Influence and Mechanism Analysis of Side Plate Wear on Moving Jaw Plate of Jaw Crusher

Introduction

As the core primary crushing equipment in sand and aggregate production, mineral processing and building material crushing industries, a jaw crusher forms an enclosed crushing chamber composed of frame double-side plates, fixed jaw plate and moving jaw plate. The inner frame side plate, also known as side guard plate, is mostly made of high-manganese wear-resistant alloy. It mainly seals gaps on both sides of the crushing chamber, limits material flow direction, isolates direct friction between ores and the frame shell, and restricts the operating displacement of the moving jaw plate laterally. Under actual working conditions, the side plate is subjected to long-term impact of hard ores, abrasive friction and lateral extrusion, developing three wear forms including uniform abrasion, edge erosion and local spalling. The wear loss accumulates continuously with operating hours, material hardness and feed particle size. As a non-independent wearing part, the deformed worn side plate changes the lateral geometric parameters and dynamic stress boundary of the crushing chamber, and further affects the moving jaw plate from multiple dimensions including motion trajectory, load distribution, wear rate and assembly stability, causing cascading equipment wear. Based on jaw crusher dynamics and on-site operation and maintenance measured data, this paper objectively analyzes the impacts of side plates with different wear degrees on moving jaw plates, sorts out fault transmission logic, and provides technical references for equipment inspection, maintenance and replacement.

1. Basic Functions and Wear Classification of Crusher Side Plates

1.1 Assembly and Stress Functions of Side Plates

Double side plates are symmetrically embedded on the left and right inner walls of the crusher frame, fitting closely with frame end beams at the top and bottom. Their inner sides face materials inside the crushing chamber, while side edges fit two end faces of the moving jaw plate. For conventional PE-series jaw crushers, an assembly gap ranging from 0.8mm to 2mm is reserved between the side plate and the end face of the moving jaw plate, to offset tiny deformation generated by reciprocating swing of the moving jaw and prevent fine crushed stones from being wedged into gaps between the moving jaw and the frame. During operation, side plates bear lateral rebound impact force from ores, share lateral extrusion force on two ends of the moving jaw plate, regularize the vertical falling path of materials, and reduce scratch wear on side edges of the moving jaw caused by lateral material drifting.

1.2 Wear Classification Standards of Side Plates

Referring to on-site maintenance standards in mining industry, side plate wear is divided into three grades based on original plate thickness, applicable to working conditions of three mainstream crushed materials: granite, iron ore and limestone:

1. Slight wear: Thickness loss of single side plate ≤15%, only dense fine scratches distributed on the plate surface without pits or edge defects, wear difference between two side plates less than 0.5mm, no obvious deformation of lateral chamber structure;

2. Moderate wear: Thickness loss of single side plate ranges from 15% to 35%, dotted surface corrosion and flattened edge chamfers appear partially, wear difference between two side plates ranges from 0.5mm to 2mm, original assembly gap expands;

3. Severe wear: Thickness loss of single side plate ＞35%, edge fracture and massive local spalling occur on the side plate, wear difference between two side plates greater than 2mm, lateral limiting structure on both sides of the crushing chamber fails, and gaps expand greatly.

Side plates with different wear grades exert differentiated action intensity and fault types on moving jaw plates.

2. Specific Impacts of Side Plates in Different Wear States on Moving Jaw Plates

2.1 Slight Wear: Slightly Aggravate Side Edge Wear and Destroy Local Stress Balance of Moving Jaw Plate

When side plates are in slight wear state, the overall contour of the crushing chamber changes slightly, and the reciprocating swing trajectory of the moving jaw plate driven by the eccentric shaft basically conforms to design parameters, with impacts mainly concentrated on local end face friction. The standard assembly gap expands slightly along with side plate abrasion, allowing fine crushed stones below 5mm in particle size to enter gaps between side plates and two end faces of the moving jaw plate. During hundreds of reciprocating swings per minute, stones wedged in gaps produce dry abrasive friction on upper and lower side edges and end faces of the moving jaw, breaking the original balanced wear rhythm between the working surface and side edges of the moving jaw plate.

With long-term cumulative slight wear, the wear speed of the wear-resistant layer at two ends of the moving jaw plate exceeds that of the central crushing working surface, uniform band-shaped scratches form on jaw plate end faces, and tiny deviation exists in bearing load on two sides of the moving jaw. This state will not cause equipment abnormal noise or discharge particle size fluctuation, but shortens the overall service life of the moving jaw plate. Under the same working condition, the replacement cycle of moving jaw plates is shortened by 8% to 12% compared with the condition with intact side plates.

2.2 Moderate Wear: Deviate Moving Jaw Trajectory and Induce Lateral Eccentric Load Stress

Moderate wear is the most common and easily neglected working condition in actual production. In this state, asymmetric wear occurs on two side plates, leading to inconsistent lateral limiting dimensions on the left and right sides of the chamber and changing the dynamic operation boundary of the moving jaw plate directly. Affected by rotary force of the eccentric shaft and material extrusion force, the moving jaw plate swings laterally toward the severely worn side with fixed-direction displacement deviation, and the measured lateral deviation of small and medium-sized jaw crushers reaches 1mm to 3mm.

