Inappropriate adjustment of the jaw plate in rock crushing production lines is the fundamental hidden cause of loss in the mining, aggregates, and infrastructures construction industries globally. Most foreign construction teams, aggregate processing plants, and mines regularly face a lot of issues due to inappropriate adjustment. In case the gap is too wide, the resulting rock aggregate will have non-uniform particle size distribution with excessive flaky and elongated particles and become inferior in quality and unable to meet any delivery standards. In case the gap is set too small, it can very easily result in stalling, chamber clogging, increased wear of the jaw plates, equipment vibration, and overloading and overheating of the motor, which not only leads to increased cost of replacement parts and repair downtime but also reduces the production line capacity twice and brings about significant economic losses to the engineering project.
Based on 15-year experience in design, R&D, manufacture, sale, after-sale services, and hands-on work in overseas facilities, MP comprehensively analyzes the standard procedure of stone crusher jaw plates' adjustment, the two prevalent methods, parameters for the certain working conditions, typical mistakes and how to cope with damages they cause.
The Core Role of Rock Crusher Jaw Plate Adjustment
The moving and fixed jaw plates of a rock crusher are the core components in order to achieve rock compression crushing. The size of gap between these two jaw plates directly defines the size of the output particle size, production capacity, wear of equipment, and the quality of the product, which makes it one of the crucial parameters of a crushing production line. Proper adjustment of the jaw plates guarantees the crushing of various raw materials, including granite, basalt, limestone, and construction waste according to the standard and the maximum reduction of equipment wear, elimination of failures and breakdowns, as well as stabilization of capacity output, which will comply with construction standards for mining, infrastructure aggregates production, and solid waste recycling projects in different countries.
Conversely, arbitrary adjustment results in the following losses and equipment failures. Improper adjustment leads to: unqualified output causing aggregates' unsalability and failure of the project acceptance; frequent stalling and blockage of the machinery leading to shutdowns of the production line and delays in overseas projects implementation; increased wear of the key components, namely, jaw plates, toggle plates, and bearings, which greatly increases operating and maintenance expenses; as well as constant overload operation of the motor, which decreases the equipment's service life and increases the likelihood of the machinery being scrapped.
Essential Preparations Prior to Adjusting Rock Crusher Jaw Plates
Safety standards for equipment operation and maintenance in different construction and mining sites around the world require that the jaw plates adjustment should be conducted only during full shutdown of the machine. Adjustment while carrying material, powered on or under pressure is not allowed to prevent mechanical trapping, material collapse and other hazards, as well as guaranteeing accuracy of the adjustment.
First, you need to shut down the machine, turn off the power and lock out: completely turn off the main power supply, put up the maintenance sign to prevent accidental startup of the equipment in conformity with the safety operation standards in Europe, America, Southeast Asia, Africa and other regions worldwide. Secondly, clean out the material from the crushing chamber: clean out the rock, dust and other impurities remaining in the chamber in order to avoid material jamming, which will lead to inaccurate measurement of the gap or clogging of the machine after the adjustment. Thirdly, check the condition of the key components: make sure that there is no serious wear, looseness and cracks on the jaw plates and that toggle plate, springs, bolts and adjustment seat are in good condition, which will avoid malfunction of the equipment due to abnormal wear after adjustment. Fourthly, get prepared with measuring tools and instruments: prepare feeler gauges, wrench, shims and torque tools to make sure that the whole process of adjustment, measurement and tightening is accurate and under control.
Two Mainstream Standard Adjustment Methods of Rock Crusher Jaw Plates
Currently available in the market jaw type rock crushers and mobile jaw crushers use the shim-type adjustment method or wedge-type adjustment method. These methods are suitable for different conditions, such as stationary production lines or mobile crushing sites and have standardized procedures and high universality, thus becoming the key practical skill that foreign equipment technicians should know.
Shims-Type Jaw Plates Adjustment Method
This method is suitable for large scale industrial rock crushers and fixed mine crushing production lines. It provides high adjustment accuracy, many settings and great stability and therefore is the prevalent adjustment method of large scale global mining projects. The core principle of this method is changing the gap at the bottom of the jaw plates by addition or removal of shims with varying thickness between the rear toggle plate support and the rear part of the machine frame in order to achieve accurate controlling of the output particle size.
The standard adjustment procedure is as follows. After stopping the machine and cleaning out the chamber, loosen the bolts of the adjustment seat of the equipment. Based on the required particle size, add or remove shims with appropriate thickness: to decrease the discharge gap and to make aggregates smaller, use thicker shims; to increase the gap, increase the output and avoid clogging, use fewer shims. After laying out shims flat and aligned, evenly tighten all bolts to equalize the load on the equipment. And finally, conduct a no-load trial run of the machine: in case there is no vibration or abnormal sound, run the machine with material to calibrate the discharge particle size to the required standard.
Wedge-Type Jaw Plates Adjustment Method (specifically for small machines and mobile crushers)
This method has simple structure and convenient adjustment without frequent disassembling of the components. It is suitable for small to medium-size rock crushers, as well as tire-type or crawler-type mobile crushing equipment. It is widely used in urban infrastructure construction, road renovation, small aggregate plants and construction waste recycling, and other lightweight global construction applications.
