Selecting Core and Cavity Positioning in Injection Molding: A Comprehensive Guide

Here at HLH Proto, we understand the importance of a high-quality mold for injection molded parts. This is why we meticulously review our customer’s designs. As your manufacturing partner, we will also work with you and support your decision-making, especially when it comes to choosing the core and cavity positioning in your design. Let this blog serve as your guide so you can make informed decisions for your project.

About cores and cavities

In a mold cavity, the closed volume is made with at least two mold halves. Molds with two parts have halves that are either cavities or cores. The core is the tool mold’s side with the non-cosmetic or interior side of the part. It’s where the injector system is in most designs. On the other hand, the cavity is on the cosmetic or exterior side of the part. At HLH Proto, we polish this to a finish that represents your desired final surface finish.

When put together, the core and cavity provide a thin-walled cavity where the melted plastic will be introduced and allowed to cool.

Factors affecting the placement of the core and cavity

Proper core and cavity placement is essential for the successful injection molded parts. Otherwise, failure is inevitable. Where you place them can depend on these factors:

  • Part shape
  • Material
  • Ejector system
  • Sprues, gates, and runners

Considerations for core and cavity placement

By considering these rules, you can design injection molding cavities that are less likely to cause defects and ensure seamless part ejection:

  • Include rounded edges or corners
  • Add ribs for supports
  • Avoid vertical walls
  • Include bosses for threaded inserts
  • Add hollow cavities in thick sections
  • Maintain uniform wall thickness as much as you can

These rules limit the orientation of these features, so they impact the core and cavity placement in injection molded parts. For instance, you should avoid arranging bosses or ribs vertically so the part won’t get caught in the mold. Additionally, know how the material can fill the cavity and core to identify the best orientation for your mold design.

Need design tips?

Let our experts take the guesswork out of selecting core and cavity positioning for your injection molded parts. Contact us now!


Industry InsightsDownloadsQA/QCDesign Tips


CNC Machining ServicesDie CastingRapid Injection Molding3D PrintingSheet MetalVacuum Casting


Aerospace & UAVAutomotiveCommunicationsConsumer ProductsIndustrialMedical
Product DevelopmentRobotics & Automation


CNC Machining ServicesDie CastingExport ToolingRapid Injection MoldingLow Volume Manufacturing Whitepaper


Room 1231, Wanjiali International Mall, Wanjiali Middle Road No.99, Furong District,Changsha,Hunan province,China,410016