Weld Line:
When two or more streams of molten resin meet and the temperature drops during flow, the resin at the junction fails to fully fuse or bond. This results in a fine line formed along the surface or inside the molded part at the point of convergence.
| 6.1 Causes | 6.2 Solutions |
|---|---|
| 6.1.1 Low nozzle temperature or low mold temperature. | 6.2.1 Increase melt and mold temperatures to improve resin flowability. |
| 6.1.2 Injection speed too slow or too fast. | 6.2.2 Adjust injection speed—either increase or decrease as needed. |
| 6.1.3 Improper gate location, too many gates, improper runner design, long flow path, or high flow resistance causing rapid temperature drop. | 6.2.3 Change gate location, reduce the number of gates, shorten runner length, or increase runner cross-section to reduce flow resistance. |
| 6.1.4 Improper mold cooling system. | 6.2.4 Improve the cooling system. |
| 6.1.5 Poor part design—thin walls, uneven wall thickness, causing melt convergence at thin sections. | 6.2.5 Improve wall uniformity, enhance processability, or adjust runner/gate design to ensure melt convergence occurs at thicker sections. |
| 6.1.6 Poor resin flowability or fast cooling. | 6.2.6 Use resin with better flowability. |
| 6.1.7 Moisture or lubricant in mold, excessive melt aeration, or excessive mold release agent. | 6.2.7 Wipe moisture and lubricant from cavity, minimize trapped gas, and reduce mold release agent usage. |
| 6.1.8 Poor mold venting. | 6.2.8 Add vents at appropriate locations. |
| 6.1.9 High screw speed and low back pressure. | 6.2.9 Reduce screw speed and increase back pressure. |
| 6.1.10 Low injection and holding pressure. | 6.2.10 Increase injection and holding pressures. |
| 6.1.11 Mixing incompatible resins, different grades, or different brands. | 6.2.11 Prevent mixing of different brands or grades; label material bags clearly and seal immediately after use. |
| 6.1.12 Improper mold release agent containing incompatible oils. | 6.2.12 Use a suitable mold release agent. |
| 6.1.13 Using thin-sheet colorants such as aluminum foil. | 6.2.13 Use appropriate colorants. |
| 6.1.14 Poor distribution or fusion of fiber fillers. | 6.2.14 Use reinforced materials with uniform fiber distribution. |
| 6.1.15 Presence of cold material. | 6.2.15 Improve or enlarge cold slug wells or increase mold temperature. |
| 6.1.16 Faulty heater in hot runner mold, causing low melt temperature. | 6.2.16 Replace the faulty heater and increase melt temperature. |
follow us :
-- get updates with latest topics
e-mail
English
français
Deutsch
русский
italiano
español
português
العربية
日本語
한국의
中文