replacing models without screwing up constraints and references??

[jdonovan-2]

using Creo2 ... simple example

Scenario:  upper level assembly p/n 12345.asm  ..... pcb assy with (5) connectors p/n pcb123.asm .... sheet metal panel p/n 6789.prt  ...... The cutouts in the sheet metal panel are created in the upper level assembly using the connectors in the pcb assembly as references.  (this is typical top-down parametric design process).

Case: Need to replace pcb assy with new part number ..... when I do replace command it makes me re-do the original placement constraints in the upper level assy and it also creates errors so that I need to basically re-do the sketches/references for the cutouts in the sheet metal panel.

I am a former Solidworks user and this type of thing was never a problem.  With Creo I can't figure out the proper way to do this without doubling my work (maybe the solution is there but I just can't find it).

[StephenW]

Using the replace command, select the "unrelated component" option (also good to uncheck "remember these components" unless you want a permanent reference to remain on how to replace the parts in the future).

Select your new component.

Use the "edit reference table" button. Creo makes an assembly of the 2 parts, and generates a list of the references used by the existing part.

Choose the coresponding reference for each on the new part.

[DaveMartin]

"it also creates errors so that I need to basically re-do the sketches/references for the cutouts in the sheet metal panel"

Are you using Project (formerly Use Edge) and/or Offset in Sketch mode a lot to reference external components? If so, that is not a great design practice.

[jdonovan-2]

Just creating cutouts in sheet metal using the edges of the connectors as references … ie. rectangular cutout – right edge of cutout 0.5mm off of referenced edge of connector; top edge of cutout 0.5mm off of referenced edge of connector etc etc

[DaveMartin]

So are you using Data Sharing Features like Copy Geom, or are you selecting the edges from the other parts directly?

If the latter, are you breaking the External References in the sketch?

[jdonovan-2]

selecting the edges of the individual connector models

why would you break the references?

[DaveMartin]

I would either use Data Sharing Features or break the External References. Direct External References to other components using Project or Offset Edges in Sketch mode can cause issues later on if you open the model with out having the source parts and assemblies in session. Data Sharing Features allow you to control the dependency later to prevent unwanted changes to the model later, for example, after you release the part.

[jdonovan-2]

Thank You

[jbob]

Just to add onto using the replace by unrelated component, I would do the replace command in your upper level assembly and not the lower level.

[jhaston-3]

@jdonovan-2, I thought the question you posted here was good, interesting, and I wanted to try to help you out.

I didn't have the time to formulate my answer when you posted and had to wait to consider it and decide the best way to answer. In the meantime you got frustrated and blew-off some steam. I'm sure we all did that at some point.

Back to your question.

Top-down design is easily misunderstood. Perhaps I misunderstand it myself.

Attached you will find a procedure, 2 pages, describing the steps performed in a short video you can find here https://youtu.be/SiG2UikQs64

Sorry, cheap video and no sound.

From the procedure and video (only 12 minutes), I hope you can re-create the model and learn about some important features of 'top-down' design using Creo, from my understanding anyway.

The example introduces the use of parameters, relations and program editing, using a simple example of the kind you described. I hope it demonstrates a method you can learn and develop to suit more complex cases.

The final model in this example allows you to choose between two assembly configurations, when regenerating the top-level model.

[jdonovan-2]

thank you for your input, helpful .... appreciated.

One more question: Do you, or anyone else out there, find yourself using top-down design practice with Creo2? or do you shy away from it? and if not using it, why??  ..... the reason I ask is because I took a quick seminar trying to learn Creo2 and the guy who was giving examples kept on saying "once you get the design complete, go back in and delete all of your references etc etc" ..... I couldn't understand what he was trying to convey.

Thank You again.

[DaveMartin]

I have used Top Down Design with External References in multiple industries, including consumer electronics, unmanned aerial vehicles, and aerospace.

There are pros and cons to using External References. When used improperly, they have severe negative repercussions.

I believe your instructor was irresponsible for blindly advocating deleting all references, which would be bad modeling and might not be in accordance with your Design Intent.

[jdonovan-2]

Thank you

[jhaston-3]

Many thanks, @jdonovan-2

Top-down design modelling predates Creo to the earliest days of Pro/Engineer. You should be able to use these tools in any version, although the way they work and their user interfaces might have changed through the years.

Don't shy away from it, learn it and master it.

I can't comment about the seminar you attended specifically, but as you know, when you work on a complex model over a protracted period you'll create many features, all of which require references. After several design iterations, some of your modifications are likely to have involved changing features or their references. Maybe you'd think 'this reference would be better than the one originally used', so you change the reference. The old reference could still be there and not used as a reference for any other feature.

So I think it's good practice to get into the habit of using the reference viewer, deleting old references, taking care of outdated references and keeping all your model's references in good order.

Not only part models but also assemblies.

[jhaston-3]

I almost forgot to mention Precision LMS, which is an excellent learning tool.

Another great source is the knowledge base (PTC Website).

https://www.ptc.com/en/education

[jdonovan-2]

thank you