Track Roller for Caterpillar CAT 305 306 Mini Excavator

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Applicable Models: CAT 305E / 306E / 307
EOEM Part Number: 352-6217
English Description: Durable excavator undercarriage parts, stable quality, sufficient stock, fast delivery.

E-mail : info@fortune-parts.com

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PRODUCT DESCRIPTION

✅ Fitment: Direct replacement track roller for Caterpillar CAT 305E, 306E, 307E mini excavator, OEM part number 352-6217.
✅ Premium Quality: Made of high-grade alloy steel with precision casting/forging and full heat treatment. Surface hardness reaches HRC50-56, hardening depth 8-12mm for superior wear resistance.
✅ Long Life & Reliability: Equipped with high-quality oil seals and bearings to prevent leakage. Designed for harsh working conditions with 2000+ working hours warranty.
✅ Perfect Fit & Performance: Ensures smooth track movement, low noise, and stable operation. Easy to install as a direct replacement part.
✅ Service Support: ISO9001 certified quality. Fast delivery from FOB Xiamen port. OEM/ODM service is acceptable. Video and online technical support available.

CAT 306 Mini Excavator Track Roller Technical Specifications and Engineering Documents

1. Executive Summary and Component Overview

This document comprehensively describes the track roller assembly (also known as the idler roller or bottom roller), a core chassis component of Caterpillar 305E, 306E, and 307E series mini hydraulic excavators. Designed for the complex operating scenarios of 1–6 ton mini excavators, this assembly can stably withstand static and dynamic impact loads under various conditions, including construction, agricultural reclamation, and municipal engineering. The core part number 352-6217 mentioned in this document is the original equipment manufacturer (OEM) standard number for this assembly, corresponding to the complete track roller assembly and direct replacement parts. As a high-quality aftermarket alternative, this assembly, manufactured by a professional construction machinery parts manufacturer, strictly adheres to CAT OEM technical standards, meeting or exceeding OEM specifications in material selection, structural design, and performance, providing a reliable, economical, and long-lasting solution for mini excavator chassis maintenance. 2. Main Functions and Operation of the Track System

The bottom roller assembly is a key load-bearing component of the tracked walking system of a mini excavator, performing the following three basic functions:

2.1 Load Bearing and Weight Distribution

Directly supporting the total weight of the CAT 306 series excavator (approximately 5.7–7 tons), it evenly distributes the weight of the upper body and the working load to the track chain through the roller frame, and then further distributes it to the ground. The multi-point distribution of the support rollers effectively reduces the ground pressure, ensuring the equipment’s passability on soft ground while preventing track damage caused by localized stress concentration.

2.2 Track Guiding and Alignment

The rollers feature a precision-machined double-flange structure on both sides, accurately fitting the inner edge of the track links to form reliable lateral restraint. This design effectively prevents lateral deviation and derailment of the tracks during turning, climbing, or operating on rough terrain, ensuring smooth track movement along the chassis frame and improving overall machine handling stability.

2.3 Track Sag Control

Through the synergy with guide wheels and tensioners, maintaining a reasonable preload and sag on the upper track chain (typically controlled at 1–2% of the track overhang length) is crucial for optimizing the meshing effect between the drive wheels and tracks, reducing operating vibration, and minimizing power transmission losses. It also extends the service life of the tracks and other wheel systems.

3. Detailed Technical Specifications and Engineering Design

3.1 Scope of Application and Original Equipment Manufacturer (OEM) Reference

• Main Applicable Models: Caterpillar 305E, 306E, 307E mini hydraulic excavators and their derivatives.

• OEM Part Number: 352-6217 (Core Assembly Number). Corresponding replacement parts can be matched using the certified manufacturer’s cross-reference database, ensuring complete interchangeability with OEM equipment.

• Compatible Track Specifications: Compatible with CAT 306 series standard tracks (400mm width, 154mm pitch), with precise matching between the rim width and the inner width of the track plate (difference 2–5mm) to avoid interference and abnormal wear.

3.2 Mechanical Design and Structure

• Type: Sealed & Lubricated (S&L) heavy-duty load-bearing track roller with integrated bearing unit design.

• Wheel Body / Forging: Made of high-carbon, high-strength alloy steel (40Mn2, 50Mn) using a closed-die forging process. Compared to castings, forging ensures continuous metal grain distribution, significantly improving the wheel body’s impact resistance and fatigue strength, and enabling it to withstand frequent dynamic load impacts.

• Shaft: Precision-machined from 42CrMo chromium-molybdenum alloy steel, with a hardened journal surface to ensure high tensile strength (≥1080MPa) and wear resistance, meeting the requirements of long-term high-speed rotation.

• Flange Design: Dual-flange integrated forged structure, flange height 18–22mm, with an inner arc transition design to reduce lateral wear on track links and improve guiding accuracy.

• Overall Weight: Approximately 7–9 KG/pc, with balanced weight distribution to ensure operational stability and load-bearing efficiency.

3.3 Materials Science and Metallurgy

• Material Grade: Wheel body selected from high-carbon alloy steels such as 40Mn2 and 50Mn; shaft body selected from 42CrMo chromium-molybdenum alloy steel; bearing housings made of ZG35SiMn cast steel, ensuring each component is suitable for operating conditions.

• Heat Treatment: The wheel tread and critical wear surfaces of the flange undergo controlled induction hardening to achieve a surface hardness of HRC52–62 and a hardened layer depth of 7–10 mm (HRC45 or higher), forming a “hard surface with a tough core” structure that ensures both surface wear resistance and core impact resistance. The shaft body undergoes quenching and tempering (HB280–320) followed by surface hardening to ensure comprehensive mechanical properties.

