Case Study: A 72-Cavity Preform System Making 14.8 g Preforms on a 9.28-Second Cycle

A Latin American customer is running a 72-cavity preform system producing 14.8 g preforms on a 9.28-second cycle — 27,931 preforms an hour, about 670,000 a day and roughly 223 million a year at 8,000 running hours. The shot weight is 1,065.6 g, and the system moves 413 kg of PET an hour, close to 3,300 tonnes a year.

At 9.28 seconds, this is not a machine running a mould. It is a system in which the dryer, the mould, the injection unit and the take-out device all have to be sized for each other, or the cycle simply does not exist.

What 9.28 seconds buys

Output. 9.28 seconds is 387.9 cycles an hour — 1.40× more cycles per hour than a 13-second cycle. Across 72 cavities that produces 27,931 preforms an hour, roughly 670,000 a day.

Output per cavity. Per cavity, the system delivers 387.9 preforms an hour. Compare that with a 48-cavity tool on a 13-second cycle running at 276.9 per cavity: the 72-cavity system is not better because it has more cavities — the cavity count drives total output, while the per-cavity rate is set entirely by the cycle. Two independent decisions, two independent levers.

Material flow. 27,931 preforms × 14.8 g is 413 kg/h of PET, about 9.9 tonnes a day and roughly 3,300 tonnes a year.

Why 9.28 seconds is a system number

The injection unit must plasticise at least 115 g/s. The barrel has to melt the next 1,065.6 g shot while the mould is cooling the current one. Shot weight divided by cycle time gives 114.8 g/s as the floor — below that, the barrel becomes the bottleneck and the mould never sees 9.28 seconds. On a job this size the injection unit is not a detail to be trimmed; it is the constraint.

Drying capacity follows the throughput. At 413 kg/h and the standard 4–6 hour residence time at 160–180 °C to below 0.005 % moisture, the drying system has to hold roughly 1.7–2.5 tonnes of resin in process. This is the step most often underestimated on high-cavitation projects, and it is the first place insufficient drying shows up — as haze, brittleness and unstable wall distribution.

Cooling has to clear 72 cavities evenly. With preform mould temperature held around 10–20 °C to prevent premature crystallisation, and cooling taking the dominant share of 9.28 seconds, the tool has to remove heat uniformly across all 72 cavities. A single slow cavity sets the pace for all 72 preforms. Uniform cooling at this cavity count is what makes the cycle repeatable rather than occasional.

Take-out has to clear 72 parts inside the cycle. At 9.28 seconds there is no slack. The end-of-arm tooling must lift and transfer a 72-piece array without marking neck finishes, and the stroke has to complete within the same window as the mould open and close.

The mould has to be valve-gated. Multi-cavity preform moulds at this level rely on valve-gated hot runners — they control fill balance across 72 cavities and avoid the material waste of a cold runner.

What a 72-cavity system is good at — and what it is not

It is good at concentrating output and cost. 223 million preforms a year from one mould means fewer machines, fewer operators, less floor space and less energy per kilogram of PET than the same volume spread over several smaller tools. For a plant running a stable product mix, that is the whole argument.

It is not good at flexibility. 72 cavities assume a product that does not change often. A plant that needs to switch bottle formats weekly should not buy this machine — it should buy two smaller ones. High cavitation is a bet on product stability, and it pays off only when that bet is correct.

It raises the cost of everything that is not the machine. Drying, material handling, cooling, take-out, inspection and spare-part discipline all scale with the system, not with the tonnage. This is the real distinction between a preform machine purchase and a preform system project.

Support in the region

efficent maintains local service teams in Latin America, with engineering support based in Colombia and Panama alongside teams in South Africa and Saudi Arabia — the practical reason a Latin American customer can commit to a 72-cavity system rather than a smaller, safer tool. Remote troubleshooting is available for day-to-day issues, and our engineers work on-site for commissioning, training and process optimisation.

If you are evaluating a high-cavitation preform project, send us the preform weight, cavity count and target output. We will tell you what the injection unit, the dryer and the tooling each have to deliver — and whether the answer is a 72-cavity system or two smaller machines. 

Notes on the figures

Given by the project: 72 cavities, 14.8 g preform weight, 9.28 s cycle, region.

Derived in this article (stated so you can check the arithmetic):

• Shot weight = 72 × 14.8 g = 1,065.6 g

• Cycles per hour = 3,600 ÷ 9.28 s = 387.9

• Output = 387.9 × 72 = 27,931 pcs/h; × 24 h ≈ 670,000 pcs/day

• Annual output assumes

8,000 running hours per year

(a common planning basis, not a measured availability figure)

• Material throughput = 27,931 pcs/h × 14.8 g = 413 kg/h; × 24 h ≈ 9.9 t/day

• Plasticising requirement = 1,065.6 g ÷ 9.28 s = 114.8 g/s

• Drying hopper size = 413 kg/h × 4–6 h residence = 1.7–2.5 t

• Per-cavity rate = 387.9 preforms per cavity per hour

Supporting process requirements (drying conditions, preform mould temperature, cavity balance, valve-gated hot runner practice) follow published PET processing guidance — see the sources below.

Sources

• Alpine Mold,

PET Injection Molding Guideline: A Complete Guide for Engineers and Manufacturers

, published 2025-08-01 — PET drying conditions (160–180 °C, 4–6 h, <0.005 % moisture), preform mould temperature (10–20 °C), valve-gated hot runner practice, machine and tooling requirements.

• Cavity Mold,

PET Preform Injection Molds: Design and Process Basics

, updated 2025-09-01 — cavity balance, cooling, cavity-to-cavity variation and preform approval criteria.

• efficent preform injection machine series information (Efficient / servo energy-saving series, 16–96 cavity range) and regional service footprint.