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A Comprehensive Guide to PET Preform Moulds and Chair Moulds for Injection Molding

Injection molding is a popular manufacturing process used to produce a wide variety of plastic parts and products. Two common items produced via injection molding are PET preforms and plastic chairs. PET preform mould and chair mould are specially designed to create these products efficiently and cost-effectively.

This comprehensive guide will provide an overview of PET preform moulds and chair moulds – explaining what they are, how they work, the design process, materials used, manufacturing considerations, and common applications. Whether you are looking to have custom preforms or chairs made, or just want to learn more about these injection moulding tools, this article covers everything you need to know.

Comparison of Common PET Preform and Chair Mould Materials

Material	Hardness	Machinability	Wear Resistance	Corrosion Resistance	Typical Uses
P20 Steel	28-32 HRC	Excellent	Good	Low	General purpose preform & chair moulds
S136 Steel	50-55 HRC	Difficult	Excellent	Low	High wear resistance preform & chair moulds
420 Stainless Steel	50-52 HRC	Good	Moderate	High	Short run preform moulds, chair prototype moulds
H13 Steel	48-54 HRC	Moderate	Excellent	Moderate	Highly durable, long lasting preform & chair moulds
Aluminum	60-90 BHN	Excellent	Poor	High	Prototype and concept moulds

What is a PET Preform Mould?

A PET preform mould is used to produce PET preforms via injection molding. PET (polyethylene terephthalate) is a commonly used type of plastic polymer.

PET preforms are test tube-shaped plastic precursors that will later be stretch blow molded into final PET bottles or containers. The preform establishes the overall shape and thread finish of the final container.

The preform mould consists of two primary components – the cavity component (with negatives of the inner and outer surfaces of the preform) and the core component (forms the inner surface). When closed together and filled with molten PET plastic, the mould shapes the material into preforms.

PET preform moulds are precision-engineered tools, usually made from hardened tool steel. They must withstand high temperatures, pressure, and repetitive use. Proper cooling is also critical to produce quality preforms efficiently.

What is a Chair Mould?

A chair mould is an injection mould tool engineered for producing plastic chairs. The mould comprises two halves, namely the core and cavity side, which come together to shape the chair when closed.

Chair moulds enable the creation of all chair components as a single integrated piece during the injection molding process. This encompasses the seat, backrest, legs, and any integrated features or accessories.

Typically crafted from tool steel, chair moulds undergo precision machining. They incorporate cooling channels, ejector pins, and other technical elements to facilitate chair production. The mould’s design must strike a balance between factors such as ergonomics, aesthetics, strength, and manufacturability.

The PET Preform and Chair Mould Design Process

Creating a PET preform or chair mould is an intensive design and engineering process. It involves the following key steps:

Conceptualization: We conceive the initial product design based on requirements, the target market, production goals, and other factors.

CAD Modeling: We use 3D CAD software to model the preform or chair. We iteratively modify this digital prototype to perfect the design.

Mold Flow Analysis: Specialized software simulates how melted plastic flows through the mould to optimize filling and cooling.

Mould Design: We design the mould components and features, considering parameters such as shrinkage, ejection, cooling, strength, and machining.

CNC Machining: CNC machines cut and mill mould components from metal blocks to precise specifications.

Mould Assembly & Testing: We assemble the mould, test it, and make necessary modifications until parts are produced to specifications.

Final Machining and Polishing: We machine the mould to achieve a fine finish for smooth part surfaces.

The result is a high quality injection mould ready for mass production injection molding. The process requires extensive engineering expertise, advanced software, machining technology, and testing.

Common Materials for PET Preform & Chair Moulds

PET preform and chair moulds must withstand high pressure, heat, and wear. As such, they are typically constructed from hardened tool steel alloys. Some common mould materials include:

P20 Steel – General purpose pre-hardened mold steel that offers good wear resistance. It can be machined easily and has high impact strength.
S136 Steel – An oil hardened steel that can be heat treated to high hardness levels. Provides excellent wear resistance and compressive strength. Difficult to machine.
420 Stainless Steel – A stainless steel used for lower cost moulds. Machines easily but has lower hardness than tool steels. Good corrosion resistance.
H13 Steel – A versatile chromium-molybdenum-vanadium alloy steel that can be heat treated to high hardness. Offers great wear resistance and strength.
Aluminum – Lightweight and affordable but much lower hardness than tool steels. Only viable for prototype moulds or very short production runs.

The choice of material depends on production volume, part geometry, cost targets, and other factors. Pre-hardened P20 and S136 are some of the most common and reliable mould materials.

Manufacturing Considerations for PET Preform and Chair Moulds

There are several important manufacturing considerations when producing PET preform and chair moulds:

Mould Cooling – Effective cooling channels must be designed into the core and cavity to dissipate heat and solidify parts quickly. This improves cycle times and part quality.
Draft Angles – Angled surfaces that allow parts to eject cleanly from the mould. Insufficient draft can lead to jamming.
Surface Finishes – Proper polishing provides glossy, aesthetically pleasing finishes. SPI surface finishes define standards.
Tolerances – Critical dimensions must be precise to ensure preforms and chairs meet specifications.
Automation – remove parts, trim sprues, conduct quality checks, and pack finished items.
Preventative Maintenance – Schedule maintenance cleans debris, applies release agents, and replaces worn components to maximize mould longevity.

With thoughtful design and robust machining and manufacturing processes, preform and chair moulds can reliably produce hundreds of thousands of high quality parts over years of service.

Typical Applications of PET Preforms and Plastic Chairs

PET preforms produced via injection moulding make a vast range of PET bottles and containers. Common applications include:

Beverage bottles – Soda, water, juice, sports drinks, etc.
Food jars – Peanut butter, jelly, sauces, condiments, etc.
Consumer product bottles – Cleaners, soaps, shampoos, household chemicals, etc.
Medical packaging – PET’s clarity and safety suit it for pill bottles, saline containers, etc.

Injection molded plastic chairs are ubiquitous in both residential and commercial settings. Typical applications include:

Outdoor patio furniture – Durable and weather-resistant.
Kitchen and dining chairs – Budget friendly and stylish.
Office furniture – In offices, cubicles, waiting rooms, cafeterias.
Stadium seating – Durable enough for big crowds.
Stackable chairs – For flexible seating arrangements.
School chairs – Affordable and safe for classrooms.

Thanks to mass production injection molding with preform and chair moulds, these plastic items can be produced efficiently and economically at a huge scale to meet constant global demand across industries.

Conclusion

PET preform moulds and chair moulds play a vital role in high volume manufacturing of popular plastic products using the injection molding process. Creating these moulds requires extensive engineering and design work, specialized machining, precise manufacturing, and testing.

When produced correctly, PET and chair moulds can deliver hundreds of thousands of flawless, consistent injection molded parts over years of use. The combination of quality moulds and optimized injection molding enables mass production of affordable and reliable preforms and chairs that make our modern lifestyles possible.