When you’re working with injection molds or stamping dies, have you ever wondered why those compression springs come in different colors? It’s not just for aesthetics – each color tells a crucial story about the spring’s load capacity, compression limits, and service life. Today, we’re diving deep into the world of JIS die springs and their color classification system, helping you make the right choice for your mold applications.
What Are JIS Die Springs and Why Do They Matter?
JIS die springs are precision-engineered compression springs manufactured according to the Japanese Industrial Standard (JIS B5012). These springs are the workhorses of the mold and die industry, providing consistent force and reliable performance in demanding applications ranging from plastic injection molds to metal stamping dies.
Think of them as the shock absorbers of the manufacturing world – they cushion impacts, return parts to their original positions, and ensure your mold operates smoothly cycle after cycle. But unlike regular springs, die springs are built to withstand millions of compression cycles without losing their spring characteristics.
The Five-Color Language of Load Capacity
Here’s where it gets interesting: JIS die springs use a brilliant color-coding system that allows engineers and technicians to instantly identify a spring’s load rating. No need to pull out specification sheets or measure dimensions – just look at the color, and you’ll know what you’re working with.
| Color Code | Load Type | Maximum Safe Compression | Typical Applications |
|---|---|---|---|
| 🟡 Yellow (YEL) | Extra Light Duty (轻小负荷) | 50% | Delicate part ejection, light pressure applications, small components |
| 🔵 Blue (BLU) | Light Duty (轻负荷) | 40% | Standard ejector pins, moderate pressure plates, general-purpose molds |
| 🔴 Red (RED) | Medium Duty (中负荷) | 32% | Standard plastic injection molds, medium stamping operations |
| 🟢 Green (GRE) | Heavy Duty (重负荷) | 24% | High-pressure systems, heavy stamping dies, large part ejection |
| 🟤 Brown (BRO) | Extra Heavy Duty (极重负荷) | 20% | Extreme pressure applications, large-scale industrial stamping |
Critical Data: Compression Rate vs. Service Life for Each Color
This is where it gets really important – and this information is rarely discussed but absolutely critical for your tooling design. Each color of JIS die spring has different recommended compression rates depending on your target service life. Operating a spring at higher compression rates dramatically reduces its cycle life.
Here’s the complete data table showing the maximum recommended compression rate for each color at different service life targets:
| Spring Color | Load Type | 300,000 Cycles (30万回) | 500,000 Cycles (50万回) | 1,000,000 Cycles (100万回) |
|---|---|---|---|---|
| 🟡 Yellow | Extra Light Duty | 56.0% | 45.0% | 40.0% |
| 🔵 Blue | Light Duty | 43.0% | 36.0% | 32.0% |
| 🔴 Red | Medium Duty | 32.0% | 28.8% | 25.6% |
| 🟢 Green | Heavy Duty | 24.0% | 21.6% | 19.2% |
| 🟤 Brown | Extra Heavy Duty | 20.0% | 18.0% | 16.0% |
💡 How to Read This Table
This table shows the maximum recommended compression rate (percentage of free length) for each spring color to achieve the target service life.
Example: If you want a Blue spring to last 1,000,000 cycles, you should design your tooling so the spring compresses no more than 32.0% of its free length.
Key Insight: Notice how heavier-duty springs (Green, Brown) must operate at lower compression percentages to achieve the same cycle life. This is because they use thicker wire and higher stress levels.
Understanding the Trade-offs
As you can see from the table, there’s a clear relationship between compression rate and service life:
- Higher compression = Shorter life: If you need to compress a spring more, expect fewer cycles before replacement
- Heavier springs = More restricted: Brown and Green springs must operate at lower compression percentages than Yellow and Blue
- Design flexibility: If you need long life (1M+ cycles), you must either accept lower compression or choose a longer spring
How to Select the Right Color Spring for Your Application
Now that you understand the color classification and compression-life relationships, let’s walk through a practical selection process:
Step 1: Calculate Your Required Load
First, determine the force needed for your application. For injection molding, use this formula:
Ejection Force (N) = Part Surface Area (mm²) × Ejection Pressure (MPa)
Typical ejection pressures: 0.5-2.0 MPa depending on material
Total Force = Ejection Force × Friction Factor (1.2-1.3) × Safety Factor (1.5-2.0)
Force Per Spring = Total Force ÷ Number of Springs
Step 2: Determine Your Stroke Distance
Measure how far the spring needs to compress during operation. This is typically your ejection distance plus 1-2mm of preload.
