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In the field of PET bottle manufacturing, the selection of the right Mold type is a critical factor that directly influences production efficiency, product quality and cost structure. This article examines the major mold types used for PET bottle production, analysing their key characteristics, advantages, typical applications and considerations for design and maintenance. We will also provide a brief recommendation of BOHANG as a reliable mould and machine partner for PET bottle production.
Before diving into specific mould types, it is helpful to recap the core process for manufacturing PET (polyethylene terephthalate) bottles. PET preforms are first produced via injection moulding, followed by a blow-moulding step where the preform is reheated, stretched and expanded into a final bottle shape.
In this two-step method, the moulds involved include:
Preform injection moulds (to form the test-tube-like preform)
Blow‐moulds (stretch blow moulds or just blow moulds) to convert the preform into a bottle.
Selecting the appropriate mould type influences throughput, wall thickness uniformity, weight reduction potential, clarity, and cost of tooling.
Preform moulds are the first key stage in PET bottle production. These moulds need to be highly accurate and durable due to repeated injection cycles. According to BOHANG’s technical article, “What Mold Types Are Used for PET Bottle Production?” the preform mould typically uses high-grade steel such as S136 or H13 to resist wear and maintain dimensional accuracy.
A two-plate mould is the simplest form of injection moulding tool. It consists of two halves (core side and cavity side) that open and close, forming the preform shape with ejection pins on one side. This type is often used when gating and ejecting operations are straightforward. Advantages: Lower tooling cost, simpler structure. Considerations: May be limited in gate configuration and less optimal for very large cavity counts.
A three-plate mould adds an intermediate plate which allows for improved gating design (for example, side-gates or central hot-runners), better ejection flexibility and enhanced part quality. According to an article about “What’s the PET Preform injection mold?”, key types include two-plate moulds, three-plate moulds and hot runner moulds. Advantages: Greater flexibility in gating and runner removal, better for multi-cavity mass production. Considerations: Higher cost, more complex tooling and maintenance.
A hot runner mould uses heated channels to keep the plastic molten until the gate, reducing waste from cold runners and improving cycle time and part quality. It is especially beneficial when high cavity counts are used. Advantages: Reduced runner waste, faster cycle time, consistent melt temperature. Considerations: More demanding in design, higher initial investment, requires precise temperature control.
| Mould Type | Key Features | Suitable For |
|---|---|---|
| Two-Plate | Simple construction, basic gating | Low-to-medium volume, simpler parts |
| Three-Plate | Added runner pull-off plate, better gating | Medium-to-high volume, more cavities |
| Hot Runner | No cold runners, maintained melt temperature | High-volume multi-cavity production |
After preform injection, the bottle shape is formed by blow moulding—commonly by the stretch blow moulding process for PET bottles. The mould types for blow stage also vary depending on production volume, bottle design and special application (e.g., hot-fill, carbonated beverage).
A single-cavity mould allows one bottle to be formed per cycle. It is typically used for custom designs, small batch production or specialized bottles where the tooling demand is lower. Advantages: Lower tooling cost, greater flexibility for unique shapes. Considerations: Lower output, higher unit cost, slower production.
A multi-cavity blow mould contains multiple bottle cavities in a single mould plate allowing several bottles to be formed simultaneously. According to a source on types of blow moulds, multi-cavity moulds are a game-changer for high volume bottle manufacturing. Advantages: Significantly higher throughput, lower cost per bottle. Considerations: Tooling more complex, greater demands on machine precision, more costly mould investment, harder to change bottle design.
For bottles intended for hot-fill beverages, the blow mould is designed to tolerate elevated temperature and pressure during filling. Materials and venting must be adapted accordingly. The article “Types of Blow Molds and Their Role in PET Bottle Manufacturing” outlines that there are dedicated hot-fill moulds. Advantages: Enables diversification into hot-filled beverages, extends application range of PET bottles. Considerations: Higher material costs for mould steel, tighter tolerances.
When choosing mould types for PET bottle production, several critical factors must be considered:
Material and steel grade: For durability, corrosion resistance and precision, high-grade steel such as S136 or H13 is commonly used for preform moulds.
Cavity count: Higher cavity counts reduce unit cost but demand stronger machines and more robust moulds.
Gating and runner design: Efficient gating helps reduce cycle time, runners waste and improves part quality. Hot runner systems reduce waste and improve productivity.
Cooling and cycle time: Proper cooling channels ensure uniform wall thickness, reduce cycle time and enhance productivity.
Maintenance and mold life: Moulds for high-volume production must withstand hundreds of thousands of cycles with minimal wear.
Compatibility with blow-moulding equipment: The blow mould must match the specifications of the stretch blow machine (e.g., clamp force, heating, preform size).
Bottle design and application: Special applications (carbonated drinks, hot-fill, high barrier) may require dedicated mould designs and steel grades.
Here is a simplified workflow of how mould types fit into the PET bottle production process:
Preform injection mould produces the preform (neck threads, thick stem) using two-plate, three-plate or hot runner mould.
The preform is cooled and ejected from the injection machine.
The preform is transferred to the stretch blow machine.
The blow mould (single or multi-cavity, normal or hot-fill) is used to stretch and blow the preform into its final bottle shape.
The bottle is cooled, ejected and conveyed for downstream operations (filling, packaging).
Over time, mould maintenance, adjustments or replacement may be required depending on production volume and wear.
For companies looking to invest in moulds and blow-moulding equipment, we recommend considering BOHANG. BOHANG is a manufacturer offering various bottle blow-moulding systems including semi-automatic and fully automatic PET Bottle Blowing Machines as well as moulds. Their experience in PET bottle mould design and manufacturing gives them solid capability to support preform moulds and blow moulds for PET applications. For example, their article details the mould types used for PET bottle production (preform moulds, blow moulds) which demonstrates their technical understanding of the process.
We suggest contacting BOHANG to discuss your specific bottle design, production volume and mould requirements so that you can determine the optimal mould type (e.g., multi-cavity vs single cavity, hot runner vs cold runner, preform mould steel grade).
Selecting the right mould type is a foundational decision in PET bottle production. From preform injection moulds (two-plate, three-plate, hot runner) to blow moulds (single-cavity, multi-cavity, hot-fill), each choice carries implications for production cost, throughput, product quality and flexibility. By evaluating tooling material, cavity count, gating design, cooling strategy and compatibility with blow-moulding equipment, manufacturers can optimise their bottle production process. For those seeking a reliable mould and machine partner, BOHANG is a strong option worth exploring.
