A Sendzimir mill is a 20-high reversible precision cold rolling mill, mainly used to roll ultra-thin steel strips and non-ferrous metal foils with thicknesses ranging from 0.001 to 1 mm. The mill consists of six main systems: the main drive system, roll system, housing system, screwdown and roll gap adjustment system, lubrication and cooling system, and electrical control system. These systems work together to drive the rolls, transfer rolling loads, adjust the roll gap, control strip tension, and correct strip flatness.
Main drive system
The main drive system supplies power to the rolls and keeps them running at the specified speeds. It mainly consists of the motor and reduction unit, together with the drive spindles.
Motor and reduction unit
The main motor is usually a variable-frequency AC motor or a DC motor with speed control. Depending on the mill specifications, the power of a single motor ranges from 500 to 3000 kW to provide the torque required for rolling.
The gearbox uses a multi-shaft power-splitting planetary gear structure. It reduces the high motor speed to the lower speed required by the rolls while keeping the linear speeds of all 10 upper rolls and 10 lower rolls fully synchronized.
Drive spindles
The drive spindles usually use universal plum-blossom spindles or cross-type universal spindles to transmit rolling torque. They also compensate for positional deviations that occur during roll adjustment, allowing the drive system to accommodate changes in the roll gap and axial position.
For non-standard connecting components and other precision mechanical parts used in rolling mill assemblies, we provide drawing-based custom machining. Hansheng Automation can manufacture these parts according to customer drawings, including the specified materials, dimensions, and machining requirements.
Roll system
A Sendzimir mill uses a 20-roll arrangement. Rolls of different diameters and positions work together to withstand and transfer rolling loads. The roll system consists of work rolls, intermediate rolls, and support rolls. Each group has a different role in load transmission and roll gap adjustment.
Work rolls
Work rolls are the smallest rolls in the roll system and make direct contact with the strip. Their standard diameters range from φ20 to φ80 mm. Available roll surface materials include high-carbon high-speed steel, cemented carbide, and ceramic composites. The surface roughness can be controlled to Ra ≤ 0.05 μm to meet the precision and surface quality requirements of ultra-thin strip rolling.
The upper and lower work rolls are arranged symmetrically and equipped with axial adjustment mechanisms. Adjusting their positions helps compensate for thermal expansion and uneven wear, maintaining parallelism across the roll gap.
Intermediate rolls
The intermediate rolls are divided into first-stage and second-stage groups. They transfer rolling loads and work with other adjustment mechanisms to control the roll gap profile. Their diameters range from φ80 to φ150 mm, and they are made of forged alloy structural steel.
Both stages of intermediate rolls can move axially within a range of ±10 mm. Their axial positions can be adjusted in conjunction with the roll bending system to correct strip flatness.
Support rolls
Support rolls are located on the outermost sides of the roll arrangement. They have the largest diameters in the roll system, typically ranging from φ150 to φ300 mm, and are made of high-strength cast steel or forged steel.
Each side has 8 to 10 support rolls. They support the intermediate rolls and work rolls, transferring the rolling loads through the roll assembly. The multiple support points reduce roll deflection and help maintain rolling accuracy.
Housing system
The housing supports the rolls and related drive and adjustment components. It must withstand the loads generated during rolling. Its main components are the closed-type housing body, housing cover, and locking device.
Closed-type housing body
The housing body is made from cast steel or a welded structure. It has high rigidity and can withstand a maximum rolling load of 10000 kN. The housing window width is customized according to the strip specifications, with a range of 100 to 2000 mm.
High-precision guideways and locating holes are machined inside the housing to position the rolls accurately and reduce roll displacement caused by installation errors during operation.
Housing cover and locking device
The housing cover is made of cast steel and secured to the housing window by a hydraulic locking device. This prevents the rolls from moving out of position during rolling.
The cover also has an observation window and connections for lubrication and cooling media. These features allow operators to inspect the equipment, carry out routine maintenance, and replenish the operating fluids.
