{"id":14857,"date":"2026-03-01T12:00:00","date_gmt":"2026-03-01T04:00:00","guid":{"rendered":"https:\/\/zetarmold.com\/?p=14857"},"modified":"2026-04-09T08:05:41","modified_gmt":"2026-04-09T00:05:41","slug":"eviter-le-jetting-moulage-par-injection","status":"publish","type":"post","link":"https:\/\/zetarmold.com\/fr\/eviter-le-jetting-moulage-par-injection\/","title":{"rendered":"Comment \u00e9viter la formation de jets dans le moulage par injection ?"},"content":{"rendered":"
\n Principaux enseignements<\/strong>
\n La conception de la porte p\u00e9riph\u00e9rique dirige l'\u00e9coulement de la mati\u00e8re fondue contre la paroi de l'empreinte
\n \u2013 The primary fix is reducing injection speed during the initial fill phase to 10\u201330% of normal speed, then ramping up once the melt contacts the opposite cavity wall.
\n \u2013 Gate design is the most important mold factor\u2014switching from a pinpoint gate to a fan gate or tab gate eliminates jetting at the source.
\n \u2013 Increasing melt temperature by 10\u201320\u00b0C reduces material viscosity and promotes smoother flow entry into the cavity.\n<\/div>\n

What Is Jetting in Injection Molding?<\/h2>\n

Le jetage est un d\u00e9faut de surface o\u00f9 la mati\u00e8re plastique fondue entre dans l'empreinte du moule sous forme d'un jet \u00e9troit et \u00e0 haute vitesse au lieu de s'\u00e9taler en un front de mati\u00e8re lisse et expans\u00e9. Le r\u00e9sultat est un motif distinctif en forme de serpent ou de trace de ver sur la surface de la pi\u00e8ce, g\u00e9n\u00e9ralement visible pr\u00e8s de la zone d'attaque. Dans notre usine, le jetage est l'un des d\u00e9fauts les plus reconnaissables \u2014 une fois que vous l'avez vu, vous ne le confondez plus avec autre chose.<\/p>\n

\n \"Examples
Injection molding defects\u2014jetting creates distinctive surface patterns<\/figcaption><\/figure>\n

Le jet de plastique traverse l'empreinte et se replie sur lui-m\u00eame en s'accumulant contre la paroi oppos\u00e9e. Parce que la mati\u00e8re projet\u00e9e a partiellement refroidi pendant son vol, elle ne fusionne pas correctement avec la mati\u00e8re qui remplit l'espace autour d'elle. Cela cr\u00e9e des lignes visibles, une texture rugueuse et potentiellement des points faibles l\u00e0 o\u00f9 le jet rencontre le remplissage principal.<\/p>\n

What Causes Jetting to Occur?<\/h2>\n

Jetting happens when the vitesse d'injection<\/a>1<\/a><\/sup> est trop \u00e9lev\u00e9e par rapport \u00e0 la g\u00e9om\u00e9trie de l'attaque, ce qui fait que la mati\u00e8re fondue jaillit \u00e0 travers l'attaque au lieu de s'\u00e9couler contre la paroi la plus proche de l'empreinte. Nous avons identifi\u00e9 plusieurs conditions sp\u00e9cifiques qui cr\u00e9ent le jetage.<\/p>\n

\n \"Injection
Understanding flow dynamics helps prevent jetting<\/figcaption><\/figure>\n\n\n\n\n\n\n\n\n\n\n
Cause<\/th>\nMechanism<\/th>\nLikelihood<\/th>\n<\/tr>\n<\/thead>\n
Excessive initial injection speed<\/td>\nMelt accelerates through the gate and becomes a free jet<\/td>\nTr\u00e8s \u00e9lev\u00e9<\/td>\n<\/tr>\n
Small gate with large cavity behind it<\/td>\nHigh velocity through small orifice with no wall to redirect flow<\/td>\nHaut<\/td>\n<\/tr>\n
Gate facing open cavity (not a wall)<\/td>\nNo nearby surface to contact and start fountain flow<\/td>\nHaut<\/td>\n<\/tr>\n
Low melt temperature<\/td>\nHigher viscosity increases jet velocity through the gate<\/td>\nMoyen<\/td>\n<\/tr>\n
Cold slug in nozzle<\/td>\nSolid slug pushes through gate, followed by high-velocity melt<\/td>\nMoyen<\/td>\n<\/tr>\n
Sharp gate edges<\/td>\nAbrupt transition creates a nozzle effect that accelerates the melt<\/td>\nMoyen<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The single most common cause we see is a small gate (pinpoint or submarine) directing melt into a large open cavity with no opposing wall nearby. The melt has nowhere to contact and spread\u2014so it jets.<\/p>\n

