Meaning
Machining process used to create the recesses in a mould base that hold the cavity and core inserts. Precise execution of tool steel pocketing ensures that the functional parts of the mould are perfectly aligned and supported under high clamping forces. These pockets must have flat floors and perpendicular walls to prevent insert shifting during the injection cycle.
This step follows the rough squaring of the mould plates but precedes the final fitting of the components.
Structural Integrity
Structural integrity of the entire tool depends on the tight tolerances maintained during the machining of these openings. When the injection pressure reaches several hundred bar, the walls of the tool steel pocketing area prevent the inserts from expanding outward. Gaps larger than five microns can lead to parting line mismatch or premature tool wear.
High-speed milling or electrical discharge machining provides the necessary accuracy for these critical features.
Thermal Management
Clearance around the inserts affects how heat moves from the plastic to the cooling plates. While a tight fit is necessary for strength, the tool steel pocketing must account for the thermal expansion of different materials. Some designs include a small air gap or insulation to isolate hot runners from the rest of the plate.
This thermal isolation prevents the base from warping.
Maintenance Access
Removal of inserts for cleaning or repair is easier when the pocket design includes pry slots or jacking screw holes. This tool steel pocketing feature reduces the risk of damaging the precision ground faces during maintenance.
