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Basic design conceptsBeginner16 min

Combine, cut and soften edges

Experiment with union, difference and intersection, then compare a fillet with a chamfer in 3D.

DESIGN LAB · Learn by doing

Think in volumes: add what you need, remove what you do not, then finish the edges. Watch both the shape and its volume as you work.

Two bodies, three outcomes

A is the main block. B is the offset tool. Move B into and out of A, and compare the three operations on the same inputs.

Boolean operation

Keep all material in either body. Overlapping solids join; separated inputs remain separate volumes.

Result volume

78,880 mm³

Your turn

Cut a notch: choose Difference and place B at X = 20 mm. Then move B to 50 mm to discover why the cut disappears.

  • Difference selected, B at 20 mm

Keep experimenting. The checklist updates as you work.

Round or bevel?

Switch between a sharp corner, a circular fillet and a flat chamfer. Orbit the part to inspect the vertical edges.

Treat the four vertical edges

The fillet rounds four vertical edges with a circular arc; the chamfer replaces them with flat 45° faces. Top and bottom edges stay sharp. Large radii can consume small features or fail in CAD.

Order and target matter

A − B removes material from A; B − A is a different result. Union keeps either volume; intersection keeps their common volume. A cutter must overlap the target to remove anything. Edge treatments are often added after the main cuts so later changes are easier to understand. A fillet is not automatically a strength guarantee: loading, radius, orientation and material still matter.

The same plate as a solid: its outline becomes side faces, and the inner circle becomes a through-hole. Notice the rounded corners.Ex.ungue.leonem · CC0 1.0 · Wikimedia Commons

Words you can now use

Union
All volume in A or B, counting their overlap once.
Difference
The part of a target that remains after removing a tool volume.
Intersection
Only the volume shared by both inputs.
Fillet / chamfer
A curved edge transition / a flat bevel replacing an edge.

Use it in your CAD

Look for Combine/Boolean with Join or Union, Cut or Difference, and Intersect. In Tinkercad, overlap a Hole shape with a solid and Group to subtract. For edge finishing, select the edge first and find Fillet or Chamfer; check the preview before accepting.

Check yourself

Pick an answer for each question.

1. Which operation cuts tool B out of target A?

2. A and B do not touch. Their intersection is…

3. Which tool creates a flat bevel?

Sources (9)

Figures such as temperatures and drying times are typical ranges. Always check the label on your own spool and your printer manufacturer's guidance.