Today's KN0WLEDGE Share : ⭐ 3 Design Rules That Make or Break Your Plastic Part

 Today's KN0WLEDGE Share

⭐ 3 Design Rules That Make or Break Your Plastic Part

Most failures in molding don’t come from tooling—they start in the CAD model.

If you design plastic parts, three decisions will determine whether your mold runs smoothly or becomes an expensive source of defects, delays, and redesigns:

� Parting Line

� Draft Angle

� Wall Thickness

These look tiny on a drawing.

But in real manufacturing?

They control quality, cost, cycle time, and the entire success of your project.

Here’s what most teams underestimate �

� 1. Parting Line — The boundary that decides your appearance & mold feasibility

A misplaced parting line can ruin a part before the mold is even cut.

Common issues:

• visible flash

• cosmetic mismatch

• steps or deformation

• restricted mold-open direction

A great design hides the PL.

A weak design forces the toolmaker to place it somewhere visible.

Best practices:

✔ Follow natural edges or non-cosmetic areas

✔ Never cross logos or Class-A surfaces

✔ Confirm mold orientation early with your tooling engineer

A well-chosen parting line reduces tool complexity and improves appearance.

� 2. Draft Angle — The difference between smooth release and damaged parts

If you skip draft, the part grips the steel like glue.

Real consequences:

• drag marks

• stuck parts

• stronger ejection force

• premature tool wear

Even 0.5° can change everything.

Best practices:

✔ 0.5°–1° for polished surfaces

✔ 2°+ for textured surfaces

✔ Add draft to all vertical faces, cores, ribs

Draft isn’t “nice to have”—

It’s mandatory if you want stable, repeatable molding.

� 3. Wall Thickness — The quiet killer of flow, shrinkage & cycle time

Wall thickness impacts almost every molding outcome:

Too thick → sink marks, warpage, slow cooling

Too thin → short shots, weak structure

What matters most is uniformity, not absolute thickness.

Best practices:

✔ Keep walls consistent (1.5–3.0 mm typical)

✔ Use ribs/gussets instead of adding mass

✔ Core out thick areas

✔ Avoid sudden transitions

Good thickness control =

fewer defects, shorter cycles, happier customers.

� Why these “simple” choices matter

Together, these three fundamentals shape:

✔ tooling complexity

✔ part quality & appearance

✔ production speed

✔ long-term dimensional stability

✔ total manufacturing cost

In plastic design, small decisions create big consequences.

� Which of these three has caused the most issues in your projects?

If you’re working on a new part and want early feedback, feel free to connect.

#InjectionMolding#MoldDesign #PlasticDesign

source : Coco Ho