Ensuring consistent quality in blow molding with stable air pressure

In today’s plastics industry, blow molding has evolved into a high-precision, high-efficiency, air-intensive manufacturing process. Whether producing PET bottles, automotive ducting or consumer packaging, maintaining stable compressed air pressure during forming is critical. Even small fluctuations in air delivery can cause inconsistent wall thickness, poor surface finish and increased reject rates, especially in high-output lines.

In new facilities, and for new production lines, there are greater options for meeting the needs of an operation, often high-pressure compressors. In cases where there are existing facilities and lines, limited space or budget, or other constraints, air amplifiers from Haskel can offer a smart, efficient solution.

Why stable compressed air matters in blow molding

Blow molding involves two pressure stages:

• Low-pressure pre-blow (7–8 bar) to shape the plastic
• High-pressure final blow (30–40 bar) to form the precise geometry

The quality of this final blow, responsible for the integrity and appearance of the product, depends heavily on the consistency and reliability of the high-pressure air supply.

As Danny Yue, Commercial Lead for Haskel APAC, explains:

“If you don’t have good, stable compressed air, you’ll get poor surface finish and product quality. Modern plastics demand smooth, uniform casing - whether it’s a PET bottle or a phone housing. And that’s only possible with consistent, clean high-pressure air.”

Unstable supply creates spikes or drops during the critical inflation stage, leading to:

• Incomplete molding
• Asymmetrical shapes
• Weak or uneven walls
• Higher scrap rates

These issues don’t just affect quality control; they can also disrupt downstream filling, labeling or sealing operations.

The amplifier advantage over high-pressure compressors

Some production teams consider installing dedicated high-pressure compressors to meet 30–40 bar requirements. But this route brings high capital expenditures (CapEx), complexity, and energy costs. For lower-volume or batch operations, it can be often overkill.

Air amplifiers, by contrast, offer a targeted and cost-effective way to boost existing plant air for final blow stages. Haskel’s amplifiers use standard compressed air as a drive medium to generate higher outlet pressure, automatically compensating for downstream pressure drops, without the need for complex controls or electrical systems.

“ Haskel’s amplifiers are essentially pressure intensifiers. The simplicity is the strength, no need for sophisticated electronics, and no energy use when the system stalls at set pressure,” says Yue. “That’s ideal for operations running 24/7 who want to avoid maintenance downtime.”

Selecting the right amplifier: Haskel models for blow molding

Depending on flow rate and pressure needs, Haskel offers several models well-suited to this application. For PET blow molding at 30–40 bar, the AAD series is particularly relevant. Models like the AAD-2 and AAD-5 are capable of:

• Boosting standard 7 bar shop air up to 20–86 bar (300–1250 psi)
• Delivering consistent output even under variable demand
• Handling dynamic cycles due to their double-acting design

The AAD-5, for example, offers a 5:1 pressure ratio, max outlet pressure of 86 bar, and a displacement of 316cc per cycle, making it ideal for moderate to high-pressure applications where flow reliability is key.

For very high throughput, the 8AAD-2 provides even greater cycle volume (6.5 liters per stroke) while maintaining stable 20 bar output which is suitable for multi-cavity blow molders or hybrid systems. The Haskel team, and distribution partners, are always available to design configurations and unique solutions.

Engineering simplicity and operational stability

Blow molding engineers typically aim to:

• Minimize system downtime
• Easy Care and Cost-effective maintenance
• Avoid over-engineered solutions that risk failure

Haskel’s air amplifiers meet these objectives. Unlike electric-driven boosters, Haskel units are pneumatically powered and can operate cleanly in sensitive environments, no oil carryover, no heat generation, and minimal footprint.

Their “stall and boost” design also ensures that energy is only consumed when needed, helping reduce operating costs and wear.

“Customers can often build hybrid systems,” says Yue. “They’ll use a standard compressor for the initial low-pressure blow and then install a Haskel unit at point-of-use for the high-pressure finish. This setup gives them flexibility without major CapEx.”

Reducing reject rates and improving finish

Ultimately, the payoff for plastics manufacturers is in consistency - fewer rejects, tighter tolerances, and better finish. In industries where branding, clarity or safety standards matter, even minor defects can have commercial consequences.

Haskel’s air amplifiers help maintain a stable compressed air supply for blow molding, ensuring product quality, reducing maintenance downtime, and delivering operational efficiency.

Interested in improving your blow molding performance?
Click here to download our air amplifier product guide.