The Bambu website specs the drying for their TPU at 70°F for 8 hours. But when I select TPU for drying in the HT AMS, it shows 75°F for 18 hours. Seems like quite a discrepancy. What’s the correct settings and why are they so different?
You’re not wrong to question that discrepancy—70 °C for 8 hours vs 75 °C for 18 hours is a big difference, and it’s not unique to Bambu. Here’s the deal:
Filament drying is often simplified in ways that make the numbers look authoritative, but they’re not absolute. Bambu’s website likely gives a general-purpose baseline that avoids risk to the filament. The AMS HT preset probably assumes more moisture content or a more conservative dry-out target—maybe overcompensating to account for ambient humidity, spool mass, or inconsistent prior storage.
Moisture removal depends on two things: heat and time. Higher temperatures increase molecular mobility, helping moisture diffuse out faster. But with enough time, lower temps can get you to the same end state. That’s why the AMS might run a longer cycle at a slightly higher temperature—it’s just a different path to dry.
If you really want to settle it, try this:
- Saturate two identical TPU spools: put them in a sealed container with an open jar of water, place it in a warm area, and monitor humidity with a hygrometer. Weigh the spools before and after a few days to confirm moisture uptake.
- Dry one spool using the Bambu website or filament manufacturer’s recommendation. Dry the other using the AMS preset.
- Weigh them periodically during drying. Once their weights stabilize, compare print quality.
Chances are both methods work, just with different tradeoffs between safety margin and efficiency.
Bottom line: There’s no single “correct” number. Manufacturer specs are best guesses wrapped in caution tape. AMS presets are tuned for hands-off consistency. If you want precision, trust your scale and your printer—not just the screen.
Or skip all of that and take my word for it—I already ran the experiment when I asked the same question. LOL. 
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Thanks for the detailed reply. Makes sense. I guess I was just wondering why the same company would use such hugely different settings in their recommendations. I assume they test these things, at least to some degree, and would use the same results in both places.
But apparently not. Probably a typical large-company problem of one hand not knowing what the other is doing. Likely one team created the settings for the HT AMS and another posted the settings on the website.
Thanks again.
This likely reflects the Chinese manufacturing mindset of “close enough,” or chabuduo (差不多). It’s very possible the specs we’re seeing aren’t from Bambu directly, but from the design house that developed the AMS or from their contract manufacturer.
Unlike Japanese or Western firms, which tend to rebrand and validate everything they sell—even if outsourced—many Chinese companies are less meticulous. Some even highlight the design house behind the product. For example, Polymaker openly markets a dryer designed by industrial design house FabNotion. In such cases, it’s often the design house—not the brand—that publishes the specs, and the brand may do little to standardize or verify them.
