Hydraulic Arm (Boom and Stick) for Mini Excavators

Product Specifications

Technical details and manufacturing context for Hydraulic Arm (Boom and Stick)

Definition

The hydraulic arm, comprising the boom and stick, is the core digging and material handling assembly of a mini excavator. It is a multi-jointed, hydraulically actuated mechanism mounted to the excavator's upper structure (house). The boom provides the main vertical and horizontal reach, while the stick (or dipper) connects the boom to the attachment (e.g., bucket), enabling precise digging depth and dumping angle control. This assembly translates hydraulic power from the machine's pumps into controlled linear and rotational motion for excavation tasks.

Constructed primarily from high-strength steel grades such as Q345B or Q550D, the arm is designed to withstand heavy loads and abrasive conditions. Hardened steel pins and bushings at the joints ensure durability and reduce wear. The arm's performance is characterized by several key parameters that must be verified for the specific model and application: operating pressure typically ranges from 1.0 to 1.6 MPa, boom length from 2.5 to 4.5 m, stick length from 1.5 to 2.5 m, boom swing angle from 50 to 90 degrees, bucket digging force from 20 to 50 kN, arm digging force from 15 to 35 kN, operating temperature range from -20 to 60 °C, material grade Q345B (per GB/T 1591), weight from 300 to 800 kg, pin diameter from 40 to 80 mm, cylinder stroke from 500 to 1200 mm, and cylinder bore diameter from 60 to 120 mm. These values are reference ranges; actual specifications must be confirmed with the legal manufacturer or supplier.

The hydraulic arm is a critical component that directly influences the excavator's productivity and safety. Proper selection involves matching the arm's dimensions and force capabilities to the intended digging depth, reach, and material hardness. Interfaces include hydraulic connections to the machine's pump and control valves, as well as mechanical mounting points to the house and attachment. Verification questions should address the exact model's compliance with relevant standards and the availability of technical documentation. Maintenance signals include unusual noises, reduced digging force, or hydraulic fluid leaks, which may indicate worn seals or bushings. Failure boundaries are defined by the maximum operating pressure and temperature; exceeding these can cause seal failure or structural damage.

Working Principle

Hydraulic cylinders, controlled by the operator via joysticks and hydraulic valves, extend and retract to pivot the boom and stick at their respective hinge points. The system operates on pressurized hydraulic fluid supplied by the excavator's hydraulic pump. The coordinated movement of the boom cylinder(s) and stick cylinder allows for complex compound motions to position the attachment for digging, lifting, and dumping. The operator's inputs modulate the flow and pressure of the hydraulic fluid, enabling precise control over the arm's speed and force. The mechanical linkage of the boom and stick converts the linear motion of the cylinders into rotational motion at the joints, providing the necessary digging and lifting capabilities.

Common Materials

High-strength steel (e.g., Q345B, Q550D), Hardened steel pins and bushings

Technical Parameters

Parameter	Typical range	Notes & selection driver
Boom Length	2.5–4.5 m	Determines reach and digging depth
Stick Length	1.5–2.5 m	Affects digging force and depth
Boom Swing Angle	50–90 °	Larger angle improves maneuverability
Bucket Digging Force	20–50 kN	Critical for digging in hard soil
Arm Digging Force	15–35 kN	Important for prying and lifting
Operating Temperature Range	-20–60 °C	Outside this range, seals may fail
Material Grade	Q345B	High-strength steel for durabilityGB/T 1591
Weight	300–800 kg	Affects machine stability and transport
Pin Diameter	40–80 mm	Determines joint strength and wear life
Cylinder Stroke	500–1200 mm	Defines range of motion
Cylinder Bore Diameter	60–120 mm	Affects force output

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Boom
The primary structural member that provides vertical lift height and horizontal reach. It pivots at the house and connects to the stick.

Material: High-strength steel
Stick (Dipper) Part
The intermediate structural member connecting the boom to the work attachment (e.g., bucket). It controls digging depth and dumping angle.

Material: High-strength steel
Boom Cylinder
Hydraulic actuator that controls the raising and lowering (pivoting) of the boom.

Material: Steel (cylinder barrel, piston rod)
Stick Cylinder
Hydraulic actuator that controls the extension and retraction (pivoting) of the stick relative to the boom.

Material: Steel (cylinder barrel, piston rod)
Pivot Pins and Bushings Part
Provide low-friction rotational joints between the boom, stick, house, and cylinders, allowing for smooth articulation.

Material: Hardened steel, bronze/bronze alloy bushings

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Hydraulic Arm (Boom and Stick).

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Mini Excavator

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Manufacturers of Hydraulic Arm (Boom and Stick)

Manufacturer profiles associated with Hydraulic Arm (Boom and Stick).

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Frequently Asked Questions

What is the function of the hydraulic arm in a mini excavator?

The hydraulic arm, consisting of the boom and stick, is the primary structural assembly that enables digging, lifting, and material handling. It translates hydraulic power into controlled motion to position the attachment (e.g., bucket) for excavation tasks.

What materials are typically used for the hydraulic arm?

The arm is commonly made from high-strength steel grades such as Q345B or Q550D, with hardened steel pins and bushings at the joints. These materials provide durability and resistance to wear under heavy loads.

What are the key parameters to consider when selecting a hydraulic arm?

Key parameters include operating pressure, boom and stick lengths, swing angle, digging forces, operating temperature range, material grade, weight, pin diameter, and cylinder dimensions. These values must be verified for the specific model and application.

How should maintenance be performed on the hydraulic arm?

Regular inspection of hydraulic cylinders, pins, and bushings is recommended. Watch for signs of wear such as unusual noises, reduced digging force, or hydraulic fluid leaks. Always follow the manufacturer's maintenance guidelines and verify replacement parts with the supplier.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records.

Preliminary Technical Classification

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pressure:	Max 350 bar (5076 psi)
flow rate:	20-120 L/min (5.3-31.7 GPM)
temperature:	-20°C to 80°C
slurry concentration:	Max 15% solids by weight

Hydraulic Arm (Boom and Stick)

Product Specifications

Industry Taxonomies & Aliases

Applied To / Applications

Industrial Ecosystem & Supply Chain Structure

Application Fit & Sizing Matrix

Reliability & Engineering Risk Analysis

Compliance & Manufacturing Standards