Eight smartwatch prototypes before moving to steel
A connected-health start-up had the 3D model of its watch. Before committing to steel manufacturing, it wanted it on the wrist. We printed eight complete variants, designed an assembly with no visible screws and handed over a file set ready for the manufacturer.
- Client
- Connected-health start-up
- Sector
- Connected health
- Location
- Remote
- Deadline
- 15 October 2026
- Production
- FDM, champagne PLA Metal, titanium grey PLA Silk+, black PLA
The brief
Choosing a shape on the wrist, not on a screen
The client sent us the model of its case: a four-part shield (case, glass, bezel, back) drawn in SolidWorks. It was undecided on the bezel thickness and on the shape of the corners. Rather than a single prototype, we proposed two families: the original shape in four thicknesses, and the same shape with rounded corners. Eight complete watches, to compare side by side and to wear.
The constraints
What made the project tricky
- 01
A model with no fixings
The original file had nothing to hold the glass and the bezel. They had to be secured without changing the outside of the watch.
- 02
Differences of 1 to 2 mm
The variants differ by only one or two millimetres of thickness or radius. The print had to be fine enough for these differences to be seen and felt on the wrist.
- 03
A finish close to metal
The final watch will be steel. The prototypes had to give a fair idea of it: champagne or titanium grey bezel, black case, no plastic look.
- 04
Preparing what comes next
The prototype is only a step. The files handed over had to let the client go straight to a steel manufacturer.
The part, taken apart
- 01
Four parts, one watch
Case, glass, bezel and back. Once closed, the watch shows no screw and no fixing.
- 02
The bezel and its three pins
Under the bezel, three 2 mm pins. They go into the case where it is solid, centre the bezel and stop it from turning.
- 03
The glass and its collar
A 0.8 mm collar under the edge of the glass fits into the rebate of the bezel: the glass is held without glue.
- 04
The screwed back
Four screws from the back, as on the original model. The electronics go into the case before closing.
Our technical choices
How we solved it
- 01
Two families, eight variants
Family A: the original shape in 7, 8, 10 and 12 mm. Family B: the 10 mm reference with corners rounded to 2, 4 and 6 mm, plus an 8 mm version. Each variant changes one parameter at a time, so the comparison stays readable.
- 02
Glass held captive by the bezel
A 0.8 mm collar runs under the edge of the glass and fits into a rebate cut under the bezel. The glass can no longer come out at the front, and nothing shows once the watch is closed.
- 03
Three pins to fit the bezel
Three 2 mm pins under the bezel go into three holes in the case, placed where the material is solid. They centre the bezel, stop it from turning and push in by hand. The back stays fixed with four screws, as on the original model.
- 04
Clearances checked on real parts
Drawn at 0.30 mm, the clearances come down to 0.10–0.20 mm after printing: the glass drops into place, the bezel pushes in with a finger. These values are specific to PLA; the file set states that the steel manufacturer must adapt them to its process.
- 05
Two materials for the bezel
Champagne PLA Metal and titanium grey PLA Silk+ in alternation; case, glass and back in black PLA. 0.08 mm layers for bezels and glasses, 0.12 mm for cases, full infill, visible face printed upwards on a raft for a surface free of support marks.
Key figures
- variants printed and assembled
- 8
- variants printed and assembled
- parts printed
- 32
- parts printed
- layer height for bezels and glasses
- 0.08 mm
- layer height for bezels and glasses
- file versions: with and without fixings
- 2
- file versions: with and without fixings
The schedule
Delivered, ready for the manufacturer
The eight prototypes shipped on 15 October with a complete file set: STEP files and dimensioned 2D drawings for each variant, with and without fixings, source files, STL files and print plates for reprints. The client is trying the variants on the wrist, then will send the chosen one to its steel manufacturer.
- Done
Delivery of the eight prototypes and the complete file set
Services involved
What we did for this client
Other projects
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