One Continuous Cycle

ISBM combines preform injection, axial and radial stretching, and blow moulding into a single uninterrupted machine cycle. The result is a biaxially oriented container with superior clarity, barrier properties, and mechanical strength compared to extrusion blow moulded alternatives.

One-Step vs Two-Step

In one-step ISBM the preform is injected and blown while still thermally active, eliminating reheating energy and preform storage contamination risk. Two-step processes cool and store preforms before reheating — efficient at very high commodity volumes, but not optimal for premium containers or diverse material portfolios.

Why Biaxial Orientation Matters

Stretching the polymer in both the axial and hoop directions simultaneously aligns the molecular chains in two planes. This biaxial orientation measurably increases tensile strength, gas barrier performance, optical clarity, and drop-impact resistance — the reason biaxially oriented PET dominates global beverage and pharmaceutical packaging.

Resin Drying and Plasticisation

Before any moulding begins, raw PET, PETG, PC, PP, or Tritan pellets must be rigorously dried. PET is highly hygroscopic — if moisture exceeds 50 ppm entering the barrel, hydrolytic degradation occurs during melting, reducing molecular weight and producing hazy, structurally weakened preforms. A crystallising dryer at 160 to 175 degrees Celsius run for four to six hours is standard for PET.

Once dry, the resin feeds into the extruder screw, which uses mechanical shear and conductive heat from barrel heaters to progressively melt and homogenise the polymer. The uniformity of this melt directly governs the clarity and structural integrity of every container produced downstream.

Preform Injection

The molten polymer is injected at high pressure through the hot runner system into the closed injection mould cavity, forming the preform — a thick-walled, test-tube-shaped intermediate part. Injection clamping force must keep the mould halves fully closed against injection pressure. Insufficient force causes flash on the parting line and dimensional inaccuracy in the bottle neck threads.

In the EP-HGY50-V3-EV, injection clamping force is 50 KN, suitable for single-cavity cosmetic containers. In the EP-HGY200-V4 this rises to 300 KN for large multi-cavity pharmaceutical moulds. Hot runner temperature must be zone-controlled to prevent cold slugs appearing as inclusions in the finished bottle wall.

Simultaneous Stretch and Blow

This is the defining operation. A stretch rod descends axially through the preform neck while high-pressure compressed air — 2.0 to 3.5 MPa in all Ever-Power machines — simultaneously inflates the preform radially against the blow mould cavity. The combined action forces polymer chains to orient in both directions at the molecular level.

Timing is critical. If pre-blow air arrives before the stretch rod reaches its lower limit, material rushes toward the neck and the base becomes dangerously thin. If the stretch rod leads too far without air support, the base develops stress whitening. Ever-Power PLCs execute these events with millisecond precision, adjustable from the touchscreen without mechanical intervention.

Cooling, Depressurisation and Ejection

Once the container fills the blow mould cavity, cooling begins. The mould surface is maintained at 5 to 15 degrees Celsius by chilled water circulating through internal channels. Insufficient cooling contact time causes thermal deformation when the bottle is released, leading to ovality variation and base push-up failures that fail quality inspection.

After cooling, high-pressure air vents, the mould opens, and a take-out arm transfers the finished bottle to the outfeed conveyor. In the single stage injection stretch blow molding machine design this happens simultaneously with injection of the next preform and conditioning of another, creating a fully parallel production cycle with zero idle time between shots.

Polyethylene Terephthalate

The most widely processed resin in the stretch blow moulding process. PET delivers exceptional clarity, high oxygen barrier, and strong mechanical performance. Its narrow blow window of 95 to 115 degrees Celsius requires precise zone-level temperature control. Suitable for beverages, cooking oils, pharmaceutical syrups, and personal care products.

PET Glycol-Modified

PETG processes at lower temperatures, has a broader processing window, and delivers glass-like clarity without crystallisation drying. Ideal for luxury cosmetic jars, premium food containers, and medical device packaging where optical clarity is a primary brand requirement and complex shapes are required.

BPA-Free Copolyester

Inherently BPA-free with exceptional chemical and shatter resistance. Tritan’s temperature sensitivity demands a 4-station machine with precise conditioning control. Material of choice for infant nursing bottles, reusable sports containers, and medical packaging where BPA-free certification and optical clarity are both required.

Polypropylene

Excellent chemical resistance, low density, and microwave-safe profile. PP requires a very narrow processing window and benefits significantly from 4-station conditioning. Applications include yoghurt containers, personal care packaging, and hot-fill food service containers requiring FDA compliance.

Polycarbonate

Processes at significantly higher temperatures than PET, requiring careful melt temperature control to avoid yellowing. Produces containers with outstanding impact strength and optical clarity for water cooler bottles, reusable containers, and specialty optical applications. The 4-station conditioning stage is essential for defect-free output.

High-pressure blow air delivered through Parker valves fills the preform against the cold mould wall. Insufficient pressure causes incomplete bottle formation and surface defects.

Chilled water at 8 to 12 degrees Celsius circulates through the blow mould, determining cooling rate and cycle time. Consistent water temperature is essential for repeatable bottle geometry.

