# Patches Required for Boundary Conditions **URL:** \ **Category:** Tips & Tricks\ **Created:** [September 20, 2023, 7:13pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105 "2023-09-20T19:13:15Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![arnie](https://avatars.discourse-cdn.com/v4/letter/a/ba9def/32.png) [@arnie](https://prepomax.discourse.group/u/arnie)\ **Post date:** [September 20, 2023, 7:13pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/1 "2023-09-20T19:13:15Z")
Good day, Does anyone have a sure proof way of importing patches along with the geometry into PrePoMax. I usually use Spaceclaim to save my geometry as STEP file. However, when I import into PrePoMax, the geometry does not include the patches that I need to apply my boundary conditions. For instance, when we want to create a ‘washer’ face to apply a fixed boundary condition or an arbitrary patch (see examples shown below). I realize that to a certain extent we can use the feature “Geometry-\> CAD Part-\> Split a Face Using Two Points” However, this is only possible where there is already an existing vertex point in the geometry and to draw straight lines only. ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/b/bc94d898476f798b35c83214e91c3a591c8c4b03.png) ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/c/c80c0856fc2217e3d0f8ef09e186944c18e5093f.png) ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 20, 2023, 9:11pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/2 "2023-09-20T21:11:00Z")
You can use [Part BooleanFragments - FreeCAD Documentation](https://wiki.freecad.org/Part_BooleanFragments) in FreeCAD for this purpose. Just create a sketch, select it together with the 3D geometry and use the tool. ---
**Author:** ![synt](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/synt/32/4658_2.png) [@synt](https://prepomax.discourse.group/u/synt)\ **Post date:** [September 20, 2023, 10:06pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/3 "2023-09-20T22:06:15Z")
> [@arnie](#): > > I usually use Spaceclaim to save my geometry as STEP file try using IGES file format instead. ---
**Author:** ![arnie](https://avatars.discourse-cdn.com/v4/letter/a/ba9def/32.png) [@arnie](https://prepomax.discourse.group/u/arnie)\ **Post date:** [September 21, 2023, 11:29am UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/4 "2023-09-21T11:29:12Z")
@Synt, unfortunately IGES format exported from SpaceClaim produces the same results ie. no patches ---
**Author:** ![arnie](https://avatars.discourse-cdn.com/v4/letter/a/ba9def/32.png) [@arnie](https://prepomax.discourse.group/u/arnie)\ **Post date:** [September 21, 2023, 11:55am UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/5 "2023-09-21T11:55:55Z")
> [@FEAnalyst](#): > > ou can use [Part BooleanFragments - FreeCAD Documentation](https://wiki.freecad.org/Part_BooleanFragments) in FreeCAD for this purpose. Just create a sketch, select it together with the 3D geometry and use the tool. Understood; but I was trying to avoid this extra effort. It would also require creating either Compound Parts or using Contacts or Ties ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 21, 2023, 12:20pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/6 "2023-09-21T12:20:34Z")
> [@arnie](#): > > It would also require creating either Compound Parts or using Contacts or Ties Not if you just use Boolean fragments with a sketch on the surface: ![patches](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/5/557e69cfcd8e9a86e57a24567ff88a9bb20639c9.png) The other boolean tools (used on volumes) can cause this but there are some ways to avoid that as well. ---
**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\ **Post date:** [September 21, 2023, 12:30pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/7 "2023-09-21T12:30:46Z")
HI arnie, You could also select single faces directly with a negative angle. By the way, a THICK PINCELL would be useful to allow fast selection. ![imagen](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/e/ed5e143a4e7664ccb6c095a8bb3e61be93846ee4.jpeg) ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 21, 2023, 12:32pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/8 "2023-09-21T12:32:54Z")
> [@ANYS](#): > > You could also select single faces directly with a negative angle. Yes, but it would make the edges jagged in the case of a curved (e.g. circular) patch. So it’s usually best to prepare the patches in CAD software before importing the model to PrePoMax. ---
**Author:** ![arnie](https://avatars.discourse-cdn.com/v4/letter/a/ba9def/32.png) [@arnie](https://prepomax.discourse.group/u/arnie)\ **Post date:** [September 21, 2023, 1:00pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/9 "2023-09-21T13:00:42Z")
> [@FEAnalyst](#): > > Not if you just use Boolean fragments with a sketch on the surface: I see; I will give it a try then. Thank you. ---
**Author:** ![arnie](https://avatars.discourse-cdn.com/v4/letter/a/ba9def/32.png) [@arnie](https://prepomax.discourse.group/u/arnie)\ **Post date:** [September 21, 2023, 1:02pm UTC](https://prepomax.discourse.group/t/patches-required-for-boundary-conditions/1105/10 "2023-09-21T13:02:38Z")
> [@ANYS](#): > > You could also select single faces directly with a negative angle. > By the way, a THICK PINCELL would be useful to allow fast selection. Yes, I have done it this way before, but it’s not the most efficient method and relies on the mesh edge shapes. But thank you.