The vertical roller mill rocker arm (also called swing lever or rocker arm assembly) is the core connecting and force-transmitting component between the grinding roller and the hydraulic system. Think of it as a “mechanical arm” that transfers grinding force and performs adjustment functions. It mainly consists of the upper rocker arm, lower rocker arm, rocker arm shaft, bearings, and bearing housings.
The upper rocker arm is used to mount the grinding roller, while the lower rocker arm connects to the hydraulic system. The two arms are joined together through a shaft, taper sleeve, and taper pin to form a single integrated unit.
AGICO has been focusing on the production of plain carbon steel and low alloy steel castings for over 20 years, with rich experience and guaranteed product quality. Our rocker arms fit all major VRM brands, including Loesche, Pfeiffer, Polysius, ATOX, HRM, LM, and ZGM.
Working Principle of Vertical Mill Swing Lever
The rocker arm is essentially a lever mechanism that transmits force. Its main functions include:
- Grinding Force Transmitting: It transfers the immense thrust generated by the hydraulic system to the grinding roller, pressing it tightly against the material layer on the grinding table.
- Grinding Roller Assembly Supporting: It serves as the load-bearing pivot for the grinding roller device, bearing the reaction force, vibrations, and impact loads during the grinding process.
- Grinding Roller Lifting & Lowering: During startup, shutdown, or maintenance, the hydraulic system controls the rocker arm to raise and lower the grinding roller, facilitating no-load startup and maintenance.
- Angle Adjustment: In certain models, by adjusting the support point or length of the rocker arm, the relative angle between the grinding roller and the grinding table can be fine-tuned to optimize the grinding path.
Think of it like your arm: your shoulder is the pivot point, your upper arm is the upper rocker arm holding the roller, and your forearm is the lower rocker arm connected to the hydraulic system. When your forearm pushes, your upper arm presses down. Simple but powerful.
For the rocker arm, strong wear resistance and high strength are essential qualities to prevent breakage during use, which could disrupt production continuity. The rocker arm must withstand heavy loads, constant impact, and alternating stress every day.
Structure of the VRM Rocker Arm Assembly
The rocker arm is a lever mechanism that transmits force. Each group of rocker arms is a complete assembly installed in the bearing housing on the vertical mill bracket. It mainly consists of the following components:
| Component | Function |
|---|---|
| Upper Rocker Arm | Used to install the grinding roller |
| Lower Rocker Arm | Connected to the hydraulic system |
| Center Shaft | Connects the upper and lower arms |
| Taper Sleeve & Taper Pin | Lock the connection tightly |
| Bearing Seat | Holds the bearings |
| Bearings | Allows smooth rotation |
The upper rocker arm is used to install the grinding roller, and the lower rocker arm is connected to the hydraulic system. The two arms are connected integrally through the shaft, taper sleeve, and taper pin. The entire assembly is then mounted in the bearing housing on the vertical mill bracket.
This clear structure makes the rocker arm assembly easy to understand and maintain.
Technical Specifications
- Weight: 5–50 tons (customizable)
- Materials: ZG270-500, ZG30SiMnMo, or as requested
- Heat Treatment: Normalizing + tempering
- NDT Standards: Level-2 flaw detection (UT, MT)
- Surface Treatment: Arc gouging + shot blasting
- Quality System: ISO 9001:2015
- Compatibility: Loesche, Pfeiffer, Polysius, ATOX, HRM, LM, ZGM
- Customization: Yes, according to drawings
Manufacturing Process of Grinding Mill Rocker Arm
1. Wood Pattern Making → 2. Sand Modeling → 3. Steel Smelting → 4. Component Analysis → 5. Pouring → 6. Cleaning → 7. Polishing → 8. Heat Treatment → 9. Finish Machining → 10. Flaw Detection → 11. Shot Blasting → 12. End Product Delivery
Material of Vertical Roller Mill Rocker Arm
The rocker arm bears huge forces during operation. Choosing the right material is critical. AGICO offers high-quality cast steel options:
| Material | Yield Strength | Key Features |
|---|---|---|
| ZG270-500 | ≥270 MPa | Good strength and toughness, widely used |
| ZG30SiMnMo | Higher | Excellent wear resistance and fracture resistance |
These high-quality steel materials ensure strong wear resistance and fracture resistance of the rocker arm. AGICO selects high-quality scrap raw materials and strictly tests the ingredients before production. During smelting, we take three samplings — before the furnace, as-cast, and after the furnace — and use a German spectrometer to test the chemical composition, ensuring that every batch meets the required standards.
