プラスチック射出成形の欠陥 - 原因と解決策

Common Injection Molding Defects

Injection molding defects can affect part appearance, function, and cost. Understanding root causes enables quick troubleshooting and prevention.

1. Sink Marks

登場： Depressions on part surface, typically near thick sections.

Causes:

• Excessive wall thickness variation
• Ribs too thick relative to wall
• Insufficient cooling time
• High packing pressure needed

Solutions:

• Reduce rib thickness to 50-70% of wall
• Increase cooling time
• Optimize packing pressure and time
• Use gas-assist molding for thick sections

2. Flash

登場： Thin excess plastic at parting lines or around features.

Causes:

• Insufficient clamp force
• Worn mold components
• Excessive injection pressure
• Poor mold alignment

Solutions:

• Increase clamp tonnage
• Repair or replace worn components
• Reduce injection pressure
• Check mold alignment and guide pins

3. Short Shots

4. Warpage

登場： Part distortion after ejection.

Causes:

• Non-uniform cooling
• Asymmetric part design
• Incorrect ejection timing
• Material shrinkage variation

Solutions:

• Optimize cooling channel design
• Balance wall thickness
• Adjust ejection timing
• Use material with lower shrinkage

5. Weld Lines

登場： Visible lines where flow fronts meet.

Causes:

• Multiple gates or flow fronts
• Holes or inserts creating flow splits
• Low injection speed
• Cold material at meeting point

Solutions:

• Move weld lines to non-critical areas
• Increase injection speed
• Raise mold temperature
• Add overflow wells at weld locations

Defect Prevention Checklist

• Design parts with uniform wall thickness
• Include adequate draft angles
• Provide proper venting
• Optimize gate location
• Ensure balanced cooling

結論

Most injection molding defects stem from design, processing, or mold issues. Early detection and systematic troubleshooting minimize production downtime and scrap rates.

関連リソース

• エンジニアリングプラスチックのコスト要因
• PEEKとPEIの比較
• Flame Retardant Plastics
• Food Grade Plastics Guide
• Nylon Moisture Treatment

関連リソース

• エンジニアリングプラスチックのコスト要因
• PEEKとPEIの比較
• Flame Retardant Plastics
• Food Grade Plastics Guide
• Nylon Moisture Treatment

関連リソース

• エンジニアリングプラスチックのコスト要因
• PEEKとPEIの比較
• Flame Retardant Plastics
• Food Grade Plastics Guide
• Nylon Moisture Treatment

よくあるご質問

When does Plastic Injection Molding Defects — Causes and Solutions make sense?

Plastic Injection Molding Defects — Causes and Solutions makes sense when the part volume, material choice, geometry, and repeatability needs justify mold design and tooling investment.

What design factors matter most for Plastic Injection Molding Defects — Causes and Solutions?

Wall thickness, ribs, bosses, draft angle, gate location, shrinkage, parting line, and ejection all affect molded part quality.

What information is needed before mold production?

The supplier should confirm the 3D model, material, expected annual volume, appearance requirements, tolerance needs, and any assembly or functional testing requirements.

What is the biggest risk in Plastic Injection Molding Defects — Causes and Solutions?

The biggest risk is approving tooling before material behavior, shrinkage, flow, and part function are fully checked against the real application.