Step 3: Calculate Compression Rate
This is the critical calculation:
Compression Rate (%) = (Stroke Distance ÷ Free Length) × 100
Example: 20mm stroke ÷ 80mm free length = 25% compression rate
Step 4: Determine Your Target Cycle Life
How many cycles do you need?
- 300,000 cycles: Suitable for prototype tooling, short production runs, low-volume manufacturing
- 500,000 cycles: Good for standard production tooling, medium-volume manufacturing
- 1,000,000+ cycles: Required for high-volume production, automotive tooling, critical applications
Step 5: Select Color Using the Table
Now refer back to the compression rate vs. service life table above. Match your calculated compression rate with your target cycle life to determine which colors are suitable.
✓ Selection Example
Your Requirements:
- Stroke distance: 20mm
- Available space for spring free length: 80mm
- Compression rate: 20mm ÷ 80mm = 25%
- Target cycle life: 1,000,000 cycles
From the table:
- 🟡 Yellow at 1M cycles: 40.0% max ✓ (25% is well within limits)
- 🔵 Blue at 1M cycles: 32.0% max ✓ (25% is within limits)
- 🔴 Red at 1M cycles: 25.6% max ✓ (25% is just within limits)
- 🟢 Green at 1M cycles: 19.2% max ✗ (25% exceeds limit)
- 🟤 Brown at 1M cycles: 16.0% max ✗ (25% exceeds limit)
Decision: Yellow, Blue, or Red springs are suitable. Choose based on your required load force – use load tables to verify which color provides adequate force at 20mm compression.
Real-World Application Examples
Let’s examine three real scenarios to see how color selection and compression rate calculations work in practice:
🟡 Scenario 1: Consumer Electronics Mold
Application: Injection mold for smartphone back covers
Requirements:
- Part weight: 40g, delicate surface finish required
- Ejection stroke: 15mm
- Spring pocket depth allows 35mm free length maximum
- Production volume: 800,000 parts expected
Calculations:
- Compression rate: 15mm ÷ 35mm = 42.9%
- Target life: 1,000,000 cycles (for full production + safety margin)
Selection from table:
- Yellow at 1M cycles: 40.0% max – NOT suitable (42.9% exceeds limit)
- Need to redesign: Use longer springs (40mm) to reduce compression: 15mm ÷ 40mm = 37.5% ✓
Solution: Yellow springs with 40mm free length, providing gentle ejection force perfect for delicate plastic parts while achieving 1M+ cycle life at 37.5% compression.
🔴 Scenario 2: Automotive Dashboard Mold
Application: Large injection mold for automotive interior trim panels
Requirements:
- Part weight: 450g, textured surface
- Ejection stroke: 25mm
- Spring free length: 100mm
- Expected production: 2,000,000 parts over tool life
Calculations:
- Compression rate: 25mm ÷ 100mm = 25.0%
- Target life: 2,000,000+ cycles
Selection from table (using 1M cycle data as baseline):
- Red at 1M cycles: 25.6% max ✓ (25% is just within limit)
- Blue at 1M cycles: 32.0% max ✓ (25% well within limit – better for long life)
Solution: Red or Blue springs depending on required force. For 2M+ cycles, Blue springs operating at 25% compression provide better safety margin and more reliable long-term performance.
🟤 Scenario 3: Heavy Metal Stamping Die
Application: Progressive die for automotive seat bracket stamping
Requirements:
- Heavy stamping force, material springback issues
- Return stroke: 30mm
- Spring free length: 200mm (ample space available)
- Expected cycles: 1,500,000 parts
Calculations:
- Compression rate: 30mm ÷ 200mm = 15.0%
- Target life: 1,500,000+ cycles
Selection from table:
- Brown at 1M cycles: 16.0% max ✓ (15% is within limit)
- Green at 1M cycles: 19.2% max ✓ (15% well within limit)
Solution: Brown (Extra Heavy Duty) springs provide maximum force for overcoming material springback while operating at conservative 15% compression ensures reliable 1.5M+ cycle life in harsh stamping environment.
