The cone crusher counter weight, a key dynamic balancing component mounted on the eccentric bushing, offsets centrifugal forces from eccentric rotation, reducing vibration, enhancing stability (500–1500 rpm), optimizing energy use, and balancing frame loads.
Structurally, it comprises a high-density (7.0–7.8 g/cm³) body (HT350/QT600-3), 2–6 annular segments, bolt holes (class 8.8+), locating pins, balancing tabs, and reinforcement ribs, with a corrosion-resistant coating.
Manufactured via sand casting (1350–1380°C pouring), it undergoes annealing (550–600°C) and precision machining (CNC turning/grinding) for dimensional accuracy. Quality control includes material testing (density ≥7.0 g/cm³), NDT (UT/MPT), dynamic balancing (≤5 g·mm/kg residual imbalance), and load testing (150% rated force).
This ensures reliable operation in mining/aggregate processing by minimizing stress and extending component life.
Detailed Introduction to the Cone Crusher Counter Weight Component
1. Function and Role of the Counter Weight
The cone crusher counter weight (also known as the balance weight or eccentric counterbalance) is a critical dynamic balancing component mounted on the eccentric bushing or main shaft assembly. Its primary functions include:
Dynamic Balancing: Offsetting the centrifugal force generated by the eccentric rotation of the moving cone and eccentric bushing, reducing vibration and noise during operation. This minimizes stress on the frame, bearings, and other structural components.
Stability Enhancement: Ensuring smooth rotation of the eccentric assembly at high speeds (500–1500 rpm), preventing uneven loading that could lead to premature wear or failure of the main shaft and thrust bearing.
Energy Optimization: Reducing the power consumption associated with vibration damping, improving the crusher’s overall energy efficiency.
Load Distribution: Balancing the lateral forces exerted on the crusher frame during the crushing cycle, preventing excessive deflection and maintaining consistent crushing gap accuracy.
Operating under high centrifugal forces (often exceeding 10,000 N), the counter weight requires high density, structural rigidity, and precise mass distribution to achieve effective balancing.
2. Composition and Structure of the Counter Weight
The counter weight is typically a segmented or one-piece annular component, designed to match the eccentric bushing’s geometry. Its key components and structural details include:
Weight Body: A heavy-duty structure made of high-density cast iron (HT350), ductile iron (QT600-3), or concrete-filled steel (for large crushers). The material density ranges from 7.0–7.8 g/cm³ to provide sufficient mass (50–500 kg, depending on crusher size).
Annular Segments: For large crushers, the counter weight is often divided into 2–6 segments (e.g., 4 equal parts) to facilitate installation. Each segment has a radial width of 100–300 mm and thickness of 50–150 mm.
Mounting Features:
Bolt Holes: Circumferentially spaced holes (8–24) for securing the weight to the eccentric bushing, with thread class 8.8 or higher to withstand centrifugal forces.
Locating Pins: Cylindrical protrusions on the mounting surface that fit into corresponding holes in the eccentric bushing, ensuring precise angular positioning.
Balancing Tabs: Small adjustable plates or threaded holes on the outer circumference for fine-tuning the weight distribution. These allow adding/removing small weights (100–500 g) to achieve optimal balance.
Reinforcement Ribs: Internal or external radial ribs that enhance structural rigidity, preventing deformation under centrifugal stress. Rib thickness ranges from 10–30 mm, depending on segment size.
Smooth Outer Surface: A machined outer circumference with low roughness (Ra3.2–6.3 μm) to reduce air resistance and minimize dynamic drag during rotation.
Corrosion Protection Layer: A painted or galvanized coating (50–100 μm thick) to resist rust in dusty or humid environments.
3. Casting Process for the Counter Weight
Given its need for high density and complex geometry, the counter weight is primarily manufactured via sand casting:
Material Selection:
High-Density Cast Iron (HT350): Preferred for its high density (7.2–7.3 g/cm³), compressive strength (≥350 MPa), and cost-effectiveness. Chemical composition: C 3.2–3.6%, Si 1.8–2.4%, Mn 0.6–1.0%, with low sulfur/phosphorus (≤0.035% each).
