By the way, this tutorial was written with the simplified RapidWorks interface in mind. That said, all the instructions here also apply to Rapidform XOR, but the commands may be in a different place than we describe here. Anyway, without further ado, here is our guide to trimming complex meshes…

Parting Lines 101:

How to Get Those Pesky Meshes to Trim

1. Run the Healing Wizard to get rid of all defects in the mesh. Optionally, run it a second time to
iron out any remaining defects.

2. Perform a Global Remesh, keeping the default settings. Check the box “Make clean and
manifold solid mesh” if the mesh encloses a volume (i.e. is not just a surface shell).

3. Accept the edits to the mesh at this point.

4. Create/edit a parting line as a 3D Mesh Sketch. Make sure the curve is a closed loop (indicated
by a red dot where the start and end points join together).

5. Rebuild the parting line with a very tight tolerance. Optionally, split the curve into several
smaller pieces and then rebuild all of them with a tighter tolerance. See the two pictures below:

6. Copy the mesh and paste it at the bottom of the Feature Tree. Edit this new copied mesh.

7. Try to trim the mesh using the “By Curve” method, and choose “Rearrange Poly-Vertices” at the
bottom of the command tool.

8. If this doesn’t work, or you get a message like the one below, you need to tighten the tolerance
on the parting line curve even more. Exit out of mesh-editing mode, then edit the 3D Mesh
Sketch of the parting line.

9. Select the whole parting line (i.e. all the segments that make up the closed loop). It’s time to try
some edits that will help the trim run smoothly:

– a. If you did not split the curve before, do so now by choosing the Split command with the
“Pick Points” option and clicking on several points around the curve.

– b. Double-check that the curve is closed by identifying a red point somewhere on the
curve.

– c. In the “Rebuild” tab at the top of the screen, make the allowable deviation (of the curve
from the mesh) smaller by a factor of 10. You should notice that the number of control
points increases drastically to meet the stricter tolerance.

Accept the changes to this 3D Mesh Sketch.

10. Edit the copied mesh again. Trimming should now work for you. If not, repeat steps 9 and 10
until it does trim well.

Choose both the inner and outer portions as “remaining regions,” and accept the command.

11. Choose the “Flood Fill” selection tool at the bottom left of the screen (i.e. the paint bucket).
Hide all meshes besides the one you are editing, and then click on one side of the active mesh.

When you have selected one half of the trimmed mesh using the Fill tool, hit Crl+C or select
Edit.Copy. Now accept the changes to the mesh and hit Ctrl+V or select Edit.Paste outside of
any mode to paste a new mesh into the Feature Tree. This new mesh is made up of only those
polyfaces that were selected before, so it is one half of our desired result.

12. Edit the complete, trimmed mesh once again. Choose the Flood Fill selection filter, and use it to
select the other half of the trimmed/split mesh. Copy this portion just as you did in step 12
above, then exit out of the mesh editing mode. Outside of any particular editing mode, paste
the selected polyfaces as a 2nd (or 3rd) new mesh in the Feature Tree. You now have both pieces
split along the same curve and saved as individual meshes. Save the RapidWorks project, export
your split meshes and continue with your overall workflow! Here is a shot of the final result:

Happy mold making!

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When you create a mesh, you typically use the Mesh Buildup Wizard. If scan data is constituted by line-type point clouds, however, boundaries are not easy to maintain in their original shape while you generate the mesh.

If you manually triangulate using the 3D Triangulation command in the Addins menu, you will get better a result than the automatic Mesh Buildup Wizard method, as shown in the image below.

Method:
1. Before you apply triangulation on line-type scan data which is already aligned by a scan device, we recommend that you accurately align the scan sets again in the software. Select the Align button in the bottom pallet menu, or Click Tools > Scan Tools > Align in the menu.

Use the Global And Fine method with the “Apply Only Small Transform” option as shown in the below image. This option considers that the initial alignment is already done and accurately aligns scan shots, removing gaps among scan shots via small transformations. Plus, if overlapped regions have a planar shape, the alignment may slide along the planar area. This option prevents such featureless scan shots from sliding during alignment.

2. Apply the Addins > Combine command to make a single scan data set.

3. Click Add-ins > 3D Triangulate in the menu and check the “Assume Vertices Are Densely Placed Along A Direction” option. Especially, when you try to triangulate line type point cloud, this option is appropriate for keeping edges or boundaries as shown in the below image.

4. If necessary, execute the Enhance, Global Remesh and Fix Normal commands in Mesh mode to get a mesh which is well optimized and featured.

This technical tip is useful when you export a surface or solid body as a neutral format (IGES or STEP) into CATIA to create a complete, watertight solid model.

