Engineering guide with real DFM examples

Injection Mold Components and Functions

Injection mold components work as a system. Core and cavity form the part while the runner, cooling, side actions and ejection control how resin fills, cools and releases.

Core and cavityRunner and gateCooling circuitsSlides, lifters and ejection

Injection Mold Components by Function

Part forming

Core and cavity

Form the internal and external part surfaces and carry the agreed finish, shutoffs and dimensional strategy.

Melt delivery

Sprue, runner and gate

Deliver melt to the cavity. Their size and location affect fill, weld lines, pressure and gate vestige.

Thermal control

Cooling system

Removes heat through channels, inserts and local strategies so cycle and dimensional stability can be balanced.

Part release

Ejection system

Pins, sleeves, blades, stripper plates or lifters release the part without unacceptable marks or deformation.

Side action

Slides and lifters

Create undercuts or side features that cannot release in the main mold-open direction.

Alignment

Mold base and guidance

Plates, pillars, bushings and locating parts align and support the working inserts.

Air management

Venting

Provides an escape path for trapped gas near fill-end and shutoff zones.

Runner choice

Hot-runner or cold-runner parts

Control how melt reaches each cavity; the trade-off includes balance, waste, maintenance and investment.

How Components Appear in Project DFM

De-identified DFM gate location and size page — **Gate and runner**A project page records the proposed gate location and the mark the buyer should expect.

De-identified injection mold main parting line page — **Core, cavity and parting**The main split is reviewed against release direction and visible parting-line risk.

De-identified injection mold ejection system page — **Pins and lifters**Round pins and angled ejection were mapped to the surfaces where marks could appear.

Component Choices Are Not Isolated

A gate location changes flow and weld-line risk. A lifter can solve an undercut but may add a witness line. Cooling can improve cycle and stability but must fit around inserts, pins and bolts. The mold concept therefore needs one coordinated review.

Destination-factory standards also matter. The quotation should state mold-base and component preferences, connection standards, spare parts and maintenance expectations.

Injection mold opened during a whiteboard-holder project

Component Review Checklist

Area	Buyer question	Typical record
Parting and shutoffs	Where will the witness line appear?	DFM views and appearance-zone approval
Gate	Is the vestige acceptable and is filling balanced?	Gate proposal, flow reasoning and sample review
Side actions	Can an undercut be redesigned or must it move mechanically?	Slide/lifter concept and maintenance note
Ejection	Where can marks occur and how is force distributed?	Ejector map and first-trial observation
Cooling	Are there local hot spots or dimensional risks?	Circuit layout and trial settings

Review the Mold Structure Before Release

Send the 3D model, drawing, resin, expected volume and destination standard for a component-level DFM discussion.

Discuss Your Mold Structure