Silicone Compression Molding Complete Guide
Alternatively, you can learn more about the compression molding process via Wikipedia.
About Us: Dabojin Custom Silicone Product Manufacturer specializes in silicone compression molding with a focus on quality and efficiency. Our team includes engineers with 18 years of experience and a suite of industry certifications including ISO 9001, ISO 45001, ISO 14001, and FDA approval.
For further assistance or inquiries, contact us at info@siliconedabojin.com.
Understanding the Material
Silicone: Its Forms and Uses
Types of Silicone
Making Silicone Work
Know the Silicone Properties
- Silicone Rubber Test Report: For insights into specific silicone’s compliance with standards like RoHS, EN 71-3, and Prop 65, visit Silicone Rubber Test Report.
- 17 Types of Silicone: Applications, Features, and Tests: To explore the resilience, uses, and versatility of 17 different silicone types, along with their specific applications and the tests they undergo, visit 17 Silicone Types.
Silicone Compression Molding Process Parameters.
Optimal Temperature Range.
For silicone, the optimal molding temperature ranges between 160°C to 232°C . This range ensures proper flow and curing without degrading the material.
Too High 232°C. If the temperature exceeds this range, the silicone can burn or discolor parts. Overheating can result in premature cross linking or vulcanization. This can lead to distorted shapes, weaker parts, or material degradation.
The specific temperature within this range can vary and it depends on:
- The type of silicone,
- The intended application,
- And the desired properties for the final product.
Product Manufacturers often need to conduct tests. These tests help determine the optimal temperature for a new material or mold design.
In summary: Silicone molds well between 160°C and 232°C. Too cold, it won’t fill the mold; too hot, it burns. The right temperature varies with the silicone type, use, and desired product quality.
Silicone Compression Molding Pressure Application.
Key Considerations for Pressure Application:
Material Flow Properties.
Mold Design and Complexity:
Part Thickness and Geometry:
Impact of Pressure Variation:
Too Low Pressure.
Too High Pressure.
Overall Quality:
Right pressure is key.
Curing time.
Consider this example:
- Platinum Agent: High purity, cures fast, especially with set concentrations.
- 135°C Temperature: Speeds up curing. Must control precisely.
- 2-Minute Time: Indicates a quick cure, typical for this system at this temperature.
- 15 MPa Pressure: Ensures mold fill and affects curing rate.
To determine curing time:
- Likely based on tests and recommendations. Fast reaction needs exact ratios and conditions for full cure.
Consequences and Mitigation:
- Under Curing: Silicone might be weak. Mitigate by ensuring correct temperature and maintaining time and pressure.
- Over Curing: Silicone might become brittle. Mitigate with precise timers and temperature controls. Check quality regularly.
Operating the Press in 5 steps.
1. Clean the mold:
Clean mold for silicone compression molding
2. Apply Mold Release:
Applying mold release to prevent silicone adhesion.
3. Check for Damage:
4. Assemble the Mold:
5. Heat the Mold:
Ensuring Correct Alignment and Security in 5 steps.
1. Alignment Checks:
2. Clamping and Securing:
3. Double-checking Tightness and Positioning:
4. Safety Measures:
5. Test Run:
Material Placement and Mold Closure.
Guidelines for Material Placement and Mold Closure:
Pre-forming the Material:
Measure and cut the silicone precisely for less waste and complete filling. Shape it for easy placement and distribution in the mold.
Silicone measurement for efficient mold placement.
Placement:
Put the silicone evenly in the mold cavity. Make sure it’s centered for uniform filling. Lay it carefully to prevent air pockets.
Silicone placement for uniform filling, avoiding air pockets.
Mold Closure:
Heat and Pressure Application.
- Understand Material Specifications: Check the datasheet for the silicone you’re using for temperature and pressure ranges. Understand its viscosity, curing, and reaction to heat and pressure.
- Consider Product Specifications: Factor in part design like size and complexity for the right settings. Different designs need different conditions.
- Start with Baseline Settings: Begin with manufacturer’s recommended settings. Adjust from these baselines based on your mold and material.
- Adjust Based on Experience and Testing: Refine settings after testing initial parts. Look for signs of improper curing or defects to guide adjustments. Keep track of changes.
- Check and Control Temperature and Pressure: Use precise instruments for temperature and pressure control. Ensure the whole mold is uniformly at the right temperature.
Optimizing cooling and ejection in compression molding:
- Cooling Time: Varies with part thickness, shape, and silicone type. Ensure part is solidified and safe to handle.
