The rocker arm is a critical structural link in every vertical roller mill, transmitting the grinding force from the hydraulic cylinder to the grinding roller. LIMING manufactures rocker arms from cast or forged steel with precision machining, ensuring reliable transmission of high cyclic loads for decades of mill operation.
The rocker arm (also known as the rocker lever or swing lever) of a vertical roller mill is a pivot-mounted structural component that converts the linear force from the hydraulic tensioning system into the downward grinding pressure applied by the roller on the material bed. It functions as a lever: the hydraulic cylinder applies force to one end, and the grinding roller — connected to the other end — is pressed down onto the rotating grinding table.
In modern VRMs, each grinding roller (typically 2-4 rollers per mill) has its own rocker arm and hydraulic cylinder, allowing independent pressure control. This individual roller suspension enables the rollers to move vertically in response to changes in the material bed thickness, preventing excessive vibration and protecting the mill from damage when tramp material enters the grinding zone.
The rocker arm operates under severe cyclic loading — the grinding pressure fluctuates continuously as the roller passes over variations in the material bed. Over a typical service life of 15-20 years, a rocker arm may experience millions of load cycles. This demands steel of exceptional fatigue strength and castings free from internal defects that could initiate fatigue cracks. LIMING's rocker arms are manufactured using controlled casting and forging processes, with full ultrasonic and magnetic particle inspection to ensure structural integrity.
LIMING offers rocker arms in two primary manufacturing routes, selected based on the mill size and loading conditions:
After the casting or forging process, each rocker arm undergoes precision CNC machining to achieve the tight tolerances required at the bearing bores, pivot points, and hydraulic cylinder mounting surfaces. Machining tolerances of H7/h7 are maintained on all critical bores to ensure proper bearing fit and alignment.
In-house foundry, precision machining, and comprehensive NDT for mission-critical VRM components.
30,000-ton annual casting capacity with dedicated large-component molding pits for rocker arms up to 20 tons cast weight.
Every rocker arm undergoes UT (ultrasonic), MT (magnetic particle), and dimensional CMM inspection. Full MTC certification provided.
Our engineering team can perform FEA (finite element analysis) to verify the rocker arm design for your specific mill loading conditions.
Rocker arms supplied and installed in VRMs across cement plants in Asia, Africa, Middle East, and South America.
| Parameter | Specification |
|---|---|
| Component | Vertical Roller Mill Rocker Arm (swing lever) |
| Material Options | ZG35CrMo, ZG42CrMo (cast steel); 42CrMo, 34CrNiMo6 (forged steel) |
| Manufacturing Process | Casting → Heat Treatment → Shot Blasting → CNC Machining → NDT |
| Heat Treatment | Normalized + tempered (cast); Quench + tempered (forged) |
| Cast Weight | 2 – 20+ tons per arm |
| Machined Weight | 1.5 – 18+ tons per arm (depending on size) |
| Bearing Bore Tolerance | H7 (ISO) on all critical bores |
| Surface Finish (Machined) | Ra 1.6-3.2 µm on bearing surfaces |
| Tensile Strength (Cast) | ≥ 590-690 MPa (material dependent) |
| Yield Strength (Cast) | ≥ 390-490 MPa |
| Inspection | UT (100% volume), MT (100% surface), dimensional CMM, hardness |
| Lead Time | 90-150 days (cast + machine); 120-180 days (forged + machine) |