Gauge-Correlated Asymmetry in Polymer Cooling

Edge of Practice · Steward’s Falsification Protocol

One-Sentence Assumption Under Test

Standard injection molding cooling times are sufficient to suppress internal thermal asymmetry such that no reproducible downstream defect emerges in finished polypropylene parts under nominal process conditions.

Why This Assumption Is Tolerated

Fixed cooling times simplify cycle design and maximize throughput. Internal thermal gradients are difficult to observe directly without intrusive instrumentation, and downstream inspection often averages cooling-driven effects such as warpage, sink, or shrink within tolerance limits. Low rejection rates are treated as confirmation, allowing the assumption to persist without direct falsification.

Minimal Plant-Ready Falsification Experiment

Setup

  • Mold a standard polypropylene part (approximately 4 mm nominal wall thickness) at steady state.
  • Hold all parameters constant: material lot, melt temperature, mold temperature, packing profile, and ejection timing.
  • Run three cooling-time conditions:
    • Nominal production cooling time
    • Nominal minus 20 percent
    • Nominal plus 20 percent
  • Produce 30 parts per condition.

No invasive sensors, mold modifications, or proprietary instrumentation are required.

Single Primary Readout

Select one downstream artifact metric appropriate to the part geometry and use it consistently across all conditions:

  • Warpage magnitude and direction at fixed datums
  • Sink depth at a defined rib or boss
  • Shrink differential along flow versus transverse direction
  • Optical haze or crystallinity banding under fixed lighting conditions

Pass / Fail Criteria

Pass: The artifact metric remains within specification and shows no systematic trend across cooling-time variation.

Fail: A reproducible defect signature appears at nominal cooling time and shifts predictably with reduced or increased cooling time.

Flag for review: Persistent but sub-threshold artifact signatures appear without clear monotonic trend, indicating potential emerging asymmetry requiring further investigation.

Embarrassing Flip Condition

A consistent warpage vector, sink location, or banding pattern appears at nominal settings and improves or worsens monotonically as cooling time is increased or decreased.

If this condition is documented, the associated symmetry assumption loses its operational exemption and must be formally addressed through documented process adjustment, tooling modification, or control strategy revision.

Protocol Safeguards and Artifact Controls

  • Numeric gate validation: Thresholds reflect representative polypropylene injection molding conditions and must be empirically validated for material grade, geometry, and equipment.
  • Reference frame verification: Physical datums and measurement reference points must be verified and logged prior to each run.
  • Reproducibility requirement: Artifact signatures must persist across multiple parts within the same cooling-time condition.

Corrected Interpretation if Flip Occurs

The nominal cooling time does not sufficiently eliminate internal thermal asymmetry. The assumption of uniform solidification is operationally invalid for process control purposes, and downstream defects are being tolerated rather than prevented.

Steward’s Note

This experiment does not aim to demonstrate the existence of internal thermal gradients. That fact is already established. Its purpose is to determine whether the selected cooling time suppresses those gradients below the threshold of operational consequence.

By correlating asymmetry with a product artifact the plant already measures, the protocol removes plausible deniability while remaining executable with standard production tools.

Canonical Principle

Gauge-Correlated Asymmetry Clause: A symmetry claim that cannot withstand reproducible, product-correlated asymmetric signatures is operationally void for process control purposes.

Part of the Edge of Practice short-cycle experiment index.