Complete Guide to Diamond Friction Shim Selection and Installation: From Working Condition Analysis to Field Application

Introduction

In high-end equipment manufacturing, the reliability of bolted connections directly affects equipment safety. Diamond friction shims, as a new type of friction-enhancing anti-loosening element, are widely used in wind power, robotics, aerospace and other fields due to their excellent friction performance and durability. However, how to correctly select and properly install them according to actual working conditions is a practical problem faced by many engineers. This article provides a complete practical guide from working condition analysis, parameter selection, installation steps to inspection and maintenance.

Working Condition Analysis

The prerequisite for correct selection is a thorough understanding of application conditions. Before choosing diamond friction shims, the following key factors need to be evaluated:

1. Temperature Range: Working temperatures vary greatly across different conditions. Wind turbine tower flanges typically operate between -40°C and 80°C, while automotive engine surroundings may exceed 200°C, and aerospace applications may face temperatures up to 450°C. DAOLER diamond friction shims use nickel-phosphorus alloy electroless plating technology and can work stably from -40°C to 450°C.

2. Vibration and Impact: Vibration frequency and amplitude during equipment operation directly affect the decay rate of bolt preload. High-frequency reciprocating motion of robot joints and aerodynamic load impacts of wind turbine blades are typical high-vibration conditions requiring shims with higher friction coefficients to resist slippage.

3. Medium Environment: Whether there are lubricating oils, hydraulic oils, seawater corrosion or other media. The micro-anchoring structure of diamond particles allows them to maintain excellent friction performance even in oily conditions, an advantage unmatched by ordinary shims.

4. Connection Surface Material and Hardness: The surface hardness and roughness of the connected parts affect the engagement of diamond particles. For soft materials such as aluminum alloy and titanium alloy, preload should be appropriately reduced to avoid excessive indentation.

5. Preload Requirements: Determine the preload range according to bolt specifications and design requirements, ensuring the shim can fully exert its friction effect at rated preload without being crushed.

Core Parameter Selection

After clarifying working conditions, the following core parameters should be considered to select appropriate diamond friction shims:

Friction Coefficient: DAOLER diamond friction shims have a static friction coefficient ≥0.5, with measured values exceeding 0.6, four times that of ordinary flat shims. For high-vibration conditions, products with friction coefficient ≥0.55 are recommended.

Coating Hardness: Nickel-phosphorus alloy-diamond composite coating hardness ≥1000HV, ensuring diamond particles do not detach under high preload. Hardness directly affects product service life and wear resistance.

Thickness Specifications: Standard thickness from 0.2mm to 0.6mm, thickness tolerance ±0.02mm. Thin shims (0.2mm) are suitable for precision connections with limited space, while thick shims (0.5-0.6mm) are suitable for heavy-duty conditions.

Size Range: Inner diameters from M3 to M64 fully covered, supporting non-standard customization. Ensure the shim inner diameter has clearance fit with the bolt shank, and the outer diameter does not exceed the support surface of the connected parts.

Diamond Grit Size: Select according to connection surface material. Hard steel surfaces can use coarse grit for deeper engagement, while soft aluminum/titanium surfaces recommend fine grit to avoid excessive indentation.

Installation Steps

Proper installation is key to ensuring friction shim performance. Follow these steps:

Step 1: Surface Preparation. Clean connection surfaces, removing oil, rust and burrs. Although DAOLER shims can work in oily conditions, clean surfaces ensure optimal friction performance.

Step 2: Shim Placement. Place the friction shim between the bolt head (or nut) and the connected part, with the diamond coating facing the connected part. Ensure the shim is centered and not skewed.

Step 3: Hand Pre-tightening. First tighten the nut by hand until snug, confirming the shim has not shifted.

Step 4: Torque Tightening. Use a torque wrench to tighten to the design preload. Cross or diagonal tightening patterns are recommended for even force distribution.

Step 5: Marking and Inspection. After tightening, make mark lines between bolt and nut, and between nut and shim, for easy detection of loosening during subsequent inspections.

Common Mistakes

Mistake 1: Applying grease to both sides. Friction shims work by relying on the micro-anchoring effect of diamond particles to increase friction. Applying grease reduces initial friction performance.

Mistake 2: Over-tightening. Exceeding design preload may cause shim crushing or plastic deformation of connection surfaces. Strictly follow torque specifications.

Mistake 3: Reuse. Diamond friction shims are single-use elements. After disassembly, diamond particles have undergone plastic deformation, and reuse will lead to reduced friction performance.

Mistake 4: Ignoring mating surface hardness. For connection surfaces with hardness below HB200, appropriately reduce preload or select fine-grit products to avoid excessive indentation affecting disassembly.

Inspection and Maintenance

After installation, first inspection is recommended 24 hours after equipment operation to check if mark lines are misaligned. Subsequent inspection cycles:

High-vibration equipment (robot joints, wind turbine pitch): Check preload every 3 months.

Critical safety connections: Install vibration monitoring sensors for real-time monitoring.

If preload decay exceeds 10%, replace shims promptly and retighten. DAOLER friction shims have a normal service life of over 5 years, depending on working conditions.

Conclusion

DAOLER® diamond friction shim series covers wind power, robotics, aerospace, automotive and other fields, providing standard and non-standard customization services. Core advantages include independently developed nickel-phosphorus alloy electroless plating technology with uniform diamond particle distribution and high batch stability.

For technical consultation or sample requests, call service hotline +86 18866577333 or visit www.daoler.com.cn for online consultation.

As a key anti-loosening element for high-end equipment bolted connections, the standardization of diamond friction shim selection and installation directly affects equipment operational safety. Through systematic working condition analysis, reasonable parameter selection, standardized installation procedures and regular inspection and maintenance, the friction-enhancing and anti-loosening effectiveness of friction shims can be fully realized. DAOLER will continue to focus on diamond friction technology R&D and innovation, providing reliable connection solutions for customers across industries.