Firstly, load distribution loses balance. During material crushing, jaw teeth on one side of the moving jaw plate bear major crushing pressure, resulting in uneven stress on jaw teeth. The tooth root on the offset side bears continuous alternating lateral shear stress, where micro fatigue cracks germinate and expand faster than under uniform stress state. Secondly, assembly fastening load of jaw plate changes. Lateral offset of the moving jaw causes uneven stress on locking bolts and pressure plates at the back of the jaw plate, raising tensile load on unilateral bolts and reducing the fitting degree between the moving jaw plate and moving jaw base indirectly. Thirdly, material crushing angle changes. Expanded lateral chamber space offsets material accumulation angle, ores strike jaw teeth obliquely instead of vertically, aggravating spalling wear on unilateral jaw teeth further. According to field data of iron ore crushing working conditions, eccentric wear rate of moving jaw plates rises by 25% to 40% under moderate side plate wear.

2.3 Severe Wear: Trigger Structural Displacement of Moving Jaw and Cause Compound Mechanical Damages

Severe wear and edge failure of side plates completely invalidate the lateral limiting structure of the crushing chamber, which belongs to a high-risk working condition. Damages caused to moving jaw plates are sudden and irreversible, mainly divided into four types:

First, loss of control over reciprocating swing stroke. Without lateral constraint from side plates, the lateral floating range of the moving jaw plate increases greatly, and its swing trajectory deviates from factory design parameters. The gap between moving jaw and fixed jaw differs largely on left and right sides, bringing unstable ore crushing extrusion force. In addition, corners of the moving jaw may collide with the frame inner wall directly, causing corner cracking and massive tooth fracture of the moving jaw plate.

Second, normalized end face impact damage. Large ores enter side gaps of the moving jaw through defective positions of worn side plates, striking moving jaw end faces directly during crushing and forming irregular impact pits that damage the overall structural integrity of jaw plates, meanwhile impact vibration transmits to jaw plate assembly surfaces.

Third, accelerated linkage wear of matching components. Lateral displacement of the moving jaw increases assembly deviation among jaw plate, moving jaw base, toggle plate and eccentric shaft bearing. The back of the moving jaw plate bears torsional force, easily causing base deformation of jaw plates and fracture of fastening bolts. Partial loosening and dislocation of the moving jaw plate may occur in some conditions, worsening disordered impact inside the crushing chamber.

Fourth, vicious cycle of abrasive media. Alloy debris peeled off from side plates and crushed ore fragments remain in chamber gaps, grinding assembly surfaces and working surfaces of moving jaw plates continuously. This forms a vicious cycle including debris abrasion, component wear and debris increase, raising the risk of sudden scrappage of moving jaw plates.

3. Core Transmission Mechanism of Side Plate Wear Affecting Moving Jaw Plate

3.1 Geometric Boundary Mechanism

Side plates define lateral geometric dimensions of the crushing chamber. Wear changes effective chamber width and lateral gap parameters, disturbing material accumulation flow field inside the chamber. Varied falling, extrusion and discharging paths of materials offset the acting direction and position of resultant force on the moving jaw plate, which is the basic physical mechanism of side plate wear affecting moving jaw plates. Intact symmetric side plates ensure vertical compressive crushing of materials, while asymmetric worn side plates generate lateral component force and change stress vector of jaw plates.

3.2 Alternating Stress Transmission Mechanism

Jaw crushers operate under alternating load. Side plates buffer alternating rebound impact force from ores and share lateral stress borne by moving jaw plates. The stress buffering capacity of side plates declines after wear, most lateral alternating stress acts directly on end faces and side edges of moving jaw plates. Long-term fatigue stress on jaw plate metal structure damages the hardened wear-resistant surface layer preferentially, then accelerates wear and cracking of the base material. This mechanism is the main cause of fatigue cracking at jaw tooth roots.

3.3 Amplification Mechanism of Abrasive Wear

Qualified assembly gaps avoid embedding friction of hard ores. Expanded gaps caused by side plate wear allow more embedded abrasive particles. The friction mode changes from single working surface material wear to composite abrasive wear on working surface plus end face, increasing friction contact area and friction coefficient, and continuously raising the wear efficiency of moving jaw plates.

4. Operation and Maintenance Measures to Reduce Negative Impacts of Side Plate Wear

Based on the above influence mechanisms, frequent replacement of moving jaw plates is unnecessary. Targeted maintenance on side plates can reduce linkage wear damage and adapt to regular production:

1. Establish periodic inspection mechanism for side plates. Formulate inspection cycles according to material hardness: measure side plate thickness every 15 days for soft materials such as limestone, and every 7 days for hard materials such as iron ore and granite. Replace double side plates symmetrically when single plate thickness loss reaches 30% to avoid asymmetric eccentric wear;

2. Control feeding conditions. Restrict feeding of oversized ores and angular hard impurities to reduce directional unilateral impact on side plates, lower local edge erosion risk, and keep synchronous wear of double side plates;

3. Optimize assembly gaps. Calibrate the gap between side plate and moving jaw end face in accordance with equipment manuals during side plate replacement, keep the gap within 1mm-2mm, and install wear-resistant gaskets for fine adjustment to prevent fine stones from embedding into gaps;

4. Adjust side plates timely in mid wear stage. Adjust side plate position via frame lateral adjusting jacks when moderate asymmetric wear occurs, compensate wear dimension, correct lateral displacement of moving jaw plates and reduce eccentric load stress.