What is the reason for hearing a "dang dang" metallic impact sound coming from the jaw plate during the operation of the crusher?

During the operation of the jaw crusher, a "dang dang" metal impact sound appears in the jaw plate area, which is a common and diagnostic fault signal with clear diagnostic value. The generation of this sound indicates abnormal relative motion or contact within the device, with different characteristic sounds pointing to different types of faults. Starting from the working principle of jaw crusher, this article systematically sorts out the possible causes of metal impact sound.

1、 Overview of the working principle of jaw crusher

The working mode of the jaw crusher is the curved extrusion type, and its working principle is that the electric motor drives the belt and pulley, and the movable jaw moves up and down through the eccentric shaft. When the movable jaw rises, the angle between the elbow plate and the movable jaw increases, pushing the movable jaw plate closer to the fixed jaw plate, and the material is crushed or split during this process; When the movable jaw descends, the angle between the elbow plate and the movable jaw decreases, and the movable jaw plate separates from the fixed jaw plate under the action of the pull rod and spring. The crushed material is discharged from the lower outlet of the crushing chamber. During normal operation of the equipment, the coordination between the moving parts should remain stable and no abnormal sounds should be emitted. Once there is a metallic impact sound, it indicates that there is some abnormality in the equipment.

2、 Direct collision between toothed plates

Production mechanism. When the size of the ore discharge port is adjusted too small, the movable jaw plate will directly contact and collide with the bottom of the fixed jaw plate during the swinging process, thereby emitting a metallic impact sound. There should be a certain gap between the movable jaw and the fixed jaw toothed plate. If the gap is too small due to improper adjustment of the discharge port, the two jaw plates may collide with each other under no-load or light load conditions.

Characteristics of sound and phenomena. This sound is usually a periodic impact sound, with a frequency that is basically consistent with the swinging frequency of the moving jaw. The impact sound is relatively crisp, similar to a direct strike between metal objects. This sound is usually more pronounced when the crusher is idling or when the material in the crushing chamber decreases. If the situation of the discharge port being too small persists, not only will it produce impact sound, but it may also accelerate the wear of the jaw plate teeth, and in severe cases, it may cause the jaw plate teeth peak to crack.

Troubleshooting and handling methods. The actual size of the discharge port should be checked while the machine is stopped. If it is confirmed that the discharge port is smaller than the specified value, the discharge port should be adjusted according to the operating method in the equipment manual, increasing the gap between the fixed jaw plate and the bottom of the moving jaw plate, and ensuring that the gap between the two jaw plates after adjustment meets the recommended value of the equipment manufacturer.

3、 Loose or failed pull rod spring

Production mechanism. The tension rod spring of the jaw crusher is a key component for maintaining the return movement of the moving jaw plate, which is used to ensure that the moving jaw plate can leave the fixed jaw plate in a timely manner and keep the elbow plate in close contact with the elbow plate pad. When the elasticity of the buffer spring of the pull rod disappears or is damaged, or the spring is not compressed tightly, there will be looseness between the movable jaw plate, elbow plate, and body, and the mating relationship will be destroyed. The head of the elbow plate will collide with the support pads at both ends, producing abnormal sounds. In addition, the spring and spring seat may also collide with each other due to improper installation or looseness.

Characteristics of sound and phenomena. This kind of sound mostly occurs at the rear of the equipment, mainly in the area of the thrust plate support or gasket adjustment device, and the sound is a periodic knocking sound. As the operating time of the device prolongs, the frequency and intensity of the knocking sound may gradually increase. This phenomenon is more pronounced when the crusher is idling or when the load is light.

Troubleshooting and handling methods. The machine should be stopped to check whether the compression state of the tension rod spring is normal, and observe whether there are signs of cracks, fractures, or permanent deformation in the spring. If the spring fails, it should be replaced. If the spring itself is intact but the compression is insufficient, the compression force of the spring should be appropriately increased by adjusting the tension rod nut until the knocking sound disappears.

4、 Wear or looseness of elbow pads and elbow pads

Production mechanism. The elbow plate (thrust plate) is an important component for transmitting crushing force and achieving overload protection in jaw crushers. The elbow plate is connected to the moving jaw and the body through the elbow plate pad. If the elbow plate support slider is severely worn or loose, or if the head of the elbow plate is severely worn, the clearance between the elbow plate and the elbow plate pad will increase, causing the elbow plate to collide with the supports on both sides during movement. When the wear of the thrust plate support pad exceeds 2mm, the contact area between the support pad and the thrust plate decreases, and the impact sound and vibration will significantly intensify. In addition, if the tension rod is not tightened properly during installation or if the tension rod nut becomes loose due to long-term vibration of the equipment during operation, there will also be a gap between the elbow plate and the elbow plate pad, causing them to collide.

