Injection Molding Defects And Solutions -- Cracks

Blog

Catégories

nouveau blog

Tags

Injection Molding Defects and Solutions -- Cracks 2025-10-17

Cracks:
Cracks occur when poor part design or inferior plastic material properties cause high internal stress, uneven cooling, poor demolding, or other defects. These stresses lead to cracks forming at stress concentration points or near the gate. Under overload or the influence of solvents, these cracks may propagate, resulting in part failure.

No.	Causes	Solutions
15.1.1	Low material temperature, poor demolding	Increase material temperature, repair mold
15.1.2	High holding pressure, long holding time	Reduce holding pressure and holding time
15.1.3	Screw rotation speed too high	Reduce screw speed
15.1.4	Low back pressure	Increase back pressure
15.1.5	Poor ejection or ejection speed too fast	Balance ejection, adjust speed appropriately
15.1.6	Mold temperature too low or uneven	Adjust mold temperature, ensure uniform cooling based on part structure
15.1.7	Cooling time too long or too short	Adjust cooling time according to wall thickness
15.1.8	Insert not preheated or insufficiently preheated	Preheat inserts to match thermal expansion before molding
15.1.9	Insert not cleaned properly	Clean inserts thoroughly
15.1.10	Thin walls, small draft angles, sharp corners or notches, high internal stress	Increase draft angles, add OR at sharp corners where possible, reduce stress concentration
15.1.11	High injection pressure, excessive stress (see warpage)	Reduce injection pressure, post-process to relieve internal stress if needed
15.1.12	Large or improperly designed gate, high internal stress at gate	Adjust gate size and design to reduce stress
15.1.13	Uneven cooling after demolding or post-processing	Ensure uniform cooling after demolding or post-processing
15.1.14	Brittle plastic or contaminated with foreign materials	Do not use materials mixed with impurities
15.1.15	Improper mold release agent, poor demolding	Choose appropriate release agent or repair mold for easier demolding
15.1.16	Material not dried properly	Dry materials thoroughly
15.1.17	ABS or HIPS may show fine white lines at ejector pin area (disappear after heat treatment)	Heat-treat to remove stress, repair mold, or reduce injection/holding pressure
15.1.18	Excessive directional shrinkage or uneven filler distribution	Increase mold/material temperature, reduce injection speed, improve filler distribution
15.1.19	Warpage, poor weld lines	Adjust process parameters, mold temperature to reduce warpage and weld line defects
15.1.20	Improper storage or contact with solvents	Use proper packaging to avoid solvent contact
15.1.21	Hot runner temperature too high or too low	Adjust hot runner temperature