

ashinbrot — Tue, 08 Apr 2025 23:03:43 GMT

You've convinced me you might conceivably have some reason to not need to lock the rotation or vertical position down, but you haven't convinced me as to why I can't if I want to. Obviously the coders had better things to do, but from my point of view it would be very useful to allow me to do so.

Re: Assembly constraints

Drewpan — Wed, 09 Apr 2025 00:02:30 GMT

Hi,

You CAN lock a joint in a particular position if you want to. Not only can you set the orientation

when you set it up, once it is set up you can then lock the degree of freedom of that joint. The

simplest example is a Revolute joint where you simply lock the rotation to the degree of rotation

you want it orientated by setting the degree of freedom to the same values. The reason that you

can do this is so that when you are modelling that you can test as you go and make sure that

there are no crashes or unwanted behaviour. Sure, you may want it orientated a certain way to

model but fusion gives you the flexibility to also test. I'd say the coders worked overtime.

Cheers

Andrew

Re: Assembly constraints

ashinbrot — Wed, 09 Apr 2025 00:14:15 GMT

I'm not familiar with the Revolute Joint and will certainly give it a try. But I've been using Cylindrical constraints, and I see just the opposite of what you are telling me.

When setting up a Cylindrical joint I am offered the option of dialing in a rotation, and my part does rotate to that constraint, but as soon as I move on to other things I discover the rotation is not constrained. Again, I can see why someone might want to specify an angle of rotation to see something, but why not allow me the choice of locking that rotation down while I'm there? That's clearly a deficit.

Re: Assembly constraints

g-andresen — Wed, 09 Apr 2025 05:30:49 GMT

Hi,

A cylindrical joint is a combination of a slider and a revolut joint.
However, if no rotation is desired, I use a pure slider.

I think it would be better if you could provide a sample file for analysis and explanation.

günther