Using CAD Tools to Edit Your Mesh

There may be times when all you need is a nice water-tight mesh. Scan the part, run the Healing Wizard, maybe a Rewrap command, and presto! But what if you want to add a precise feature? Perhaps a few quarter inch holes for fastening locations or maybe you want to trim the part so that its an exact height. Well its a good thing you have Rapidform! In this post, I’ll show you how to use some of our CAD Tools on mesh bodies.

Overview

The main trick is that you need to remember that Rapidform is a history-based modeler. This means that if you want to use any surfaces or ref. geometry to edit your mesh, those features need to be above the mesh in the feature tree. I personally like making a copy of the mesh. This allows you to have an original copy in the file that you can always reference back to. So we just need to make the CAD entities we want to use to edit our mesh. Then we copy our mesh and use those entities on our copied mesh using the mesh tools.

The Scenario

In this post, we’ll use our Quick Start Guide sample model, the bottle. (C:\Program Files\INUS Technology\Rapidform\Sample\QuickStartGuide\Bottle.stl).

Our customer wants to take this scan of his and make a print out of the stl, but of course he wants some quick edits done. The printed bottle will eventually be made into a trophy on a stand, so they’ve requested that the height of the bottle be shortened by 0.315 inches. They’ve also requested that a clearance hole be modeled in so that they can tap and thread the bottle. It’ll be a 1/4-inch threaded post, so the hole needs to have a 7/32-inch diameter and be at least an inch deep.

Getting It Done

First we’ll create a plane that’s 0.315 inches above the bottom of the bottle. We’ll use this plane not only to shorten the height, but it will also serve as the sketch plane for our hole.

Conveniently the bottle scan is already aligned and its sitting on the Top plane. We can quickly generate a plane by using the CTRL key.

Thinking ahead, now we’ll use this plane for our 2D mesh sketch to make our clearance hole. The cross-section can referenced to make sure the hole is concentric (it happens to be centered around the origin), and the smart dimension tool will guarantee the size of the hole.

Using the sketch, we can extrude a surface (or a solid) that we’ll use to create the hole in the mesh. We need at least a 1-inch deep hole so we’ll extrude to about 1.15 inches.

Now that we have our tools ready, we’ll make a copy of the mesh using the copy and paste commands (Edit Menu).

In Mesh Mode (double-click on the Copied Mesh), we’ll be using the split command (Tools>Mesh Tools> Split). First we’ll split the mesh using Plane 1. Be sure to have “Cap Section Ends” checked, or if you prefer, you can use the fill hole command.

Then we’ll split the mesh again and use the surface body as the entity.

With a quick fill hole on the bottom, we have our mesh!

The result is a mesh file that has been modified with CAD precision, a unique feature found in your Rapidform Software.

Notes

A slightly different workflow can be used to generate the hole (or more complex shapes that one may encounter). Instead, you would convert the solid body into a mesh by making an empty mesh feature and using the “Convert Body” command. Then use the Mesh Boolean command (Tools>Scan Tools>Boolean) to cut (or merge or intersect) the shape.

This means that, if you’re using more than one surface or solid to split a face, the order in which you pick your tool entities matters.

In the example below, picking the curvey surface first and the flat surface second results in the image on the left, while picking in the other order results in the image on the right.

Using Split Face (found under Insert>Modeling Feature>Split Face), you can project a curve onto a face (surface or solid) and then trim or split that face.  But the projection method is different depending on whether you use 2D sketches or 3D sketches as your too entity to do the cutting. A 2D sketch will be projected normal to the plane that the sketch lies on, whereas a 3D sketch will be projected normal to the direction of the target face.

As you can see, using one or the other type of sketch will let you get the desired result depending on what you’re trying to do.

Using Split Face to create parting lines

1) Go to Insert>Modeling Feature>Split Face in XOR

2) Select the Silhouette radio button

3) Define the pull direction (this is the direction the mold will be pulled when separating).  In the example below, we’re going to use the axis of one of the cylinder features of this part, but you can use other reference geometries or features.

4) Pick the target entities that you want to split apart.  Since this is the split faces command, you’ll need to pick one or more faces here.

5) Click the check mark to run the command, and you’re done.

When you import scan data, the data will be loading in the software, and a new Mesh Feature will be added in the Feature Tree. Sometimes, you can have additional items created after the Mesh Feature, but you will not be able to immediately be able to trim the mesh using these items. This is because parametric CAD systems have a history, meaning that it not only records what you do, but when you did them, and what the current state of the model was at that time. When we Rollback to edit the model, we are going back in time. Any items that did not exist at that time will not be available. We have three possible solutions to this situation, as follows:

Preparation
1. Click the (Import) button, Click Insert > Import to open the Import dialog box.
2. Select all files.

3. You can see an unedited mesh data as shown in the image below.

1. Using Ref.Plane

First at all, when you create a Ref. plane, the plane feature is recorded under the mesh feature. In this case, you will not be able to select of use the Ref. plane. We can, however, chage the order of the events in our history. By moving the plane to occur before the mesh, we will the be able to use it while editing our mesh feature.

You must move the Plane 1 up before the mesh feature, as shown in the image below.

Double click the Mesh Feature in the Feature Tree or click the (Mesh) button. You will enter the Mesh mode, and then you can edit the mesh by using the Ref. plane.
You can see the Ref. Plane in the Mesh mode as shown in the below image.

Click the (Split) button, or click Tools > Mesh Tools >Split in the menu.

Check By Entity as Method and select Plane1 as the Tool Entity. If you want a closed mesh, you can check the Cap Section Ends option. Click the (Next) button.

Select the remaining region and click the (OK) button.
Shown below is a split mesh.

2. Using a 3D Sketch

This method is to use the 3D Mesh Sketch. First at all, you must sketch a line by using the spline command, and then copy and to move it.

Click the (3D Mesh Sketch) button. Click the (Spline) button, or click Tools > 3D Sketch Entities > Spline in the menu.

Sketch the spline on the mesh as shown in the image below.

Click the (OK) button. You can see 3D Sketch 1 Feature located under the Mesh Trim Feature. In this case, you cannot edit the mesh with the 3D Sketch.

Select 3D Sketch 1 in the Feature Tree and copy it using Ctrl + C on the keyboard.

Click the Ok button.

To paste the Copied Sketch (Ctrl + V)

Select Copied Sketch and move it up before the mesh feature as shown in the image below.

Double Click the mesh and enter the Mesh mode.

Click the (Trim) button and check By Curve as the Method. Select the previously created spline as the Curves. Click the (Next) button.

Select the Remaining region and Click the (OK) button.

Shown below is a Trimmed mesh

3. Moving the mesh

This method is to use the copy & paste command and is very similar the previous method.

Click the (3D Mesh Sketch) button. Click the (Spline) button, or click Tools > 3D Sketch Entities > Spline in the menu. Sketch the spline on the mesh as shown in the image below. Click the (3D Mesh Sketch) button again to escape this mode.

Select the mesh in the Feature Tree and copy it using Ctrl+C on the keyboard.
Click the OK button.

Paste the Copied Sketch (Ctrl +V) and it is automatically placed at the end of the Feature Tree as shown in the image below.

Note

If the mesh is not placed in the appropriate place, under the 3D Sketch; you must click-and-drag to move the mesh feature below the sketch feature desired.

Double click the Copied Mesh to enter the mesh edit mode.

Click the (Trim) button and check By Curve as the Method. Select the created spline as the Curves. Click the (Next) button.

Select the remaining region and Click the (OK) button.

Shown below is a trimmed mesh.