Subassemblies falling apart in next assembly
"Also is there a way to add multiple joints to a component? For instance, having a tube t-fitting concentric to two separate tubes. Or having one component rotate relative to a 2nd component but always be parallel (perpendicular, at an angle) to a third component."
yes, a component can have more than one joint. Here, the cylinder has two rigid joints, one to each box on either side of it.
"I constantly get "the component already has a joint" and I'm like, "So, give another one". What am I missing?"
Actually, the message is:
which is very different than "the component already has a joint". This warning exists because, in most cases, you do not need more than one joint between any two components. One is usually sufficient. But, the question here is a yes/no question. You can answer "yes" and add another joint. There are cases where this is useful.
One warning here: Do not try to use a Planar Joint as a "mate" constraint. It is not the same thing. Don't try to force-fit a constraint-based workflow into a joint system. Yes, it takes some getting used to, definitely, but there are few component/component relationships that cannot be defined using the joint system in Fusion. Using Joint Origins can extend the basic model to cover lots of additional cases.
And, as @TrippyLighting requests, if you share your design here, and some indication of what you are trying to do, there will be lots of people who will help.
Jeff Strater
Engineering Director
I can address that, but will need some time to compile that information and create a screencast.
The problems you are encountering are not unusual, but can be remedied by a better workflow, which isn't all that difficult, but very different for people that come from Inventor, SolidWorks etc.
@Ridesm1969 wrote:
I just updated the subassembly, removing the multiple rigid groups and created just one rigid group. When I updated the top assembly, it blew apart again.
Well, then stop doing that 😉
1. While in theory you can create a functioning assembly like that in Fusion 360 my recommendation would be not to have a bodies folder with one or more bodies in it at the same structural level as other components.
That body should be a component. A good practice is to decide which is the fixed component in that small assembly and then use a rigid group joint (disable "include child components") to lock it to the main origin of the assembly.
You can also use an as-built rigid joint (works only if the assembly/design has a timeline).
If you don't convert that body to a component, you'll be missing the AL profile on your BOM!
This is just one Issue I can see. You also appear to have double-dipped on some joints. You created regular joints between some parts and then used a rigid group joint that includes some of the components that have already been joined.
Few more observations:
You ground/unground/ground a lot of times in the timeline. I usually have only one component grounded even in complex assemblies. That means I have one ground feature in the timeline and no unground features.
A mechanical assembly such as this should have no position capture features.
When importing small assemblies such as this,:
1. Do not enable the timeline. It's not needed, because you unlikely ever need to make a parametric change to that assembly.
2. If the parts import as assembled, then use one rigid group joint that includes the top level origin. That is what rigid group joints do. thy lock all referenced origins together in space. No geometry needed. IN tis case the counter should be 6 components, not 5!
Grounding is only local to an assembly.
If you insert that assembly into another design, then grounded components become floating in that design.
Rigid grouping grounded components is not recommended.
Converting bodies into components in a simple single component design is not recommended, or needed. It creates an unneeded structure level.
Mirroring assemblies can "mess with" BOM creation.
Instead of having one item on the BOM with an instance counter of 12 you'll have 2 separate items, each with an instance count of 6.
@Ridesm1969 wrote:
I only capture the positions for better access to the joint surfaces. Otherwise they are hidden and I have to hide/unhide other parts to see them, unless I'm unaware of another method.
Sometimes that is still needed. I usually delete those once I've collected a few as they are not needed anymore. Any feature in the timeline will be reevaluated when parametric changes are made. The fewer features (within reason) the better.
@Ridesm1969 wrote:
Sometimes I need a mirror (left/right opposites) while other times just placing the original, flipped, would work. noted. Thanks.
If you mirror one component, use an as-built rigid joint and assemble it to the grounded main component or another assembled component.
If you mirror more than one component, immediately join them to another already joined component with a rigid group joint.
I would recommend joining liked component immediately after insertion. I would refrain from assembling any component to any non-assembled(floating) component.
@Ridesm1969 wrote:
For God's sake and my sanity, can anyone explain why, after jointing every component within my subassembly, it falls apart when added to its next assembly? I've use joints, as-built joints and rigid groups only to have it come in incorrectly or fall apart when I add motion in the next assembly, or even lock the top assembly from moving! I've wasted so much time having to re-joint the subassembly components within the next assembly.
Also is there a way to add multiple joints to a component? For instance, having a tube t-fitting concentric to two separate tubes. Or having one component rotate relative to a 2nd component but always be parallel (perpendicular, at an angle) to a third component. Editing an assembly Is very difficult if jointed components won't move relative to each other and I'm constantly having to measure and move or "eyeball" and drag. I constantly get "the component already has a joint" and I'm like, "So, give another one". What am I missing?
Yes, I am used to being able to mate multiple parts together relative to other parts and those mates/parts being mirrored, moved, or otherwise relocated with a simple change, without my assembly puking all over itself, so please forgive my frustration. Thanks in advance.
I don't think anyone ever answered your original question here: "why, after jointing every component within my subassembly, it falls apart when added to its next assembly?". The answers are in here, but I thought I'd summarize it here. First, the subassembly does not "fall apart" when inserted. However, it can fall apart if you drag part of it. The reason is: You are using Ground to "constrain" the air line here, instead of Rigid Group, or a Rigid Joint in that subassembly. That will appear to do the right thing, in the subassembly itself, but when you insert that into another design, as @TrippyLighting states: Ground does not come along when inserted. So, those components are suddenly unconstrained in the top-level assembly. Instead, you should use Rigid Joints or Rigid Group to "glue" the whole subassembly together, not Ground. The best test of this is to have nothing grounded, and then just drag around the design - any parts that are left behind need to be joined to the rest.
In the screencast below (sorry, no sound - screencast does not record sound on my machine for some reason), I have created a copy of the CRADLE, RING component where I removed all the ground features, so everything is free to move. You can see that I can still separate the air line from the frame. Instead of grounding, I use an As-Built Rigid Joint to stick those two sets of components together. Then, once I insert that version, you can see that they can no longer be separated.
One more thing: I notice you are using Contact Sets in these designs. Feel free to do so, but know that that is an expensive thing to do: If you have performance problems, the first thing to do is to turn those off...
screencast:
Jeff Strater
Engineering Director
Hmmm, very odd indeed. I thought I had posted this, but I guess I never clicked on the reply button.
I recreated just the base frame with relatively few timeline items, no joint origins, and no assembly context.
It is much more interactive to update dimensions and updates quickly and reliably.
Also, a lot fewer joints are needed for this method.
Model is attached.
