topic Re: Constrain feature limitations for assemblies - Fusion in Fusion Design, Validate & Document Forum

Constrain feature limitations for assemblies - Fusion

aleksei_ovsienko — Fri, 14 Nov 2025 18:45:12 GMT

Let's say I'm constraining a subassembly of three components (lets call them A, B and C) using Constrain feature. I normally need three references to constrain it in 3 directions.
So I select a reference on the subassembly - a surface on component A of that subassembly and select a reference surface on the mating component. Works fine.

Then I create a second pair of references within the same Constrain feature dialog to constrain it further. And I find that I can now only select references on the component A. All other components - B and C - of that subassembly can not be selected for references.

This is a problem. It should not work like that. I must be able to select any object on any component of the subassembly to constrain that subassembly. Because I'm constraining the subassembly, not its individual components that are already constrained within the subassembly.

Can this be fixed please?

Currently the workaround is using multiple constrain features to constrain a single subassembly.

This post has been edited due to: @heather_tracy added the product to the title to help more community members find this topic.

Re: Constrain feature limitations for assemblies - Fusion

heather_tracy — Tue, 18 Nov 2025 22:52:49 GMT

Hi @aleksei_ovsienko,

I wanted to check in and see if you still needed assistance, or if you found a solution to your question already? Let us know if you need further assistance by providing an update or if you have found a solution, please share it with the community so other members who may have the same question could learn from your experience.

All the best,

Heather | Community Manager

Re: Constrain feature limitations for assemblies - Fusion

aleksei_ovsienko — Wed, 19 Nov 2025 08:21:56 GMT

Thank you @heather_tracy . I know how to work around that, I don't need asstistance. I'm just drawing attention to the problem with how Constraints work so it can get fixed.

Re: Constrain feature limitations for assemblies - Fusion

TrippyLighting — Wed, 19 Nov 2025 15:04:00 GMT

@aleksei_ovsienko wrote:

Thank you @heather_tracy . I know how to work around that, I don't need asstistance. I'm just drawing attention to the problem with how Constraints work so it can get fixed.

I would not hold my breath. We've argued for many, many years for the need for constraints (mates in SolidWorks and other CAD systems), before they were implemented.

Re: Constrain feature limitations for assemblies - Fusion

TheCADWhisperer — Wed, 19 Nov 2025 21:56:09 GMT

@aleksei_ovsienko wrote:
Currently the workaround is using multiple constrain features to constrain a single subassembly.

@aleksei_ovsienko

Can you Attach the workaround so that I understand the issue?

Re: Constrain feature limitations for assemblies - Fusion

aleksei_ovsienko — Thu, 20 Nov 2025 10:04:21 GMT

Yeah. Here's the link. I created a simple assembly of some random plate and a subassembly. You can see that I use three separate Constraint features to constrain the subassembly relative to the grounded part and each of these constrains references a different subassembly part because it is not possible to reference multiple subassembly parts within one constrain set.

https://a360.co/4oMOwz1

Re: Constrain feature limitations for assemblies - Fusion

TrippyLighting — Thu, 20 Nov 2025 16:04:05 GMT

That can be achieved with a single rigid joint.

Constraints were not introduced to replace joints!

Re: Constrain feature limitations for assemblies - Fusion

aleksei_ovsienko — Fri, 21 Nov 2025 08:48:46 GMT

In this particular case - yes, it can be done with joints. I just created an example to demonstrate the issue. But in principle Constraints still need to allow the user to select references from all subassembly parts. It's just common sense.