I. Main Classifications of Controllers
A controller is a command device that controls the starting, speed regulation, braking, and reversing of a motor by changing the wiring of the main circuit or control circuit and changing the resistance value in the circuit according to a predetermined sequence. It consists of a program counter, instruction register, instruction decoder, timing generator, and operation controller. It is the "decision-making body" that issues commands, that is, it coordinates and directs the operation of the entire computer system.
Controllers are divided into combinational logic controllers and microprogrammed controllers, each with its own advantages and disadvantages. Combinational logic controllers are difficult to design and have complex structures; once designed, they cannot be modified or expanded, but they are fast. Microprogrammed controllers are easy to design and have simple structures; they are easy to modify or expand. To modify the function of a machine instruction, only the corresponding microprogram needs to be rewritten; to add a machine instruction, only a microprogram needs to be added to the control memory, but it is done by executing a microprogram. A detailed comparison is as follows: Combinational logic controllers, also known as hardwired controllers, are composed of logic circuits and rely entirely on hardware to implement the functions of instructions.
II. Application Settings of Stepper Motor Controller
1. Set the microstepping value of the stepper driver. Generally, a higher microstepping value results in higher control resolution. However, too high a microstepping value will affect the maximum feed speed. Generally, for mold making machine users, a pulse equivalent of 0.001mm/P (maximum feed speed 9600mm/min) or 0.0005mm/P (maximum feed speed 4800mm/min) can be considered. For users with lower precision requirements, the pulse equivalent can be set higher, such as 0.002mm/P (maximum feed speed 19200mm/min) or 0.005mm/P (maximum feed speed 48000mm/min). For two-phase stepper motors, the pulse equivalent is calculated as follows: Pulse equivalent = Lead screw pitch ÷ Microstepping value ÷ 200.
2. Start-up Speed: This parameter corresponds to the start-up frequency of the stepper motor. The start-up frequency is the highest frequency at which the stepper motor can start working directly without acceleration. Properly selecting this parameter can improve machining efficiency and avoid the low-speed range where the stepper motor's motion characteristics are poor; however, if this parameter is too high, it will cause the machine to stall, so a margin must be left. The motor's factory specifications usually include the start-up frequency parameter. However, this value may change after the machine tool is assembled, generally decreasing, especially when performing load-bearing movements. Therefore, this setting parameter is best determined by actual measurement after referring to the motor's factory specifications.
3. Single-axis acceleration: This describes the acceleration and deceleration capability of a single feed axis, measured in millimeters per second squared. This indicator is determined by the physical characteristics of the machine tool, such as the mass of the moving parts, the torque of the feed motor, resistance, and cutting load. A higher value means less time is spent in the acceleration and deceleration process, resulting in higher efficiency. Typically, for stepper motors, this value is between 100 and 500, while for servo motor systems, it can be set between 400 and 1200. When setting this value, start with a lower setting, run the machine for a period of time, repeat various typical movements, and observe carefully. If no abnormalities are found, gradually increase the value. If any abnormalities are detected, decrease the value, leaving a 50% to 100% safety margin.
4. Cornering Acceleration: This describes the acceleration and deceleration capabilities of multiple feed axes operating in tandem, measured in millimeters per second squared. It determines the maximum speed of the machine tool during circular motion. The higher this value, the greater the maximum permissible speed during circular motion. Typically, for machine tools with stepper motor systems, this value is between 400 and 1000, while for servo motor systems, it can be set between 1000 and 5000. For heavy-duty machine tools, this value should be lower. During the setting process, start with a lower value, run the machine for a period of time, repeat various typical linked movements, and observe carefully. If no abnormalities are found, gradually increase the value. If abnormalities are found, decrease the value, leaving a 50% to 100% safety margin. Considering the driving capacity of the stepper motor, the friction of the mechanical assembly, and the load-bearing capacity of the mechanical components, the maximum speed of each axis can usually be modified in the manufacturer's parameters to limit the maximum speed of the three axes during actual use by the machine tool user.
