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## Create minimal surfaces by equation

Hello,

Please, I need to create differently minimal surfaces. I know how to create gyroid, diamond, and schwarz P throught engineering - lattice - formula driven. (https://support.ptc.com/help/creo/creo_pma/r6.0/usascii/index.html#page/part_modeling/part_modeling/...)

But It is not exactly what I need. Because I am creating structures with differently porosity and I am limited by wall thicknes and it can not be smaller than some value... Also I want to create other structures like Neovius, Schoen IWP... (And in Formula driven are just three structures) So is the way how to create minimal surfaces by equation ? Or is the another solution how to create this structures with small porosity (about 10%) ? I tried curve from equation, but still had errorr...

Please I really need it.

Thanks for help, and sorry for my english language.

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9 REPLIES 9

## Re: Create minimal surfaces by equation

Creo does not support explicit creation of surfaces from equation, only curves from equation. To create surfaces from equations in Creo you must use curves (from equation) as construction geometry to build surfaces as children of the curves.

I think you are looking to employ a custom lattice.

If you can define a unit cell parametrically in math terms you can create the 3D surfaces in another tool such as Mathematica and then export the unit cell to Creo using a neutral file format. Mathcad may be an option as well to get the unit cell geometry.

## Re: Create minimal surfaces by equation

Thank you for your answer. I created one cell with gyroid structure by equation... Saved it to STL format. And then I Opened this STL file in Creo and changed to PRT. So Now I have one cell of gyroid structure in prt file. So I tried to use custom lattice structure, but when I added this cell into it I still got  error: Incompatible part size/accuracy. Change PRT0001 accuracy to 0.000000 or use absolute accuracy to match part accuracies.
Failed to create the required lattice template. Something is wrong because when I changed accuracy to absolute, I got next Error: Incompatible part size/accuracy. Change PRT0001 accuracy to 0.000003 or use absolute accuracy to match part accuracies.Do you know what to do with this?

Thank you

## Re: Create minimal surfaces by equation

In Creo 7 absolute accuracy is the default. If you are not using Creo 7 to create these models then they may use relative accuracy.

I believe the warning error is suggesting to match the absolute accuracy of your design model and the model of the unit cell.

In this specific instance it sounds like the error is due due incompatible accuracy between your unit cell and the model you are applying it to.

Change to absolute accuracy in your design model (e.g. if units of length is mm then set accuracy to .001 mm). Create a start part with absolute accuracy matching that of your design model. Import your unit cell into a new part using the abs accuracy template. You can then try again to apply the custom lattice.

## Re: Create minimal surfaces by equation

I did what you siad, and both accuracies are same now. But I got this error:

Incompatible part size/accuracy. Change SDF accuracy to 0.000025 or use absolute accuracy to match part accuracies. Failed to create the required lattice template.

## Re: Create minimal surfaces by equation

Without seeing your data I would guess that it is the STL file triangulation that is the culprit. Can you export your gyroid surfaces as a STEP file for the unit cell?

I am not familiar with the term SDF accuracy so I would have to do some research on that one.

## Re: Create minimal surfaces by equation

I can not send it here, because the maximum attachment size is 47Mb, and unit call in step format has 67MB. But I am sending prt file...

## Re: Create minimal surfaces by equation

Your model was created with an educational license which can not be opened with a commercial license so I can not see the geometry.

You need to insure that your unit cell geometry satisfies the geometry constraints I noted previously in order to use it as a custom lattice. You can export the STL and then use the RESTYLE function in Creo to convert the faceted geometry from .stl to BREP surfaces. It is probably not going to be an automated process depending on the geometry of the cell you will have to provide input in restyle tool.

## Re: Create minimal surfaces by equation

Does your cell model satisfy this requirement?

``In Creo Parametric 6+ you can create a lattice, based on a Creo part file, where the cross sections of opposite faces of a cube are the same, and the geometry is a full boundary representation (BREP). This gives you the flexibility to define your own cell types.``

If this condition is not met it is not going to work. So firstly you need to make sure that your STL import is converted to BREP surfaces in the reference part used for a custom lattice.

## Re: Create minimal surfaces by equation

I do not know if my cell have this requirement. All I did is, that I opnened STL file and then: File - Save As and choosed Shrinkwrap and then I checked Faced Solid and level quality set to 8. Because 10 was too long and 1 had very bad quality. If I tried use cell with quality level: 1. It worked. But quality is really bad. On quality level 8. Does not work.. Idk why is that. And I do not know how to check if this model is full BREP 😞

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