The main reason for the noise of the roller mill and its noise reduction measures

The roller mill is the main equipment for grinding corn, wheat or miscellaneous grains. Its main component is a pair of grinding rollers whose surfaces have a speed difference and rotate in opposite directions. When the material passes between the two grinding rollers, the endosperm is peeled off from the husk and ground into flour by extrusion, shearing, and scraping, and the noise of the mill is generated. It is inevitable to generate noise in the working project of the roller mill, but how to reduce the noise and control it to a minimum is an eternal task for the users and manufacturers of the roller mill, and it is also a requirement for the quality.

The main reason for the noise of the roller mill.

The noise of the roller mill is not only related to the material, manufacture, and assembly of the parts but also has a close relationship with the rationality of the structural design.

1. Equipment manufacturing

(1). The unreasonable design of the body structure and the low processing precision will result in noise.

(2)When the two parallel grinding rollers have opposite rotation, the rolling distance (gap) between the two grinding rollers is very small in the closed state. Generally, the rolling distance of the skin grinding system is 0.1~0.8mm, and the core grinding system is 0.01~0.05 mm. Due to the manufacturing error of the grinding roller, its radial runout is relatively large, the operation is not stable and the vibration is generated. Two grinding rollers are not calibrated, Unsmooth running and noise when grinding.

(3)The grinding roller is processed by pressing both ends of the roller body into the shaft head. The roller body is made of double: metal centrifugal casting, the outer layer is high-hardness chilled alloy cast iron, and the inner layer is gray iron. The grinding roller body is long (300~1000 mm), and the inner holes at both ends are processed but the middle is not processed. Due to the processing error of the grinding roller and the uneven material of the roller body, the grinding roller is unbalanced and vibrates.

(4)The low positioning accuracy of the grinding roller, the improper selection and adjustment of the bearing, and the unreasonable design of the parts and structures matched with the bearing will cause the bearing to have low rotation accuracy, short service life, and increased noise under load.

(5)Due to the machining error of the fast and slow roller drive wheel, the wheel is unbalanced and vibrates. In addition, the tension of the belt is too large, and a huge shock occurs when it is started. The diameter of the grinding spring between the fast roller and the slow roller is small, and the strength and rigidity are not enough. Unstable operation under load produces noise.

2. Operation problems

(1)The smooth roller generates a lot of heat during grinding, which increases the temperature of the grinding roller, and the roller body expands. The maximum heat is generated near the bearing, and the diameter of the two ends expands more than the middle; the grinding roller has a slight bending strain under the grinding pressure. The above reasons make the two ends of the grinding roll protrude more than the middle, and the rolling distance at both ends is tight and the middle is loose during production, which makes the grinding effect on the entire length of the grinding roll uneven, and the noise increases during grinding.

(2)When the two grinding rollers grind relative to each other, due to the certain humidity of the material, the roller sticks locally, and the surface of the roller body forms a circle, and the grinding brush cannot be cleaned in time, resulting in vibration.

(3)When the material passes through the feeding mechanism, the material is fed along the entire length of the feed roller, and the thickness of the material layer is not uniform. In addition, the incoming material is unstable, and the time is long and the time is short, which affects the grinding effect and produces a lot of noise.

3. Effective measures to reduce the noise of the roller mill

For the above reasons, take corresponding measures and methods to reduce noise.

（1）Reduce the noise caused by grinding roller mills

Strict requirements are put forward for the cylindricity and outer circle runout error of the grinding roller, and the processing method of CNC lathe and CNC grinding is used to control the outer circle runout of the grinding roll within 0.02 mm.The smaller the runout, the higher the precision and the smaller the vibration.

（2）Dynamic balance of grinding rollers

Strict requirements should be put forward for the dynamic balance of the grinding roller. After the grinding roller is processed, the action balance experiment must be carried out before it can be assembled. The unbalanced allowable amount is less than or equal to 5g. The smaller the dynamic balance error, the smaller the vibration of the grinding roller.

（3）Step Design of Roller mill Bearings

The step design of the grinding roller bearing is improved, and the grinding roller bearing and the grinding roller shaft head are directly connected with a conical surface to improve the rotation accuracy of the grinding roller, thereby reducing the noise.

（4）Improve roller mill material

Improve the stiffness, strength and damping of grinding rollers. Improving the rigidity and strength of the grinding roller can increase its natural frequency and make it less prone to resonance. The material of the grinding roller shaft head can be made of alloy quenched and tempered steel (usually 45 steel), because the quenched and tempered steel has high heat resistance and wear resistance and high strength and good plasticity and toughness, that has good comprehensive mechanical. Increasing the damping can make the vibration attenuated quickly. The easiest way is to groove the end face, glue the rubber, or drill the muffler hole in the end face of the roller body.

（5）Roller mill brush design

Improve the structure design of the grinding roller brush (automatic clutch), in the closed state, the grinding brush is always in contact with the grinding roller, and the flour on the roller body is removed in time.in the off state, the grinding brush automatically leaves the roller body, thereby reducing the friction between the grinding roller and the grinding brush, reducing the noise, and improving the service life of the grinding roller and the grinding brush.

（6）Adjust the size of the feeding gate to keep feeding evenly

With the amount of material in the feeding barrel, the opening size of the feeding door is automatically adjusted by the mechanical sensing and air control system to keep the feeding uniform (floating feeding), thereby reducing noise.

（7）roller mill cover

The roller mill adopts a glass fiber reinforced plastic casing, and some sound-absorbing materials are added to the casing to reduce noise.

（8）Roller Mill installation

Correct installation of the pulverizer can also reduce vibration and noise. The method is as follows: after the mill is installed in the flour mill, use a spirit level to make it relatively flat with the fast roller as the benchmark. After it is flat, ensure that the machine has no signs of swinging. The bottom of the machine should be installed with skids and rubber shock-absorbing pads, and finally fixed with anchor bolts.

The above are some effective noise reduction measures, which have certain reference and use value, and have a positive effect on improving noise pollution. Our company Hongdefa Machinery believes that it is necessary to improve the grinding effect of the mill and reduce noise hazards. Therefore, our technical team analyzes and studies the milling equipment, and combines practical experience to propose a series of noise reduction measures and apply them to actual operations. protect the physical and mental health of workers and the public.