The Motion Core of an SG Gyratory Crusher

The eccentric assembly is the motion core of an SG series primary gyratory crusher. Located in the lower section, it converts rotary power from the drive system into the gyrating movement of the mainshaft and mantle. Its condition directly affects gear contact, lubrication, vibration, crushing stability and component service life.

A complete assembly normally includes the eccentric body, eccentric bushing and eccentric spiral bevel gear. Depending on the crusher model, eccentric throw and counterweight design, keys, fasteners, seals, wear rings and counterweight components may also be included.

17CrNiMo6 Spiral Bevel Gear

Our SG eccentric gears are manufactured from 17CrNiMo6, a nickel-chromium-molybdenum case-hardening steel.z

The large spiral bevel gear transmits high torque and is subjected to repeated tooth contact and bending loads. With controlled carburizing and hardening, 17CrNiMo6 can provide a hard, wear-resistant tooth surface while retaining a tough core for impact and fatigue resistance.

Reliable gear performance also depends on correct heat treatment, tooth geometry, hardness and machining accuracy.

Why Replace the Gear and Pinion as a Pair?

The eccentric gear and pinion operate together as a spiral bevel gearset. For gearsets manufactured, lapped or inspected as matched pairs, both members should normally be replaced together.

Installing a new eccentric gear against a worn or unmatched pinion may change the tooth contact pattern, concentrate loads and cause abnormal noise, overheating or accelerated wear. After installation, backlash and tooth contact should be checked and adjusted according to the technical drawing.

ZCuPb10Sn10 Eccentric Bushing

The eccentric bushing is a large sliding bearing component installed inside the eccentric body. It supports the lower end of the mainshaft and helps create the required eccentric throw.

Our SG eccentric bushings are manufactured from ZCuPb10Sn10 cast leaded tin bronze. Its sliding and wear characteristics make it suitable for heavy-load bearing applications.

For a bushing of this size, however, the alloy designation alone is not enough. Chemical composition, material uniformity, casting soundness, hardness, bore dimensions, roundness, cylindricity and oil-groove geometry must all be carefully controlled.

Correct operating clearance helps maintain a stable lubricating oil film and reduces the risk of scuffing and overheating.

Precision and Correct Part Selection

Reliable operation depends on how all components fit together. Eccentric throw, gear runout, bushing clearance and overall assembly accuracy must comply with the confirmed technical drawing.

Since the same SG model may have different generations, throws or counterweight arrangements, replacement parts should be selected using the crusher model, serial number, existing part number and drawing.

Conclusion

A correctly manufactured and properly matched eccentric assembly helps SG42-65, SG50-65, SG54-75, SG62-75, SG60-89 and SG60-110 crushers maintain stable motion, reduce premature gear and bushing damage, and deliver dependable primary crushing performance.