\n

<\/svg> \u00ab Le jetage est un d\u00e9faut purement esth\u00e9tique et n'a aucun effet sur la r\u00e9sistance de la pi\u00e8ce. \u00bb<\/b>Faux<\/span><\/p>\n

Bien que le jetage soit tr\u00e8s visible en tant que d\u00e9faut de surface, la mati\u00e8re projet\u00e9e ne fusionne pas bien avec la mati\u00e8re environnante car elle a partiellement refroidi pendant son vol libre. Cela cr\u00e9e des fronti\u00e8res faibles \u00e0 l'int\u00e9rieur de la pi\u00e8ce, r\u00e9duisant potentiellement la r\u00e9sistance aux chocs de 20 \u00e0 40 % dans la zone affect\u00e9e. Les pi\u00e8ces pr\u00e9sentant un jetage s\u00e9v\u00e8re peuvent rompre sous contrainte \u00e0 l'interface entre le jet et la masse.<\/p>\n<\/div>\n

\n

<\/svg> \u00ab R\u00e9duire la vitesse d'injection initiale est le correctif de processus le plus rapide et le plus efficace contre le jetage. \u00bb<\/b>Vrai<\/span><\/p>\n

By slowing the injection speed to 10\u201330% of normal during the first 5\u201315% of cavity fill, the melt enters gently enough to contact the nearest cavity wall and establish proper fountain flow. Once fountain flow is established, speed can be ramped up to normal for the remainder of the fill.<\/p>\n<\/div>\n

How Do You Adjust Process Parameters to Prevent Jetting?<\/h2>\n

Les ajustements de processus sont la premi\u00e8re ligne de d\u00e9fense contre le jetage car ils ne n\u00e9cessitent pas de modifications du moule. Nous avons d\u00e9velopp\u00e9 une s\u00e9quence \u00e9prouv\u00e9e qui r\u00e9sout le jetage dans 80 % des cas uniquement par les r\u00e9glages machine.<\/p>\n

\n \"Injection
Precise machine control is essential for preventing jetting<\/figcaption><\/figure>\n

1. Use Multi-Stage Injection Speed:<\/strong> This is the most effective fix. Set the first stage (0\u201315% of fill) to 10\u201330% of normal injection speed. Once the melt has established contact with the cavity wall and formed proper fountain flow<\/a>2<\/a><\/sup>, ramp up to full speed for the remaining fill.<\/p>\n

2. Increase Melt Temperature:<\/strong> Raise barrel temperature by 10\u201320\u00b0C. Lower viscosity at higher temperature means the melt is less likely to form a coherent jet\u2014it spreads out more readily on entering the cavity.<\/p>\n

3. Increase Mold Temperature:<\/strong> Raise mold temperature by 10\u201315\u00b0C. A warmer mold surface helps the melt spread instead of solidifying on contact, promoting adhesion between the initial jet (if any) and subsequent fill.<\/p>\n

4. Reduce Holding Pressure Switch Position:<\/strong> Si vous passez de la phase d'injection \u00e0 la phase de maintien de pression trop tard, la mati\u00e8re est encore inject\u00e9e \u00e0 haute vitesse lorsque le jetage se produit. Ajustez le point de commutation V\/P pour r\u00e9duire la phase de remplissage \u00e0 haute vitesse.<\/p>\n