Clamping force must exceed the separating force from injection pressure. Ever-Power machines range from 50 KN for cosmetic applications to 400 KN in the EP-HGY650-V4.

For PET, an ASR of 2.0 to 2.5 combined with a hoop stretch ratio of 3.5 to 4.5 achieves optimal biaxial orientation. Deviation reduces barrier performance and mechanical strength.

All Ever-Power ISBM machines operate on standard 3-phase industrial power at 370 to 400 V, compatible with Europe, Australia, the Middle East, and most global markets.

Wall Thickness Variation

Cause: Non-uniform preform temperature at stretching. Thinner sections show where the preform was hotter. Most common with asymmetrical shapes on 3-station machines.

Solution: Switch to a 4-station machine with independent conditioning, or review the hot runner zone temperature map to achieve more uniform preform temperature before blow.

Stress Whitening

Cause: Preform temperature too low at blowing. The polymer orients below its glass transition temperature, creating micro-voids that scatter light and produce white haze.

Solution: Increase conditioning temperature in 2-degree increments. Verify injection mould cooling water is not pulling excessive heat from the preform before it reaches the blow station.

Cloudy Base

Cause: PET base held above the crystallisation range of 90 to 160 degrees Celsius for too long. PET crystallises within this range and loses transparency permanently.

Solution: Reduce cycle time to minimise preform exposure. Increase cooling water flow rate in the injection mould to cool the base section faster.

Flash on Neck Threads

Cause: Injection clamping force insufficient to hold neck ring inserts closed against injection pressure. Molten polymer escapes and solidifies as flash, preventing correct cap seating.

Solution: Verify measured clamping force matches machine specification. Check neck ring insert wear and consider whether resin viscosity has changed between batches.

Full Servo vs Hydraulic: How Much Energy Does ISBM Use?

Traditional hydraulic ISBM machines run a variable displacement pump continuously, circulating oil at constant pressure regardless of whether the machine is injecting, blowing, cooling, or pausing. The energy consumed during cooling — up to 40 percent of total cycle time — accumulates into significant utility bills over 24/7 production months.

Full servo systems, used in the EP-HGY50-V3-EV and EP-HGY150-V4-EV, replace the central pump with individual electric servo motors that only draw power when actively producing movement. During the cooling phase, servo motor energy consumption drops to near zero.

Under standard factory test conditions, Ever-Power full servo machines consistently achieve energy reductions of 30 to 40 percent versus legacy hydraulic machines — translating into tens of thousands of dollars in annual savings per machine in high-electricity markets like Germany, Australia, and the UK.

How Mould Design Shapes the ISBM Process Outcome

A perfectly configured machine with ideally conditioned polymer will still produce defective containers if the mould is poorly designed. In one-step injection stretch blow moulding, two distinct tooling elements work in sequence: the injection mould, which defines the preform geometry and neck thread accuracy, and the blow mould, which defines the final container’s external shape and surface finish.

Mirror-polished blow mould cavities produce high-gloss containers; satin-finish cavities produce a matte aesthetic. Uneven wall thickness in the preform translates directly into uneven wall thickness in the final container. Ever-Power designs and manufactures custom one-step ISBM moulds in-house, matching every cavity geometry precisely to the machine’s injection volume, stretch ratios, and production resin.

View Custom Mould Options

Pharmaceutical Packaging

Syrup bottles, eye drop vials, tablet containers, and nasal spray bottles require precise neck thread geometry, high barrier against moisture and oxygen, and a hygienic one-step process that minimises contamination risk. ISBM in PET or PP meets all these requirements within a single compact machine.

Luxury Cosmetics

Prestige skincare and perfume brands demand heavy-wall jars and bottles that replicate the aesthetic and weight of glass. PETG on 4-station machines produces cosmetic containers with wall thickness exceeding 4 mm, glass-like transparency, and complex oval or asymmetrical profiles impossible on simpler equipment.

Food and Condiment Jars

PET jars for peanut butter, honey, spices, and cooking oils require superior oxygen barrier and structural integrity to survive retail stacking. Biaxial orientation in the ISBM process significantly reduces oxygen permeation, extending shelf life beyond what injection moulded PP containers achieve at equivalent wall thickness.

Baby and Infant Products

Infant nursing bottles require BPA-free materials, optical clarity, shatter resistance, and precise neck threading to accept standard silicone teats. Tritan and PP on 4-station ISBM machines deliver all these requirements. The closed-loop one-step process minimises contamination versus two-step manufacture with preform storage.

Beverage Containers

Niche and premium beverage producers use one-step ISBM for superior material distribution in complex bottle shapes and the ability to process premium resins like PETG for differentiated shelf presence at moderate volumes where two-step machinery would be over-specified and inflexible.

Chemical and Household Products

Essential oils, cleaning concentrates, fabric softeners, and agrochemicals require containers with excellent chemical resistance and leak-free closure sealing. Biaxially oriented PET containers produced by ISBM show significantly improved stress-crack resistance and precise neck thread geometry versus injection moulded alternatives.

All technical parameters cited refer to measured performance data from Ever-Power machines under standard factory test conditions. For data sheets and machine configuration advice, contact [email protected] or visit our contact page.