Ductile Iron (QT600-3): Used for high-stress applications, offering better impact resistance (elongation ≥3%) and tensile strength (≥600 MPa).
Pattern Making:
A full-scale pattern (foam, wood, or resin) is created for each segment, including bolt holes, locating pins, and ribs. Shrinkage allowances (1.2–1.8%) are added to account for cooling contraction.
Molding:
Resin-bonded sand molds are prepared, with cores used to form bolt holes and internal features. The mold cavity is coated with a refractory wash to improve surface finish and prevent sand inclusion.
Melting and Pouring:
Cast iron is melted in a cupola or induction furnace at 1380–1420°C, with carbon equivalent controlled to 4.2–4.6% for good fluidity.
Pouring is performed at 1350–1380°C, with a controlled flow rate to ensure complete filling of the mold, minimizing porosity in high-stress areas like bolt hole bosses.
Heat Treatment:
Annealing: Castings are heated to 550–600°C for 2–4 hours, then slowly cooled to relieve internal stress, reducing the risk of cracking during machining or operation.
Normalization (Optional): For ductile iron, heating to 850–900°C followed by air cooling refines the microstructure and improves mechanical properties.
4. Machining and Manufacturing Process
Rough Machining:
Cast segments are mounted on a CNC lathe or milling machine to trim excess material, with focus on the mounting surface and outer circumference. Dimensional tolerance is controlled to ±1 mm.
Precision Machining of Mounting Features:
Bolt Holes: Drilled and tapped using a CNC machining center, with thread tolerance 6H and positional accuracy (±0.2 mm) to ensure alignment with the eccentric bushing.
Locating Pins: Machined to diameter tolerance h6, with perpendicularity (≤0.05 mm/100 mm) relative to the mounting surface.
Mounting Surface: Ground to flatness (≤0.1 mm/m) and roughness Ra3.2 μm to ensure uniform contact with the eccentric bushing, preventing load concentration.
Balancing Tabs Preparation:
Tabs are machined or welded to the outer circumference, with threaded holes for attaching balance weights. These features are positioned to allow adjustment in 15–30° increments.
Surface Treatment:
The outer surface is sandblasted to remove scale, then painted with epoxy primer (60–80 μm) and topcoat (40–60 μm) for corrosion resistance.
Threaded holes are coated with anti-seize compound to prevent galling during installation.
5. Quality Control Processes
Material Testing:
Chemical composition analysis (spectrometry) verifies compliance with HT350 or QT600-3 standards.
Density testing (via water displacement) ensures the material density meets specifications (≥7.0 g/cm³).
Dimensional Accuracy Checks:
A coordinate measuring machine (CMM) inspects critical dimensions: segment weight (tolerance ±0.5%), bolt hole positions, and mounting surface flatness.
A laser scanner verifies the outer circumference profile, ensuring aerodynamic efficiency.
Structural Integrity Testing:
Ultrasonic testing (UT) detects internal defects (e.g., shrinkage pores) in bolt hole bosses, with defects >φ3 mm rejected.
Magnetic particle testing (MPT) checks for surface cracks in high-stress areas like ribs and mounting edges.
Dynamic Balancing Testing:
Assembled segments are mounted on a balancing machine and rotated at operating speed (500–1500 rpm). Imbalance is measured and corrected using balancing tabs, with residual imbalance limited to ≤5 g·mm/kg.
Load Testing:
A static load test applies 150% of the rated centrifugal force to the mounting bolts, with no deformation or thread stripping allowed.
Through these manufacturing and quality control processes, the counter weight effectively balances the cone crusher’s eccentric assembly, reducing vibration, extending component life, and ensuring efficient operation in mining and aggregate processing applications
