When to Use Tension Chains vs Tension Links for Mold Plate Control
Key Takeaway: Tension links are for precision stroke control during production (configurable in 5 mm increments). Tension chains are for safety backup during maintenance and emergencies (slack during normal operation). They serve different purposes and most multi-plate molds should have both.
Different Functions, Different Applications
| Criterion | Tension Link | Tension Chain |
|---|---|---|
| Primary function | Precision stroke control | Safety restraint (backup) |
| Active during production? | Yes — controls every cycle | No — slack during normal operation |
| Stroke precision | ±2.5 mm (5 mm increments) | ±10-20 mm (chain link increments) |
| Adjustability | Configurable oval hole length | Add/remove chain links |
| Load capacity | Moderate (stroke control forces) | High (must hold full plate weight) |
| Failure consequence | Incorrect stroke distance | Complete plate separation (hazard) |
When You Need Both
Most production multi-plate molds should have both tension links and tension chains:
- Tension links: Control the precise plate travel distance at each parting line during every production cycle.
- Tension chains: Provide safety backup — never engage during normal operation, but prevent plate fall if a tension link bolt fractures or a stopper bolt fails.
Think of tension chains as the "seat belt" of mold opening control — you hope they never engage, but they must be there when needed.
When Chains Alone Are Sufficient
- Two-plate molds with no stroke control requirement: The machine controls opening distance. Chains provide a safety limit only.
- Molds with machine-controlled multi-stage opening: If the injection molding machine has programmable opening positions, tension links may be redundant. Chains still provide safety backup.
Frequently Asked Questions
Can tension chains replace tension links?+
Only when precision stroke control is not needed (machine provides it). Chains lack the precision for production stroke control — their increments are too coarse and they do not provide hard stops.
Should the chain length match the tension link stroke?+
No. Chain length should be 10-20 mm longer than the maximum normal stroke. The chain should never engage during normal operation — it is a safety backup only.
Where should I mount tension chains relative to tension links?+
On the same side of the mold, below the tension link mounting point. Use dedicated chain holders for secure mounting.