Incomplete forming occurs when the sheet fails to reach full contact with the tool before it cools and stiffens. Soft corners, shallow ribs, rounded lettering, incomplete cavities, and weak texture replication are common signs.
Low sheet temperature is only one possible cause. Slow vacuum response, inadequate pressure differential, blocked vents, excessive dead volume, cold tooling, premature contact, and poor sequence timing can produce nearly identical parts. Fine details and deep corners fail first because they require rapid air removal and high local deformation.
Separate heat from airflow
The sheet condition should be verified before heat is increased. If faster vacuum or pressure application improves detail without changing the heating cycle, airflow is the stronger suspect. A defect limited to one corner or cavity points toward local venting or tool geometry. Uniform loss of definition across the part points toward sheet temperature, overall pressure differential, mold temperature, or system capacity.
Vents and channels should be cleaned, leaks checked, and valve response confirmed. Heat should be increased only after those checks. Excessive heat may hide an airflow problem while creating thinning, sag, webbing, degradation, or difficult release.