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Guest rudis

How To Model A Lobster Nose?

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Guest rudis

csven and chris - thanks for the modeling advice. I'm just starting to become familiar with Pro/E Wildfire 3.0 so I won't be ready to actually use that advice just yet!

 

I'm currently just working on exporting some practice parts (nuts, bolts...) as STL files since this is critical for my work. I'm having some difficulty with refining the triangulated mesh - it seems that there's a limit based on "part accuracy," but I think I found some help files on that. Hopefully, I can refine "part accuracy" as much as I want, and thus get some very smooth meshes.

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Guest rudis

Pro/E experts: Maybe someone can point me in the right direction regarding my "part accuracy" problem? I want to save a part as a very refined (smooth) mesh in an STL file but cannot get past about 4000 triangles. The options for an STL file are chord height and angle control, and it seems the smallest chord height is governed by "part accuracy." I was able to turn the "absolute accuracy" option on for the model, but when I tried to make this value very small, it seems the smallest allowable value is about 1E-4. Not sure where this limit is coming from - shouldn't I be able to go down to machine precision? I saw a few other options like "Geom Tol" and "Tol Setup" but I'm not sure how to change these/if they should be changed.

 

The part I was trying to save as STL was a practice bolt from a tutorial (unfortunately the forum won't let me attach the bolt.prt file). Any ideas on how to enable higher mesh refinement?

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Guest csven
Pro/E experts: Maybe someone can point me in the right direction regarding my "part accuracy" problem? I want to save a part as a very refined (smooth) mesh in an STL file but cannot get past about 4000 triangles. The options for an STL file are chord height and angle control, and it seems the smallest chord height is governed by "part accuracy." I was able to turn the "absolute accuracy" option on for the model, but when I tried to make this value very small, it seems the smallest allowable value is about 1E-4. Not sure where this limit is coming from - shouldn't I be able to go down to machine precision? I saw a few other options like "Geom Tol" and "Tol Setup" but I'm not sure how to change these/if they should be changed.

 

The part I was trying to save as STL was a practice bolt from a tutorial (unfortunately the forum won't let me attach the bolt.prt file). Any ideas on how to enable higher mesh refinement?

Something that might be relevant is that - and this is from what a PTC guy once mentioned, as best as I can recall - Pro/E is sensitive to the real size of objects. In other words, those small bolts don't need to be more accurate for most manufacturing conditions. This makes some sense to me since the default values have never raised an "accuracy" problem in production on any projects I've worked.

 

The solution is probably as simple as scaling it up in Pro/E, in essence tricking it into thinking the part is much larger in real life and thus - for manufacturing needs - requiring a more detailed mesh. After export, just scale it back down.

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Guest rudis

FYI, found a well hidden Pro/E option called "accuracy_lower_bound" which solved that problem. Been diligently learning Pro/E - hopefully will be proficient enough to draw some noses soon!

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Guest JD Mather
(unfortunately the forum won't let me attach the bolt.prt file). Any ideas on how to enable higher mesh refinement?

 

You should zip the file before attaching here. You can zip a file in Windows Explorer by right clicking on the file name and selecting Send to Compressed (zipped) Folder. Attach the resulting *.zip here.

 

I'm not sure about Pro/E but in another software (that simply offered Low, Medium, High mesh selections) I found a Registry hack where the parameters for those settings was controlled.

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Guest w i l l
sven,

 

I will be in the Eastern side of CT in January. Any chance we can get together for dinner and or beers?

 

:D

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Guest under-dog
rhino is not parametric and hardly even makes parent child relationships. You get what you pay for you know. I am surprised so many designers use it.... I mean we teach it too but only because of the demand. At the end of the class we always show Pro/E and the designers are like "why did we not learn that instead" I just laugh.

 

In Pro/E you might be able to use a graph feature to randomize the curve growth. So your sweeps would appear random.

 

I think what I would do after thinking about it for a sec.

 

In Pro/E: Pattern a group of curve sweeps combo. Then unpattern the pattern so you can go in and edit each trajectory a little different on each one so it appears random. I don't think you can unpattern in SW tho. ;)

 

I agree

 

Rhino is however a cheap option and is easier to use for freeform. This is not always a good thing though. You can quickly end up with something that looks ok but is unusable. Plus since it is non parametric you have no history to make modifications, everything you do is in a sense a start from scratch effort. Best used for rough 3-D conceptualization.

 

 

I am an ID an I use SW and try to do so in such a way that files can be used directly into a desig - engineering phase. Nearly every 3D concept we have recieved from outside help have been just that.....concept. Sort of a "thanks for the pretty model and images unfortunately your files are useless" The files often have to be rebuilt from ground up so they are tool safe etc. So what thier modeling accomplished could have been done with a series of 2D sketches and some simply breadboard and conceptual modeling to demonstrate certain conceptual elements. for alot less and have given the design engineer more time to make a truly usable file.

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Guest rudis

This newest creation of the "lobster nose" by ZXYS is definitely the most creative so far! Thanks to Underdog and others for Rhino comments - I agree and although tempted by Rhino's ease of use, I think parametric Pro/E may be better long term when I begin tinkering with the model.

 

I've gone through quite a bit of tutorial Pro/E material, and yet still don't know how to put some smaller cylinders (straight hairs) onto a big cylinder! In Pro/E, do I somehow use the curved surface of the big cylinder as a sketching plane, or do I create some other datum plane, or would do it as an assembly?

 

Might anyone have comments on the books Pro/E Wildfire Instructor or Pro/E Wildfire for Designers? Other good ones? Perhaps my main problem is that Pro/E Help is not working for whatever reason in my temporary trial version of the program...

 

Thanks!

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Guest csven
how to put some smaller cylinders (straight hairs) onto a big cylinder! In Pro/E, do I somehow use the curved surface of the big cylinder as a sketching plane, or do I create some other datum plane, or would do it as an assembly?
Are you modeling as if it's all one surface/solid model or as pieces exported independently and reassembled in your CFD app? This would be determined really by what it is you need/want in that app.

 

Assuming it's a single solid model that will be exported as a single mesh and imported as one mesh, you can do any number of operations.

 

If you're trying to follow my guideline, you'd create a curve on the surface of the nose. Can Project one onto that surface. Can Intersect using other surfaces/datums. aso. Up to you. After that you'd put a Point on that Curve. Different ways to approach that as well.

 

And when you're doing these operations, keep in mind you'll want to pattern them. That might make things a bit more tricky for you since modifying things after can cause a complete regeneration failure. Might want to save often.

 

Might anyone have comments on the books Pro/E Wildfire Instructor or Pro/E Wildfire for Designers?
Sorry. Haven't read a book on this topic.

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