1, roller length
The length of the roller represents the maximum amplitude of the calenderable product. Because both ends need to reserve positions for placing baffles, the effective length of the roller is the length of the roller minus the length of the non-working surface (about 15% of the roller length).
2. Length-diameter ratio of roller
The ratio of the length to the diameter of the working part of the drum is called the length-diameter ratio. The length-diameter ratio of the roller (or the diameter of the roller) mainly affects the thickness dimension accuracy of the calendered products (except the reducing roller). It is not only related to the performance of calendering material, the material of roller and the length of working part, but also mainly depends on the quality requirements of calendering products.
3. The relationship between drum diameter and transverse pressure and power, length-diameter ratio and stiffness.
The relationship between roller diameter and transverse pressure and power is shown in the figure. The larger the diameter of the drum, the greater the transverse pressure and the greater the required driving power, which is almost linear.
The length-diameter ratio of the roller mainly affects the stiffness of the roller. The figure shows the stiffness ratio of a drum with a diameter of Φ 610 mm under different aspect ratios. As can be seen from the figure, the greater the aspect ratio, the worse the rigidity.
4. Determination of drum length, diameter and length-diameter ratio
The length, diameter and length-diameter ratio of the roller are mainly determined according to the production process requirements of the product, that is, according to the types of raw materials to be processed, the thickness range and width range of the calendered product, and the calendering speed of the roller (that is, the output requirements).
In order to ensure the thickness dimension accuracy of calendered products, according to the actual production experience, the length-diameter ratio of rollers should be limited to the following range (except reducing rollers):
When processing soft materials (such as rubber), the length-diameter ratio is generally 2.5 ~ 2.7. The maximum does not exceed 3;
The length-diameter ratio of the hard material to be processed is about 2.0 ~ 2.2.
Standard series of drum length and diameter: φ 360×1120; φ450 × 1200; φ550 × 1600; φ6 10 × 1730; The roller linear speed of φ7 10× 1800 calender refers to the peripheral speed of the roller, and the unit is "m/min". Roller linear speed is a parameter to characterize the production capacity of calender, and it is also one of the parameters to characterize the advanced degree of calender.
1, drum speed
The roll speed is mainly determined by the technical use of the calender and the automation level of production. The roll speed should meet the requirements of calendering process operation, that is, the roll speed should be adjustable.
The rolling speed in the world generally reaches 50 ~ 90 m/min, and some of them reach 1 15 m/min. The average speed of steel wire calendering can reach 50 m/min, and the average speed of cold calendering can reach 30 m/min when two layers of calendering films are directly pressed on the weft-free steel wire cord fabric.
2. Speed range
The range of stepless speed change of roller is called speed regulation range. Due to the variety of processing materials and great performance differences, in order to meet the requirements of production capacity and slow start-up operation at the same time, the speed regulation range of calender is generally required to be around 10 times.
The maximum speed is mainly determined according to the requirements of production capacity, and the minimum speed is mainly determined according to the safety and convenience of equipment start-up and operation.
3. Speed ratio
Due to the different technological requirements of gluing, wiping or tabletting during calendering, the speed ratio of the roller is also different, and the requirements of different positions on the same calender are different, and the speed ratio is also different.
The speed ratio of the roller is related to the calendering process and material properties.
1) In order to eliminate bubbles in the rubber compound, the general feeding roller has a speed ratio, which is often1:1~1:1.5, which is widely used in China. Soft rubber has a small value.
2) For the rubber wiping operation, in order to make the rubber penetrate into the fabric, the rubber wiping roller needs a speed ratio. The greater the speed ratio, the greater the shear force and the better the rubber wiping effect. However, if the speed ratio is too large, the strength of the textile will be damaged and the rubber will be easily burnt. However, if the speed ratio is too small, the permeability of the compound will be poor. 1:1.2 ~1:1.5 is generally adopted, and1:1.5 is mostly used in China.
3) For tabletting, gluing, gluing and other operations, constant speed calendering is generally adopted because extrusion force is mainly needed, and the speed ratio is 1: 1.
4. Factors to be considered when selecting roll speed
Roller speed directly affects the power consumption and production capacity of calender. The higher the roll speed, the greater the power and output, and the higher the requirements for the mechanization and automation level of the calender. Therefore, when selecting the roller speed, we should consider:
1) calendering process requirements;
2) The manufacturing level of calender;
3) Automation level of calendering unit.
4) The roll speed should be adjusted smoothly in a wide range;
5) When calendering, the roll speed should be as high as possible, which is beneficial to give full play to the equipment capacity.
It can be seen that the roll speed marks the advanced level of the calendering unit.
Because the motors are used to drive the rollers respectively, the speed ratio between the rollers can be adjusted at will within a certain range (from 1: 1 to as high as 1: 1.3), so that various operations can be completed on one calender, which makes the machine more adaptable and is beneficial to improving the roller speed. (A) the characteristics of lateral pressure
1, the concept of transverse pressure: When rubber material passes through the gap between rollers, radial force and tangential force are generated on the rollers. The radial force is perpendicular to the roller surface and tries to separate the roller. This force is called lateral pressure, also called separation force.