5. Ensure Proper Nozzle Temperature:<\/strong> A cold nozzle can create a cold slug that blocks the gate, then breaks free as a projectile followed by high-velocity melt. Maintain nozzle temperature at or slightly above barrel temperature.<\/p>\n

What Gate Design Changes Eliminate Jetting?<\/h2>\n

Si les ajustements de processus ne r\u00e9solvent pas compl\u00e8tement le jetage, la conception de l'attaque est presque toujours la cause racine. Une bonne conception d'attaque pr\u00e9vient le jetage en dirigeant la mati\u00e8re fondue contre une paroi de l'empreinte imm\u00e9diatement apr\u00e8s son entr\u00e9e, \u00e9tablissant un \u00e9coulement en fontaine d\u00e8s le d\u00e9part.<\/p>\n

\n \"Edge
Edge gate design directs melt flow against the cavity wall<\/figcaption><\/figure>\n\n\n\n\n\n\n\n\n\n\n
Type de porte<\/th>\nLe logiciel de simulation peut-il pr\u00e9dire le jaillissement ?<\/th>\nPourquoi<\/th>\nMeilleur pour<\/th>\n<\/tr>\n<\/thead>\n
Pinpoint Gate<\/td>\nHaut<\/td>\nSmall orifice creates high-velocity jet<\/td>\nSmall parts (use with slow initial speed)<\/td>\n<\/tr>\n
Porte sous-marine<\/td>\nMoyenne-\u00e9lev\u00e9e<\/td>\nBelow parting line, often into open cavity<\/td>\nAuto-degating (requires speed profiling)<\/td>\n<\/tr>\n
Porte de bordure<\/td>\nFaible<\/td>\nMelt directed along cavity wall<\/td>\nMost applications<\/td>\n<\/tr>\n
Fan Gate<\/td>\nVery Low<\/td>\nWide entry spreads melt across cavity<\/td>\nFlat parts, panels<\/td>\n<\/tr>\n
Tab Gate<\/td>\nVery Low<\/td>\nSacrificial tab absorbs initial jet<\/td>\nParts with high cosmetic requirements<\/td>\n<\/tr>\n
Cashew Gate<\/td>\nMoyen<\/td>\nCurved path reduces velocity<\/td>\nAuto-degating with reduced jetting<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The most reliable anti-jetting gate design is one where the melt enters the cavity and immediately hits an opposing wall within 2\u20133 mm. This forces the melt to spread out and establish fountain flow. When we design new molds for jetting-prone geometries, we always specify gate orientation toward the nearest cavity wall.<\/p>\n

\n

<\/svg> \u00ab Augmenter la vitesse d'injection aide \u00e0 r\u00e9soudre le jetage car elle force la mati\u00e8re fondue \u00e0 remplir plus vite. \u00bb<\/b>Faux<\/span><\/p>\n

Increasing injection speed makes jetting worse, not better. Jetting is caused by excessive melt velocity through the gate. The correct approach is to decrease the initial injection speed to allow the melt to contact the cavity wall and establish fountain flow before ramping up speed for the remainder of the fill.<\/p>\n<\/div>\n

\n

<\/svg> \u00ab Une attaque en languette ou une attaque en \u00e9ventail \u00e9limine pratiquement le jetage en r\u00e9partissant l'entr\u00e9e de la mati\u00e8re fondue sur une zone plus large. \u00bb<\/b>Vrai<\/span><\/p>\n

Fan gates and tab gates distribute the melt across a wider cross-section, dramatically reducing the local velocity at the gate entry point. Fan gates spread melt across the full part width, while tab gates absorb the initial high-velocity jet in a sacrificial tab that is trimmed after molding.<\/p>\n<\/div>\n

What Role Does Material Choice Play in Jetting?<\/h2>\n

Material viscosity and flow characteristics significantly influence jetting tendency. In our experience, lower-viscosity materials are more prone to jetting because they flow more easily through small gate openings at high velocity.<\/p>\n

\n \"Plastic
Material flow characteristics affect jetting susceptibility<\/figcaption><\/figure>\n