Key points of CNC transformation and mechanical structure design for ordinary lathes

Lathe is a key tool in mechanical processing, which can process a variety of workpieces. With the continuous improvement of mechanical processing technology, CNC lathes have gradually replaced traditional lathes. So, in the face of this development situation, many processing enterprises have started to innovate mechanical processing technology. In order to fully utilize ordinary machine tools, it is necessary to achieve scientific CNC machine tool transformation. However, in order to improve the CNC machining effect of the renovated machine tool, it is necessary to design the mechanical structure of the machine tool reasonably and achieve the goal of popularizing the use of CNC machine tools.
1, Analysis of the overall plan for the mechanical structure transformation of ordinary lathes
1. Conduct a thorough process analysis
For ordinary lathes, their main function is to process threaded parts and rotary parts, and the types of parts are diverse. Different parts require different shapes and technical standards, and the processing methods need to be targeted and personalized. There are also certain differences in the requirements after lathe transformation. Therefore, before carrying out mechanical structure transformation, it is necessary to scientifically analyze the overall process, accurately calculate the cutting force and cutting power, and understand the corresponding parameter indicators required for the feed system and spindle.
2. Master the original lathe data
During the transformation of the lathe, some parts may be removed, and it is often necessary to add new parts accordingly. Therefore, it is important to grasp the dimensions and connection methods of related parts. Before the formal transformation of the lathe, it is necessary to have a comprehensive understanding of the corresponding parameter indicators. Considering the current defects of the lathe, problems can be solved in a timely manner in future transformation operations. In addition, other indicators that need to be clarified include the actual load of the lathe, component stiffness, overall machine stiffness, etc., to ensure effective enhancement of performance and accuracy after the lathe transformation.
3. Develop an overall renovation design plan
After comprehensively analyzing and mastering the current situation and technical process of the lathe, it is necessary to determine the model and quantity of parts that need to be applied during the transformation period according to the existing specifications of the lathe. During the process of transforming the mechanical structure, the main tools used include tool holders, bearings, screw nuts, and screws. During the electrical renovation period, it is necessary to apply strong electrical components, frequency converters, and drive motors. For example, when renovating an ordinary lathe with numerical control, it is necessary to analyze key technical parameters, scientifically select stepper motors and ball screw pairs, and propose practical renovation plans.
2, Mechanical structure in CNC transformation of ordinary lathes
design scheme
1. Transformation objectives
Taking the numerical control transformation of CQ6123 lathe as an example, the design quality level of mechanical transmission components is closely related to the surface smoothness of the workpiece and the machining accuracy of the lathe. During the CNC transformation of ordinary lathes, it is necessary to comprehensively analyze various factors, such as capital investment and transformation technology, to fully ensure that the transformed lathe system can meet the following standards.
(1) Maintain the main transmission system in a constant state, remove the thread machining system, and the modified lathe will no longer be used in thread machining.
(2) The feed system is open-loop control. In order to achieve longitudinal feed mode, the main implementation is to implement ball screw transmission measures. In order to achieve lateral feed, it is usually achieved through ordinary thread transmission mode.
(3) To achieve automatic positioning, the main method is to use a microcomputer controlled tool holder.
2. Design of renovation plan
(1) Design longitudinal feed system. During the modification of the feed system in the CQ6123 lathe, it is necessary to remove the original slide box in the system, as well as the transmission and operating components in the feed box, and keep the box.
After the first gear reduction, the stepper motor will drive the screw and tightly fix the nut in the slide box, promoting the movement of the tool holder and small drag plate to drive the rotation of the longitudinal drag plate, achieving longitudinal feed motion. To save costs and expenses, the original feed box in the lathe was transformed and developed into a first level gear reducer, ensuring that the ball screw position is not changed. A handwheel facility was also established on the right side of the screw, facilitating flexible manual and tool setting operations. When in use, install it and disassemble it promptly after completion.
Fix the drag plate in the original lathe, keep the position unchanged, set up the nut seat and connect the nut. At the left end of the screw feed box, place a screw on the stepper motor, fix it at the motor stop, and tightly connect it to the body through positioning and screws. On both sides of the screw, support brackets and bearing brackets are established, and the centripetal ball is tightly fixed at one end to avoid movement, while the bearing supports the other end.
