PTA Plastics - Performing DFM (Part 1): Wall Thickness/Nominal Wall

Performing DFM (Part 1):

Wall Thickness/Nominal Wall

By: PTA Plastics February 25, 2021

One reason customers rate the quality of parts delivered by PTA Plastics so highly is our Early Supplier Involvement (ESI) services including design, DFM, and mold flow analysis. In this four-part mini-series, we will be discussing the importance of ESI including:

  • Part 1: Wall thickness/nominal wall
  • Part 2: Sink marks and read through
  • Part 3: Boss and rib design
  • Part 4: Draft angles

    It’s important to engage with a mold builder early on during design in an effort to reduce any problematic issues. With today’s advances in additive manufacturing, engineers have the ability to prototype via 3D printing and develop parts with features that cannot be produced during injection molding. This mini-series contains some of the key factors to consider when performing Design For Manufacturing (DFM).


The critical decision to determine the wall thickness incorporated into a design will influence the overall moldability of a part including all other design decisions. There are many factors to consider, including:

  • - Part stiffness
  • - Impact/ruggedness
  • - Weight
  • - Cost (material usage and cycle time)
  • - Machine size (tonnage)
  • - UL-94 FR rating
  • - Cosmetics
  • - The depth of bosses needed, structural ribs, and fastening features
  • - Moldability (material viscosity vs. flow length)

    Part stiffness is directly affected by wall thickness. For example, if the wall thickness increases or changes by 10%, this can add roughly 33% more stiffness. Larger parts with longer flow lengths require thicker nominal walls to allow the part to fill properly, otherwise this can impact resistance and entail cracking at high stress areas. Another area to consider is the UL-94 FR rating. Wall thickness of a part has a direct correlation to the UL rating as most materials achieve a higher UL rating as the wall section gets thicker. Part cosmetics are also influenced by wall thickness in addition to part cost which dictates material usage and cycle time.

    There are many factors to consider when selecting the proper nominal wall and PTA Plastics has the knowledge and expertise to help with these decisions. Contact us today for your next project.

    Ready to learn more?

    Be on the lookout as we discuss the importance of maintaining uniform wall thickness and the adverse effects of non-uniform wall thickness in Part 2 of this series: Sink Marks and Read Through.