Top-Down design using Inventor professionally

[marcrichard]

Hi all,

My objective is to create parametric assemblies. If some of you use Inventor professionally, i would be very glad to know which technique do you use to design with the Top-Down approach.

My first idea was to create a 'master' assembly and create each part in-context. In that case, all the parts are fixed together, the assembly can't have motion. So i create a second assembly, i import all the parts previously created in context and i mate the parts together so i can have motion. A change to the 'master' assembly is propagated and all the parts adapt.

I don't know if it's a correct practice. Is that approach used in industry?

Another modeling process i found on the web is to use multibodies: create all bodies (each body will become a separate part) in a 'master' part file and then use 'Make components' to transform each body into a separate part. I can then create an assembly with all the parts. A change to the 'master' part file and the assembly is updated automatically.

What are the pros and cons of my modeling approach VS the multibody approach?

Sorry for my imperfect English.

Thanks,
Kind Regards,
Marc

 

[btrueblood]

Ask yourself this question: if a change is made to an individual part, will other part files be "automatically updated", and will you know which ones? I.e. think about how you will maintain change control when the parts reach the production/shop floor.

 

[Sparweb]

I have done both practices. They are correct, in some circumstances. In other cases, they could be wrong. I don't know of a "perfect" answer.
Other techniques use adaptive sketches, or derived parts. All 4 of these approaches are different and have different limitations, so the only guide is your own experience with them.
Sorry, no general rule that I know of.
Parts created from any of these modeling techniques can have difficulty, at some point, adapting to changes in their geometry. Some will have limited degrees of freedom (motion), others will not scale properly without relaxing the constraint you tried to set up with the "prototype" model you started with.


STF

 

[marcrichard]

Thank you very much btrueblood and SparWeb for your feedback.

SparWeb, what do you think about the multibody VS "in-context parts" approach? Can you give pros and cons? Actually, at the moment i am not using multibodies but i wonder if it is or not a better practice to use them to do what i want to do (building a parametric assembly "with motion").

I must say at the moment i stay away from the skeleton modeling approach.

 

[Sparweb]

All I can say is that I make "multibody" parts all the time, but I rarely make parts within assembly models. I sometimes start some assemblies with geometric sketches that don't have any parts at all, just sketches - then Derive all of the parts that will go into the assembly so that I can control a "master" sketch in that first one I created. This is just my habit, and it may not be the simplest way to go about it, but it works in my office. I also don't need to design moving parts very often. When the design is finalized I can freeze the geometry, but while making adjustments during the prototyping phase, I can ajust the master sketch and update all of the derived parts quickly.


STF

 

[marcrichard]

Thank you SparWeb for these precisions.

Marc