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[Allan]

Hey there, I’m designing a flexible watch strap that will be injection molded in TPU (Shore 85A). I want to include some small embossed text (branding and serial number) directly on the strap, but I’m unsure about the minimum dimensions that will mold cleanly without issues like incomplete fill or poor definition. Have any of you had good results with small embossed features in TPU? Specifically wondering what minimum height and width you’ve found to work reliably.

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[niklas lindborg]

I’ve worked with TPU (Shore 90A) before, and embossed text can be tricky. For clean results, I’d recommend keeping the text height at least 0.3–0.5 mm and the line width ≥ 0.25 mm. Anything smaller risks poor fill or blurring, especially since TPU is flexible and can stick in the mold. Remember to consider the draft angle on the text walls to help with the release for demolding.

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[Allan]

Thanks for the specs! Do you think a serif vs. sans-serif font makes a difference in TPU?

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[Theodore Carr]

Sans-serif (like Arial) usually works better—fewer thin details to fill. Serifs can get clogged or torn during demolding. Also, make sure your text isn’t too close to edges or bends; TPU shrinks slightly, which can distort fine features. I also recommend placing gates so the text fills last, avoiding flow hesitation. A fan gate near the buckle end (away from text) often works well for TPU straps. Maybe do a small test mold with just the text first.

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