Adjustment process consists of the following stages. First, turn off the machine, disconnect the power supply, and clear the chamber. Next, unscrew the wedge locking bolts and tensioning nuts. Adjust the wedge vertically by turning the adjusting nut, namely increasing the height of the wedge results in decreasing the gap of jaw plates, and vice versa. After achieving the required size of the gap, fix it with all the fastening elements symmetrically to avoid asymmetrical load distribution and machine vibration. Run the machine without load for 3-5 minutes, and after ensuring smooth operation start mass production operation.
Stone Crusher Jaw Plates Gap Adjustment Parameters Depending on Different Working Conditions
There is no universal parameter for jaw plates gap in stone crusher. Dynamic adjustment is necessary depending on the hardness of material, size of the final particles, output capacity goals and construction conditions of the plant in different countries and ore conditions around the world. Otherwise, it will be impossible to balance the above-mentioned parameters.
For the processing of high-hardness rocks (granite, basalt, iron ore, river pebbles): high-hardness rocks are abrasive and have significant impact force, therefore, the size of the gap should be increased to avoid the crushing and jamming of material, excessive wear of the jaw plates and motor overload caused by small gap. It allows balancing the output capacity and reducing the equipment wear due to adequate compression stroke. For the processing of medium-soft materials (limestone, bluestone, dolomite, construction waste): these materials can be easily crushed and their flowability is high enough, hence, the gap should be decreased to improve the quality of final products, to minimize the number of elongated particles, and to achieve the aesthetic appearance of the final products. In case of high-output production, priority is to increase the size of the gap to increase the material throughput and ensure the capacity of the line, and then use sieving and secondary crushing to achieve the optimal product. In case of high-grade aggregate production, it is necessary to gradually reduce the gap to strictly control the size of discharged particles, and combine it with the stable speed of the equipment to get high-grade sand and aggregate meeting the requirements for high-standard projects in Europe, America, and the Middle East.
Typical Mistakes in Jaw Plates Adjustment and Targeted Solutions for Avoiding the Damages Caused by Them
Based on MP's rich experience in exporting and setting up mining crushing equipment abroad, the majority of failures and wear of the production line equipment result from the incorrect jaw plates adjustment. Below are listed common and frequent mistakes that occur in all the regions. Their exact avoidance allows significantly reducing operation costs and increasing productivity.
First of all, the most frequent mistake is performing adjustment to the target gap in one attempt without any trials and fine-tuning. Such blind adjustment can easily lead to either an oversized gap resulting in poor quality of the output or small gap, which can stall the machine and cause a total shutdown of the production line. The solution is the multiple small adjustments of the gap; after each of them, it is necessary to perform no-load run, then run the machine with material and take samples to test the discharge particle size and to calibrate to the required one.
Secondly, it is the tightening of only one part of fastening bolts, which causes asymmetric load distribution. Thus, asymmetrical fixing of jaw plates after the adjustment leads to its misalignment, machine vibration, and uneven wear of the jaw plates, which significantly shortens the lifetime of the equipment. The solution is the symmetrical and equal fixing of all fastening bolts to provide the balanced load on the adjusting seat, wedges and shims, and to make the work of the equipment without deviations.
Thirdly, it is the neglect of the state of wear of the jaw plates before the adjustment. In case the tooth surface of jaw plates is flattened and worn out severely, the grip capacity is reduced. Simple adjustment of the gap cannot help with the problems of non-uniformity of output, slippage and blocking of material. The solution is to check the degree of wear of the jaw plates before the adjustment; in case of exceeding the standard, it is necessary to replace the elements first and then calibrate the gap to avoid futile adjustment.
Fourthly, it is the use of the same gap for different types of material. If a single gap is used for the processing of hard rocks, soft rocks, wet material, and dry material, then blockage or substandard product will definitely occur. The solution is dynamic adjustment of the gap depending on the type of material: it should be increased for wet or dry-wet material, and minimized for dry and clean material.
Acceptance Procedure After Completing the Adjustment
The completion of the process of adjustment of jaw plates does not mean the end of the job. Standardized acceptance is essential to prevent future failures and to provide a stable capacity of the production line, in accordance with international standards for the operation and maintenance of engineering equipment. At first, run the machine with no load for 3-5 minutes to check it on any noise, vibration, or sticking. Next, perform a trial production run with the material and take samples to check whether the discharge particle size meets the standards. And finally, run the machine in mass production mode for 10 minutes, monitoring the current, condition of the machine body, and stability of the discharge, and if there are no abnormalities, start the production officially. From now on, simply check the gap before starting up the equipment every day to avoid the shift of the gap due to the vibration in order to provide stable operation of the production line.
The adjustment of the stone crusher jaw plates, although seeming a simple job, is the main key to ensure the profitability of the production line, equipment wear and the quality of the final product. Precise knowledge of the two standard adjustment methods: shim method and wedge method, dynamic adjustment of the gap depending on the hardness of material and construction conditions, and the avoidance of adjustment mistakes will completely solve such problems as non-uniform output, machine stalling and blocking, and insufficient capacity. It will also allow to significantly reduce economic losses from replacing the parts, repair, and delay of the project due to incorrect adjustment of the machine.
MP is actively involved in designing, researching, manufacturing, selling, and operating & maintaining crushing equipment internationally. MP can provide precise guidance on adjusting the jaws of stone crushers, setting up equipment according to specific conditions, and optimizing the entire production line for customers in Asia, Africa, Europe, America, Australia, and other parts of the world. Remote technical guidance and on-site operating and maintenance service are available. Any assistance required? Feel free to contact us.
