An injection mold feed system carries material from the machine nozzle through the sprue and runner network to the gate or gates. Its design affects how the cavities fill, the amount of runner material, the tool layout, and the maintenance tasks required. Dimensions and component choices depend on the part, resin, cavity arrangement, molding process, and tool construction; generic sprue or cold-slug-well measurements should not be copied into a project specification.
Start with the part, resin, and production plan
Give the mold designer the current part model and drawing, intended resin grade, expected production quantity, appearance requirements, permitted gate locations, and any constraints on trimming or material recovery. Identify whether the tool is single-cavity, multi-cavity, or a family mold, and confirm the intended production machine and process assumptions.
Review the system as connected components
- Sprue: Confirm the interface with the machine nozzle and the tool design used to retain and remove the sprue.
- Runners: Review the layout, cavity balance, material volume, pressure-drop assumptions, and any geometry needed to support the planned fill pattern.
- Gates: Review gate type and location against appearance, function, cavity geometry, material, and the way the gate will be removed or separated.
- Cold-slug management: Ask where cold material may travel and how the design addresses it for this specific feed layout.
- Hot-runner components, if proposed: Compare tool complexity, controls, material and color changes, maintenance, support, and project volume with the alternative system.
Autodesk Moldflow’s runner-layout guidance describes the feed system as a combination of sprue, runners, and gates and identifies cavity count, material, process conditions, and flow balance as design inputs. Its gate-design guidance also identifies appearance, gate removal, cavity complexity, material, and shot volume as considerations.
Request evidence before tool release
Ask for a current feed-system drawing or CAD view, the design assumptions, and an explanation of how the cavities are expected to fill. For a multi-cavity design, agree how cavity balance and sample results will be assessed. If simulation is used, record the resin data, boundary conditions, and limitations so the result can be compared with sampling evidence.
Include maintenance and change control
Document how the feed system will be cleaned, inspected, maintained, and changed for the approved resin and production plan. Identify which parts are tool-specific, what replacement information is available, and how a gate or runner change will be reviewed for its effect on the part, process, and acceptance plan.
For the gate-location question specifically, see DAYIN’s gate-position selection guide. For a project review, see the custom injection molding service and the contact page.