From mould to production: how a cap is born
A cap comes out of an injection press in a few seconds. Before that first part came weeks of drawing, machining and trials. Here is the path, step by step, from a closure idea to series production.
By Tecmom editorial team · 2 min read
1. The specification
It all starts from a need: a neck to close, a product to protect, a function to perform. The bottle's neck finish sets the diameter and thread. The product sets the material and the level of sealing. The market adds its functions: a tamper-evident band, a child-resistant mechanism, a desiccant. And the annual quantity says how many cavities the mould will need.
For a medicine, one more constraint applies from the outset: the cap will be part of the primary packaging, and so of the product's file. The material chosen will have to stay the same.
2. Mould design
This is the step that decides almost everything. The designer draws the part, then the mould that will form it: material shrinkage on cooling, which the cavity must compensate for; the parting line, where the mould will open; the gates, through which material will enter; the cooling circuit, which sets the cycle time; and ejection, which for a threaded cap often means unscrewing.
None of these choices can be corrected later without reworking the steel. That is the trade carried in the company's name: Technologies Moules et Matrices.
3. Machining
The mould is cut from steel on CNC machines: milling, drilling the cooling channels, electrical discharge machining for shapes a cutting tool cannot reach, polishing the surfaces that will give the part its look. Tecmom's workshops are equipped with CNC machines, which keeps design and development lead times short. See our expertise.
4. Tryout
The mould is mounted on a press for its first trials. The first parts are measured and compared with the drawing: thread dimensions, appearance, warping, how the tamper-evident or child-resistant feature works. Press settings, temperature, pressure, cooling time, are adjusted; if a dimension stays out of tolerance, it is the steel that gets reworked.
Tryout ends when the part conforms and keeps conforming from one cycle to the next.
5. Validation, then production
For pharmaceutical packaging, a conforming part is not enough: a process that reproduces it is needed. The customer qualifies the bottle-and-cap system; the manufacturer freezes settings and material, and any later change goes through change control, as ISO 15378 requires.
Then comes production: manufacturing in a controlled environment, checks on raw materials and finished products throughout, traceability of every lot. See quality.
The first conforming cap is not the end of the work; it is the proof that the work was done well. A mould's real success is measured years later, when the millionth part closes like the first.
Glossary
- Specification
- The document that sets what the part must do, with its constraints.
- Tryout
- The phase of trials and adjustments that brings a mould to produce conforming parts.
- Shrinkage
- Contraction of the material as it cools, which the cavity must compensate for.
- Change control
- The rule that forbids changing, unilaterally, an item that is part of a medicine's file.