Common Mistakes to Avoid
Even experienced engineers sometimes make these critical errors when selecting or using JIS die springs:
❌ Mistake #1: Ignoring the Compression Rate vs. Life Relationship
The Error: Selecting springs based only on load capacity without checking compression rate against target cycle life.
Why It Fails: A spring might provide adequate force but fail prematurely if operated beyond its compression limits for the desired life.
✓ Correct Approach: Always use the compression rate vs. service life table to verify your selection will achieve target cycle life.
❌ Mistake #2: Mixing Different Spring Colors
The Error: Using springs of different colors (load ratings) in the same mold cavity or stripper plate.
Why It Fails: Uneven force distribution causes:
- Tilted or cocked mold components
- Inconsistent part ejection
- Accelerated wear on one side
- Premature failure of weaker springs
✓ Correct Approach: Use only one color per application. Replace springs as complete matched sets, preferably from the same production batch.
❌ Mistake #3: Exceeding Maximum Compression Rates
The Error: Compressing Yellow springs beyond 50%, Blue beyond 40%, Red beyond 32%, etc.
Why It Fails: Over-compression causes:
- Permanent set (spring doesn’t return to free length)
- Dramatic reduction in cycle life
- Risk of spring breakage
- Coil contact and binding
✓ Correct Approach: Design tooling to keep compression within rated limits. If more compression is needed, use longer springs or switch to a heavier duty color (accepting its lower maximum compression percentage).
❌ Mistake #4: Installing Without Adequate Preload
The Error: Installing springs with zero or minimal initial compression.
Why It Fails: Springs experience impact loading each cycle, causing:
- Accelerated fatigue from repeated impacts
- Loud banging noise during operation
- Reduced service life by 50% or more
✓ Correct Approach: Always install with 1-2mm minimum preload (initial compression) to ensure springs remain under load throughout the operating cycle.
❌ Mistake #5: Using Without Proper Guidance
The Error: Operating springs without guide pins, or with inadequate guide length.
Why It Fails: Lateral deflection causes:
- Uneven stress distribution across coils
- Coil contact and scrubbing
- Premature spring breakage
- Inconsistent mold operation
✓ Correct Approach: Use guide pins extending through at least 50% of compressed spring length, with 0.5-1.0mm clearance per side.
Maintenance and Replacement Guidelines
Knowing when to replace springs is crucial for preventing unexpected downtime and maintaining part quality. Watch for these warning signs:
Visual Inspection Indicators
- Permanent Set: Spring doesn’t return to original free length when removed (measure and compare to specification)
- Surface Damage: Coating wear, corrosion, or rust visible on coils
- Cracks or Fractures: Any visible cracks, especially at coil ends
- Coil Contact Marks: Shiny wear marks indicating coils are touching during compression
Performance-Based Indicators
- Inconsistent Ejection: Parts eject unevenly or require additional force
- Timing Changes: Mold cycle time increases or becomes erratic
- Part Quality Issues: Ejector pin marks, part deformation, or surface defects
- Load Loss: Measured force decreased >15% from specification
Cycle-Count Based Replacement
Based on the compression rate vs. service life data, implement this replacement schedule:
| Operating Condition | Inspection Frequency | Replacement Interval |
|---|---|---|
| High-volume 24/7 production (Operating near maximum compression limits) | Every 3 months | Every 12 months or at rated cycle count |
| Standard production (1-2 shifts) (Operating at moderate compression rates) | Every 6 months | Every 18-24 months |
| Low-volume/prototype tooling (Operating well below compression limits) | Annually | As needed based on visual inspection |
✓ Best Practice: Preventive Replacement
Don’t wait for complete spring failure – it usually happens mid-production, causing expensive downtime. Instead:
- Track cycle counts and schedule replacement before reaching rated life
- Keep spare spring sets in inventory for each mold
- Replace springs as complete sets, even if only one shows wear
- Document spring specifications and replacement dates in mold maintenance records
Why Material Quality and Manufacturing Matter
Not all JIS die springs deliver the performance promised by their color code. The quality of materials and manufacturing processes directly impact whether springs achieve their rated cycle life.
