🔥 High-volume keyword

Verzug
Ursachen, Lösungen und Prävention beim Spritzgießen

Verzug ist eine Dimensionsverformung durch ungleichmäßige Schwindung bei unterschiedlicher Kühlung oder Eigenspannungen.

PP PA6 PA66 POM PBT PPS

🔍Symptome und visuelle Erkennung

Part bends or twists after ejection. Does not fit assembly.

Wichtige Prozessparameter

KühlzeitWerkzeugtemperatur differentialNachdruckAnschnittpositionWandstärke uniformity

⚠️Ursachen nach Kategorie

⚙️ Prozess

Kühlzeit too short or too long
Nachdruck too high
Bridge water connections causing uneven cooling

🔲 Werkzeug

Unequal cooling between cavity and core
Anschnittposition causing flow along long axis
Ejector imbalance
Limescale in cooling channels

🧪 Material

Crystalline material (PP 1-3%, PA 1-2%, POM 2-3.5%) high shrinkage
MFI too high more shrinkage
Glass fiber anisotropic shrinkage

🏭 Maschine

Machine precision insufficient.
Machine pressure deviation exists
Machine selection incorrect
Screw selection incorrect
Check valve leaking material

🗂 Werkzeugkonstruktion

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

🔧 Werkzeugzustand

Blockage or limescale in mold cooling channels
Parting line crushing exists

📐 Teiledesign

Excessive wall thickness variations in part design
Asymmetric part design
Sharp corners in part design
Insufficient reinforcement in design

📋 Allgemein

Wandstärke variation
Sharp corners no radius
Asymmetric part design

✅Lösungen und Korrekturmaßnahmen

⚙️ Prozess

Calculate correct cooling time
Fix water connections no bridge equal temperature everywhere
Verify holding pressure via gate-freeze test

🔲 Werkzeug

Equal cooling both mold halves
Descale channels periodically
Rebalance ejector system
Use valve gate for minimal stress

🧪 Material

Add nucleating agent to PP
Use lower MFI grade
GF addition to reduce overall shrinkage

🏭 Maschine

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.

🗂 Werkzeugkonstruktion

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.

🔧 Werkzeugzustand

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.

📐 Teiledesign

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.

🛠Schritt-für-Schritt Fehlersuche

Prozessparameter prüfen

Calculate correct cooling time

Werkzeug prüfen

Equal cooling both mold halves

Materialzustand prüfen

Add nucleating agent to PP

Maschineneinstellungen prüfen

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.

❓Häufig gestellte Fragen

Was verursacht Verzug beim Spritzgießen?

Verzug wird durch mehrere Faktoren verursacht: Kühlzeit too short or too long; Nachdruck too high; Unequal cooling between cavity and core; Anschnittposition causing flow along long axis; Crystalline material (PP 1-3%, PA 1-2%, POM 2-3.5%) high shrinkage; MFI too high more shrinkage.

Wie behebt man Verzug beim Spritzgießen?

Zunächst die wichtigsten Parameter prüfen: Kühlzeit, Werkzeugtemperatur differential, Nachdruck, Anschnittposition. Calculate correct cooling time

Welche Kunststoffe sind am stärksten von Verzug betroffen?

Gängige Materialien: PP, PA6, PA66, POM, PBT, PPS. Besondere Beachtung von Trocknung, Schwindung und Werkzeugtemperatur für jeden Typ.

Wie verhindert man Verzug in zukünftigen Produktionen?

Prävention basiert auf drei Säulen: (1) Prozessoptimierung — prüfen: Kühlzeit, Werkzeugtemperatur differential; (2) Werkzeugwartung — Anschnitte, Entlüftungen und Kühlkanäle prüfen; (3) Materialkontrolle — korrekte Trocknung und Neuware/Mahlgut-Verhältnis sicherstellen.

Was ist der Unterschied zwischen Verzug und ähnlichen Fehlern?

Part bends or twists after ejection. Does not fit assembly. Dies unterscheidet es bei der visuellen Inspektion von ähnlichen Oberflächenfehlern.