- Mechanical structure
Workbench structure: The workbench of a surface grinder is usually a high-precision rectangular or circular workbench. Taking a rectangular workbench as an example, its motion accuracy requirements are extremely high, and high-precision guide rails such as rolling guide rails or hydrostatic guide rails are generally used. Rolling guide rails achieve linear motion of the workbench through the rolling of rolling bodies (balls or rollers), with a small friction coefficient, which can ensure the motion accuracy and speed uniformity of the workbench. Hydrostatic guide rails use pressure oil to form an oil film between the guide rail surfaces to float the workbench. This method can obtain wear-free, high-precision motion and can withstand large loads. When performing grinding processing, the workbench also needs to have stable reciprocating motion, which is usually driven by a hydraulic system or a ball screw transmission mechanism to achieve precise position control.
Grinding wheel frame structure: The grinding wheel frame is a key component of a surface grinder. It is mainly used to install and drive the grinding wheel. The spindle precision of the grinding wheel frame is very high, and high-precision bearings such as hydrostatic bearings or angular contact ball bearings are generally used. The hydrostatic bearing forms an oil film between the inner and outer rings of the bearing through the external pressure oil supply, so that the spindle is suspended in the oil film, thereby greatly reducing the rotation friction of the spindle, improving the rotation precision, and realizing the high-speed and high-precision rotation of the grinding wheel. The angular contact ball bearing ensures the axial and radial stiffness of the spindle through reasonable preload setting to meet the precision requirements of grinding processing. The grinding wheel frame is also equipped with a balancing device for the grinding wheel, because when the grinding wheel rotates at high speed, if it is unbalanced, it will vibrate and affect the quality of the processed surface. The balance state of the grinding wheel can be adjusted through the balancing device.
Bed structure: The bed of the surface grinder is the basic supporting component of the entire machine tool. It is generally made of high-quality cast iron materials, such as HT300, which has good shock absorption and stability. The structural design of the bed must ensure sufficient rigidity to resist the cutting force generated during the grinding process. In order to improve the rigidity of the bed, a box-type structure or a reinforcing rib design is usually adopted. The box-type structure has multiple compartments inside, which can effectively disperse stress; the reinforcing ribs are raised ribs added to the key parts of the bed to increase the bending and torsion resistance of the bed.
Ordinary machine tools (taking ordinary lathes as an example)
Bed and guide rails: The bed of an ordinary lathe is generally made of cast iron, but its precision requirements are slightly lower than those of a surface grinder. The guide rails of a lathe are mainly used to support and guide the movement of the tool holder and tailstock. Common ones are sliding guide rails. The sliding guide rail achieves movement through sliding friction between the guide rail pairs. Its structure is relatively simple and the cost is low. However, compared with the high-precision guide rails of a surface grinder, its movement accuracy and friction characteristics are slightly worse. The shape of the lathe bed is generally designed according to the type of lathe (such as horizontal lathes, vertical lathes, etc.). The bed of a horizontal lathe is usually a horizontal long strip to accommodate the rotation of the workpiece and the longitudinal and lateral feed movement of the tool.
Spindle box and tailstock: The spindle box is one of the core components of the lathe, which is mainly used to install and drive the spindle. The lathe spindle generally uses ordinary rolling bearings, and its accuracy and speed are slightly lower than the surface grinder grinding wheel frame spindle. The spindle box contains multiple transmission gears to achieve different spindle speeds to meet different processing requirements. The tailstock is mainly used to provide auxiliary support when processing long shaft parts. It can move along the bed rails and be fixed at the required position. Its structure is relatively simple, mainly composed of sleeves, tops and other parts.
Tool holder structure: The tool holder of an ordinary lathe is used to install turning tools. Common ones are square tool holders or turret tool holders. The movement of the tool holder is mainly achieved through manual or electric feed mechanisms to achieve lateral and longitudinal feeds to cut the rotating workpiece. The accuracy of the tool holder is mainly reflected in the installation accuracy and feed accuracy of the tool, but its accuracy requirements are generally lower than the accuracy of the workbench and grinding wheel frame of the surface grinder.