Screwdown and roll gap adjustment system
The screwdown and roll gap adjustment system controls the clearance between the rolls. It also changes roll deflection and axial position to regulate strip flatness. The main components are the hydraulic screwdown mechanism, roll bending system, and axial adjustment mechanism.
Hydraulic screwdown mechanism
Most configurations use a servo-hydraulic screwdown system. A servo valve controls the extension and retraction of the hydraulic cylinder to adjust the roll gap. The adjustment accuracy can reach ±0.1 μm, with a maximum adjustment speed of 1 mm/s.
Some small experimental rolling mills use an electric screwdown mechanism with ball screws. The system first makes a coarse adjustment and then uses hydraulic control for fine adjustment, balancing adjustment efficiency and accuracy.
Roll bending system
The bending system includes work roll bending and intermediate roll bending. Hydraulic forces ranging from 0 to 500 kN are applied to both ends of the roll necks to change roll deflection and adjust strip flatness.
The bending force can be adjusted in real time according to the rolling process parameters to control strip shape under different rolling conditions.
Axial adjustment mechanism
The axial adjustment mechanism controls the axial movement of the intermediate rolls, with an adjustment stroke of ±10 mm. By changing the axial position of the intermediate rolls and coordinating the adjustment with the bending system, the mill can correct strip edge thinning and waviness.
Lubrication and cooling system
During rolling, friction between the rolls and strip generates heat. The lubrication and cooling system reduces friction, controls rolling temperature, and maintains proper lubrication of the roll bearings.
Roll surface lubrication and rolling cooling
The work roll surfaces use small-quantity oil-air lubrication or dedicated rolling oil spray lubrication. This reduces the friction coefficient between the strip and rolls, limits roll surface wear, and removes heat generated during rolling.
The mill uses a circulating cooling system with three-stage filtration. Its filtration accuracy can reach 5 μm, reducing the risk of surface scratches caused by contaminants. Emulsion or dedicated rolling oil can be selected as the cooling medium according to the material being rolled.
Bearing lubrication
The rolling bearings of each roll use an oil-air lubrication system to provide lubrication during high-speed operation. The system keeps the bearing operating temperature at ≤60°C, helping extend bearing service life.
Electrical control system
The electrical control system coordinates drive speed, strip tension, and rolling flatness while monitoring the operating condition of the mill. Its main functions include speed and tension control, closed-loop flatness control, and safety protection.
Speed and tension control
The main drive uses a vector-controlled variable-frequency speed control system to synchronize roll linear speeds. Speed control accuracy can reach ±0.01%.
The mill also has a closed-loop tension control system. Tension sensors continuously measure strip tension and transmit the data to the control system, which adjusts the main motor output torque accordingly. This keeps strip tension stable during rolling and helps prevent strip breakage and wrinkling.
Closed-loop flatness control
A flatness gauge installed at the mill outlet collects strip flatness data and sends the signals to the PLC controller. The controller automatically adjusts the bending force and axial movement of the intermediate rolls to correct strip flatness in real time.
The flatness control accuracy can reach a thickness deviation of ±1 μm and a flatness deviation of ±0.5I, where I is the flatness unit.
Safety protection system
The mill has multiple protection functions to monitor conditions such as excessive rolling force, roll gap deviations, abnormal strip tension, and high temperatures. When an abnormal condition occurs, the system automatically triggers an emergency shutdown.
Multiple emergency stop buttons and audible and visual alarms are also installed to protect operators and equipment.
Custom precision machining for industrial equipment
Sendzimir mills contain various mechanical components used in drive connections, roll support, and equipment assembly. Our precision machining services also extend beyond components for rolling mills to parts used in other industries.
Hansheng Automation provides drawing-based custom machining for tobacco and packaging machinery components, filling machinery parts, and precision structural components for yacht equipment and remote-controlled racing cars. Customers can submit their drawings and specify the required materials, dimensions, and machining requirements for custom part production.
