Subtracting One Part from Another Part

[NEALROSENBLUM]

All,

I am creating some 3D data for a CFD analysis. I have created a part with a bunch of holes, but for the CFD analysis, I need to create a large "mass" and then subtract my part from the mass.

So how can I create a negative of my part? TIA.

Sincerely,
Neal Rosenblum
Geometrix Engineering, Inc.
201 N. 13th Avenue
Hollywood, FL 33019
Ph: 954-920-2049
Fax: 954-920-9574
Cell: 954-649-9399
neal@geometrixeng.c

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[TomU]

Do a solid surfs copy, then use this closed volume to remove material (solidify, cut) from your large block.

Tom

[JoshuaHouser]

I agree, a solid surface copy will work.

Another alternative is to create your new volume part, and then insert a merge/inheritance of the cut-away part using the "Remove Material" option. The nice thing about this is it allows a little more control as far as independant/independant and/or making other modifications to the geometry.

Joshua Houser

(have I talked to you about FIRST robotics yet?)

Pelco by Schneider Electric

Methods & Tools Sr. Engineer

[A.DelNegro]

Wouldn’t a ‘cut out’ be simpler? Create the new ‘block’. Go to ‘Component operations’ and select ‘Cut out’ and follow the prompts. If you’re only using it for CFD, you probably don’t care so much about the robustness of the part. I think the solid surfs copy is more robust, but will take a while to copy all the surfaces. Cutout is just 2 clicks.



Also, what CFD package are you using that doesn’t create this for you?

[ptc-1932745]

Merge and cutout have issues with matching accuracy of the source and target parts. Setting the part accuracy to a common absolute value rather than relative can help, but still problematic.

It is more straightforward to do an external copy geom, etc... which uses surfaces and will be more robust. Especially if you use publish features or all solid surfaces options to keep this up to date.



Once you have the surfaces water tight, do a solidify to get the solid volume.



AFAIK, you need a license of TDO, or Manufacturing, or AAX (?) to get extern copy geom though.





Christopher F. Gosnell



FPD Company

124 Hidden Valley Road

McMurray, PA 15317

PH:724.941-5540

FX:724.941.8322

www.fpdcompany.com

[TomU]

You don’t need AAX to do a “copy - paste” in the context of an assembly. Sure, you can’t redefine it or make it independent like a true copy geom feature, but the geometry is all still there. By the way, a “Solid Surfs” copy is very robust.

Tom U.

[DamianCastillo]

We have been using the Merge/Cutout process for Decades without issues. All our start parts use absolute accuracy. The big advantage for us is that the reference model (the one you used to cutout or merged from) will update it's changes to any model that uses it.

We have situations where one reference model is used in 20 products. We update the reference model once and all the other models and drawings update automatically.

This is also a very popular choice for people that need to make a casting drawing and a machined drawing of the same product. The casting or forging is the main model and then you create an empty reference merge part from it. Now you can do all your machining operations on the machined part without chaning anything on the casting. If you make a change to the casting, it updates the machined model.

"Too many people walk around like Clark Kent, because they don't realize they can Fly like Superman"

[mjenkins]

I like to save a solid shrinkwrap of the assembly and then assemble it using the coordinate system of the shinkwrap to the coordinate system of the assembly. Then when you do the cut out, there is no mess to clean up around the edges.

Applications>Mechanica and convert all units to inches.

Info> Tolerance Report and change all accuracies to .0012

Applications>Standard

File>Save A Copy>Shrinkwrap

Merged Solid: Level 8: Fill Holes

Assemble Shrinkwrap using coordinate system to assembly coordinate system.

Edit>Component Operations>Cut Out

Then you import the Shinkwrap into your CFD package...

In Reply to Neal Rosenblum:

All,

I am creating some 3D data for a CFD analysis. I have created a part with a bunch of holes, but for the CFD analysis, I need to create a large "mass" and then subtract my part from the mass.

So how can I create a negative of my part? TIA.

Sincerely,
Neal Rosenblum
Geometrix Engineering, Inc.
201 N. 13th Avenue
Hollywood, FL 33019
Ph: 954-920-2049
Fax: 954-920-9574
Cell: 954-649-9399
neal@geometrixeng.c