Advantages of AGICO Cement Vertical Mill Rocker Arm
High-strength cast steel material
AGICO uses ZG270-500 and ZG30SiMnMo high-quality cast steels. These materials have excellent fatigue resistance, impact resistance, and long-term stability. Under long-term and frequent pressure from the grinding roller, the rocker arm is not easy to deform.
Advanced casting technology
We adopt CAE simulation to assist the gating system design, ensuring optimal pouring conditions. We are also equipped with an LF refining furnace and VD vacuum degassing furnace, which can meet customers’ high-end steel casting needs.
Standard wooden pattern with special coating
We adopt a standard wooden model, and the surface of the core is brushed with a special coating layer to prevent cracking and ensure that the surface of the casting is smooth and smooth.
Precision CNC machining
AGICO uses advanced CNC machining equipment to ensure high precision of hole positions, axes, and installation surfaces. This guarantees a perfect fit between the rocker arm and other components, reducing vibration and wear.
Level-2 flaw detection standards
Every rocker arm undergoes Level-2 flaw detection standards. We use ultrasonic testing (UT) and magnetic particle testing (MT) to check for any hidden cracks, pores, or other internal defects. We prevent any defective products from leaving our factory.
Arc gouging and shot blasting surface treatment
We use arc gouging and shot blasting for finishing. Arc gouging removes oxide scale and defect layers. Shot blasting removes impurities and forms a cold-work hardening layer, which improves surface hardness and wear resistance. This gives the rocker arm a uniform metallic luster and better appearance quality.
Full traceability – ISO 9001:2015 certified
AGICO operates under the ISO 9001:2015 Quality System. Every process step — including heat treatment, chemical composition test, mechanical properties test, non-destructive test, and dimensional check — is fully documented and traceable.
Long service life – rarely needs replacement
Under normal operating conditions, the upper and lower rocker arms do not need to be replaced. Only the connecting parts, like taper pins, taper sleeves, and disc springs, are wear parts that need periodic inspection. This saves you significant maintenance costs.
Customizable according to your drawings
AGICO can produce rocker arms according to your specific drawings and technical requirements. We can also reverse-engineer from your worn samples. We provide not only customized rocker arm assemblies but also individual components, such as main arms, connection ends, arm shafts, bearings, and bearing housings.
Applications
Our vertical roller mill rocker arm is suitable for:
- Cement plants – Cement vertical mill
- Raw meal grinding – Raw meal vertical mill
- Power stations – Coal vertical mill
- Steel plants – Slag vertical mill (GGBS plants)
- Building materials – Mineral powder vertical mill
FAQ about VRM rocker arm
Q1: What is the function of the rocker arm in a vertical roller mill?
A: The rocker arm transfers the pressure from the hydraulic cylinder to the grinding roller, converting it into grinding force on the material bed. It also supports the grinding roller assembly, controls roller lifting and lowering, and participates in angle adjustment. It is the core force transmission component of the VRM.
Q2: What materials are used for the rocker arm?
A: AGICO rocker arms are mainly made of ZG270-500 and ZG30SiMnMo high-quality cast steel. These materials have excellent strength, toughness, and wear resistance.
Q3: What is the weight range of AGICO rocker arms?
A: AGICO rocker arms typically range from 5 to 50 tons. We can customize according to your specific requirements.
Q4: How is the rocker arm quality inspected?
A: Every rocker arm undergoes Level-2 flaw detection (ultrasonic testing and magnetic particle testing). We also provide a full material test report with chemical and mechanical property data.
Q5: How long does a rocker arm last?
A: Under normal operating conditions, the upper and lower rocker arms do not need to be replaced. Only the connecting parts (taper pins, taper sleeves, disc springs) need periodic inspection and replacement.
Q6: Can AGICO produce rocker arms according to my drawings?
A: Yes. AGICO accepts custom orders based on customer drawings and technical requirements. We can also reverse-engineer from your worn samples.
Q7: What is the lead time for a rocker arm?
A: The production cycle typically ranges from 25 to 45 days, depending on the casting process and technical requirements. Contact us for specific timelines.
Q8: Do you supply other VRM spare parts?
A: Yes. AGICO supplies a complete range of VRM spare parts, including roller shells, grinding table liners, separators, roller hubs, and bearings.
