SPI Mold Classifications: Key Types and Their Uses

The Society of the Plastics Industry (SPI) has established detailed classifications for injection molds, aiming to provide guidelines for obtaining quotations and placing orders for uniform types of molds. his classification not only helps manufacturers and customers communicate more effectively but also assists in determining the expected performance, lifespan, and application of the molds.

The SPI mold classification is divided into several categories, each representing a specific level of mold quality and durability. These categories are often referred to as “SPI Mold Classifications” and are typically numbered from Class 1 to Class 5.

Class	Uses	Lifetime Cycles
Class 101	Extremely High Volume	Exceeding 1 million
Class 102	High Volume	Not to exceed 1 million
Class 103	Medium Volume	Not to exceed 500,000
Class 104	Low Volume	Not to exceed 100,000
Class 105	Prototype Only	Not to exceed 500

SPI Class 101 Molds

Class 101 molds are designed for extremely high production volumes, with an expected lifespan of one million cycles or more. These molds are built for high precision and consistency, making them ideal for high-volume, high-precision parts.

All components, including slides and lifters, must be made from hardened tool steels. Guided ejection systems and wear plates on slides are crucial, along with effective temperature control provisions in cavities and cores. Corrosion-resistant materials are recommended for cooling channels, and parting line locks are required.

SPI Class 102 Molds

Class 102 molds are suitable for medium to high production volumes and are good for abrasive materials and/or parts requiring close tolerances. They are high-quality molds with a fairly high price. While Class 102 molds share many similarities with Class 101 molds, some features like guided ejection, hardened slide wear plates, plated water channels, and wear-plated cavities are not required. All other extras are optional, making Class 102 molds versatile for various applications.

SPI Class 103 Molds

Designed for medium production volumes, Class 103 molds offer a balance between cost and performance. They cater to applications that require durability but do not necessitate the highest-grade materials used in Classes 101 and 102. Mold design is recommended, though it may not be as detailed. Design flexibility is a key feature, allowing for customization based on specific production requirements.

SPI Class 104 Molds

Class 104 molds are intended for low production volumes, typically under 100,000 cycles. They utilize more cost-effective materials, making them suitable for applications where precision or long mold life is not critical. Mold design is recommended but can be less detailed. The mold base can be made of mild steel or aluminum, while cavities and cores may be constructed from aluminum, mild steel, or other mutually agreed-upon metals. Optional features further enhance cost savings and design flexibility.

SPI Class 105 Molds

Exclusively designed for prototype production, Class 105 molds are meant for very low production runs of no more than 500 cycles. These molds prioritize cost and ease of manufacture, using materials that provide sufficient strength for producing a limited number of prototype pieces. The mold base can be constructed from cast metal, epoxy, or any other material that offers adequate strength. Class 105 molds are ideal for initial testing and validation of product designs before transitioning to more durable and expensive mold types.

Conclusion

Choosing the appropriate mold class is critical for ensuring the success of a production run. Class 101 molds cater to high-volume, high-precision needs, while Class 105 molds are ideal for prototyping with minimal cost and complexity. Understanding these classifications allows manufacturers to optimize their processes, ensuring efficiency and quality in their production.

Considerations for Mold Selection

When selecting an SPI mold class, several factors must be considered:

• Higher volumes necessitate higher-class molds for durability and precision.
• The choice of materials for the mold impacts the production quality and lifecycle.
• Initial costs should align with production goals and budget limitations.
• Consider the end product’s requirements for durability, precision, and aesthetics.

Class	Material Requirements	Ejection Systems	Hardness Requirements
101	High-quality steels, hardened surfaces	Guided ejection needed	Base: 280 BHN, Cavities/Cores: 48 R/C
102	High-quality steels, hardened surfaces	Optional	Base: 280 BHN, Cavities/Cores: 48 R/C
103	Durable materials, lower-grade than higher classes	Optional	Base: 165 BHN, Cavities/Cores: 280 BHN
104	Cost-effective materials, mild steel or aluminum	Optional	Base: not specified
105	Cast metal, epoxy, or other sufficient materials	Optional	Not specified

BOYI offers high-quality mold manufacturing services for your plastic parts projects, covering all types within SPI mold classifications. Their expertise ensures that you receive the right mold for your specific production needs, whether for high-volume precision parts or prototyping.