In agricultural mechanization operations, incomplete threshing of harvesters is one of the most common faults. It not only causes grain waste and reduces harvesting efficiency, but also increases the workload of subsequent cleaning processes, bringing unnecessary economic losses to farmers. Incomplete threshing is mainly manifested in unthreshed grains remaining in straw, or excessive straw, glumes and other impurities mixed in grains. Its root causes are mostly related to improper adjustment of equipment parameters, component wear, poor operating conditions and other factors. This article will analyze the core reasons for incomplete threshing of harvesters in detail, put forward targeted solutions, and provide daily preventive measures to help farmers complete harvesting operations efficiently.

I. Main Reasons for Incomplete Threshing of Harvesters

The core principle of harvester threshing is to separate grains from ears or cobs through the high-speed rotation of the drum, with the help of impact, kneading, brushing and other actions, and then screen out clean grains through the cleaning device. Any problem in any link may lead to incomplete threshing, and the specific reasons can be divided into the following categories:

(1) Unreasonable Adjustment of Equipment Parameters

This is the most common reason for incomplete threshing, mainly involving three key parameters: drum speed, threshing gap and feeding amount. The three parameters need to be matched with each other to achieve the best threshing effect.

1. Too Low Threshing Drum Speed: The drum is the core component of threshing operations, and its speed directly determines the impact and kneading force. When the speed is lower than the rated standard of the equipment, the impact strength on the crop ears is insufficient, and it is impossible to effectively break the connection between grains and ear axes. Especially for crops with strong grain adhesion such as corn and rice, grain residue is very easy to occur. Low speed is mostly caused by the engine not reaching the rated speed, loose and slipping transmission belt, or improper transmission wheel ratio.

2. Too Large Threshing Gap: The threshing gap refers to the distance between the drum and the concave plate. When the gap is too large, the kneading and extrusion effect of crops between the drum and the concave plate is weakened, making it difficult for grains to fall off from the ears. At the same time, the straw will pass through the threshing chamber quickly without being fully processed, resulting in incomplete threshing. Different crops and crops with different maturity have different requirements for threshing gaps. If they are not adjusted according to the actual situation, faults will occur.

3. Excessive or Uneven Feeding Amount: When the feeding amount exceeds the rated load of the equipment, crops accumulate in the threshing chamber and cannot fully contact with the drum and concave plate, and some ears are discharged without effective threshing; uneven feeding will lead to uneven stress in the threshing chamber, with excessive crops in local areas, which also affects the threshing effect. This situation is mostly caused by too fast forward speed of the harvester, improper adjustment of the header height, or uneven crop growth.

(2) Wear or Damage of Equipment Components

After long-term operation of the harvester, the core threshing components will be worn, deformed or damaged, which directly reduces the threshing performance and is an important reason for incomplete threshing.

1. Wear of Threshing Elements: The ribs, tines on the drum, and screen bars, tooth plates on the concave plate are components that directly contact with crops. After long-term use, they will be worn, deformed or even broken. After the ribs are worn, the kneading ability decreases; after the tines are worn, missing or deformed, the impact and brushing effect is weakened, making it impossible to effectively separate grains. Especially for tine-type drums, the threshing effect will be greatly reduced when the tines are severely worn.

2. Damage or Blockage of Concave Plate: If the sieve holes of the concave plate are blocked by straw and soil, the residence time of crops in the threshing chamber will be too short, and they cannot be fully threshed; if the concave plate is deformed, the threshing gap will be uneven, and the gap in local areas will be too large, resulting in threshing dead angles and residual unthreshed grains. In addition, improper configuration and insufficient quantity of tines on the concave plate will also affect the threshing effect.

3. Failure of Transmission Components: Loose, aged, cracked transmission belts, or worn sprockets and gears will lead to unstable or insufficient drum speed, thereby affecting the threshing effect. At the same time, if the drum bearing is damaged, the drum will run stuck and bear uneven force, which will also cause incomplete threshing.

(3) Influence of Operating Conditions and Crop Characteristics

In addition to the problems of the equipment itself, the operating environment and the characteristics of the crops themselves will also affect the threshing effect. If these factors are ignored, incomplete threshing will also occur.

