Splitting and Combining Bodies for Advanced Part Design

1. The Core Concept: Bodies, Splits, and Combines

Before we dive in, let's briefly revisit a concept from our last lesson. Both Split Body and Combine operate on bodies. Remember, a body is a continuous 3D volume. A single component in your design can contain multiple bodies. These tools allow you to manage those bodies.

• Split Body: Uses a "tool" (like a plane or surface) to slice a body into multiple new bodies.
• Combine: Performs a boolean operation (Join, Cut, or Intersect) between two or more bodies.

This workflow—modeling a solid and then cutting it up—is often much easier than trying to model separate, perfectly-fitting parts from the beginning.

2. Dividing Models with the Split Body Tool

The Split Body command is your primary tool for dividing a single solid body into two or more separate bodies. Think of it as a precision saw. You choose the body you want to cut and the "blade" you want to cut it with.

This "blade," or Splitting Tool, can be:

• A construction plane
• A face of another body
• An entire body
• A surface (which you can create from a sketch)

Let's start with a straightforward video demonstration.

Now, let's look at a detailed, step-by-step example in a training document. This shows how to create a two-part enclosure for a utility knife.

This exercise demonstrates a key use case: ensuring that when you split a housing, any internal components that cross the split line are also split in the exact same place to ensure a perfect fit.

3. Merging and Subtracting with the Combine Tool

The Combine tool is the counterpart to Split Body. It allows you to take multiple bodies and perform a boolean operation on them.

The dialog box is simple:

• Target Body: The primary body that will be modified.
• Tool Bodies: The body (or bodies) that will act on the target.
• Operation:
  • Join: Fuses all selected bodies into a single body.
  • Cut: Subtracts the volume of the tool bodies from the target body.
  • Intersect: Creates a new body from only the overlapping volume of the selected bodies.
• Keep Tools: This is a crucial checkbox! When using Cut or Intersect, checking this box preserves your tool bodies after the operation. This is essential for things like creating a mold or an inlay where you need both the final part and the tool that shaped it.

Let's see this in a practical context for creating a custom keychain—a perfect example of a gaming or DIY accessory.

Now, let's revisit the utility knife example to see the Join operation in action. After splitting the handle and the pin, the designer needs to join the corresponding halves together.

4. Advanced Workflows and Practical Applications

In practice, you'll rarely use these tools in isolation. Complex part construction involves a sequence of operations. The following video explores several different strategies to achieve the same result—separating a piece from a larger body—and introduces the critical concept of adding tolerance for 3D printing.

Application: Creating Interlocking Joints

Now for a powerful technique that directly applies to your goals of building sturdy DIY projects. By creating a custom splitting tool, you can create strong, self-aligning joints like dovetails. This is invaluable for assembling larger 3D prints or even for your woodworking projects.

5. Your Turn: Practice Task

Let's put this into practice by designing a simple two-part container.

Task: Model a Small Project Box (10 minutes)

1. Create the Solid Form:

   • Create a new design.
   • Sketch a Center Rectangle on the ground plane, 60mm wide and 40mm deep.
   • Extrude this rectangle up by 30mm to create a solid block.

2. Hollow it Out:

   • Use the Modify > Shell tool.
   • Select the top face of the block.
   • Specify a wall thickness of 2mm. You should now have an open-topped box.

3. Split it into a Lid and Base:

   • Create a construction plane to serve as your "saw." Go to Construct > Offset Plane.
   • Select the bottom face of the box as your reference.
   • Offset the plane upwards by 20mm. This plane should now be floating inside the box walls, 10mm from the top.
   • Go to Modify > Split Body.
   • For Body to Split, select your box.
   • For Splitting Tool, select the construction plane you just created.
   • Click OK. In your Browser, under the Bodies folder, you should now have two bodies: a shorter base and a taller lid. You can hide one to see the other.

You've just created a basic two-part enclosure, a fundamental step in designing cases for your gaming accessories!

Conclusion

Today you've learned how to deconstruct and reconstruct solid models using the Split Body and Combine tools. These commands move you beyond modeling single objects and into the realm of creating functional, multi-part assemblies.

Key Takeaways:

• Split Body divides a body using a plane, surface, or another body as a cutting tool. It's perfect for creating enclosures or breaking up large models for printing.
• Combine performs boolean operations: Join to merge bodies, Cut to subtract them, and Intersect to find their common volume.
• The Keep Tools option in the Combine command is essential for workflows where you need to preserve the cutting object, such as when creating inlays or molds.
• Complex parts are often made by combining these tools in sequence, such as sketching a profile, creating a surface, thickening it, and using it as a custom splitting tool.

Next Lesson Preview:
As you've seen, using tools like Split, Combine, Pattern, and Mirror can create a long and complex design history in your timeline. Sometimes, a change made early on can cause errors in later features. In our next lesson, we will learn how to diagnose and resolve timeline errors, a critical skill for maintaining and editing your sophisticated designs.