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Thin-Wall Injection Molding: Key Rules to Avoid Short Shot & Deformation

Created on 05.21

Meta Description: Learn the key rules for thin-wall injection molding, including minimum wall thickness standards, mold design tips, and parameter optimization, to avoid common issues like short shot and deformation.

Thin-wall injection molding (wall thickness ≤1.5mm) is widely used in consumer electronics, medical devices, and automotive parts—offering lightweight, compact designs and faster production. However, it comes with unique challenges: filling difficulty, short shots, deformation, and poor dimensional stability. These issues can lead to high scrap rates and project delays, but they are avoidable with the right design, mold, and process controls.

Rule 1: Follow Minimum Wall Thickness Standards for Different Plastics

The minimum wall thickness depends on the plastic’s flowability—poor flowability materials require thicker walls to avoid short shots. Below are standard minimum wall thicknesses for common plastics:

• PP, PE: 0.3-0.5mm (good flowability, ideal for ultra-thin parts)

• ABS: 0.5-0.8mm (moderate flowability)

• PC: 0.8-1.0mm (poor flowability, requires thicker walls)

• TPU: 0.4-0.6mm (flexible, good flowability for thin parts)

Tip: Avoid designing walls thinner than the minimum standard—even 0.1mm below the standard can cause filling failures. Additionally, control the flow length ratio: PP can reach 200:1 (flow length: wall thickness), PC up to 100:1, ensuring full filling without short shots.

Rule 2: Optimize Mold Gating Design for Fast, Uniform Filling

Thin-wall parts require fast, uniform plastic flow to fill the cavity before cooling. Poor gating design leads to short shots and uneven filling.

Key Gating Tips:Use large, multiple gates: Increase gate size (1.5-2x wall thickness) and add multiple gates for large thin-wall parts (area >100cm²) to reduce flow distance.Choose the right gate type: Hot runners are ideal for thin-wall molding—they maintain plastic temperature (±5℃), improving flowability and reducing material waste by 5-10%.Position gates strategically: Place gates near thick-walled areas or the end of the flow path to ensure full filling and uniform pressure distribution.

Rule 3: Optimize Injection Parameters for High-Speed Molding

Thin-wall molding requires high-speed, high-pressure injection to fill the cavity quickly. Here are key parameter adjustments:

•	Injection speed: Use high speed (50-100mm/s), adjusting based on wall thickness—thinner walls (≤0.8mm) require 80-100mm/s, while thicker thin walls (1.0-1.5mm) use 50-70mm/s to fill the cavity before plastic cools.

• Injection pressure: Increase pressure (150-200MPa) to overcome flow resistance in thin walls.

• Melt temperature: Increase melt temperature by 10-20°C (vs. standard molding) to improve plastic flowability.

• Mold temperature: Maintain a high mold temperature (40-80°C) to slow cooling and allow full filling.

Rule 4: Strengthen Part Design to Avoid Deformation

Thin-wall parts are prone to deformation after ejection due to weak structural strength. Add small ribs (50-70% of wall thickness) or flanges to strengthen the part without increasing overall thickness. Avoid large, flat surfaces—use slight contours to improve rigidity.

Our facility specializes in thin-wall injection molding, with high-speed injection machines and custom mold designs to ensure consistent quality. We can help you optimize your thin-wall part design and process to avoid short shots and deformation.