📈 Mid-volume keyword

Líneas de soldadura
Causas, Soluciones y Prevención en Moldeo por Inyección

Las líneas de soldadura se forman donde dos frentes de fusión se encuentran. Si los frentes están demasiado fríos, la unión es débil.

🔍Síntomas e Identificación Visual

Visible line where two flow fronts meet. Can be structural weakness. Often near holes or multiple gates.

Parámetros Clave del Proceso

Velocidad de inyecciónTemperatura de fusiónVenteo en línea de soldaduraTemperatura del moldePosición de entrada

⚠️Causas Raíz por Categoría

⚙️ Proceso

Velocidad de inyección too low fronts cool before meeting
Temperatura de fusión too low
Temperatura del molde too low
Cold startup mold not pre-heated

🔲 Molde

No vent AT the weld line location
Vents crushed inspect after each lot
Runner is half-round must be full round
Posición de entradaed so weld falls in critical area

🧪 Material

Material not dried moisture at weld makes it weak
Metal flake pigments make weld visible
MB carrier resin incompatible with base polymer

🏭 Máquina

Vent channels crushed by mounting mold on oversized machine
Clamp force selected too high for projected area.
V/P transfer point incorrect. Profile not suitable.
Machine performance — screw position repeatability

🗂 Diseño Molde

Mold vent channel depth insufficient.
Runner design incorrect
Flow analysis not properly done
Mold process not properly selected
Design errors in handle areas.
Gate location incorrect
Multiple gate application for large and long parts
Multiple hot runner application for large parts

🔧 Estado del Molde

Mold vent channels crushed
Mold temperature insufficient

📐 Diseño Pieza

Hole design in part
Design not suitable

📋 General

Square holes worse than round add radii
Wall too thin at weld location
No sequential valve gate control

✅Soluciones y Acciones Correctivas

⚙️ Proceso

Aumentar velocidad de inyección
Aumentar temperatura de fusión
Increase mold surface temperature
Pre-heat mold before production start

🔲 Molde

Open vent AT the weld location
Use sequential valve gate system
Reposition gate using flow simulation
For visual parts use H&C system to eliminate weld lines
Change to full-round runner cross-section

🧪 Material

Additives and fillers may not move at the same speed as polymer where flow is interrupted. Weld line visibility increases or decreases depending on additive ratio. Appropriate carrier material must be selected for the additive.
Plate-shaped flake types make weld lines more visible than they already are. If suitable, spherical flake types can be used instead.
Low MFI material reaches the weld point later — increasing the mark. Higher MFI material should be selected; if not possible, switch to mold heating method.

🏭 Máquina

Each machine has max-min mold size specifications. Going below minimum increases load on the mold and crushes it. Proper machine selection should be determined by calculation.
Excessive clamp force both reduces mold life and causes deformation. Per the "breathing mold" approach, machines with automatic pressure adjustment should be selected even if high pressure is applied.
If V/P transfer point is not correctly set, packing pressure and time may be insufficient. Polymer arriving late at the weld point freezes early and creates a mark.
Machine performance is determined by movement repeatability. The screw must stop at the same set point in both forward and back positions. Deviation to the back position causes short shots and increased weld marks.

🗂 Diseño Molde

Vent channels must be opened per material requirements.
If runner cross-section is not selected as full round, polymer entering the mold creates problems.
Weld line locations should be identified in flow analysis to guide mold design. If changes cannot be made, cartridge heater application is used.
For visual parts, H&C system should be selected to raise mold surface temperature above the material Tg point. In this case, weld lines are eliminated.
Filter inserts are preferred for venting air in handle areas. They are pressed into the air trap location.
In complex parts, gate position should be changed according to weld line data.
Weld lines should be predicted with flow analysis and eliminated with cooling analysis.
Valve gate with sequential method should be used. If valves are servo-controlled, overlap issues are also eliminated.

🔧 Estado del Molde

Mold vent channels get crushed after sustained pressure exposure. Channels should be inspected after each production lot.
Some startup scrap is caused by weld lines — as the mold warms up during runtime, the marks decrease. Production should start after pre-heating the mold.

📐 Diseño Pieza

If holes are square or rectangular, radii must be added to corners.
Wall thickness at weld line location should be increased.

📋 General

Use higher MFI grade fronts still hot when meeting
Secar el material completamente
Change square holes to round with radii

🛠Solución Paso a Paso

Verificar parámetros de proceso

Aumentar velocidad de inyección

Inspeccionar el molde

Open vent AT the weld location

Verificar estado del material

Additives and fillers may not move at the same speed as polymer where flow is interrupted. Weld line visibility increases or decreases depending on additive ratio. Appropriate carrier material must be selected for the additive.

Verificar ajustes de máquina

Each machine has max-min mold size specifications. Going below minimum increases load on the mold and crushes it. Proper machine selection should be determined by calculation.

❓Preguntas Frecuentes

¿Qué causa las Líneas de soldadura en moldeo por inyección?

Líneas de soldadura es causado por varios factores que incluyen: Velocidad de inyección too low fronts cool before meeting; Temperatura de fusión too low; No vent AT the weld line location; Vents crushed inspect after each lot; Material not dried moisture at weld makes it weak; Metal flake pigments make weld visible.

¿Cómo se corrige las Líneas de soldadura en moldeo por inyección?

Comenzar verificando los parámetros clave: Velocidad de inyección, Temperatura de fusión, Venteo en línea de soldadura, Temperatura del molde. Aumentar velocidad de inyección

¿Qué plásticos son más afectados por las Líneas de soldadura?

Materiales comunes: PA6-GF30, ABS, PC, PP-GF30, PPO. Preste especial atención al secado, contracción y temperatura del molde para cada grado.

¿Cómo prevenir las Líneas de soldadura en futuras producciones?

La prevención se basa en tres pilares: (1) optimización de proceso — verificar Velocidad de inyección, Temperatura de fusión; (2) mantenimiento del molde — verificar entradas, venteos y canales de enfriamiento; (3) control de material — asegurar secado correcto y proporción virgen/remolido.

¿Cuál es la diferencia entre las Líneas de soldadura y defectos similares?

Visible line where two flow fronts meet. Can be structural weakness. Often near holes or multiple gates. Esto lo distingue de defectos de superficie similares durante la inspección visual.