The ball mill head — also called the trunnion or end cover — is a critical structural component that closes the mill shell at both the feeding and discharge ends. It supports the hollow trunnion journal, houses the inlet/outlet openings, and must withstand the full axial load and thermal stresses of grinding operations. LIMING manufactures precision cast steel mill heads to exact OEM specifications.
A ball mill head is the heavy end cover bolted to the mill shell flange at both the feed and discharge ends of the grinding mill. Each head includes the central hollow trunnion journal that rotates in the trunnion bearing, the flange face that mates with the mill shell, and internal ribs that provide structural reinforcement against bending and torsional loads. The feeding head incorporates the material inlet opening (feed chute entry), while the discharge head includes the outlet opening (discharge grate or overflow exit).
Because ball mill heads carry the combined weight of the rotating shell, grinding media charge, material load, and dynamic impact forces during grinding, they must possess exceptional structural integrity. Any casting defect, misalignment, or fatigue crack in the mill head can lead to trunnion bearing failure, seal leakage, and structural instability. LIMING's mill heads are produced using advanced sand casting techniques with rigorous quality control — each casting is normalized, tempered, and fully machined on CNC boring mills to achieve precise trunnion alignment and flange flatness.
We manufacture both feeding heads (inlet end) and discharge heads (outlet end) for all types of horizontal ball mills used in cement production, including raw material grinding mills, cement clinker grinding mills, and coal pulverizing mills. Custom drilling patterns, flange dimensions, and trunnion diameters are manufactured to your drawings or reverse-engineered from existing components.
LIMING manufactures ball mill heads from two primary cast steel grades, selected based on mill size, grinding duty, and operating conditions:
| Material Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Hardness (HB) | Typical Application |
|---|---|---|---|---|
| ZG270-500 | ≥500 | ≥270 | 140-200 | Standard cement ball mills, raw mills, coal mills |
| ZG35 (Carbon Cast Steel) | ≥500 | ≥280 | 143-197 | Large-diameter mills, high-load heavy-duty service |
ZG270-500 is the standard material for most cement ball mill head applications, offering an excellent combination of castability, machinability, and mechanical strength. For the largest mills operating at high material throughput — particularly raw material grinding mills processing abrasive limestone and clay — ZG35 provides enhanced structural strength and fatigue resistance. Both grades are normalized and tempered to relieve casting stresses and achieve uniform hardness before machining.
Superior cast steel metallurgy, precision CNC machining, and comprehensive quality assurance.
Large-capacity sand casting with full metallurgical control — chemical composition verified by spectrometer for every heat.
Every mill head undergoes ultrasonic testing and magnetic particle inspection. Complete UT/MT reports and mill test certificates provided.
CNC boring mills machine trunnion journals, flange faces, and bolt holes to exact tolerances for proper bearing fit and shell alignment.
Custom manufactured to match or exceed original specifications. Reverse engineering from worn components available for retrofit.
| Parameter | Specification |
|---|---|
| Product Type | Ball Mill Head — Feeding end / Discharge end |
| Material Options | ZG270-500, ZG35 (cast steel) |
| Manufacturing | Sand casting → Normalizing + Tempering → CNC machining |
| Trunnion Diameter | 500 mm – 2,500 mm (custom per mill design) |
| Flange Diameter | Matched to mill shell ID/OD per drawings |
| Unit Weight | 2 – 30+ tons per head |
| Flange Face Flatness | ≤0.05 mm/m |
| Trunnion Bearing Surface | Machined to Ra 1.6 μm surface finish |
| Heat Treatment | Normalized + tempered; stress relief annealing |
| Inspection | UT, MT, dimensional CMM, hardness test, spectrometer analysis |
| Design Standard | GB, ASTM, DIN, JIS — per customer requirement |
| Lead Time | 45-90 days (depending on size and complexity) |
From pattern making to final inspection — every step controlled for quality and precision.
Wood or resin patterns built to exact head geometry including casting shrinkage allowance and machining stock.
Molten cast steel poured into sand molds with controlled pouring temperature and solidification rates.
Normalizing and tempering to relieve casting stress and achieve uniform mechanical properties throughout.
Boring of trunnion journal, facing of flange, drilling of bolt holes on CNC horizontal boring mills.
UT, MT, dimensional CMM verification, hardness testing, and chemical analysis before release.