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
| Material | Features | Suitable Applications |
|---|---|---|
| Brass (CuZn35/40) | Corrosion resistant, easy to press-fit | Electronics, medical, lighting |
| Carbon steel | High strength, low cost | Automotive, mechanical devices |
| Stainless steel | Rust-proof, cleanroom safe | Medical, food equipment |
| Aluminum | Lightweight, thermally compatible | Drones, portable electronics |
Available specs:
- 📏 Inner diameter: Ø3mm ~ Ø12mm
- 📐 Length: 5mm ~ 50mm (custom cut)
- 🧩 Outer designs: plain, knurled, ribbed, slotted, flanged
- ⚙️ Wall thickness: from 0.3mm to 1.2mm standard
- 🎨 Finish: natural, passivated, zinc, nickel plating
6. Installation Guidelines
- 🔧 Designed for press-fit using arbor press or ultrasonic insertion
- 🔄 Can be molded-in or installed post-molding
- ✅ Boss hole tolerance should allow for interference or slip fit
- ⚠️ Avoid misalignment—use a press tool with flat or chamfered tip
We provide insertion force data, hole sizing recommendations, and CAD support for your designs.
7. Case Study: Compression Limiters in Automotive Connector Housing
Client: Tier-1 automotive connector manufacturer (Germany)
Problem: Plastic bosses cracking after 4–5 reassemblies in field service
Sango Solution:
- Supplied brass knurled compression limiters Ø5.5 × 12mm
- Added flange to prevent axial pull-out
- Shipped in tray packaging with insertion force spec sheet
Result:
- Field failure rate dropped to <0.3%
- Assembly torque increased by 20% without plastic stress
- Customer approved limiter in new global platform
8. Why Choose Sango Hardware?
🏭 Vertical Integration
- Cold forming, CNC turning, knurling, trimming—all in-house
📐 Full Engineering Support
- Design validation, CAD models, sample kits within 5–7 days
🧪 Quality Guarantee
- Dimension, material, insertion force, and plating all tested
📦 Global Export Support
- RoHS, REACH, PPAP, IMDS, and English documentation included
9. Conclusion: Protect Your Plastic with Smart Engineering
A small compression limiter can make a big difference in the long-term reliability of plastic assemblies—especially under clamping, vibration, or environmental stress.
Reach out to Dongguan Sango Hardware Fasteners Co., Ltd. for precision-made, application-tested compression limiters designed for your assembly's success.