1 The importance of transforming ordinary machine tools
Current market competition is fierce and demand is changing. Ordinary machine tools are no longer suitable for the requirements of multi-variety and mass production. CNC machine tools combine advanced technologies such as CNC technology, PLC control and sensing technology to meet the requirements of batch, high precision and complex shape parts with short production cycle requirements. Only the machining part program needs to be changed to meet different processing objects without any adjustment of the machine tool. For ordinary lathes that have been overhauled several times, the dimensions of their parts have changed significantly, and the main transmission components have been replaced and adjusted many times, but the failure rate still remains high. Traditional repair solutions are difficult to meet processing requirements and maintenance costs are high. It is therefore necessary to transform the CNC system.
In the machining industry, CNC machine tools are increasingly used. The development of CNC machine tools should be comprehensive, efficient, simple and practical, and should have basic functions of automatic processing, easy operation and maintenance.
2 Advantages after CNC transformation
(1) Improve processing precision and production efficiency.
(2) Improve the quality and performance of machine tools to meet the processing requirements of complex shaped parts.
(3) By realizing the automation of mechanical processing, the efficiency can be increased by 2-6 times.
(4) It can reduce the time of frequent transportation of parts between machine tools, reduce positioning errors, and realize process centralization.
(5) Various self-checking functions such as automatic alarm, monitoring and compensation can be realized, and the working status of the machine tool can be monitored.
(6) The use of CNC machine tools can not only reduce the labor intensity of workers, save labor and greatly reduce tooling time, but also shorten the trial production cycle and test cycle new products, allowing a rapid response to market demand.
3 Main problems solved by CNC transformation
(1) Find out the problems existing in ordinary machine tools and restore their functions.
(2) Install a digital display device or CNC system.
(3) Restore mechanical precision.
(4) In the transformation project, there should be innovations in processes and technologies to maximize CNC transformation.
4 Selection of different control systems
4.1 Selection of the servo system
Servo systems are divided into three types: open-loop control systems, closed-loop control systems, and semi-closed-loop control systems. When transforming, you can choose according to the actual situation.
4.2 Drive motor selection
For cost-effective CNC processing, the design uses stepper motors for servo control. The stepper motor is an open-loop control component that converts electrical pulse signals into linear displacement or angular displacement. In normal operation, the speed and stopping position of the motor are determined by the number of pulses and the frequency of the pulse signal. Load changes have no effect on it. When the motor receives a pulse signal, the motor rotates through a pitch angle. Because of this linear relationship, the stepper motor also has periodic errors without accumulated errors. This way it becomes very simple to use a stepper motor to control speed, position, etc.
4.3 Selection of control system
According to a series of conditions such as different actual situations, individual usage habits, modification costs, etc., designers’ choices of CNC systems and PLCs are also different. This requires designers to obtain maximum optimization options under existing conditions.
4.4 Spindle motor selection
The spindle motor should be equipped with corresponding control components, which can realize spindle forward, reverse and stepless control and motor thermal protection. The rotation direction command must be written to the PLC program and the forward rotation relay. Is controlled by PLC output port. Or reverse the relay to actuate the contactor, completing the forward and reverse rotation switching of the spindle. The spindle motor has high power and generates large current when starting. Three contactors are therefore used in the design to complete the star switching of the motor. In order to meet the requirements of thread processing, the encoder is installed on the spindle and the signal is fed back to the PCU unit. In thread processing, the operator must know the spindle speed and calculate the feed speed according to the spindle speed. Therefore, an encoder is installed on the spindle to detect the spindle speed and meet the processing requirements.
Daguang focuses on providing solutions such as precision CNC machining services (3-axis, 4-axis, 5-axis machining), CNC milling, 3D printing and rapid prototyping services.
