---
title: "Why Do Identical Plastic Parts Come Out Different Sizes Between Production Runs?"  
description: "Why Do Identical Plastic Parts Come Out Different Sizes Between Production Runs?"  
author: "Signe Poulsen"  
published: 2026-10-18  
canonical: https://answers.mindstick.com/qa/117787/why-do-identical-plastic-parts-come-out-different-sizes-between-production-runs  
category: "Mix Category"  
tags: ["manufacturing", "Injection molding", "quality control"]  
reading_time: 1 minute  

---

# Why Do Identical Plastic Parts Come Out Different Sizes Between Production Runs?

We’re seeing small but noticeable size differences in a molded plastic part between production runs. The mold hasn’t changed, and the measurements are being taken at the same points, yet some batches are close to the upper tolerance and others are not.

Which process variables are worth checking first—material moisture, cooling time, machine settings, or something else? I’d also like to know how manufacturers separate actual **dimensional variation between batches** from differences caused by measurement or conditioning.


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Original Source: https://answers.mindstick.com/qa/117787/why-do-identical-plastic-parts-come-out-different-sizes-between-production-runs

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