- Circuit construction
Motor control circuit: Surface grinders usually have multiple motors, including grinding wheel motors, table drive motors, cooling pump motors, etc. The grinding wheel motor is the key power source. Since the grinding wheel needs to rotate at high speed, the grinding wheel motor is generally a high-speed motor, and has high requirements for the motor’s speed stability and torque characteristics. The motor control circuit needs to accurately control the speed of the grinding wheel motor, usually using variable frequency speed regulation or DC speed regulation technology. For example, the use of a frequency converter can conveniently adjust the speed of the grinding wheel motor according to the different requirements of the grinding process, ensure the constant linear speed of grinding, and improve the processing quality. The control circuit of the table drive motor must realize the precise reciprocating motion control of the table, generally through a programmable logic controller (PLC) or a numerical control system to achieve precise control of position and speed. The control of the cooling pump motor is relatively simple, mainly to realize the start and stop of the motor to provide coolant circulation during the grinding process.
Electrical safety circuit: The electrical safety of the surface grinder is crucial. Because during the grinding process, the operator may come into contact with the moving parts and grinding wheels of the machine tool, there is a greater safety risk. Therefore, the electrical safety circuit of the surface grinder includes emergency stop button, safety light curtain, limit switch, etc. The emergency stop button is generally installed in a conspicuous position of the machine tool. Once pressed, it can immediately cut off all power sources of the machine tool and stop the operation of the machine tool. The safety light curtain uses infrared sensing. When the operator’s hand or other parts of the body block the light curtain, it will trigger the safety circuit and stop the dangerous actions related to the machine tool. The limit switch is used to limit the range of motion of components such as the workbench and the grinding wheel frame to prevent them from exceeding the limit position and causing collision damage.
CNC system circuit (if it is a CNC surface grinder): The circuit of the CNC surface grinder also includes a complex CNC system circuit. The CNC system controls the various motion axes of the machine tool through programming to achieve complex grinding trajectories. It includes parts such as CNC devices, servo drives and servo motors. The CNC device is the core of the CNC system. It receives programming instructions and converts them into electrical signals and sends them to the servo drive. The servo drive accurately controls the rotation angle and speed of the servo motor according to the received signal, thereby achieving high-precision movement of components such as the grinding wheel frame and the workbench. For example, when grinding a surface with a complex shape, such as grinding a workpiece with a curved contour, the CNC system can accurately control the relative position between the grinding wheel and the workpiece according to the pre-written program to achieve high-precision processing.
Ordinary machine tools (taking ordinary lathes as an example)
Spindle motor control circuit: The spindle motor of an ordinary lathe is mainly used to drive the workpiece to rotate, and its control circuit is relatively simple. Generally, the motor starter (such as a contactor) is used to realize the start, stop and forward and reverse control of the motor. The speed of the motor is usually adjusted by a mechanical transmission mechanism such as a gearbox, and there is a certain level of speed selection, unlike the surface grinder grinding wheel motor, which requires high-precision speed regulation. For example, an ordinary lathe may have several fixed spindle speeds, such as 450r/min, 710r/min, 1400r/min, etc., and the appropriate speed is selected by manipulating the speed change handle to adapt to the processing of workpieces of different diameters and materials.
Feed motor control circuit: The feed motor of the lathe is used to control the lateral and longitudinal feed movement of the tool holder. The control circuit of the feed motor generally uses simple control elements such as contactors to realize the start, stop and direction control of the motor. The feed amount is mainly adjusted by the feed box and lead screw in the mechanical transmission mechanism, and its accuracy and control complexity are lower than those of the surface grinder. In some old-fashioned ordinary lathes, the feed movement is even realized by manual operation. The operator controls the feed of the tool holder by shaking the handle. The feed accuracy of this method mainly depends on the operator’s experience and skills.
Lighting and cooling circuit: The circuit of an ordinary lathe also includes a lighting circuit and a cooling circuit. The lighting circuit mainly provides sufficient light for the working area of the machine tool to facilitate the operator to observe the processing situation. The cooling circuit is used to drive the cooling pump to provide coolant for the tool and workpiece during the processing process to reduce the cutting temperature and extend the tool life. This part of the circuit is relatively simple, usually a simple motor start and stop control.
