Compression Limiters in Plastic Assemblies – Preventing Creep and Stress Cracking

When using bolted joints in plastic components, designers face a recurring challenge: how to prevent plastic deformation, cracking, or stress relaxation over time.

The solution is often simple yet essential: Compression Limiters.

In this guide, Dongguan Sango Hardware Fasteners Co., Ltd., a specialist in fastening and precision turned parts, explains the role, types, and customization of compression limiters—key components for improving the durability of plastic assemblies.

1. What Is a Compression Limiter?

A Compression Limiter is a cylindrical metal insert placed inside a plastic boss or hole to prevent over-compression when a bolt or screw is tightened.

By absorbing the clamp load, it protects the surrounding plastic from crushing, creeping, or cracking, especially in thermoplastics.

🔩 Core Functions:

• Prevent stress cracking under bolt torque
• Eliminate creep or material flow over time
• Maintain clamp load in high-temperature environments
• Improve joint longevity in plastic housings
• Enable higher torque tightening of fasteners

2. Why Are Compression Limiters Important?

Plastics like ABS, PC, PP, and PA are:

• Viscoelastic (they deform over time under load)
• Sensitive to temperature and moisture changes
• Weak in compressive load compared to metals

Using a bolt or screw without a compression limiter can lead to:

• Cracked bosses
• Loosened joints
• Failed sealing surfaces
• Warranty returns or product recalls

3. Common Types of Compression Limiters

🔹 Split Seam Compression Limiter

• Slotted body allows slight expansion
• Easy to install by press-fit
• Ideal for general-purpose assemblies

🔹 Knurled or Ribbed Body Limiter

• External knurling increases retention in soft plastics
• Used in dynamic or vibration-prone applications

🔹 Solid Wall Compression Limiter

• Seamless structure for high-load or sealing joints
• Machined or cold-formed steel or brass

🔹 Flanged Compression Limiter

• Built-in shoulder ensures consistent seating
• Prevents axial movement in overmolded or blind holes

🔹 Threaded Inner Compression Limiter

• Combines internal thread with outer support
• Used when plastic cannot support thread cutting directly

4. Key Applications

Compression limiters are widely used in:

• 🖥️ Consumer electronics (enclosure bosses)
• 🚗 Automotive dashboards, lighting, and connectors
• 🧪 Medical devices and instrumentation housings
• 🧰 Plastic gearbox covers, brackets, and supports
• 🔋 Battery pack modules and EV systems
• 💡 LED fixtures and electrical housings

They’re critical for long-term mechanical integrity in assemblies exposed to vibration, torque, or thermal cycling.

5. Material Selection & Specs