EX400 Forged Front Idler Group/Mining and constuction machinery first chioce/Mine Buster
Product Specifications
Hitachi EX400 Forged Front Idler Assembly: Technical Specifications
Designed for Mining, Quarry & Heavy Construction Applications
1. Core Function & Mechanical Role
Primary Function: Front-track guidance, tension maintenance, and load distribution for Hitachi EX400 excavators (operating weight: 38-42 tons).
Critical Load Handling: Absorbs dynamic impacts (e.g., rock strikes, drop loads) and static loads up to ≥18,000 kg per track.
Tension System: Interfaces with Hitachi’s grease-injected tension cylinder for precise track adjustment.
2. Forged Construction Advantages
| Feature | Specification |
|---|---|
| Material | High-carbon chromium steel (SCM440/JIS equivalent) |
| Process | Hot forging + induction hardening (Surface: 55-60 HRC; Core: 30-35 HRC) |
| Structural Benefit | Forged grain flow → 40% higher fatigue strength vs. cast counterparts |
| Impact Resistance | Withstands 25J+ Charpy impact at -20°C (critical for mining/shock loads) |
| Weight Capacity | Rated for EX400’s max operating weight: 41,800 kg |
3. Assembly Components & Engineering
| Component | Technical Detail |
|---|---|
| Idler Wheel | Forged core; CNC-machined flanges (height: 65-75mm); ground raceway surface |
| Shaft | Alloy steel (SCM435), induction-hardened (50-55 HRC); diameter: 85-90mm |
| Bearings | Double-row tapered rollers (NSK/NTN); dynamic load rating: ≥120,000 N |
| Sealing System | Labyrinth + triple-lip seals + "DustProof" grease-purge cavity |
| Mounting Housings | Fabricated steel with reinforcement ribs; bolts to EX400 track frame (M22x1.5) |
| Lubrication | Dual grease zerks (Hitachi Genuine Grease II or equivalent EP2) |
4. EX400-Specific Design Features
Track Compatibility: Matches 216mm pitch × 560mm shoe width tracks.
Flange Profile: Optimized curvature to reduce track link wear during turns.
Mining-Grade Seals: Tungsten-disulfide coated lips + external debris deflectors.
Tensioning Interface: Compatible with Hitachi’s GD7-series tension cylinder (stroke: 120mm).
Corrosion Protection: Zinc phosphate pretreatment + electrostatic epoxy coating.
5. Performance Metrics
| Parameter | Value |
|---|---|
| Service Life | 7,000–10,000 hrs (severe duty) |
| Max Radial Load | 28,000 kg (static) / 22,000 kg (dynamic) |
| Operating Temp | -30°C to +110°C |
| Assembly Weight | 110–130 kg |
| Grease Capacity | 400–450g per service |
6. Target Applications
Primary Machines: Hitachi EX400-5/6/7, ZX400-5G/6G/7G
Severe-Duty Environments:
Hard-rock mining & quarry blasting
Demolition with hydraulic hammers
Swamp logging with partial submersion
Road construction with abrasive soils
7. Failure Prevention & Maintenance
Critical Wear Indicators:
Flange thickness reduction >12%
Vertical wheel play >2.5mm
Grease contamination (water/sand in purged sample)
Maintenance Protocol:
Lubrication: Grease purge every 50 operating hours (minimum)
Tension Check: Maintain 25-35mm track sag (measured undercarriage mid-span)
Bolt Torque: Re-tighten mounting bolts to 450-500 N·m every 500 hrs
8. Forged vs. Cast: EX400 Advantages
| Factor | Forged Idler | Cast Idler Risk |
|---|---|---|
| Crack Resistance | Near-zero porosity → no crack propagation | Sand inclusions → stress fractures |
| Abrasion Life | 2.1X longer flange life in granite | Premature wear in quartz-rich soils |
| Cost Efficiency | Lower $/hour operating cost | 2x replacement frequency |
| Collateral Damage | Protects rollers/sprocket ($18k+) | Chain derailment → frame damage |
9. Genuine Hitachi OEM Importance
Precision Compatibility: Matches EX400 track geometry (roller/sprocket alignment critical).
Load Validation: Factory-tested to Hitachi’s dynamic load simulations.
Sealing Integrity: Validated in Hitachi’s "Mud Bath" endurance testing (72hrs).
Warranty: Required for undercarriage warranty coverage (typically 3,000-5,000 hrs).
10. Technical Specifications Summary
Shaft Diameter: 88mm
Bore Tolerance: H7/g6 precision fit
Bearing Type: 32234 J2/Q (ISO)
Bolt Pattern: 6x M22 × 1.5 (Grade 10.9)
Track Contact Width: 540mm
Tension Adjustment: 0-120mm via grease injection
Conclusion
30% longer service life vs. cast idlers in abrasive environments
Zero-derailment performance under high-side-load conditions
Reduced TCO through protection of adjacent undercarriage components
Replacement Cost: $2,200–$2,800 (USD) for genuine assembly. Always verify compatibility with your EX400 serial number (critical for post-2018 models with revised flange height).