1. Insufficient or Over-maturity of Crops: When crops are not fully mature, the connection between grains and ear axes is relatively tight, making threshing difficult and prone to residue; when crops are over-mature, grains are easy to fall off, but the straw becomes dry and brittle, and is easy to break during threshing, forming excessive impurities, which in turn affects the cleaning effect. It seems to be incomplete threshing, but in fact, the grains are covered by excessive impurities. In addition, different crop varieties have different grain adhesion and ear sizes, and the difficulty of threshing also varies.

2. Unsuitable Crop Humidity: When the water content of crops is too high, the straw toughness increases, and grains are not easy to fall off. At the same time, wet straw is easy to adhere to the threshing components, causing blockage of the threshing chamber and affecting the threshing efficiency; when the crops are too dry, the straw is easy to break, impurities increase, and the cleaning device is difficult to separate them completely, resulting in the mixing of grains and impurities, which is mistaken for incomplete threshing. Especially when operating in the morning and evening, the crops are with dew and high humidity, and the problem of incomplete threshing will be more prominent.

3. Poor Operating Environment: Muddy field soil, excessive straw, or strong wind during operation will cause the harvester to walk unsteadily and feed poorly, thereby affecting the normal operation of the threshing chamber. Strong wind will also blow away the cleaned grains or prevent impurities from being discharged effectively, aggravating the problem of incomplete threshing.

II. Targeted Solutions for Incomplete Threshing of Harvesters

In view of the above different reasons, corresponding solutions should be taken, following the principle of "first adjust parameters, then check components, and finally adapt to operating conditions", to quickly troubleshoot faults and restore the threshing performance of the harvester.

(1) Optimize Equipment Parameter Adjustment

Reasonably adjusting the drum speed, threshing gap and feeding amount is the most direct and effective method to solve incomplete threshing, which needs to be flexibly adjusted according to the crop variety, maturity, humidity and other conditions.

1. Adjust Drum Speed: First, check whether the engine reaches the rated speed. If the engine speed is insufficient, clean the air filter and check the fuel supply system to ensure the normal operation of the engine; if the transmission belt is loose, adjust the belt tension and replace the aged and cracked belts to ensure the stable drum speed. For models with replaceable transmission wheels, the transmission wheel ratio can be adjusted according to the crop type to increase the drum speed. Generally speaking, for small-grain crops such as rice and wheat, the drum speed can be appropriately increased, while for large-grain crops such as corn, the speed can be appropriately reduced. For specific parameters, refer to the equipment instruction manual.

2. Adjust Threshing Gap: Adjust the gap between the drum and the concave plate according to the maturity and humidity of the crops. When the crop maturity is low and the humidity is high, reduce the gap to enhance the kneading force; when the crop maturity is high and dry, appropriately increase the gap to avoid excessive straw breakage and reduce impurities. During adjustment, ensure that the gap is uniform without excessive or insufficient local gaps. After adjustment, a trial cutting can be carried out, and fine-tuned according to the threshing effect. For corn harvesters, attention should also be paid to the adjustment of the cob conveying gap to ensure that cobs can smoothly enter the threshing chamber and fully contact with the drum.

3. Control Feeding Amount: Reduce the forward speed of the harvester to avoid excessive feeding amount; adjust the header height to make the header cut crops evenly and ensure uniform feeding; if the crop growth is uneven, adopt segmented harvesting to avoid excessive local feeding. At the same time, clean the blockages in the header auger and conveying trough to ensure that crops are smoothly conveyed to the threshing chamber and avoid accumulation.

(2) Overhaul and Replace Damaged Components

Regularly checking the wear and damage of threshing components, and timely overhauling or replacing them is the basis for ensuring the threshing effect.

1. Check and Replace Threshing Elements: Disassemble the drum and check the wear of ribs and tines. If the ribs are severely worn and the surface is smooth, or the tines are worn, missing or deformed, replace them in time; for repairable components such as slightly deformed ribs, carry out correction treatment to restore their kneading and impact performance. When replacing components, select original accessories matching the equipment model to ensure proper installation and avoid running stuck.

