SPI Mold Classifications & Standards
A practical guide to SPI Class 101–105 injection molds, including expected mold life, construction requirements, and production applications.
Understanding SPI Mold Classifications
Mold Classes at a Glance
Compare the five SPI mold classes by expected production life and typical application.
| Mold Class | Expected Mold Life | Production Level | Typical Use |
|---|---|---|---|
| Class 101 | 1,000,000+ Cycles | Extremely High | Long-term, very high-volume production |
| Class 102 | Up to 1,000,000 Cycles | Medium–High | High-volume production, abrasive resins, and close-tolerance parts |
| Class 103 | Under 500,000 Cycles | Medium | General production programs |
| Class 104 | Under 100,000 Cycles | Low | Limited-volume production |
| Class 105 | Up to 500 Cycles | Prototype | Prototype and development tooling |
General Specifications for All Mold Classes
Before mold construction begins, the customer should approve the mold design. General mold construction considerations include:
Adequate channels for temperature control
Identification of steel type and Rockwell hardness where practical
Customer name, part number, and mold number identified on the mold
Appropriate provisions for mold handling, such as eyebolt holes and pry-bar slots
101
1,000,000+ Cycles
Extremely High-Production Tooling
Expected mold life: 1,000,000 cycles or more
Class 101 molds are designed for extremely high-volume production and require the most robust construction of the five classifications.
Class 101 Requirements
- Mold design required
- Mold base minimum hardness of 280 BHN
- Cavities and cores hardened to a minimum of 48 Rc
- Slides, heel blocks, gibs, wedge blocks, and similar components should use hardened tool steel
- Guided ejection
- Wear plates on slides
- Temperature-control provisions in cavities, cores, and slides wherever possible
- Corrosion-resistant or corrosion-treated components recommended around cooling channels
- Parting-line locks required
Corrosion within cooling channels can reduce cooling efficiency over the life of the mold, potentially affecting part quality and increasing cycle time. For this reason, plates or inserts containing cooling channels should use corrosion-resistant materials or appropriate corrosion-prevention treatments.
102
<1,000,000 Cycles
Medium- to High-Production Tooling
Expected mold life: No more than 1,000,000 cycles
Class 102 molds are designed for medium- to high-volume production and can be well suited for abrasive materials and close-tolerance applications.
Class 102 Requirements
- Mold design required
- Based largely on Class 101 construction
- Guided ejection is not required
- Hardened slide wear plates are not required
- Plated water channels are not required
- Wear-plated cavities are not required
- Other additional features are optional
103
<500,000 Cycles
Medium-Production Tooling
Expected mold life: Under 500,000 cycles
Class 103 molds provide a middle ground between high-production tooling and lower-volume mold construction.
Class 103 Requirements
- Mold design recommended
- Mold base minimum hardness of 165 BHN
- Cores and cavities 280 BHN or higher
- Other additional features optional
104
<100,000 Cycles
Low-Production Tooling
Expected mold life: Under 100,000 cycles
Class 104 molds are intended for limited production volumes where the construction requirements of higher mold classes may not be necessary.
Class 104 Requirements
- Mold design recommended
- Mold base may be constructed from mild steel or aluminum
- Cores and cavities may use aluminum, mild steel, or another mutually agreed-upon metal
- Other additional features optional
Choosing the Right SPI Mold Class
Choose the appropriate SPI mold class based on expected production volume, material, tolerances, mold complexity, and long-term tooling requirements.
Lifetime production volume: Estimate the total number of molding cycles expected over the program.
Material abrasiveness: Glass-filled and other abrasive compounds can increase tooling wear.
Part tolerances: Close-tolerance applications may require more robust mold construction.
Production continuity: High-volume programs may justify additional durability and maintainability.
Tooling budget: Higher mold classifications generally require more extensive materials and construction.
Program maturity: Prototype or early-stage programs may not require production-class tooling.
Looking for SPI Surface Finish Standards?
Mold classification defines the expected construction and service life of the tooling, while SPI surface finish standards define the finish applied to mold surfaces and molded parts.
Start Your Injection Molding Project
Whether you’re in energy, defense, medical, or consumer products — we have the expertise, equipment, and certifications to bring your injection molding project to life.
Get In Touch
Call us
Monday – Friday, 8am – 5pm CT
Email us
We’ll respond within 24 hours
Visit us
Houston, TX 77034
Visit www.texasinjectionmolding.com to learn more about our capabilities.