01 / UNDERSTAND
Your design brief
Make a 70 × 70 mm stencil for a circular symbol. Its centre must stay connected to the surrounding sheet. Develop a bridge and explain how it changes the printed symbol.
What you will learn
- Identify disconnected islands in a stencil.
- Use subtraction and union for a functional purpose.
- Evaluate the trade-off between support and the appearance of a mark.
You will need: Forma, paper, a pencil and a ruler. A teacher may provide a paper stencil to demonstrate an island.
02 / EXPLORE
Make it in Forma
Menu names refer to the current browser edition. On a touchscreen, use Properties to show the inspector. A keyboard is helpful for exact dimensions.
Sketch the problem
Draw an O-shaped opening inside a square. Shade the material you intend to keep. Imagine removing the ring: what holds the central disc?
Check: Mark the disconnected centre in a different colour.
Make the blank
Create a new drawing with millimetres and scale 1:1. In Draw → Exact geometry, create a Rectangle at X 40, Y 40, Width 70, Height 70, Corner radius 0.
Check: The square is the material you plan to keep.
Make a ring-shaped cutter
Create a Circle centred at X 75, Y 75 with radius 20. Create a second circle at the same centre with radius 12. Click empty space, select the larger circle first, then Shift-click the smaller one. Choose Modify → Subtract shapes.
Check: The result is a ring with an 8 mm radial width.
Cut the ring from the blank
Deselect. Select the square first, then Shift-click the ring. Choose Subtract shapes. The central disc remains in the drawing but is separated from the outer sheet.
Check: This is the intentional design problem, not a software error.
Build a bridge
Create a Rectangle at X 73, Y 52, Width 4, Height 23, Corner radius 0. It overlaps both the upper border material and the centre disc. Select this rectangle and the stencil; choose Modify → Unite shapes.
Check: The bridge crosses the complete gap, leaving the centre connected.
Inspect the result
Zoom into both ends of the bridge. Check that unwanted internal edges have disappeared. Sketch the mark the stencil would produce, including its interruption at the bridge.
Check: A line merely touching an island is not a supporting area of material.
Redesign and evaluate
Save the design. Make a second version with a differently positioned bridge. Compare clarity of the symbol and support for the centre. Justify a preferred option.
Check: The 4 mm bridge is a classroom example, not a universal manufacturing minimum.
Save the evidence
Save the .forma project and export SVG if requested. Explain the difference between the material drawing and the mark left through its opening.
Check: Do not use Explode when you need to preserve a closed cutting outline.
03 / REFLECT
Check the design. Explain the decisions.
These ticks are temporary and are not submitted or saved. Keep your project file and written reflection as evidence.
Your design reflection
Which area would fall out before adding the bridge?
How does your bridge affect both function and appearance?
A little support
Use the supplied circle dimensions and a single top bridge. Colour a paper drawing to distinguish material from empty space.
Take it further
Develop a two-island symbol. Compare one and two bridges for each island, considering appearance and the likely direction of bending.
FOR TEACHERS
Plan the learning, not just the clicks.
Suggested timing: 10 minutes to examine a stencil, 30 for CAD, 15 for redesign and 10 for discussion. Selection order matters: first-selected shape is the area from which other shapes are subtracted. Fabrication, if used, needs a material-appropriate bridge design verified by the teacher.
Evidence to look for
An annotated island sketch, two vector versions and a functional explanation of the bridge.
Suggested curriculum connection
England KS3 Design/Technical knowledge/Evaluate: solve a design problem, consider structural performance and refine a proposal. Read the England D&T programme.
For other UK nations, use the curriculum adaptation guide. Ages and timings are suggestions, not equivalences between national stages.
Teacher discussion notes
The annular opening disconnects the central disc. The sample bridge spans Y 52–75, crossing the upper part of the ring and overlapping the disc and the outer sheet.
Original Forma2D activity · Specialised Laser Systems · Reviewed 5 October 2026
Keep .forma files for editing. Any manufacture uses the school’s approved materials, equipment and procedures.