Roll Grinder

The roll grinder is a metal cutting machine that consists of a bed, head frame, tailstock, bracket, vertical and horizontal carriage, grinding head, measuring frame, and an electric numerical control system. The machine is divided into five subsystems, including a load-bearing system, drive system, grinding system, and measuring system.

The workpiece is supported by the headstock, tailstock, and bracket and rotated by the headstock. The numerical control system controls the machine’s multi-axis movement according to the mathematical model of the roll surface, allowing for the grinding of the metal on the roller surface during the movement process.

The online measurement system provides real-time feedback of measurement data to the grinder control system, which performs closed-loop control on the machine to ensure precise machining of the workpiece.

Model

The main types of roll grinders include: MK8440, MK8450, MK8463, MK8480, MK84100, MK84125, MK84160, MK84200, MK84250, and MK84300.

Application

• Multi-roll mill
• Aluminum foil rolling mill
• Film industry
• Printing industry
• Coating roll
• Roll manufacturing
• Special application

Structure Introduction

Bed Frame

The bed structure separates the grinding wheel bed from the workpiece bed. The bed adjustment horn is short in pitch and has strong rigidity, making it less likely to change the bed’s accuracy.

The grinding wheel bed is a wide-body bed with a rail spacing of 1200mm. It is equipped with a telescopic stainless steel shield to prevent rusting. The precision ball screw installed in the grinding wheel bed drives the large carriage along the Z-axis.

Head Frame

The three-stage V-belt transmission provides smooth and accurate transmission. The AC spindle motor drive allows the headstock to rotate in both forward and reverse directions.

The head frame’s position control function allows for automatic dial angle positioning, making it easier to lift the rolls and reducing the need for auxiliary time. The headstock lubrication system uses a grease pump for automatic, timed oiling.

Tailstock

The tailstock movement uses electric drive mode and is automatically locked by hydraulic pressure. The tailstock is equipped with a large stroke (1000mm) hydraulic sleeve.

Wheel Spindle System

The grinding wheel spindle’s front and rear bearings use high-precision dynamic and static pressure bearings, and the spindle’s axial direction uses high-precision thrust bearings. The design of the rear bearing enhances the static pressure effect of the working chamber hydrostatic bearing to prevent damage caused by the large belt tension on the bearing bush.

The spindle’s dynamic and static pressure bearing offers high rotation precision, stability, strong dynamic rigidity, and low vibration.

Grinding Frame and Its Feeding Mechanism

The grinding frame uses a single-layer integral structure for high rigidity. The grinding frame rail uses plastic static pressure. The feed mechanism for the grinding frame consists of a Siemens AC servo motor with a reduction gear and a precision ball screw pair that is pre-stretched for high feed accuracy and sensitivity.

Carriage Z axis

The carriage uses a V-shaped plastic static rail. The carriage feed mechanism consists of a Siemens AC servo motor with a reduction gear and a precision ball screw pair that is pre-stretched. The NC system controls the carriage’s position through closed-loop control using the AC servo motor and circular grating.

The carriage is driven by a ball screw, which offers advantages over traditional rack and pinion transmission used by similar grinders. These advantages include a shorter mechanical transmission chain, smoother motion, higher transmission precision, and smaller clearance.

Servo Motor and Its Control System

The grinding machine uses Siemens full digital AC servo motors for all servo motor applications, providing high precision and reliability.

Head Frame Control System

The head frame is driven by a Siemens 1PH7 AC spindle motor and equipped with a Siemens Sine/Cos1Vpp and 2048 S/R photoelectric encoder for closed-loop control of the head frame’s speed and position. The headstock allows for both forward and reverse rotation and automatic dial angle positioning.

The use of the AC spindle motor significantly reduces maintenance work on the headstock motor. Due to the characteristics of the roll drive, the head frame uses an AC spindle motor with a low rated speed and high starting torque, which conserves energy while ensuring the start of heavy-duty rolls.

Wheel Control System

The grinding wheel is driven by a Siemens 1PH7 AC spindle motor and equipped with a Siemens Sine/Cos1Vpp and 2048 S/R photoelectric encoder for closed-loop control of the grinding wheel’s speed and position. The grinding wheel allows for both forward and reverse rotation and automatic angular positioning.

The use of the AC spindle motor makes maintenance of the grinding wheel motor more convenient. The grinding wheel uses an AC spindle motor with a capacity of up to 100KW, ensuring strong grinding ability and the ability to handle rapid and large load processing requirements.

