3D Printed Sharpening Jig for Luba Mammotion Blades

A simple 3D printed TPU fixture that lets you re-sharpen Luba Automower blades at the correct angle — instead of throwing them away and buying new ones. The jig holds the blade at ~12° per side (~24° inclusive), which matches the factory grind on Luba Endurance blades.

Designed for: Luba Endurance Replacement Blades (official Mammotion).

Why this exists

Automower blades dull over a season of cutting. The factory solution is replacement — you throw the old ones away and buy new ones. But the steel in these blades is perfectly capable of being re-sharpened several times before it actually needs replacing. The only thing missing is a way to hold the blade at a consistent angle while you work the edge on a stone.

That's what this jig does. No clamps, no bolts, no setup — just two printed pieces and hand pressure.

How it works

The blade sits sandwiched between the two TPU pieces. The flexible TPU grips the blade faces, and the pressure of your hand against the jig while you sharpen is what keeps everything together. When you're done, you just pull the blade out.

The geometry of the jig sets the sharpening angle automatically — you don't have to eyeball it or guess. Tilt the jig flat against the stone and the edge meets the stone at the correct angle.

Sharpening routine

1. Place the blade between the two TPU pieces, edge exposed

2. Wet the sharpening stone (I use a standard water stone — link)

3. Hold the jig flat on the stone with firm hand pressure

4. Use alternating strokes on both sides of the blade to keep the edge symmetric

5. Rinse the blade, dry it, and re-install

A short demonstration video:

Safety

Luba blades are sharp, and sharpening makes them sharper. Wear cut-resistant gloves when handling the blade itself, and pick it up by the mounting hole rather than the body. Keep the jig flat against the stone — lifting it mid-stroke can roll the edge against your fingers.

Print Settings

• Material: TPU 95A (Polymaker PolyFlex or equivalent)

• Nozzle: 0.4mm

• Layer height: 0.2mm

• Infill: 20–30% is plenty

• Supports: not required

• Tips:

  • Dry the TPU filament before printing — TPU absorbs moisture quickly

  • Slower print speeds (20–30 mm/s) give cleaner results with flexible filament

Note on other blade models

The jig is tuned for Luba Endurance blades specifically. If you try it with a different blade (other Luba models, third-party replacements, blades from other automowers), please post a Make or leave a comment with the blade model and thickness — I'd like to collect data on what fits and what doesn't.

Troubleshooting: Blade not razor-sharp after sharpening?

If the cutting edge doesn't fully contact the stone during sharpening, shorten the base (the surface resting on the stone) by 0.1–0.2 mm in your slicer. This lowers the entire fixture slightly, increasing the effective contact angle just enough for the edge to reach the stone — while keeping the blade in full flat contact with the support.

How to do it: OrcaSlicer / Bambu Studio → right-click model → Cut → horizontal plane ~0.2 mm from base → keep upper part.

Note: stay in the 0.1–0.3 mm range. TPU 95A compresses slightly under hand pressure, and blade thickness varies between Luba production batches, so small adjustments are usually enough.

Fixture geometry: the sharpening angle is set by the inclined plane and the base. Small base adjustments (0.1–0.2 mm) compensate for blade thickness variations.