Deformazione
Cause, Soluzioni e Prevenzione nello Stampaggio a Iniezione
I risucchi si verificano quando la superficie solidifica prima del nucleo, che poi si contrae verso l’interno trascinando la superficie.
Di seguito troverete informazioni generali su questo difetto. Per ottenere una soluzione mirata su misura per la vostra macchina, materiale e parametri di processo utilizzando il database di risoluzione problemi per stampaggio a iniezione più completo al mondo — registratevi e accedete alla diagnostica assistita da IA, 7 calcolatori ingegneristici e tracciamento dettagliato dei progetti.
🔍Sintomi e Identificazione Visiva
⚠️Cause Radice per Categoria
⚙️ Processo
- Tempo di raffreddamento too short or too long
- Pressione di mantenimento too high
- Bridge water connections causing uneven cooling
🔲 Stampo
- Unequal cooling between cavity and core
- Posizione punto iniezione causing flow along long axis
- Ejector imbalance
- Limescale in cooling channels
🧪 Materiale
- Crystalline material (PP 1-3%, PA 1-2%, POM 2-3.5%) high shrinkage
- MFI too high more shrinkage
- Glass fiber anisotropic shrinkage
🏭 Macchina
- Machine precision insufficient.
- Machine pressure deviation exists
- Machine selection incorrect
- Screw selection incorrect
- Check valve leaking material
🗂 Design Stampo
- Gate selection causes part warpage
- Gate selection
- Gate design incorrect
- Ejector system balance
- Ejector diameters and system not properly selected
- Cooling system faulty
- Cooling system faulty
- Multiple gates
🔧 Condizione Stampo
- Blockage or limescale in mold cooling channels
- Parting line crushing exists
📐 Design Pezzo
- Excessive wall thickness variations in part design
- Asymmetric part design
- Sharp corners in part design
- Insufficient reinforcement in design
📋 Generale
- Spessore parete variation
- Sharp corners no radius
- Asymmetric part design
✅Soluzioni e Azioni Correttive
⚙️ Processo
- Calculate correct cooling time
- Fix water connections no bridge equal temperature everywhere
- Verify holding pressure via gate-freeze test
🔲 Stampo
- Equal cooling both mold halves
- Descale channels periodically
- Rebalance ejector system
- Use valve gate for minimal stress
🧪 Materiale
- Add nucleating agent to PP
- Use lower MFI grade
- GF addition to reduce overall shrinkage
🏭 Macchina
- When screw position repeatability is insufficient, different material weight enters the mold each cycle — this causes warpage. For parts with very high quality requirements, servo machines with 1 micron position accuracy should be selected.
- Machine precision during injection and holding pressure phases is critical. Pressure deviations create internal stresses. Internal stresses cause warpage.
- Pressure ratio should be selected based on material type in machine selection. Pressure ratios differ for PP vs PC.
- L/D ratio is an important parameter in machine selection. For example, PC can be processed on a machine with 22 L/D ratio, but will have warpage issues on a machine with 18 L/D.
- Abrasive material use causes rapid check valve wear. If the machine has no wear alert, material leakage should be detected via part weight SPC analysis.
🗂 Design Stampo
- Gate should be positioned at the narrow edge if possible.
- Gate positioned at the thin section of the part.
- If gate is selected from small-area types like tunnel or banana gates, internal stresses increase — causing localized warpage. Edge gate selection reduces internal stress. Better solution is valve gate hot runner. Internal stresses are minimized with a 3-4-5-6 mm diameter entry based on part weight and size.
- Ejector system balance should push the part smoothly without strain. Otherwise, the part warps during ejection.
- In molds with different ejector diameters, thermal differences can occur based on barrel residence time. When part temperature is too high, thin ejectors sink into the plastic part — creating steps between ejectors during ejection and causing warpage. If suitable, blade plate ejectors can be selected instead of small round pins.
- Mold cooling design gives better results when done per cooling analysis. Channel diameter, proximity to mold surface, and spacing between channels affect cooling effectiveness.
- Equal attention must be given to both cavity and core sides in cooling system design. If cavity side has proper but core side has weak cooling channel design, shear stresses cause warpage.
- Warpage probability with multiple gates should be evaluated with flow analysis. Gate locations, gate area, and gate type should be changed based on warpage values.
🔧 Condizione Stampo
- Mold cooling channels should be periodically cleaned with descaling agents. Even a very thin layer on the channel surface creates insulation and desired cooling is not achieved.
- Crushing at the parting line is usually repaired with argon welding. Over time, gaps forming at the weld hold the plastic part and cause flexing during ejection. If crushing is repaired with laser welding, this issue is minimized.
📐 Design Pezzo
- Reduce wall thickness variations — add radii to corners of warped areas.
- In asymmetric part design, warpage can occur because shrinkage completion times differ. If part design must be asymmetric, mold cooling system should consist of independent circuits and Reynolds number should be properly selected.
- Minimum 0.2 mm radius should be given to corners in plastic part design. Draft angle should be maximized. Lack of draft causes orientation and part warpage.
- Reinforcement designs in areas prone to warpage can prevent bending and distortion.
🛠Risoluzione Passo-Passo
Controllare i parametri di processo
Calculate correct cooling time
Ispezionare lo stampo
Equal cooling both mold halves
Verificare lo stato del materiale
Add nucleating agent to PP
Controllare le impostazioni macchina
When screw position repeatability is insufficient, different material weight enters the mold each cycle — this causes warpage. For parts with very high quality requirements, servo machines with 1 micron position accuracy should be selected.
❓Domande Frequenti
Quali sono le cause della Deformazione nello stampaggio a iniezione?
Deformazione è causato da diversi fattori tra cui: Tempo di raffreddamento too short or too long; Pressione di mantenimento too high; Unequal cooling between cavity and core; Posizione punto iniezione causing flow along long axis; Crystalline material (PP 1-3%, PA 1-2%, POM 2-3.5%) high shrinkage; MFI too high more shrinkage.
Come si correggono la Deformazione nello stampaggio a iniezione?
Iniziare controllando i parametri chiave: Tempo di raffreddamento, Temperatura stampo differential, Pressione di mantenimento, Posizione punto iniezione. Calculate correct cooling time
Quali plastiche sono più colpite da la Deformazione?
Materiali comuni: PP, PA6, PA66, POM, PBT, PPS. Prestare particolare attenzione a essiccazione, ritiro e temperatura stampo per ogni grado.
Come prevenire la Deformazione nelle produzioni future?
La prevenzione si basa su tre pilastri: (1) ottimizzazione del processo — controllare Tempo di raffreddamento, Temperatura stampo differential; (2) manutenzione stampo — controllare punti di iniezione, sfoghi e canali di raffreddamento; (3) controllo materiale — assicurare essiccazione corretta e rapporto vergine/rimacinato.
Qual è la differenza tra la Deformazione e difetti simili?
Part bends or twists after ejection. Does not fit assembly. Questo lo distingue dai difetti di superficie simili durante l’ispezione visiva.
📐Calcolatori Correlati
Verificate i parametri di processo e prevenite questo difetto con i nostri calcolatori.
🔗Difetti Correlati
Chi siamo
Creato da ingegneri di stampaggio a iniezione, per ingegneri di stampaggio a iniezione. MBPlastiPro unisce decenni di esperienza con la tecnologia IA.