Chinese Injection Molds: Positioning Structure Scheme for Vertical Insert Molding Dies

Vertical injection molding machines are widely adopted in China’s injection mold industry for insert overmolding production, covering new energy terminals, metal nuts, conductive pins and plastic-coated precision components. Unlike horizontal molds, vertical equipment relies on manual or semi-automatic embedding of metal inserts before clamping, which frequently causes common defects including insert offset, floating height, ejection displacement, metal deformation and compression bruising. These flaws further lead to uneven plastic wall thickness, exposed metal, electrical short circuits and out-of-tolerance finished parts. To match the high-volume, high-precision mass production demands of domestic Chinese injection mold factories, an integrated positioning system combining benchmark locating, anti-shifting locking, anti-floating protection and foolproof assembly is developed. This complete structural scheme guarantees repeated positioning accuracy, stable molding quality and long-term service life for vertical insert molds.

1. Benchmark Positioning Structures for Consistent Centering

The core principle of domestic vertical insert mold design is to position metal hardware via its original contour benchmark, eliminating random displacement caused by manual placement without fixed restraints. For circular inserts such as copper nuts and annular pins, fixed positioning core pins are adopted with a tolerance of +0.01mm to +0.02mm for tight matching with inner holes, effectively preventing eccentricity and horizontal shifting. These core pins are quenched for high hardness and wear resistance to maintain precision over hundreds of thousands of molding cycles.

For flat copper sheets, square terminals and irregular metal fittings, contour-matched positioning grooves with unilateral clearance are machined on mold inserts. The groove fully fits the outer shape of hardware, leaving only minimal demolding clearance to stop rotation and reverse placement, achieving a unique assembly posture. Long strip terminals such as long conductive copper strips adopt dual-point positioning composed of front and rear positioning columns and limiting steps, controlling straightness and avoiding head-tail skew that triggers uneven plastic coating thickness. This series of benchmark positioning structures has become the standard design adopted by most Chinese precision mold manufacturers.

2. Anti-Displacement Locking Structures Against Injection Pressure Impact

High injection melt pressure easily pushes lightweight metal inserts away during filling, so independent locking structures are essential to counteract flow impact. Suspended slender terminals use movable upper pressing blocks that fully clamp hardware after mold closing, locking inserts in place throughout the injection cycle to eliminate shifting caused by melt thrust. Thin flat metal pieces adopt lateral wedge clamping structures; after mold clamping, sliders laterally hold the hardware tightly, achieving zero displacement during molding, which is ideal for high-precision wall-thickness overmolding products.

In addition, retaining walls and limiting steps are added on the melt inflow side to change the flow direction of plastic, avoiding direct high-pressure impact on insert end faces and reducing shifting risks from the source. This dual protection of mechanical locking and flow diversion is widely used in Chinese new energy component molds to cut displacement reject rates drastically.

3. Anti-Floating & Anti-Bruising Elastic Protection Structures

Insert floating up and metal compression deformation are the most frequent failures in vertical insert molds made by domestic factories. Precision limiting steps with accurate height are machined on mold inserts to lock hardware height completely, erasing height deviations from inconsistent manual placement that lead to exposed metal or crushed metal parts. For ultra-thin and soft copper strips prone to bending, spring floating positioning inserts are installed to provide flexible clamping force during mold closing, avoiding collapse and deformation while maintaining tight positioning without looseness.

All sharp edges, thin blades and protruding corners of metal inserts are designed with local relief space on the mold, only clamping benchmark surfaces without contacting non-functional edges, which completely solves compression marks and metal deformation defects. This elastic anti-pressure design balances positioning tightness and hardware protection, perfectly fitting the mixed batch production mode of Chinese injection workshops.

4. Foolproof & Rapid Assembly Structures for Mass Production Efficiency

To lower manual operation errors in large-scale domestic molding workshops, foolproof features are integrated into all positioning structures. Notch differences, flat bit chamfers and contour asymmetry are used to create reverse blocking structures, making wrong orientation assembly impossible. Multi-cavity molds with multiple inserts are equipped with independent positioning pits; missing, misplaced or incompletely set hardware will trigger abnormal mold closing, realizing automatic error prevention. Clear visual benchmark steps are reserved on positioning grooves, allowing operators to judge complete placement at a glance and reduce human-induced deviation. This humanized design greatly shortens training time for new workshop workers and improves overall production efficiency.

5. Wear-Resistant Structural Design for Long-Term Production Stability

Chinese injection mold factories pursue long service life and low maintenance costs, so all positioning components are optimized for wear resistance. Positioning core pins, contour grooves and sliding blocks are quenched to HRC 52-56 hardness, and all easily worn positioning parts are made as separate replaceable inserts instead of integrated mold plates, cutting repair downtime. Key contact surfaces between inserts and hardware are coated with PVD wear-resistant layers to stabilize positioning accuracy over long-cycle production without looseness or offset.

Summary

The positioning structure scheme for vertical insert molds developed by Chinese injection mold manufacturers follows a complete logic of fixed benchmark locking, injection pressure anti-shifting, height limiting, elastic anti-bruising, mass-production foolproofing and wear-resistant long service life. By combining contour benchmark positioning, wedge locking systems, spring floating protection and error-proof assembly design, the scheme thoroughly resolves common industry defects including insert eccentricity, melt impact shifting, floating up and metal compression deformation. It optimizes manual placement efficiency, lowers product reject rates and ensures consistent precision across all mold cavities. This standardized structural solution adapts to the mass production requirements of new energy terminals, electronic hardware and precision overmolding parts, fully matching the high-quality, cost-effective development demands of China’s domestic injection mold industry.