What Makes a Good Neck Block? Precision Where It Matters Most
In blow mould tooling, the neck block is a small component — but it carries a lot of responsibility. It’s the part of the mould that defines the bottle’s top finish: where it will seal, cap, pour, or dispense. For most products, this is the customer-facing, functional interface — and even the slightest variation in this area can cause line stoppages, failed leak tests, or customer returns.
At Beaubury, we treat the neck block as a critical element of every tool we build. Whether it’s a standalone unit or integrated into a modular system, its role in precision, repeatability, and sealing performance cannot be overstated.
Why Neck Blocks Matter
The neck block shapes the most critical zone of the bottle:
Thread or snap-fit features
Sealing ring or surface
Tamper-evident band retention
Pouring lip or dispensing fit
It’s also the one region that must consistently interface with another manufactured product: the cap. Unlike the bottle, which is blow moulded on-site, caps are injection moulded separately — and they’re far more expensive per unit. In most cases, the closure costs significantly more than the moulded bottle, especially for tamper-evident or multi-component caps.
This means even slight inconsistencies in the neck — such as ovality, shrink distortion, or misaligned threads — can cause:
Capping failures on automated lines
Leaks during filling or pressure testing
Misaligned closures and poor shelf appearance
Premature wear or jamming during application
So while the neck block may be just one element of the mould, it protects the investment made in the cap, the packaging line, and ultimately, the brand experience.
Precision and Repeatability
To meet these demands, we machine neck blocks to extremely tight tolerances — often within ±0.01 mm on key dimensions — and ensure consistency across production batches. This is especially critical when tools are used across multiple machines or when modular neck inserts are swapped in for different products.
In Summary
The neck block is where the blow mould meets the rest of the packaging system. It’s a precision component that protects your closure investment, ensures sealing integrity, and supports production efficiency.
A good neck block:
Matches cap geometry exactly
Resists wear and maintains tolerance
Cools predictably to avoid shrink distortion
Integrates cleanly with blowpin and sealing tools
Justifies the cost and function of every cap applied
At Beaubury, we treat neck blocks with the attention they deserve — because when the top of the bottle fails, everything else follows.
Material Selection and Durability
Neck blocks are subject to regular mechanical contact — not from the blowpin itself, but from clamping during mould closure and trimming operations around the finish.
To maintain dimensional accuracy and extend tool life, we typically machine neck blocks from
Copper-based alloys like Ampco® when improved thermal conductivity is needed
Stainless steel for corrosion resistance or cleanroom applications
In aluminium-bodied moulds, the neck block is always a separate steel or alloy insert, allowing for targeted durability where it’s most needed without adding weight to the full tool.
