Make a part lighter, using alternatives

"Make it lighter" sounds like one request, but there are many ways to do it: thinner walls, pockets, lightening holes, ribs, a different material, a smaller part. Each trades weight against strength, stiffness, print time, and looks. A good approach is to try several, compare honestly, and keep the winner.

That is exactly what alternatives are for (branches, with Pro terms).

Shortcut: say "try 3 versions that are lighter" (or ⌘K → Try versions…). The agent builds three different directions at once, measures each, and lets you try any of them as an alternative or use it straight away in your main design. See Variants: try 3 versions and compare. The steps below are the hands-on way.

1. Set a goal and protect what matters

Before changing anything, decide what must not change. Write it as design intent, so it holds across every experiment:

Always keep the 8 mm bore, the overall diameter of 60 mm, and the 4 mounting holes unchanged. Never let a wall be thinner than 1.6 mm.

Note the starting weight. Ask:

What does this weigh in PETG, and how long does it take to print?

2. One alternative per idea

Try an alternative for each approach (in History, Try an alternative, or just ask the agent). Name it after the idea.

Try an alternative called lightening-holes. Add a circular pattern of lightening holes through the web of the gear. Keep at least 3 mm of material between holes and around the hub.

Then go back to the main design and try another:

Try an alternative called thin-web, starting from the main design. Reduce the web thickness from 8 mm to 4 mm, keeping the hub and the rim at full thickness. Add a 1.5 mm fillet where the web meets the hub.

And a third:

Try an alternative called ribbed, starting from the main design. Thin the web to 3 mm and add 6 radial ribs, 2 mm thick, for stiffness.

Each one is a safe experiment. The main design stays untouched.

3. Compare with the main design

Select an alternative in History and press Compare with main design:

• The list of changes shows the numbers that changed, such as "Weight 142 g to 118 g".
• On Pro, the 3D view shows material you removed in red and material you added in green.

Put the results in a small table:

(The numbers here are illustrative. Yours will come from your model.)

4. Check printability and function

For each promising alternative, open Make and run the check. A lighter part that needs supports, or has thin features that will not print, is not really an improvement.

Function checks matter more than numbers. Ask:

Compare the thin-web and ribbed alternatives. Which is stiffer for a gear that sees 0.5 N-m of torque, and why? Be honest about uncertainty.

The agent can reason about it in words; for numbers, ask on each alternative “Will this hold 0.5 N·m?” or use Simulate… in ⌘K for a stress heatmap and a safety factor (see Will it hold? Simulation explained). For parts that matter, print the candidate and test it.

Want the optimiser to find the lightest shape for you? Ask “make this lighter but still hold 5 kg” (or press Make it lighter on a simulation result). Generative design gives 2–3 verified outcomes, and Try as alternative on any of them puts it next to the alternatives you made by hand (see Generative design: make it lighter, still strong).

5. Use the winner

When one alternative earns its place:

• Use this alternative brings everything across into the main design, with a preview first.
• Copy this change to the main design takes just one change, if you like parts of different alternatives, such as the ribs from one and the holes from another.

Delete or keep the losing alternatives. They cost nothing, and they are a record of what you tried and why it lost.

6. Release it

When the new version is final, press Release this version and call it something like "v1.1-lighter". It freezes the geometry together with its Make list, so you can always reproduce what you shipped.

Other ways to lighten a part

Try it

On the Spur gear template, with a plan that includes alternatives:

Try an alternative called lighter. Add 6 lightening holes through the web, evenly spaced on a circular pattern, each 10 mm in diameter. Keep the bore and the teeth unchanged. Then show me the weight change against the main design.