What Is the Best Wall Thickness for Injection Molded Plastic Parts?

What Is the Best Wall Thickness for Injection Molded Plastic Parts?

When designing plastic parts for injection molding, one of the most critical decisions a mechanical engineer must make is choosing the right wall thickness. Wall thickness affects part strength, manufacturability, cycle time, and cost — and poor choices often lead to defects like warping, sink marks, or short shots.

In this article, we’ll cover:

• ✅      Recommended wall thickness ranges by material

•      Why wall thickness matters

• ⚠️ Problems      caused by non-uniform thickness

•      How to design for optimal thickness

Recommended Wall Thickness for Common Plastics

Each plastic material has different flow and cooling behavior. Here are general guidelines for common thermoplastics:

Note: These values are typical. Your mold supplier should validate thickness based on part geometry and application.

Why Wall Thickness Matters

Wall thickness directly affects:

• Flowability of the      resin

• Cooling time (thicker walls take longer, increasing cycle time)

• Structural strength

• Risk of defects (e.g., voids, warping, and sink marks)

⚠️ Problems from Incorrect Wall Thickness

Too Thick:

• Sink marks

  
  

• Warpage during cooling

  
  

• Long cycle times and      higher material cost

Too Thin:

• Poor flow during injection

• Incomplete filling (short      shots)

  
  

• Weak or brittle parts

Importance of Uniform Wall Thickness

One golden rule of plastic part design:

Keep wall thickness as uniform as possible.

Sudden changes in thickness cause uneven cooling, which leads to internal stress, warping, and cosmetic defects. If thick areas are necessary, consider:

• Coring out thick      sections

• Adding ribs or gussets      for strength

• Gradual transitions in      thickness

How to Design for Optimal Wall Thickness

Here are some key tips:

• ✅ Start      with the minimum required strength and work up from there

• ✅ Use ribs      and structural features instead of thicker walls

• ✅ Maintain uniform      wall thickness throughout the part

• ✅ Work with      your injection molding partner to run mold flow analysis

• ✅ Choose a      material with flow properties suited to your geometry

How Goodtech MFG Can Help

At Goodtech MFG Group, an engineering-driven company that specializes in injection molding services. Our team supports you from concept through DFM, mold design, and production — helping you balance strength, cost, and manufacturability.

Need help optimizing wall thickness for your next plastic part? Contact us today for a free DFM consultation.

mark.li@goodtech-mfg.com