As you can see in the model tree as shown in the image above, the patches are broken after importing a body into CATIA. If you want to create a complete body, you need to use healing processes in CATIA, such as heal and join in the Healing Assistant.

Method:
This method is used in the Healing Assistant Workbench or Part Design Workbench. If the model has many patches and curves, it has a higher probability of producing errors. Therefore, it needs to be healed for broken patches.

In the Assistant Workbench:
1. Click Start > Mechanical Design > Healing Assistant in the menu, and click the “Heal” button in the toolbar. Select all imported surfaces and click the OK button, as shown in the image below. If CATIA cannot heal some edges, these edges are displayed in green. In that case, increase the tolerance value little by little (max. 0.1), and try to heal again.

Note
The Heal command improves surface connecting conditions. If surface connections are completely closed within the allowable tolerance, you can skip this stage.

Note
If you skip above the healing process, you can create a combined body by clicking the “Join” button in the tool bar as shown in the image below. Click the OK button.

In the Part Design Workbench:
1. Click Start > Mechanical Design > Part Design in the menu, and click the “Close Surface” button in the toolbar. Select the joined body in the model tree, as shown in the below image. Click the OK button.

2. This command converts the surface body to a solid body and registers it in the model tree. Finally, you will have created a closed solid body.

This technical tip will help you understand how to create a high quality fitting surface.

Step 1: Mesh Optimization

To get a high quality fitting surface, you will first need to prepare the mesh through some optimization processes. If the size of the poly-faces is regular and the resolution of the mesh is high enough, you will be able to fit a more ideal surface.

How to optimize a mesh to get a high quality fitting surface:

Note: XOR provides you with several methods to optimize a mesh from its current state, such as Healing Wizard, Fill Hole, Smooth, Enhance Shape, Optimize Mesh, etc.

If some abnormal faces and various defects exist in the mesh, you can easily find and clean them with the Healing Wizard command.
If some holes exist in the mesh, you can easily close them with the Fill Holes command.
You can also enhance the quality of the mesh using the Enhance Shape and Optimize Mesh commands.

1. Double-click the mesh, or click on the “Mesh” mode button in the Tool Palette, to enter Mesh Mode.

2. Click the “Healing Wizard” button or click Tools > Mesh Tools > Healing Wizard.

3. You can check which kinds of defects are in the mesh and how many there are, as shown in the image below.

4. Click the OK button

Note: The Healing Wizard automatically heals various defects in the mesh.

Folded Poly-Faces – If checked, folded poly-faces will be deleted.
Dangling Poly-Faces – If checked, you will remove any 2 or 3-sided open poly-faces.

Small Clusters – If checked, you can set a value for the Maximum Face Count In A Cluster; then all clusters (a group of connected poly-faces) that have less than the specified number of poly-faces will be removed.

Small Poly-Faces – If this is checked, you can input a value in the “Area Is Smaller Than” box, and poly-faces whose areas are smaller than this value will be removed.

Non-Manifold Poly-Faces – If checked, non-manifold faces and redundant poly-faces will be removed.
Crossing Poly-Faces – If checked, all the crossing faces will be removed. There are three methods: The Smooth method smoothly regenerates poly-faces around the crossing poly-faces. The Merge Poly-Vertices method merges poly-vertices around the crossing poly-faces. The Delete And Fill Hole method removes poly-faces around the crossing poly-faces and fills in the hole(s) there.

Small Tunnels – “Small tunnels” means that the poly-faces’ shape is constructed as a tunnel or handle. If Small Tunnels is checked, you can adjust the Poly-Face Count In Tunnel box. Then the tunnel faces whose number to the tunnel direction is shorter than this value, will be removed.

5. Click the “Defeature” button or click Tools > Mesh Tools > Defeature.

6. Select the Flat option as the “Method” and select a region to remove features and fill faces in that region, as shown in the image below.

7. Click the OK button.

Note: “Defeature” removes the selected poly-faces and fills in the space based on adjacent poly-face information.
If you want to re-form the feature after you generate whole surface body, you have to prepare a feature profile beforehand.
Another way to do this is, before Defeature operates, to copy the original feature into its own new mesh using Copy (Ctrl + C) and Paste (Ctrl + V). You will then be able to work with it later.

Note: You can fill faces in the missing area using “Fill Holes” or clicking Tools > Mesh Tools > Fill Holes.

8. Click the “Optimize Mesh” button, or click Tools > Mesh Tools > Optimize Mesh.

9. Select the “High Quality Mesh Conversion” option as the Method, and adjust the options as shown in the image below.

10. Click the OK button.

11. Check the result.

Step 2: Create Boundary Curves

Secondly, you can prepare boundary curves to create a fitting surface on the mesh. If the number of curve boundaries is 4 and the shape is a regular rectangular feature, you will get a better fitting surface.
Otherwise, a fitting surface will be twisted and have some self-intersection(s).