Premium Materials Make the Difference
At Cixi Dili Spring Co., Ltd., we manufacture our JIS die springs from premium 55Crsi conforming to JIS G 3566. This isn’t just marketing – it’s the foundation of reliable performance:
- High Carbon Content: Provides necessary strength and hardness
- Silicon Addition: Enhances elastic properties and fatigue resistance
- Chromium Content: Improves hardenability and corrosion resistance
- Vanadium Addition: Refines grain structure for better toughness
Manufacturing Process Excellence
Material quality is only half the equation. Our comprehensive manufacturing process ensures every spring meets exacting JIS B5012 standards:
- Precision CNC Coiling: Computer-controlled equipment maintains ±0.1mm tolerance on critical dimensions
- Heat Treatment: Precisely controlled quenching and tempering achieves optimal hardness (HRC 48-52)
- Shot Peening: High-velocity shot peening induces beneficial compressive stress, increasing fatigue life by 30-50%
- Color-Coded Coating: Epoxy powder coating provides both corrosion protection and instant visual identification
- 100% Testing: Every spring undergoes dimensional verification and statistical load testing
- Batch Traceability: Complete tracking from raw material to finished product
🏆 Quality Assurance at Cixi Dili Spring
Our commitment to quality means:
- ISO 9001 certified manufacturing processes
- Advanced testing equipment including CMM and computerized spring testers
- Strict adherence to JIS, DIN, ANSI, ISO, and GB international standards
- In-house materials laboratory for composition and metallurgical analysis
- Continuous improvement programs based on customer feedback
- Technical support throughout spring selection, installation, and troubleshooting
Custom Solutions for Unique Applications
While standard JIS die springs cover 90% of typical applications, some situations demand customized solutions. At Cixi Dili Spring Co., Ltd., we offer complete customization services for unique requirements.
When to Consider Custom Springs
- Space Constraints: Standard dimensions don’t fit your available envelope
- Unique Load Profiles: Need force characteristics between standard colors
- Extreme Temperatures: Operating above 120°C or below -20°C
- Corrosive Environments: Exposure to chemicals, saltwater, or aggressive substances
- Ultra-High Cycles: Requirements exceeding 3,000,000 cycles
- Special Materials: Stainless steel, Inconel, or other exotic alloys
Our Custom Design Process
- Submit Requirements: Send technical drawings (DWG, PDF, STEP), samples, or detailed specifications
- Engineering Review: Our technical team analyzes requirements and recommends optimal solutions
- Quotation: Receive detailed quote within 24-48 hours including tooling costs and lead times
- Prototype Production: Small batch prototype run for testing and validation
- Testing & Approval: Evaluate samples in actual application conditions
- Full Production: Volume manufacturing with complete quality documentation
Why Choose Cixi Dili Spring Co., Ltd.?
Since our founding in 1995, Cixi Dili Spring Co., Ltd. has been dedicated to manufacturing premium-quality springs that deliver reliable performance in the world’s most demanding applications.
What Sets Us Apart
📦 Complete Product Range
- JIS standard die springs (all colors)
- US standard die springs
- Torsion springs
- Compression springs
- Extension springs
- Music wire springs
- Custom-shaped springs
🎯 Quality Assurance
- Complete R&D, production, sales system
- ISO 9001 certified processes
- International standards compliance
- Advanced testing equipment
- 100% inspection before shipment
- Full batch traceability
🌍 Global Reach
- Products exported worldwide
- Automotive industry
- Electronics manufacturing
- Industrial machinery
- Medical device manufacturing
- Consumer products
Conclusion: Making Informed Spring Selection Decisions
Understanding JIS die spring color classification and the critical relationship between compression rate and service life transforms spring selection from guesswork into engineering precision. The key insights to remember:
🎯 Essential Takeaways
- Five colors represent five load ranges: Yellow (50% max), Blue (40%), Red (32%), Green (24%), Brown (20%)
- Compression rate directly affects service life: Higher compression = fewer cycles before replacement
- Each color has specific limits at each cycle count: Use the comprehensive table to match your requirements
- Design for longevity: Operating at lower compression percentages dramatically extends spring life
- Quality matters: Premium materials and manufacturing ensure springs achieve rated performance
Your Path to Optimal Spring Performance
- Calculate required load based on part weight and ejection force
- Determine stroke distance and calculate compression rate percentage
- Decide on target cycle life based on production volume
- Use the compression rate vs. service life table to select appropriate color(s)
- Verify selected springs provide adequate force using manufacturer load charts
- Install properly with adequate guidance and preload
- Monitor performance and replace as complete sets when indicators appear
Whether you’re designing new tooling, troubleshooting existing equipment, or planning preventive maintenance, the information in this guide empowers you to make confident, informed decisions about JIS die spring selection and application.