2. Clean and Repair Concave Plate: Clean the straw, soil and other blockages in the sieve holes of the concave plate to ensure smooth sieve holes; check whether the concave plate is deformed or damaged. If it is deformed, carry out correction; if it is severely damaged, replace it in time. At the same time, check the configuration of tines on the concave plate to ensure that the quantity of tines is sufficient and the installation is firm, avoiding threshing dead angles.

3. Overhaul Transmission Components: Check the wear of transmission belts, sprockets and gears, and replace aged and severely worn components; adjust the belt tension to ensure stable transmission; check the drum bearing, and replace it in time if it is loose or damaged to ensure flexible and stable operation of the drum.

(3) Adapt to Operating Conditions and Optimize Operating Methods

Adjusting the operating methods in combination with crop characteristics and operating environment can effectively reduce the problem of incomplete threshing.

1. Choose the Right Operating Time: Try to operate when the crops are fully mature and the water content is suitable, and avoid harvesting when the crops are immature, over-mature, or with dew and rain. Generally speaking, the threshing effect is the best when the crop water content is controlled at 15%-20%; if the crop humidity is high, it can be sun-dried for 1-2 days in advance to reduce the water content before harvesting.

2. Adapt to Crop Characteristics: Adjust equipment parameters and operating methods for different crops. For example, when harvesting small-grain crops such as rice and wheat, appropriately increase the drum speed and reduce the threshing gap; when harvesting corn, ensure that cobs fully enter the threshing chamber, adjust the drum speed and threshing gap to avoid grain breakage and residue. For crops with uneven maturity, adopt batch harvesting, first harvest the areas with high maturity, and then harvest the areas with low maturity.

3. Optimize Operating Environment: Avoid operating in muddy fields with excessive straw. If there is serious straw accumulation in the field, clean it in advance; avoid operating in strong wind weather. If the wind is strong, adjust the wind speed and direction of the cleaning device to ensure effective discharge of impurities and reduce grain blowing. In addition, keep the harvester walking smoothly to avoid poor feeding and uneven stress in the threshing chamber caused by bumping.

III. Daily Preventive Measures for Incomplete Threshing of Harvesters

The prevention of incomplete threshing lies in daily maintenance and standardized operation. Troubleshooting hidden dangers in advance can effectively reduce the occurrence of faults and extend the service life of the equipment.

1. Carry out Regular Equipment Maintenance: Before operation, comprehensively check the threshing components, transmission components and cleaning device of the harvester, clean up blockages, check the wear of components, and replace damaged components in time; during operation, stop and check every 2-3 hours, clean up straw and impurities in the threshing chamber and conveying trough, and check the belt tension and drum operation; after operation, thoroughly clean the straw, soil and impurities on all components of the equipment, lubricate the transmission components and bearings, and store them in a dry and ventilated place to avoid rusting and aging of components.

2. Standardize the Operation Process: Operators should be familiar with the equipment instruction manual, master the parameter adjustment methods, and reasonably adjust the drum speed, threshing gap and feeding amount according to the crop type, maturity, humidity and other conditions; avoid overloading operation and do not blindly increase the forward speed; pay attention to the threshing effect during operation, and if excessive grains remain in the straw, stop and troubleshoot in time, adjust parameters or overhaul components.

3. Strengthen Operator Training: Regularly organize operators to participate in agricultural machinery operation training, improve their understanding of equipment structure and working principle, and master fault troubleshooting and handling methods; cultivate the sense of responsibility of operators, standardize operation behavior, and avoid faults such as incomplete threshing caused by improper operation.

IV. Summary

Incomplete threshing of harvesters is the result of the combined action of multiple factors, and the core lies in the adaptation of equipment parameter adjustment, component status and operating conditions. To solve this problem, it is necessary to first accurately troubleshoot the cause of the fault, and then take targeted measures to optimize parameters, overhaul components and adjust operating methods. At the same time, doing a good job in daily maintenance and standardized operation, and preventing faults in advance can not only improve harvesting efficiency and reduce grain waste, but also extend the service life of the equipment and reduce operating costs. Farmers need to make flexible adjustments according to the actual situation during operation, and deal with problems in a timely manner to ensure the efficient and stable operation of the harvester and successfully complete the harvesting operation.