How to organize boundary curves to get a fitting surface:

Create 3D Mesh Sketch
• Create boundary curves which can keep the equilibrium of forces
• If the number of boundary curves is 4 and its shape is a regular rectangular feature, you will get abetter fitting surface, as shown in the image below.

• Even though you can keep that the number of boundary curves at 4, if its shape becomes suddenly narrow or twisted as shown in the image below, twisted and self-intersected faces could be created when the surface is generated.

Match Boundary Curves
• If possible, avoid “T-Junction” matching when you create curve networks
• If not, organize “T-Junction” matching so that the curve networks can keep the equilibrium of forces as shown in the image below.

• Other than the 4 sides of the curve boundary, others will create a trimmed fitting surface.
• If trimmed surfaces are neighbored with the same matching boundary, those will not be matched.
• Organize the curve network so that the surface matching conditions can be applied.

For Example:
Untrimmed Surface – Untrimmed Surface
Untrimmed Surface – Trimmed Surface – Trimmed Surface
Untrimmed Surface – T-junction matching – Untrimmed Surface

• If possible, setup the same number of control points in the each matching boundary of the surface patches to improve surface matching continuity.
• If possible, setup the boundary curves using appropriate control points to apply the fitting operation.

Create Curve Network
• If the shape is going sharp or dull, you can manage the number of curve boundaries according to the shape, as shown in the image below.

• If a fitting curve is not correctly put on the mesh, an accurate fitting surface cannot be created.
• In that case, increase the number of control points on the curve using the “rebuild” option

Step 3: Create a Boundary Fit Surface

Finally, you can create a fitting surface using the pre-defined boundary curves.
However, even if the curve networks are well organized on the mesh, the fit surface will be created a bit differently, according to the defined fitting options.

How to use options to get a high quality fitting surface:

Boundary Fit operation has been separated into 2 stages:
• In the first stage, you can set Mesh Curves, Curve Loops, and Loop options.
• In the second stage, you can define sharp edges to keep the sharpness at the boundary, as well as the number of control points in the surface to be created. This is shown in the image below.

1st Stage (Setup Curve Loops):
• Allow Hole (Boundary) – If this option is turned on, the surface will be created even though a hole exists inside the boundary of the curve, as shown in the image below.

• Allowable Convex Ratio – In the case that some feature(s) exist inside the loop, this option allows you to create a surface using a Convex Ratio.

2nd Stage (Adjust Fitting Options):
• Set Resolution – you can adjust the resolution of a surface patch via “Number of Control Points” or “Allowable Deviation.”
  • If possible, set the same number of control points along the U and V directions, as you can get a better surface body that way.
  • Using “Set Manually,” you can easily set the control points along the U and V directions of a surface patch, as shown in the image below.

• Set Sharp Edge – Use this option if a sharp area exists in a mesh, or if you need to keep the sharp feature on a surface body.
  A position matching operation will be applied to the boundary only.
  In this way, you can preserve the sharp edge in the surface body you’re creating and modify it whenever you want.

• Resample – If this option is turned on, the fitting area will be regularly simplified and a smoother surface will be generated.
  However, you can decide whether you turn the option on or not according to your particular application.
  If you want to generate a surface body as close as possible to the mesh (“as is”), even if the resulting shape would have positive or negative complex features like under-cut areas, turn off this option.

Method:
First of all, you can create a section profile from the CAD and Scan data using a Ref. Plane, as shown in the image below. (Design > Section)

Choose File > Export in the menu, then select both the CAD and Scan sections, as shown in the image below.

Click the OK button, then select AutoCAD DXF (dxf file format) as the saving file type. Check “2D section” in the “Export Section As” option at the bottom, as in the image below.

Import the file into AutoCAD, and you can make a draft or print it out with the scale option.

Create fit surfaces by drawing a patch network on the mesh:

As you can see below, there are some cases where the trimmed surfaces will produce a bad result. Specifically, the “Tangent Constraint On Boundary” option, which uses mesh normals to match continuity, sometimes gives a bad result.

(In General, you should avoid drawing patch boundary curves on the high curvature regions of a mesh.)

The following images are the result of a boundary fit rebuilt after optimizing the mesh (Optimize Mesh, then Enhance, thenSubdivide) and adjusting the curvature and size of the mesh.

You may see that the surface quality and continuity between patches are far better than before.

Therefore, the nearly class A quality of surfaces can be simply generated by mesh optimization (It takes only 1~2 min. in XOR)

It is especially indispensable when you match the continuity between patches using the “Tangent Constraint On Boundary” option.

(It’s better to optimize the triangles of meshes to be regular, even if meshes appear to be of good quality. In addition, making sufficiently dense meshes in proportion to the control points of the surface patches can help.)