How do you manage larger assemblies?

[naroarr]

do you create multiple .iam's and add them together into one final assembly?
or
do you constraint every single part together in one assembly?

haha sorry if my question was confusing..

[usbcd36]

I create sub-assemblies and place them into a final assembly.

[Molten]

It really depends. I choose whichever way makes the most sense for the project. I apologize, but it seems my answer is just as confusing as your question.

[rachal]

I generally only use sub-assemblies when they're mildly complex and need to be used multiple times, like gearboxes and wheel assemblies.

I also make the grabber a separate assembly so I can move it around in the final assembly

[KINGOFCLUBS454]

I always look at how the finished product will be assembled. For example, imagine a mecanum wheel(I'm partial to 357's, but thats just me ). It would make sense to me to make the roller and all of the bearings inside of it a single assembly, mostly because that is the way it is when it is attached to the final hub, which would be an assembly all in it's own once bushings and axles are attached. However, for a product such as an AndyMark Stackerbox, I would simply throw everything together in a single assembly because there are no noticeable pieces that would need to be pre-assembled before the final product.

Hope that was of some help.

[mlucas]

My solution...ditch inventor, run Solidworks....


But the honestly...

My final assemblies are as simple as possible. Granted i run solidworks, but same concept, easier to use product. The only assemblies i do in the final asm. are each piece like it would be assembled on the robot. Therefore tranny's are assembled in their own file, on solidworks i like to save them as parts and not assemblies, unless they need moving components, saves time and all that.

All in all, if you attach it to the robot assembled, assemble it in its own file, if you assembly it on the robot, say...oh a frame and some sheeting on top of the frame, the assemble it in the final robot assembly.

[Binome]

Simplified Components, Large Assembly Mode, and Sub-Assemblies are what keep solidworks from crashing hard when loading some of our more complex drawings. Stationary things should almost always be in a sub assembly to keep RAM, Swap, and CPU load down when dealing with moving parts, and fixing components, removing redundant relations, and defining sketches properly the first time keeps you from remaking parts when your fabricators give you suggestions later.

[JD Mather]

Originally Posted by mlucas

Granted i run solidworks, but same concept,...

I have found no difference. Do it like it would be done in the real world. If subassemblies would be used then create subassemblies. The CAD program does not make a difference in the assembly strategy.

[Tom Bottiglieri]

We have a gearbox mounted on a raised rail which is mounted on the base of the robot.

Gears and plates - parts
Gears on shafts - assemblies
Gearbox - assembly
Gearbox on rail - assembly
base - assembly
whole robot - assembly of assemblies

Abstraction is your friend. The software is designed to be parametric and its a great help to use it that way.

[Tristan Lall]

Originally Posted by Tom Bottiglieri

Abstraction is your friend. The software is designed to be parametric and its a great help to use it that way.

That actually brings up an interesting question: when should you parametrize a model, and when should you keep it separate?

I find that it's quite helpful, every time I make a feature, to try to imagine what variations on the feature might come to exist, what other features might depend on this feature, and whether or not the part will be interchanged between assemblies.

For repeated parts, tempting as it might be to link their features to another assembly member, you may encounter difficulties when the first instance of the part (from which the dependencies are derived) is changed or removed. Also, for parts that can exist in different assemblies, you might inadvertently create a dependency to an outside assembly. This can be rather painful, especially if you don't have a robust data management system in place (either software-based, or just good control over the directory tree).

Then again, for parts which can't reasonably be expected to be reused, dependencies can make it much easier to pattern features and assure yourself that geometry is aligned. It makes assemblies that much easier to work with, and simpler to maintain (because when you change the parent feature, all the children are automatically regenerated in the new state).

But to answer the original question, yes, use subassemblies! In addition to all of the reasons listed previously, you'll have advantages like reduced memory usage in an editing session, if only some of the parts need to be modified (especially a problem in Inventor, it seems), and you'll be able to more conveniently make assembly drawings.

And like others have mentioned, when complex models are needed, I tend to use Pro/E instead.

[grsnovi]

It is often a matter of trial and error. It can be very easy to create a set of very simple sketches within parts and put them together as an assembly to do simple 2D kinematic analyses. If those parts are parameter driven, making changes gets so much easier. Remember, a dimension on a sketch might be the only parameter you need. Once you start fully constraining your sketches and making certain dimensions depend on other dimensions, adjusting a complex part can be a snap!

One thing to remember (in regard to the original question) is that you can start with a large "flat" assembly (no subassemblies) and "push" parts down into logical subassemblies when and if you need to. If you push (demote) ten parts into a new subassembly, all of the constraints between those ten parts will be kept. Constraints from those parts to parts outside the group will be lost, so you will have to create them again.

[pmax]

Ultimately the notion of using subassemblies or making "flat" assemblies is up to the user. I strongly recommend making a subassembly when in doubt. The biggest benefit is that another person can work with your files and likely get a better feeling for your intentions in how everything was put together.