- Cooling Method: Natural or active cooling. Uniform cooling prevents warping.
- Ejection Mechanism: Align and maintain ejection system for gentle part removal.
- Air Pressure Pistol: Use evenly distributed, gentle air pressure for ejection.
- Handling: Use proper tools or gloves. Ensure parts are cool and retain shape. Inspect Post-Ejection: Check for defects immediately. Adjust procedures if damage occurs.
- Prevent Sticking: Apply release agent to avoid part sticking to mold.
- Training: Train personnel for proper ejection and handling techniques.
Quick check problems and solutions.
Problem | Causes | Countermeasures |
---|---|---|
Blowholes | 1. Low mold temperature 2. Insufficient vulcanization time 3. Poor exhaust 4. Material issues 5. Material discharge issues 6. Insufficient pressure | 1. Adjust temperature 2. Extend vulcanization time 3. Ensure vacuum requirements are met 4. Confirm material requirements 5. Improve material discharge position 6. Adjust pressure |
Material Shortage | 1. Insufficient material weight 2. Improper material discharge position 3. Uneven distribution of rubber fabric 4. Insufficient pressure 5. Excessive temperature 6. Expired or poor-flowing material 7. Damage to mold padding 8. Inappropriate material thickness | 1. Weigh materials properly 2. Accurately discharge materials 3. Distribute rubber evenly 4. Increase pressure 5. Lower temperature 6. Return to compounding 7. Replace mold padding 8. For deeper keying, adjust material thickness |
Translucent Appearance | 1. Excessive weight of material 2. Improper material discharge position | 1. Reduce and adjust material weight 2. Adjust discharge position and method |
Rough Surface | 1. Excessive temperature 2. Prolonged external operation time 3. Excessive exhaust frequency 4. Excessive curing agent usage | 1. Lower mold temperature 2. Shorten external operation time 3. Adjust exhaust methods 4. Reduce curing agent amount |
Cracking | 1. High temperature 2. Improper use of demolding water 3. Incorrect blowing method 4. Mold issues 5. Excessive material thickness or poor stretch resistance | 1. Lower mold temperature 2. Follow demolding guidelines, sandblast if necessary 3. Improve blowing method 4. Repair mold 5. Careful with material handling |
Color Spots | 1. Dirty hands during material handling 2. Poor workplace cleanliness 3. Inadequate material protection | 1. Ensure cleanliness in material handling 2. Implement proper workplace cleanliness 3. Ensure material is well protected |
Difficult Clearing of Flash | 1. High temperature 2. Heavy material weight 3. Worn mold edges 4. Low pressure 5. Slow material discharge | 1. Lower temperature 2. Lighten material weight 3. Repair mold 4. Increase pressure 5. Adjust exhaust and speed up discharge |
Poor Load Capacity | 1. Varying mold temperature 2. Material hardness variation 3. Material weight variation 4. Pressure variation | 1. Adjust mold temperature 2. Adjust material hardness 3. Adjust material weight 4. Adjust pressure |
Silicone compression molding mold design.
Draft Angles:
- Basics:
- Choosing Angles: Choose angles for easy removal. Often, a 2-degree angle for each mm of height is good, but adjust for material and shape.
- Too Small Angles: Small angles cause removal problems. Fix by designing better or using tapered sections.
Parting Lines:
- Layout:
- Placing Lines: Place lines carefully to keep the final product clean and functional. Simple, straight lines are best.
- Flash Control: Cut down flash with precise mold halves and thicker inserts for durability.
Venting:
- Air Flow:
- Making Vents: Design vents to stop air traps and incomplete fills. Put vents right and design helpful inserts.
- Checking Vents: Test with mold flow analysis to make sure vents work well for the material and design.
Precision and Quality:
- Standards:
- Precision Steps: Control everything from choosing materials to final checks. Fine machining is key.
- Mold Care: Keep molds in good condition for consistent quality. Heat-treated materials last longer.
Heating and Cooling Systems:
- Temperature:
- Systems Integration: Combine heating and cooling systems smartly, based on material needs.
- Uniform Heat: Solve uneven heating with hot runner systems and multiple injection points.
Ejection Systems:
- Removing Parts:
- Ejection Types: Choose standard pins or special methods based on the product and mold.
- Better Ejection: For important finishes, use stripper plates or robots to keep surfaces clean.
Preparation of Silicone will be Updated soon
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