Technology

Thermal Quality Index (TQI)

TQI is Helio’s way to summarize whether a print’s thermal conditions are staying in a “healthy” range for reliable bonding, dimensional stability, and repeatable surface quality.

This page is written to be useful (not academic). For deeper technical references, see the Helio Additive Wiki .

What TQI tells you

In practice, TQI helps you answer two questions that drive print outcomes:

  • Are layers trending too hot or too cold (a consistent bias)?
  • Are thermal conditions stable from layer to layer (repeatability), or oscillating?

When TQI improves, you generally see fewer failures (warp/deformation risk and bonding issues), more consistent quality, and a wider “safe” window for speed.

How to interpret “mean” vs “variability”

You’ll often see TQI discussed in terms of:

  • Mean (or |mean|): whether the print is consistently off-target in one direction.
  • Variability (e.g., standard deviation): whether conditions swing from layer to layer.
Rule of thumb
Lower |mean| and lower variability is the “good zone”: closer to stable, repeatable thermal behavior.
Slicer screenshot showing Thermal Index (mean) color overlay and legend.
Example in-slicer view: the TQI/Thermal Index overlay helps you see where thermal conditions are stable vs risky before you print.

How Helio uses TQI

Assess

Assess uses simulation to highlight risk zones and thermal behavior that can lead to failures or inconsistent quality—before you commit time and material.

Enhance

Enhance tunes layer-time behavior to improve throughput while protecting thermal stability—helping reduce |mean| and variability in the process.

The goal isn’t a “perfect number” in isolation—it’s to keep the print in a thermal regime that produces strong, repeatable parts with fewer surprises.

Common patterns (and what to do)

Good average, high variability
Often shows up on mixed geometry (big + tiny features) where cooling swings. Aim for steadier layer time and fewer abrupt transitions.
Biased average
When the print runs consistently off-target. This can be driven by global cooling/temperature choices or material behavior—Assess helps you see it early.
Localized hotspots
Small regions overheat or cool too fast. Look for geometry-driven risk zones; Enhance can adjust speed locally to keep conditions stable.
Want to see TQI on one of your parts?
Run a quick setup, then Assess a print to see risk zones and thermal behavior inside your slicer.