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AXIOMMOLDS

Stopper Plates for Leader Bushings

Mechanical retention plates preventing leader bushing axial migration in large injection molds. Essential for molds over 600mm under thermal cycling and high clamp force conditions.

Products in This Category

Stopper Plates for Leader Bushings — Medium to Large Mold

Matched to leader bushing OD. Pre-drilled bolt patterns. 6–20mm thickness options.

Pairing

Leader Bushing OD RangeStopper Plate SizeMin Thickness
Ø40–Ø55 mmSmall plate8 mm
Ø60–Ø80 mmMedium plate10 mm
Ø85–Ø120 mmLarge plate12 mm
Leader Bushing >Ø40
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Stopper Plate (matched bore)Plate prevents bushing migration under clamping force

Decision rule: All leader bushings over Ø40 mm require stopper plates to prevent axial migration under cyclic clamping loads. For detailed guidance, see our Why Stopper Plates Prevent Leader Bushing Migration in Large Molds.

Why Stopper Plates Prevent Migration

In large molds, leader bushing migration occurs through a progressive mechanism:

  1. Mold heats up → plate bore expands slightly more than bushing OD → interference fit loosens
  2. Clamp force (1,000+ tonnes) creates axial pressure on bushing
  3. Each cycle pushes bushing fractionally outward (0.001–0.005 mm)
  4. Over 50,000+ cycles, cumulative migration reaches 0.5–2 mm

Stopper plates bolt to the plate surface, creating a physical barrier at the bushing flange. The bushing cannot move axially regardless of fit condition.

Decision rule: Any leader bushing over Ø40 mm in a mold exceeding 500 mm requires a stopper plate — the cumulative migration from 50K+ cycles will exceed acceptable alignment tolerance without one. For detailed guidance, see our Why Stopper Plates Prevent Leader Bushing Migration in Large Molds.

Frequently Asked Questions

What happens if I don't use a stopper plate with my leader bushing?+
Without a stopper plate, the leader bushing will gradually migrate out of its bore due to the cumulative impact forces during mold open/close cycles. In large molds (>500 mm), this migration can reach 0.5–1.0 mm within 100,000 cycles, causing progressive misalignment between mold halves. The result is increasing flash, core shift, uneven parting line witness marks, and accelerated wear on all guiding components. Replacing a migrated bushing requires dismounting the mold and re-boring — far more expensive than installing a stopper plate upfront.
How thick should the stopper plate be for molds over 800 mm?+
For molds over 800 mm, use stopper plates with a minimum thickness of 6 mm. Standard 4 mm plates are adequate for molds up to 500 mm, but larger molds generate higher impact forces during mold close that can deform thin stopper plates over time. The stopper plate material (typically S45C or equivalent medium carbon steel) must have sufficient compressive strength to absorb repeated impact loading without permanent deformation.
Is the stopper plate the same for all leader bushing sizes?+
No. Stopper plates are matched to specific leader bushing outer diameters. Each stopper plate has a central bore that fits the bushing OD with H7 tolerance, and mounting bolt holes that match the bushing installation pattern. Using a mismatched stopper plate can result in incomplete bushing retention or interference with adjacent components. Always order stopper plates as part of a matched bushing + stopper plate set.

Engineering Resources

Technical

Why Stopper Plates Prevent Leader Bushing Migration in Large Molds

Physics of bushing migration and stopper plate retention mechanism.

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✓ Matched to bushing OD✓ MOQ 1 piece