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Wall Thickness Design Guide for Injection Molding

Wall thickness is the single most influential parameter in injection molded part design, affecting fill time, cooling time, shrinkage, warpage, sink marks, and strength.

Why Wall Thickness Matters

Cooling consumes 60-70% of cycle time and scales with the square of wall thickness. A 3mm wall cools 4x slower than 1.5mm. Every unnecessary millimeter adds cost.

Recommended Wall Thickness

Material	Min (mm)	Recommended (mm)	Max (mm)
ABS	0.8	1.5-3.0	4.5
PC	1.0	2.0-3.5	5.0
PP	0.6	1.2-3.0	4.0
PA6	0.6	1.0-3.0	4.0
PA66-GF30	0.8	1.5-3.0	4.0
POM	0.6	1.0-3.0	4.0
PMMA	1.0	2.0-4.0	6.0
PC/ABS	0.8	1.5-3.0	4.0
LCP	0.3	0.5-2.0	3.0
TPE	0.8	1.5-4.0	6.0

Handling Transitions

Ramp: Max 3:1 length-to-height ratio
Core out thick sections from the back
Use ribs for stiffness instead of thicker walls
Gas-assist for very thick sections

Buyer's Tip: The most common wall thickness issue with Chinese mold factories is not the nominal wall but local thick sections around bosses and ribs. Mold designers may add steel around features without adjusting the core side. Insist on a cross-section review at the design meeting.

Flow Length / Wall Thickness Ratio

Amorphous (ABS, PC, PMMA): Max L/t = 150:1
Semi-crystalline (PP, PA, POM): Max L/t = 250:1
High-flow grades: Up to 300:1
Glass-filled: Reduce by 20-30%

What This Means for Your Project: Wall thickness decisions at design stage have 10x the cost impact vs. changes during tooling. A 2.5mm uniform wall design costs ~30% less in material, cools 50% faster, and has fewer quality issues than a 2-4mm non-uniform design.

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