Nylon is one of the most versatile engineering thermoplastics and is commonly injection molded into products across industries. But can nylon actually be injection molded? The short answer is yes. When processed properly, nylon can be injection molded to produce high-quality parts with excellent mechanical properties and performance.
In this comprehensive guide, as a professional plastic injection molding manufacturer, we’ll cover everything you need to know about injection molding nylon, including its key characteristics, design considerations, suitable applications, and best practices for processing. Let’s get started.
An Introduction to Nylon Plastic
Nylon belongs to a family of engineering plastics called polyamides. The two most common types used in injection molding are nylon 6 and nylon 6/6. Nylon offers an exceptional balance of strength, stiffness, toughness, heat resistance, and chemical resistance. It also has natural lubricity, abrasion resistance, and a low coefficient of friction.
These inherent properties make nylon well-suited for injection molding a variety of mechanical and industrial components like gears, bushings, bearings, and more. Nylon can also tolerate exposure to fuels, oils, greases, and organic solvents.
With suitable fillers like glass fibers or minerals, nylon’s strength and heat resistance can be further improved. This allows glass-filled nylon products to replace metal parts in some high-temperature automotive applications.
Design Considerations for Injection Molded Nylon Parts
When designing parts to be injection molded from nylon, keep the following guidelines in mind:
- Specify uniform wall thicknesses between 0.8 – 3 mm. Avoid excessive variations.
- Use generous internal radii (≥ 0.5 x wall thickness) to strengthen parts.
- Draft angles of 1-3° aid part ejection.
- Allow for ~2% shrinkage to maintain tolerances.
- Reduce warp and sink marks with uniform wall sections.
- Include gussets and ribs to improve rigidity.
- Limit centerline deviations in core pins.
Proper part design is crucial because nylon’s higher shrinkage rate can otherwise cause warpage and dimensional inconsistencies in the final molded components.
What Products Use Injection Molded Nylon?
Thanks to its exceptional balance of properties, nylon can be injection molded into a vast range of components and products, including:
- Mechanical parts like gears, cams, bearings, and bushings
- Electrical components like connectors, switches, and coil bobbins
- Automotive parts like pistons, manifolds, clips, and valves
- Industrial parts like rollers, wear strips, and conveyor parts
- Consumer goods like combs, toothbrush bodies, and appliance components
Reinforced nylon grades allow the injection molding of high-load bearing structural components capable of replacing metal parts in certain applications.
Best Practices for Injection Molding Nylon
While nylon can indeed be readily injection molded, processing does require care and attention to detail. Follow these best practices for defect-free, consistent results:
Properly dry the nylon – As a hygroscopic material, moisture absorption can cause cosmetic issues and loss of properties. Only process at ≤0.2% moisture content.
Use optimal mold temperatures – For unfilled nylon 6, 60-80°C is recommended. Higher temperatures improve crystallinity.
Vent molds adequately – Trapped gases lead to surface defects. Provide multiple end-of-fill vents.
Set injection speeds carefully – High injection rates increase shear heating and gases. Balance fill time and temperature rise.
Control mold residence time – Extended exposure to high mold temperatures risks over-curing and degradation.
By understanding nylon’s unique processing requirements and behavior, injection molders can consistently produce high-quality molded parts for diverse applications across industries.
Commonly Injection Molded Nylon Grades
Several nylon formulations are routinely injection molded into products. Some of the most popular options include:
Nylon 6
- Excellent toughness, even at low temperatures
- Resists impact, abrasion, and chemicals
- Used for gears, bearings, connectors, and consumer goods
Nylon 6/6
- Very high strength and stiffness
- Withstands higher temperatures than nylon 6
- Used for mechanical parts and electrical components
Glass-Filled Nylon 6 or 66
- 30-60% stronger than unfillede nylon
- Improved rigidity and temperature resistance
- Replaces metal parts in some applications
FAQs About Injection Molding Nylon
Here are answers to some frequently asked questions about molding nylon plastic:
At what temperature is nylon injection molded?
Typical melt temperatures for injection molding nylon range from 220-300°C depending on the grade. Mold temperatures of 60-100°C are commonly used.
Does nylon shrink when injection molded?
Yes, nylon shrinks up to 2% during injection molding. Controlling mold temperature is key to minimizing shrinkage. Annealing also helps improve dimensional stability.
Why does moisture matter when molding nylon?
Being hygroscopic, absorbed moisture turns to steam when injected into the hot mold. This causes visual defects and reduces mechanical properties. Proper drying is essential.
Can standard molds be used for nylon injection molding?
Yes, standard steel injection molds can be used. However, venting may need enhancement to prevent trapped gases from causing defects. Using aluminum molds also reduces cycle time.
What causes parts to warp during nylon molding?
Shrinkage coupled with uncontrolled cooling produces uneven stresses and part warpage. Maintaining uniform wall sections and controlled mold cooling minimizes warp.
Conclusion
Nylon is without doubt one of the most versatile thermoplastics for injection molding diverse components across industries. By understanding nylon’s unique processing behavior and capabilities, manufacturers can consistently injection mold high quality nylon parts for demanding applications. Factors like moisture content, fillers, mold design, venting, and temperature control play key roles during nylon injection molding. With attention to these details, intricate and reliable nylon products can be mass produced via this efficient manufacturing process.