2. Lateral pressure characteristics of roller.
When the rubber compound passes through the nip of the calender, the thickness of the rubber compound gradually decreases from large to small, and the pressure gradually increases, as shown in the figure.
1) In Zone A and Zone B, the passing speed of rubber compound is slower in the center of the nip and the fastest on both sides. However, with the progress of rubber compound, this speed difference gradually decreases.
2) When reaching point B, the speed of each part is the same and the pressure reaches the maximum.
3) When it reaches the roll gap, that is, point C, the mixing speed in the center of the roll gap is higher than that on both sides of the roll gap, the pressure gradually decreases and the film thickness increases.
4) Until the film thickness at point d no longer increases, the pressure drop of rubber mixture on the roller is zero.
It can be seen that the transverse pressure of rubber compound in the nip is uneven, and the maximum value appears slightly in front of the nip.
(2) Factors affecting lateral pressure
There are many factors that affect the lateral pressure during calendering, the main aspects are:
1, types and properties of processing compounds;
Different kinds of rubber have different transverse pressures, and different hardness and viscosity of the same rubber have different transverse pressures. The greater the hardness and viscosity, the greater the lateral pressure.
2. Thickness of calendered products;
The thinner the product thickness, the smaller the roll gap and the greater the separation force. When the roll gap is extremely narrow, a great separation force will be generated between the rolls. This is because the smaller the nip, the thinner the product thickness, the rigid extrusion between rollers and the sharp rise of separation force. From the point of view of maintaining the roller, this is absolutely not allowed by the general calender.
3. Roller diameter and calendering width.
The greater the roller diameter and calendering width, the greater the transverse pressure.
4, the size of the angle of the glue (that is, the amount of material stored at the entrance);
The larger the wrap angle, the larger the working surface of the drum and the greater the lateral pressure.
5, the speed of the roller;
The relationship between roll speed and transverse pressure is complicated.
1) When the roller speed increases, the amount of rolled melt per unit time increases, resulting in an increase in transverse pressure;
2) With the increase of roll speed, the friction and heat production of molten material increase, and the increase of temperature leads to the decrease of viscosity of molten material and the decrease of transverse pressure;
3) The increase of roller speed increases the pressure, thus increasing the lateral pressure, etc.
Therefore, the relationship between roller speed and separation force is the result of several aspects. According to the actual measurement, with the increase of roller speed, the lateral pressure increases slowly.
6, the temperature of the drum
The higher the processing temperature of the drum, the lower the viscosity and fluidity of the material, and the smaller the transverse pressure. On the contrary, the bigger.
7. Glue adding method (continuous or intermittent);
When the sheet or strip material is used for swing feeding, the feeding is continuous and uniform, and the impact on the roller is small, and the lateral pressure fluctuation is small. Z When bulk materials are used, the intermittent feeding is uneven, which has a great impact on the roller and the lateral pressure fluctuates greatly. 1, transmission power:
The transmission power of calender refers to the power required to drive the roller of calender. Its characteristics are as follows:
1) has high transmission power. Because the calender is a heavy machinery, and the roller has high speed and high transmission power.
2) Power consumption is relatively stable. Moreover, because the rubber processed on the calender has been preheated and softened, the transverse pressure is small, and the rubber passes through the roll gap once, and the deformation of the rubber before and after calendering is not great, so the operation is relatively stable. Therefore, the power consumption of the calender is relatively stable, unlike the peak load of the open mill.
2. Power calculation:
Power consumption is also an important parameter in calender design, which is difficult to be accurately obtained by theoretical formula. This paper briefly introduces the approximate calculation of several empirical formulas:
1) Power calculation when driven by a single motor.
A, according to the roller linear speed calculation
N =a L v
Where a is the calculation coefficient.
L—— the length of the working part of the drum
V- calendering linear velocity
B. according to the number of rollers
N=K L n
Where k is the calculation coefficient.
L—— the length of the working part of the drum
N- number of rollers.
The same disadvantage of the above two formulas is that the performance and processing method of the processed rubber compound and the influence of roller diameter on power are not considered, and their influence on power consumption is very great. It can be seen that the above two formulas are one-sided.
C. Analogical calculation
With the help of some known machine characteristics and power consumption, calculate the calculation coefficients A and K, and then use the above formula to calculate the power of the designed (unknown) calender.
2) Power calculation when driving multiple motors
The power consumed by a calender is different in the calendering process, which is because the position of each roller is different, the process uses are different, and the rotating linear speed is different. Under normal circumstances, the feed roller consumes more energy than the laminating roller.
A. When calendering, the power consumed by the two rollers is directly proportional to the linear speed of the rollers.
If the linear speeds of the two rollers are V 1 and V2, and the power is N 1 and N2, respectively, then:
N2 = = V2
B. The power consumed in the gluing process only accounts for 6% of the total power.
N paste =0.06N total η
Where n- power of rubber roller,
N total effective total power,
η-total transmission efficiency.
According to the above two points, the power occupied by each roller can be calculated.