Ready to Optimize Your Mold Performance?
Our team of spring experts at Cixi Dili Spring Co., Ltd. is ready to help you select the perfect springs for your specific application. Whether you need standard JIS die springs, custom solutions, or technical consultation, we’re here to ensure your success.
Contact us today:
📧 Email: [email protected]
📱 WhatsApp: +86 13586942004
Frequently Asked Questions
❓ Can I mix different colors of JIS die springs in the same mold?
No, never mix different colored springs in the same application. Different colors have different load ratings, which creates uneven force distribution leading to tilted mold components, inconsistent part ejection, accelerated wear, and premature spring failure. Always use springs of the same color, ideally from the same production batch, to ensure uniform performance. If one spring fails, replace the entire set.
❓ How often should I replace JIS die springs in production molds?
Replacement intervals depend on compression rate and cycle count. Using the service life table in this article, if you’re operating Yellow springs at 40% compression targeting 1,000,000 cycles, plan replacement at or before 1M cycles. For high-volume production (24/7), inspect every 3 months and replace annually or at rated cycle count. For standard production (1-2 shifts), inspect every 6 months and replace every 18-24 months. Replace immediately if you notice permanent set (spring doesn’t return to free length), surface damage, or performance changes.
❓ What’s the difference between JIS and ISO die springs?
JIS (Japanese Industrial Standard) springs have 5 color-coded load categories (Yellow, Blue, Red, Green, Brown), while ISO has 4 colors (Green, Blue, Red, Yellow). Critical warning: The colors represent DIFFERENT loads in each system! A JIS Red spring is NOT equivalent to an ISO Red spring. Additionally, dimensions and load curves differ between standards. JIS and ISO springs are generally NOT directly interchangeable without careful verification, recalculation, and testing.
❓ Can JIS die springs be used in high-temperature applications?
Standard JIS die springs (SWOSC-V steel) are rated for -20°C to +120°C. For temperatures of 80-120°C, standard springs work but expect 20-30% reduced cycle life. For 120-250°C, standard springs are NOT suitable – use stainless steel or special high-temperature alloys like Inconel. Above 250°C, mechanical springs are generally not recommended; consider nitrogen gas springs or hydraulic systems instead. Contact Cixi Dili Spring for custom high-temperature solutions tailored to your specific requirements.
❓ How do I calculate the correct spring load for my injection mold?
Step-by-step calculation:
- Base ejection force: Part Surface Area (mm²) × Ejection Pressure (0.5-2.0 MPa)
- Add safety factors: Base Force × Friction Factor (1.2-1.3) × Safety Factor (1.5-2.0)
- Per spring: Total Force ÷ Number of Springs
- Calculate compression rate: (Stroke Distance ÷ Free Length) × 100
- Select color: Use the compression rate vs. service life table to find suitable colors
- Verify load: Check manufacturer load charts to ensure selected spring provides adequate force at your compression distance
Need help? Our engineering team offers free consultation – send your mold specifications to [email protected] and we’ll recommend the optimal configuration.
Contact Cixi Dili Spring Co., Ltd.
Your trusted partner for high-quality die springs since 1995. We combine decades of manufacturing expertise with modern technology to deliver springs that keep your production running smoothly, efficiently, and profitably.
📧 Email:
[email protected]
📱 WhatsApp:
+86 13586942004
🏭 Our Expertise
JIS Die Springs • US Die Springs • Torsion Springs • Compression Springs • Extension Springs • Music Wire Springs • Custom Springs
Whether you need standard JIS die springs in any of the five color classifications, custom-designed springs for unique applications, or technical support for spring selection and troubleshooting, we’re here to ensure you get exactly what you need.
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