{"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":"evitare-lo-stampaggio-ad-iniezione-a-getto","status":"publish","type":"post","link":"https:\/\/zetarmold.com\/it\/evitare-lo-stampaggio-ad-iniezione-a-getto\/","title":{"rendered":"Come evitare il jetting nello stampaggio a iniezione?"},"content":{"rendered":"
\n Punti di forza<\/strong>
\n La progettazione del gate laterale dirige il flusso di fusione contro la parete della cavit\u00e0
\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

Il jetting \u00e8 un difetto superficiale in cui la plastica fusa entra nella cavit\u00e0 dello stampo come un getto stretto e ad alta velocit\u00e0 invece di distribuirsi in un fronte di fuso liscio ed espandente. Il risultato \u00e8 un caratteristico pattern a serpente o a traccia di verme sulla superficie del pezzo, solitamente visibile vicino all'area del gate. Nella nostra fabbrica, il jetting \u00e8 uno dei difetti pi\u00f9 riconoscibili\u2014una volta visto, non lo si confonde mai con altro.<\/p>\n

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

Il getto di plastica attraversa la cavit\u00e0 e si ripiega su se stesso mentre si accumula contro la parete opposta. Poich\u00e9 il materiale soggetto a jetting si \u00e8 parzialmente raffreddato durante il volo, non si fonde correttamente con il materiale che riempie l'area circostante. Ci\u00f2 crea linee visibili, texture ruvida e potenziali punti deboli dove il getto di jetting incontra il riempimento principale.<\/p>\n

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

Jetting happens when the velocit\u00e0 di iniezione<\/a>1<\/a><\/sup> \u00e8 troppo alta rispetto alla geometria del gate, causando l'espulsione del fuso attraverso il gate anzich\u00e9 il flusso contro la parete pi\u00f9 vicina della cavit\u00e0. Abbiamo identificato diverse condizioni specifiche che causano il jetting.<\/p>\n

\n \"Injection
Understanding flow dynamics helps prevent jetting<\/figcaption><\/figure>\n\n\n\n\n\n\n\n\n\n\n
Causa<\/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>\nMolto alto<\/td>\n<\/tr>\n
Small gate with large cavity behind it<\/td>\nHigh velocity through small orifice with no wall to redirect flow<\/td>\nAlto<\/td>\n<\/tr>\n
Gate facing open cavity (not a wall)<\/td>\nNo nearby surface to contact and start fountain flow<\/td>\nAlto<\/td>\n<\/tr>\n
Low melt temperature<\/td>\nHigher viscosity increases jet velocity through the gate<\/td>\nMedio<\/td>\n<\/tr>\n
Cold slug in nozzle<\/td>\nSolid slug pushes through gate, followed by high-velocity melt<\/td>\nMedio<\/td>\n<\/tr>\n
Sharp gate edges<\/td>\nAbrupt transition creates a nozzle effect that accelerates the melt<\/td>\nMedio<\/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> \u201cIl jetting \u00e8 puramente un difetto estetico e non ha alcun effetto sulla resistenza del pezzo.\u201d<\/b>Falso<\/span><\/p>\n

Sebbene il jetting sia altamente visibile come difetto superficiale, il materiale soggetto a jetting non si fonde bene con il materiale circostante perch\u00e9 si \u00e8 parzialmente raffreddato durante il volo libero. Ci\u00f2 crea confini deboli all'interno del pezzo, riducendo potenzialmente la resistenza all'impatto del 20\u201340% nell'area interessata. I pezzi con jetting grave possono rompersi sotto stress all'interfaccia getto-massa.<\/p>\n<\/div>\n

\n

<\/svg> \u201cRidurre la velocit\u00e0 di iniezione iniziale \u00e8 la soluzione di processo pi\u00f9 rapida ed efficace per il jetting.\u201d<\/b>Vero<\/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

Le regolazioni di processo sono la prima linea di difesa contro il jetting perch\u00e9 non richiedono modifiche allo stampo. Abbiamo sviluppato una sequenza collaudata che risolve il jetting nell'80% dei casi solo attraverso le impostazioni della macchina.<\/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> Se si passa dall'iniezione alla pressione di mantenimento troppo tardi, il fuso viene ancora iniettato ad alta velocit\u00e0 quando si verifica il jetting. Regolare il punto di commutazione V\/P per ridurre la fase di riempimento ad alta velocit\u00e0.<\/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

Se le regolazioni di processo non risolvono completamente il jetting, il design del gate \u00e8 quasi sempre la causa principale. Il giusto design del gate previene il jetting dirigendo il fuso contro una parete della cavit\u00e0 immediatamente all'ingresso, stabilendo il flusso a fontana fin dall'inizio.<\/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
Tipo di cancello<\/th>\nIl software di simulazione pu\u00f2 prevedere il getto?<\/th>\nPerch\u00e9<\/th>\nIl migliore per<\/th>\n<\/tr>\n<\/thead>\n
Pinpoint Gate<\/td>\nAlto<\/td>\nSmall orifice creates high-velocity jet<\/td>\nSmall parts (use with slow initial speed)<\/td>\n<\/tr>\n
Porta sottomarina<\/td>\nMedio-alto<\/td>\nBelow parting line, often into open cavity<\/td>\nAuto-degating (requires speed profiling)<\/td>\n<\/tr>\n
Porta del bordo<\/td>\nBasso<\/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>\nMedio<\/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> \u201cAumentare la velocit\u00e0 di iniezione aiuta a risolvere il jetting perch\u00e9 costringe il fuso a riempire pi\u00f9 velocemente.\u201d<\/b>Falso<\/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> \u201cUn design a gate a linguetta o a ventaglio elimina virtualmente il jetting distribuendo l'ingresso del fuso su un'area pi\u00f9 ampia.\u201d<\/b>Vero<\/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