Electrical Control Cabinets

To ensure the overall reliability of the grinding machine’s electrical system, the electrical control cabinet casing, power distribution system, protection components, switching components, and control components all use imported, internationally renowned brand products such as Siemens and Rittal.

U1 Axis

The U1 shaft drive system is powered by a Siemens AC servo motor with a right-angle reducer, driving an eccentric drive that operates the center frame’s upper slide through a connecting rod. The tailstock end center frame has two layers, with the lower base layer able to move longitudinally along the bed rail. The upper slide plate can be horizontally adjusted (adjustment amount of 1.5) under the U1 axis drive to correct the roll installation accuracy.

The center frame slide’s special design allows for easy replacement of the center frame seat mounted on the skateboard, significantly reducing the auxiliary time required for seat replacement, and is particularly suitable for supporting rolls of various sizes.

CNC System

The CNC host uses Siemens’ new generation all-digital control system 840D, which integrates a S7-300 programmable controller. The I/O contacts outside the machine are transferred to the central control system through the PROFIBUS industrial fieldbus. The human interface function is handled by the high-performance SINUMERIK PCU50 module.

Compared to the industrial computer-specific system used by similar grinding machines abroad, the 840D system is more powerful, reliable, and easier to maintain. This is because the 840D system has been extensively tested by thousands of users and has been continuously improved by Siemens over many years.

The versatility of the 840D system makes maintenance of the grinding machine extremely convenient, and all electrical components can be readily purchased on the market. The grinder’s electrical system does not have the common “black box” problem encountered with imported grinders.

Human Machine Interface

The display uses a Siemens 15-inch LCD monitor OP15, with the ability to display both Chinese and English, and operates using the MS-WINDOWS XP operating system. The system has comprehensive alarm and diagnostic functions, as well as a wealth of help and operation tips. The well-designed screens and operating menus are easily mastered by both operators and maintenance personnel.

Measuring Frame System

The measuring arm guide rail uses imported linear guides from STAR. The transmission system is powered by a Siemens AC servo motor with a speed reducer and driven by a keyless connection to a precision ball screw that has been pre-stretched. The CNC system controls the measuring frame’s position through closed-loop control using the AC servo motor and linear encoder.

The measuring frame uses linear guide rails and ball screw drive, which offers advantages over the rack and pinion transmission used by similar grinders. These advantages include smoother motion, higher transmission precision, good sensitivity, and accurate positioning, greatly improving the accuracy of the measuring system.

High-precision CNC Curve Grinding Device (U-axis)

The device uses a static pressure eccentric sleeve structure with a spindle dynamic and static bearing. The transmission system is powered by a Siemens AC servo motor with a speed reducer and driven by a keyless connection to a precision ball screw. The linear guide rail moves the ball nut up and down to drive high-precision static pressure biasing for small angle swings. The grinding wheel spindle in the static pressure eccentric sleeve makes a slight gap-free incision or withdrawal movement relative to the roller surface.

This movement is combined with the carriage’s (Z-axis) movement to grind the desired curve on the roll surface. The specially designed transmission structure ensures the drive system is always in a gap-free state, resulting in high curve grinding accuracy.

Roll Grinding

(1) Grinding wheel speeds:

• Fine grinding of steel rolls: 25 to 35 m/s
• Rough and fine grinding of chilled cast iron rolls: 20 to 25 m/s
• Super fine grinding and mirror grinding: 15 to 20 m/s

(2) Workpiece (roller) speeds:

• Coarse grinding: 30 to 50 m/min
• Fine grinding: 15 to 30 m/min
• Precision polishing: 10 to 15 m/min

Note: When grinding slender rolls, low speeds should be used, particularly when grinding calender rolls with small roll size, the workpiece speed should be less than 10 m/min.

(3) Carriage longitudinal feed rate:

• Rough grinding: 240 to 600 m/min or 2/3 to 3/4 of the grinding wheel width per workpiece.
• Fine grinding: 80 to 200 m/min or 1/4 to 1/2 of the grinding wheel width per revolution of the workpiece.

(4) Pallet cross feed amount:

• Depending on the hardness of the roller and the diameter of the grinding roller surface, the cross feed amount per reciprocating stroke should be 0.03 to 0.05 mm.
• For rolls with a hard material and large roll neck, the cross feed should be reduced.
• Fine grinding: 0.005 to 0.01 mm/reciprocating stroke.
• Precision polishing: 0.002 to 0.005 mm/reciprocating stroke.