How to Choose Between Long Stroke, Stepped, and Dual-Oval Tension Links
Key Takeaway: Choose long stroke tension links for single-stage control, stepped for two stages at different vertical positions, two oval holes for independent dual-stage control (most common for three-plate molds), and two oval holes with land when you need an intermediate stop between stages.
Four Tension Link Configurations
Each tension link configuration addresses a different mold opening requirement. The choice depends on the number of stages, stroke distances, and vertical positioning of parting lines:
| Configuration | Oval Holes | Stages Controlled | Best Application |
|---|---|---|---|
| Long Stroke | 1 (single, long) | 1 stage | Two-plate molds, single-stage stroke limit |
| Stepped | 2 (different heights) | 2 stages | Three-plate molds where PL1 and PL2 are at different vertical positions |
| Two Oval Holes | 2 (same plane) | 2 stages independently | Standard three-plate molds (most common) |
| Two Oval + Land | 2 with solid land between | 2 stages + intermediate stop | Molds requiring a specific plate hold position between stages |
Sizing Each Configuration
All configurations use the same core formula: Available Stroke = Oval Hole Length − Bolt Diameter. Oval hole lengths are configurable in 5 mm increments. For detailed calculation, see our stroke calculation guide.
- Long stroke: Maximum available stroke from a single oval hole. Use for strokes over 100 mm where the full link length is one continuous slot.
- Two oval holes: Each hole is independently sized. Upper hole controls PL1, lower hole controls PL2. Combined stroke must not exceed the link body length minus end margins.
- With land: The solid section between the two oval holes creates a physical stop point where neither bolt can pass. The land width defines the dwell distance at the intermediate position.
Bolt and Retainer Pairing
Each tension link requires dedicated bolts and retainers. Standard hardware bolts are incompatible:
- Standard bolts: For strokes ≤50 mm at moderate cycle rates.
- Urethane-wrapped bolts: For strokes >50 mm or cycle rates >15/min — urethane absorbs end-of-stroke impact.
- Single flange retainers: Standard applications.
- Double flange retainers: High-load applications or when bolt pull-through resistance is needed.
Frequently Asked Questions
Which configuration is most common for three-plate molds?+
Two oval holes — it provides independent stroke control for both PL1 and PL2 in a single link body. Used in approximately 70% of three-plate mold applications.
Can I combine different configurations in the same mold?+
Yes. Use different configurations on different sides of the mold if needed. However, all links on the same side should be identical to ensure uniform stroke limiting.
What is the maximum available stroke?+
Depends on link body length and bolt diameter. Typical maximum: 100-150 mm for single-hole long stroke, 60-80 mm per stage for two-hole configurations. Contact us with your requirements for sizes beyond catalog range.