Defects are process feedback. Reading them correctly shortens any troubleshooting loop.
Flash (excess material at parting line): tooling issue — worn or mismatched plates, insufficient clamp tonnage, or a parting line that crosses a critical dimension. Fix: re-cut or re-seat the tool; raise clamp pressure within press limits.
Bubbles and porosity: trapped air or volatiles — insufficient degassing of the compound, too-rapid cure ramp, or moisture in filler. Fix: add vacuum degassing, slow the temperature ramp, dry compounds properly.
Sink marks: thickness variation — a thick section cures and shrinks after the surface has set. Fix: uniform wall design (ribs instead of mass), longer cure, or transfer molding for geometry that cannot avoid mass.
Flow lines and knit lines: material fronts meeting without fusion — cold compound, complex flow path. Fix: raise preform temperature, reposition gates and inserts, adjust preform placement.
Short shots: insufficient material or trapped gas blocking flow. Fix: weigh preforms +5~8%, add vents, verify press parallelism.
Dimensional drift across a batch: temperature variance across mold plates or cure-time drift. Fix: calibrate, map plate temperature, lock process windows in the QC plan.
At Rubbrother, first articles ship with a dimensional report precisely so drift is caught at sampling — not after 10,000 parts.