Characteristics of sound and phenomena. The knocking sound mainly comes from the elbow assembly area at the rear of the rack. If the elbow plate breaks, the device will stop swinging with a "cracking sound".

Troubleshooting and handling methods. The machine should be stopped to clean the crushing chamber, and the contact status between the elbow plate and the elbow plate pad should be checked by hammering. Observe whether the wear of the elbow plate pad is uniform and whether there are cracks on the elbow plate. When severe wear is found on the elbow head or when the movable support block is fatigued and relaxed, replacement should be carried out.

5、 Loose fixing bolts of jaw plate and lining plate

Production mechanism. The jaw crusher is subjected to strong periodic impact loads during operation, and components such as jaw plates and side liners are fixed to the frame or jaw bed by bolts and wedges. Under long-term vibration, the fixing bolts may gradually loosen due to the attenuation of pre tightening force, or directly experience fatigue fracture. Once the jaw or lining plate loses reliable fixed constraints, it will undergo relative displacement and collision with the body during the crushing process. When the fixed bolt breaks, the jaw plate may even detach and directly collide violently with the moving jaw body. For the flowing jaw plate, if the wedge surface of the clamping wedge is worn and cannot tightly press the jaw plate, it will also cause the jaw plate to move up and down, resulting in a "bang bang" impact sound.

Characteristics of sound and phenomena. This metal impact sound is often accompanied by the shaking of the lining plate, and the sound characteristics are related to changes in equipment load. When the equipment is unloaded, a "click" sound may be heard between the loose lining or jaw plate and the machine body due to vibration; When materials enter the crushing chamber for crushing operations, due to the presence of squeezing force, loose parts may be temporarily compressed, and the sound may temporarily weaken or disappear.

Troubleshooting and handling methods. After stopping the machine, use a hammer to strike the fixed wedge iron on the side wall and judge the fastening status of the area through sound. If looseness is found, tighten the fixing bolts; If the bolt has broken, it should be replaced with a bolt of the specified strength grade (such as 8.8 grade M20 high-strength bolt), and ensure that the tightening torque meets the recommended value of the equipment manufacturer.

6、 Unstoppable objects enter the crushing chamber

Production mechanism. If iron blocks, large metal parts, or other unbreakable debris are mixed into the feed of the crusher, these objects cannot be crushed and move irregularly after being squeezed in the crushing chamber. They collide with the jaw plate at high speed, forming a sharp metal impact sound. In addition, when hard foreign objects such as iron blocks pass through the crushing chamber, it may also cause the elbow plate to break.

Characteristics of sound and phenomena. This kind of metal impact sound appears suddenly, with high intensity, and is significantly different from the sound of normal fragmentation. After the sound of impact appears, if an instantaneous increase in current is observed, it should be suspected that there is an unbreakable object entering the cavity.

Troubleshooting and handling methods. Immediately stop the machine, clean the crushing chamber, and remove non crushable objects. In the subsequent operation, metal detectors or iron removal devices should be installed at the feeding end to strengthen the iron removal treatment before feeding and avoid similar situations from happening again. At the same time, check whether the elbow plate has been broken. If it has been broken, replace it with a new elbow plate.

7、 Methods for determining the impact of sound features

The metal impact sound generated by different fault sources has differences in sound characteristics, occurrence timing, and accompanying phenomena, which can be used to assist in fault localization. Periodic impact sound with frequency synchronized with equipment swing, priority should be given to investigating the size of the discharge port and the status of the tension rod spring. Accompanied by shaking of the lining plate, priority should be given to checking the tightening of bolts. The sound source is concentrated at the rear of the rack, and priority should be given to investigating the elbow components and pull rod springs. The impact sound intensity is high and accompanied by current spikes, priority should be given to investigating the entry of unbreakable objects. Priority should be given to identifying intermittent contact issues such as loose bolts or worn elbow plates that may cause abnormal noises during periods of no load and load.

8、 Preventive maintenance measures

To reduce the frequency of metal impact sound, it is recommended to take the following measures: strictly follow the prescribed tightening torque during jaw plate installation, install anti loosening washers, and regularly inspect the status of various fasteners; Reasonably adjust the size of the discharge port to ensure that the bottom of the two jaw plates do not touch each other in an unloaded state; Regularly check the compression status of the tension rod spring, and adjust or replace it promptly if elasticity weakens or cracks appear; Install iron removal devices at the feeding end to prevent metal hard objects from entering the crushing chamber; Establish an equipment inspection system, use idle time to listen to sound to identify abnormalities, and promptly shut down for handling in case of abnormal response.