• Surface Treatment: The wheel body undergoes shot peening to eliminate forging stress (residual stress ≤150MPa) and surface pretreatment. The coating consists of an epoxy primer (60–80μm thick) + a polyurethane topcoat (40–60μm thick), providing excellent corrosion resistance and adhesion, and adapting to harsh working conditions such as humidity and dust.

3.4 Bearing and Sealing System (Core of Durability)

• Bearing Type: Double-row heavy-duty tapered roller bearings, rated radial dynamic load ≥280kN, rated axial dynamic load ≥120kN, possessing high radial load capacity and moderate axial thrust bearing capacity, suitable for the load characteristics of small excavators.

• Sealing System: Multi-barrier labyrinth seal assembly, comprehensively preventing contaminant intrusion:

◦ Lubrication: Pre-filled high-temperature extreme pressure (EP) lithium-based composite grease, operating temperature range -20℃~120℃, maintaining stable viscosity and lubrication performance under extreme temperatures and pressures.

◦ Main Seal: Utilizes a polyurethane (PU) radial lip seal with a specially designed sealing lip, sealing pressure ≥0.3MPa, effectively preventing grease leakage.

◦ Secondary Seal: Floating end face seal (metal sealing ring + silicone rubber floating seal ring), metal sealing ring surface roughness Ra≤0.8μm, combined with pre-compression control (0.3–0.5mm), forming a secondary sealing barrier.

◦ Labyrinthine Channel: The junction of the wheel body and axle seat features 3-4 machined labyrinth grooves. Utilizing fluid resistance, these grooves prevent abrasive contaminants such as dirt, sand, and moisture from entering the bearing cavity, significantly extending seal life.

4. Manufacturing Process and Quality Assurance

4.1 Core Manufacturing Process

Professional manufacturers employ rigorous production processes to ensure product consistency and reliability:

1. Forging and Forming: Raw materials are heated to 1100-1200℃ and then forged in a closed die using a press with a capacity of 2000T or higher. The wheel blank dimensional tolerance is controlled within ±2mm to ensure uniform machining allowances.

2. Machining: Precision machining is performed using CNC turning centers and boring machines. The wheel outer diameter roundness is ≤0.03mm, coaxiality is ≤Φ0.02mm, and surface roughness Ra≤1.6μm; flange end face perpendicularity is ≤0.02mm, achieving a machining accuracy of IT7-IT8 grade.

3. Heat Treatment: The wheel body undergoes quenching at 860–880℃ followed by tempering at 580–600℃. The tread and flange are then locally induction hardened. An automatic temperature control system is used throughout the process to ensure uniform hardness (hardness difference within the same workpiece ≤3HRC).

4. Surface Treatment: Shot peening (shot diameter 0.8–1.2mm, strength 0.2–0.3mmA) → degreasing → phosphating → electrostatic spraying → curing at 160℃. The coating adhesion meets GB/T 9286-1998 Class 1 standard.

5. Assembly and Sealing: Assembly is performed in a Class 1000 cleanroom environment. Bearing press-fitting uses a hydraulic press with precise pressure control (5–8MPa) to avoid bearing damage. The amount of grease injected is precisely controlled (±5g) to ensure sufficient lubrication and eliminate the risk of leakage.

4.2 Quality Control (QC) System

• Dimensional Inspection: Critical dimensions are 100% inspected using a coordinate measuring machine (CMM) with an accuracy of ±0.005mm, ensuring consistency with original drawings. For mass production, dedicated inspection tools are used for rapid inspection, improving efficiency by 30%.

• Hardness Testing: 5% of products from each batch are randomly selected for Rockwell hardness testing. Tread surface hardness must be within the HRC52–62 range; unqualified products are immediately reworked.

• Sealing Testing: After assembly, a 1.5MPa air pressure sealing test is performed, maintaining pressure for 30 minutes without leakage. Some products undergo immersion rotation testing (50 rpm, 2 hours) to verify sealing reliability.

• Load Capacity Testing: Static load capacity testing (1.5 times rated load, 1 hour) and dynamic fatigue testing (1 million cycles) are performed on a dedicated testing bench to ensure no permanent deformation or damage.

• Certification Standards: Products comply with ISO9001 quality management system certification; materials meet RoHS environmental standards; and some products have obtained CE certification, meeting the market access requirements of Europe and the United States.

4.3 Warranty and After-Sales Support

• **Warranty Period**: A 2000-working-hour warranty is provided under normal operating conditions, covering malfunctions caused by material defects and manufacturing process problems.

• After-Sales Support: Video technical support and online fault diagnosis services are provided; if replacement is needed, fast replenishment services are available (15-20 days delivery for regular orders) to ensure minimal downtime for customer equipment.

PRODUCT PARAMETERS

CAT 306 Track Roller

Parameters	Details
Model	CAT 305E / 306E / 307E Mini Excavator
Part number	352-6217 (OEM reference)
Technique	Casting / Forging + Full Heat Treatment
Surface Hardness	HRC50-56, Hardening Depth 8-12mm
Colors	Black / Yellow (customizable)
Warranty Time	2000 Working Hours
Certification	ISO9001
Weight	Approx. 7–9 KG/pc
FOB Price	FOB Xiamen port US$ 12–25/Piece (based on quantity)
Delivery Time	Within 15–20 days after order confirmation
Payment Term	T/T
OEM/ODM	Acceptable
Type	Mini excavator undercarriage parts
Moving Type	Crawler excavator
After-sales Service Provided	Video technical support, Online support