What is the best organization of my project? A single Part Studios and multiple Assembly tabs?

christopher_johnson425

I’m still very new to 3d modeling and ONSHAPE, but I’m learning quickly. Right now I have two completely separate projects to build two different versions of a V8 engine intake manifold, but I want to re-organize this to have only one set of documents but two different outcomes. After a lot of thought, I think the right approach is a single Part Studio and two assemblies. I am not married to this though. I want to do this the right way, not necessarily my way.

The manifolds are identical except for the carburetor mounting flanges. The manifold will support either of two models of carburetors, both of which are two-barrel downdraft types. The difference is the barrel center-to-center spacing, one is 90 mm and the other is 120 mm.

My thinking is that I could use a couple of configuration list variables to control this. One specifies the carb barrel spacing dimension, and the other specifies a lower level Part Studio which contains the appropriate carburetor flange sketch. This sketch would be derived into the upper level Part Studio and would take on some sketch mods for a common flange reinforcement. This part of the effort is complete and appears to work. I have created a new sketch of the selected flange using USE so that I can make the appropriate geometric changes to the carb flanges.

So, here’s what I hadn’t considered. Changing the derived sketch on the fly breaks all the constraints between the derived sketch and the sketch generated with USE! Whoops! Right now, I have no idea how to work around this, so I’m looking for some advice.

Thanks in advance!

eric_pesty

It's a bit hard to follow what's going on without seeing your document, are you able to share?

You talk about "changing" the derived sketch, if you are using a different sketch it makes sense that it would break, but if you are just changing the dimensions of the sketch (via configurations), it shouldn't break as long as the sketch entities are still all the same.

christopher_johnson425

I did have one thought about this. Perhaps there could be two target sketches for the manifold-to-carbs flange and the same configuration list control could suppress the one that wasn’t being used in the current configuration. Would this prevent all the projected constraints in that sketch from being broken?

eric_pesty

https://forum.onshape.com/discussion/comment/128292#Comment_128292

No, swapping out the sketch will break references for sure!
Projected constraints are fairly "brittle", there's probably a better way to do this but hard to tell without a visual example of what you are trying to do.

Deriving "faces" instead of sketch entities might be an option, or including more the required geometry into what you are deriving

martin_kopplow

If you are controlling your sketch with variables anyway, you could have two (independent) sketches driven by the same set of variables. The workflow could be to create the second sketch by 'use' and then just break the inter sketch constraints, replace by variable driven dimensions.

Depending on how your document works inernally, it might also be an option to model up to a point where both intake manifolds are still identical, then fork the workspace, and develop the two variants in their own branch each from there.

Hard to tell without knowing the document.

christopher_johnson425

This is the current state of the document:

https://cad.onshape.com/documents/371fbecdf974d2e12cda3109/w/cf53f549ba68209179c261af/e/773fc7d42d2726946f8ead3c

I modified the dual carb flanges (with the fixed barrel spacing) to be four individually derived port flanges. Without the fixed relationship I could tie the barrel spacing to the already existing variable for this parameter that was used to calculate the manifold runner centerlines that are used to provide the paths for the runner lofts. This produces two nice results. I’m just disappointed that the carb port flanges aren’t tied to a single entity. I remain open to other possibilities that I haven’t considered yet.

Thank you for your interest and future comments!

christopher_johnson425

I’m still working on the structure of this document too, and am needing some help. At some point, the manifold will have to split out to two different types, one for the larger carbs, and one for the smaller carbs. Having two different assembly tabs seems like the logical place to do this. On-line help implies that there is a way to set a variable within the assembly tab that is effectively back-fed to the part studio so that the proper configuration of the manifold is inserted into the assembly. So far, I haven’t figured out how to do this.

Also, it has not been mentioned that a variable of this type would be “read only”, as far as an insertion would be concerned. What I want to prevent is the possibility of inserting the wrong variant of the manifold into one of the assembly tabs. How would I go about affecting something like this?

Again, thanks for the help!

eric_pesty

Had a quick look and you would be better off creating the flange solid in their own part studio and and deriving that in (rather than deriving in the sketches…)

christopher_johnson425

Regardless of what Help implies, there does not appear to be a way to control a configuration variable to protect a given assembly tab. You do get to use the configuration variable assigned under the part studio when you insert the part studio into the assembly though. I guess you just have to be careful and responsible for your own actions. With the option to insert the Part Studio as “rigid”, updates are supposed to flow right through to the assembly and should eliminate the need to do future insertions, reducing the chances of inserting the wrong configuration.

Do I have this right?