Seat belts cut the risk of fatality in a crash by half, and in rollovers their effectiveness can reach 77%, according to data from Spain's Directorate-General for Traffic (DGT) and the Ministry of the Interior. Behind these figures sits a set of mechanical parts that must respond in milliseconds, with zero margin for error: pretensioners, anchorages, and retention mechanisms.
Their reliability depends both on the pyrotechnic system that triggers them and on the metal components that bear and transmit the occupant's load. It's in this second part that zamak plays a decisive role.
Where zamak fits in, and where it doesn't
A pretensioner isn't a single part, it's an assembly. The pyrotechnic charge and gas generator that tension the belt at the moment of impact are the responsibility of suppliers specialized in passive safety systems.
Around that core sits a set of structural components that make the system work and allow the force to be distributed correctly: the housing that holds the mechanism and fixes it to the vehicle structure, the anchor brackets, the guides and pulleys the cable runs through, and the metal parts of the buckle. That's where we work at Jegan: die-casting precision zamak parts that are part of the pyrotechnic assembly.
The load path: from webbing to body
In a collision, the force the belt exerts on the occupant travels in reverse toward the vehicle structure: from the webbing to the anchorage, from the anchorage to the chassis. Every part along that path, made up of bracket, housing and guide, has to withstand that load without deforming uncontrollably or failing.
That's a different requirement than for a conventional aesthetic or functional component, since here there's no room for part-to-part variability, and mechanical strength has to stay constant across thousands of units. European type-approval regulations for belts and anchorages demand exactly that: these components must pass strength tests without breaking or detaching, and that level of demand shapes the entire manufacturing process, from mold design to dimensional control of the final part.
Why zamak fits this load path
Among the advantages of zamak production is that it reaches tensile strengths of up to 330 N/mm², a figure that allows anchor parts and housings to be sized to absorb an occupant's load without compromising the assembly.
Added to that is an advantage that's easy to overlook but decisive for this type of component: dimensional stability. An anchor bracket that varies from one part to the next, even by tenths of a millimeter, introduces a weak point in the load path. Zamak die-casting reproduces the same geometry with that repeatability, even in complex-shaped parts that have to fit into the tight space of the B-pillar or the seat structure, where the retractor, the webbing take-up mechanism and, in many cases, the pretensioner itself all coexist.
Reliability for a single-use component
A pretensioner fires only once. There's no second chance, no margin for an intermittent failure, which places a requirement of absolute reliability on every metal part in the assembly, including the ones we make in zamak. That's why we work under a zero-defects philosophy built on injection process control and the surface treatments we apply at our Eibar plant, to ensure these components keep their corrosion resistance throughout the vehicle's service life, not just at the moment of installation. A corroded anchor bracket loses strength silently, and that's exactly what these treatments prevent.
From belt engineering to the part in production
Designing a passive safety component doesn't end at simulation: it ends with a part manufactured in series with the same precision on unit number one and on unit number one hundred thousand.
At Jegan we combine zamak die-casting with our own surface treatments to deliver this type of component, from the earliest design stages through to volume production. If you're developing a restraint system or need to assess the technical feasibility of an anchor or housing part in zamak, our team at Jegan can support you through that process. Get in touch with our team and we'll take a look at your project.
