---
title: "What Causes Sink Marks on Injection-Molded Parts When the Process Seems Stable?"  
description: "What Causes Sink Marks on Injection-Molded Parts When the Process Seems Stable?"  
author: "Ryan Parker"  
published: 2026-10-22  
canonical: https://answers.mindstick.com/qa/118159/what-causes-sink-marks-on-injection-molded-parts-when-the-process-seems-stable  
category: "Mix Category"  
tags: ["manufacturing", "Injection molding", "quality control", "Plastics"]  
reading_time: 1 minute  

---

# What Causes Sink Marks on Injection-Molded Parts When the Process Seems Stable?

We’re seeing shallow sink marks on a few thicker sections of an injection-molded part, even though the machine settings and material batch haven’t changed. The defects aren’t appearing on every part, which makes the cause harder to pin down.

Could this point to uneven cooling or packing pressure, or should we be looking more closely at gate location and wall thickness? I’d be interested in which measurements or process checks are most useful before changing several settings at once.


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Original Source: https://answers.mindstick.com/qa/118159/what-causes-sink-marks-on-injection-molded-parts-when-the-process-seems-stable

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