Analysis of NC transformation of ordinary lathes
As a typical product of mechatronics, NC lathe is a kind of NC machine tool with the largest usage and the most extensive coverage in the mechanical manufacturing industry. It is mainly used to process various rotating parts such as shafts and disks. It can well solve the machining problems of complex-shaped rotating parts in modern manufacturing, can stabilize the machining quality, and improve labor productivity. However, the price is relatively expensive and the one-time investment is large, which often makes enterprises have more than enough resources. As a machine tool powerhouse in China, the road to numerical control is long, and it is a fast and effective way to save money and implement numerical control on ordinary lathes. The numerical control transformation of ordinary lathes has the advantages of being highly targeted, greatly saving raw materials and funds, and expanding the scope of application of machine tools. Therefore, it is best to take the road of transformation.
(1) Feasibility
Transformation of ordinary lathes into numerically controlled lathes refers to making certain changes to the mechanical structure of certain parts of ordinary lathes, plus numerical control devices, so that ordinary lathes have the ability to numerically control machining.
From the perspective of improving capital efficiency, transforming idle equipment can make use of the original functions of the lathe and the new functions after the transformation to increase the use value of the machine tool; the cost of CNC transformation is low, the investment amount is reduced and the economy is good. The cost of CNC transformation is only 15% of the cost of a new CNC lathe. 25%, compared with the purchase of new lathes, it can generally save 75% to 85% of costs; enhanced functions, such as arc machining, taper machining, which are difficult to achieve by traditional machining methods; short delivery time, can meet production urgent need.
(2) Market Benefits
The market for machine tool numerical control transformation in China still has a lot of room for development. Now the rate of machine tool numerical control in China is less than 3%. Products processed by ordinary lathes generally have poor quality, few varieties, low grades, high costs, and long delivery periods. The society has a large number of ordinary lathes, and transforming such lathes into CNC lathes will receive good economic benefits. There are also many internship factories in schools. If ordinary lathes are converted to CNC machine tools, while reducing costs, it will also facilitate teaching and training.
The Content Of CNC Transformation Of Ordinary Lathes
The main contents of NC transformation of lathes include the following points: First, technological updates or technological innovations. In order to improve performance or grade, or in order to use new processes and technologies, carry out large-scale technical updates or technological innovations on the original basis, and greatly improve the level and grade of renovation; the second is to restore eighteen lathes Accuracy, diagnosis and recovery of existing faults; the third is renovation. In order to improve the accuracy, efficiency and automation, the mechanical and electrical parts are refurbished, the mechanical parts are reassembled and processed to restore the original accuracy, and the CNC systems that do not meet the production requirements are updated with the latest CNCs. The fourth is NCization. Add digital display device on ordinary lathe, or add numerical control system, transform into NC machine tool, CNC machine tool. The specific contents include: the determination of the overall design plan, the transformation design of the machine tool guide rails, and the selection and installation of the automatic rotary tool post.
Choice Of CNC Device
After analyzing the feasibility of the transformation and determining the content of the transformation, a targeted selection of CNC system equipment should be made.
At present, there are many types of CNC systems on the market. Before selecting, you should have a full understanding of the functions of the CNC machine tools you want to transform. You can choose a CNC system based on the principles of reasonable prices, advanced technology, and convenient services. When the economic capacity permits, try to choose brand-name products. This type of CNC system has strict parts selection and reliable manufacturing process specifications, and has excellent preventive effects on equipment failures caused by electrical component failures or early failures. It should also pay attention to the function selection of the CNC system. The high performance index of the numerical control system should not be pursued purely, this is very important to achieve a high performance price ratio. The functions of the CNC system must match the functions of the CNC machine tool to be transformed, and minimize the excessive CNC functions. Because the CNC system has excessive functions, on the one hand, it wastes money; on the other hand, it may also hide the hidden danger of increasing the failure rate caused by the increase in the complexity of the CNC system. There are three main types of CNC systems: open-loop CNC systems, semi-closed-loop CNC systems, and closed-loop CNC systems. During the transformation, the choice should be made according to the specific conditions. In the actual transformation process, open-loop CNC systems and semi-closed-loop CNC systems are usually used.
(1) Open-loop CNC system driven by stepping motor without detection feedback
The main feature of this system is that the control circuit changes the command pulse signal once, and the motor rotates a step angle. The feed command signal output by the numerical control system controls the drive circuit through a ring distributor. It controls the coordinate displacement amount by changing the number of pulses, the displacement speed by changing the frequency of the pulse, and the displacement direction by changing the pulse distribution order. . Therefore, the biggest feature of this control method is easy control, simple structure, and low price. But the mechanical transmission error is not corrected by feedback, and the displacement accuracy is not high. This control method was adopted in the early NC transformations, and the NC devices equipped with this type of control methods were mostly composed of single-chip computers or single triggers, which made the price of the entire control system lower.
(2) Semi-closed-loop CNC system driven by AC / DC servo motor and encoder feedback
Semi-closed-loop system detection element is installed at the end of the servo motor or lead screw to indirectly measure the position of the actuator. It can only compensate the errors of some components inside the system loop. Therefore, its accuracy is lower than that of the closed-loop system, but its structure and debugging are simpler than the closed-loop system. When the angular displacement detection element is integrated with the speed detection element and the servo motor, the installation of the position detection device need not be considered. When selecting a CNC system, it is mainly based on the various accuracy, power of the drive motor and user requirements that the lathe will achieve after the CNC transformation.
Conclusion
After discussion, we believe that the NC transformation of ordinary lathes is an economic and effective way for enterprises and related professional schools to realize NC of industry and teaching. The open-loop CNC system used in the transformation is simple in structure and cheap, but the disadvantage is that the displacement accuracy is not high; relatively speaking, the semi-closed-loop CNC system has higher accuracy than the open-loop control system; and the closed-loop control system is more expensive. Relevant personnel can choose according to their own circumstances.