(2) Design a lateral feed system. After the transformation of the longitudinal system, the stepper motor can drive the screw and nut based on the action of the reduction gear, which can cause the corresponding lateral movement of the tool holder drag plate. For small desktop lathes, the screw itself has a smaller diameter, and if the finished screw is priced too high, it is not conducive to purchase. Ordinary threaded nuts can be used instead. Although it has different transmission effects, it can adapt well to longitudinal ball screw transmission, obtain information on lateral and longitudinal transmission performance, and compare them, while also meeting the design standards for renovation. The transformation of the lateral feed system is actually quite similar to the longitudinal system. During the transformation, it is also necessary to ensure that the manual mechanism of the feed system is not changed, making it convenient for manual and tool alignment. Install the corresponding stepper motor at the rear section of the screw and position it at the motor stop, tightly fixing it to the bed body through a cover plate. Based on the effect generated by the reduction gear, the motor drives the screw to move, while combining with the small drag plate to make the tool holder move in a horizontal direction, making it convenient to install the stepper motor. In the customized horizontal screw, to enhance the support effect, the main method is to use a bracket extension drag plate.
(3) Knife holder design. In a lathe, an indispensable component is the tool holder. The goal that can be achieved through scientific transformation of the knife holder is to hold multiple knives and automatically transfer positions.
In the transformation process, the original lathe tool holder was replaced with an LD4-1 automatic tool holder. The main characteristics of this product are strong rigidity, excellent process performance, precise positioning, and increased service life.
In the process of transforming the horizontal and vertical system reduction mechanism, the application of organic glass casing can achieve better dust removal effect and help to observe and understand the gear meshing status in a timely manner during the testing process. Calculate the gear transmission ratio i=360 p according to the following formula/ θ In the b · L0 formula, i θ B δ p. L0 represents gear ratio, step angle, pulse equivalent, and ball screw lead, respectively. After the renovation, the output shaft speed of the gear reducer can be significantly reduced, increasing the torque of the output shaft and exerting a good reduction and torque increase effect.
3, Key points of mechanical structure design in the CNC transformation of ordinary lathes
1. Main transmission structure design
During the CNC transformation period, the main transmission structure should be scientifically and reasonably designed to ensure that the speed can be automatically changed after the lathe transformation, while having a wide range of speed changes. By retrofitting traditional structures with multi speed motors, this standard can be achieved. To maintain the normal operation of the motor, a motor speed control system is set up, and the original spindle drive chain and other structures are removed and replaced with the main motor, which is replaced by a variable frequency speed control device. Expand and confirm the spindle position on the motor spindle, use a pulse encoder to clarify and transmit feedback information data to the control center in a timely manner. Considering the operation status of the machine tool, process and control the parts.
In the process of selecting a motor, a reasonable analysis of the equivalent torque of the motor under various working conditions should be carried out to ensure that the selected motor meets the system's machining accuracy, etc. Reasonably define the starting frequency of the motor according to the load torque, so that the motor can directly drive the load. Based on the adjustable speed range, it is necessary to ensure that the spindle motor speed is stable and avoid uneven speed problems during CNC machining. In a continuous load state, the spindle motor should ensure that the speed is stable, allowing the motor to have the smallest possible range of speed fluctuations. The motor used needs to have superior heat dissipation performance to prevent long-term excessive working vibration or the formation of high decibel noise.
2. Transmission structure design
In the process of designing the feed transmission structure, the transmission device and control structure are removed, and the motor is installed in different rotation directions to achieve the goal of automatic control of the motor and promote the effective improvement of the production efficiency of the lathe. In terms of machine tool operation, on the Z-axis, install the gear box to the original position where the screw was installed, and then tightly fix the ball screw. In the X-axis direction, first carry out the corresponding transformation of the drag board operation, and strictly control the structural accuracy.
In terms of drag plates and key transmission gears, it is necessary to do a good job in controlling the clearance between both parties. Generally, it is necessary to effectively reduce the clearance, and flexible adjustment and stiffness adjustment can be adopted to improve the sensitivity of gear transmission and enhance its accuracy. For the original guide rail, in order to reduce friction resistance, scraping and grinding methods are adopted, which can also significantly reduce the probability of gear wear.
3. Other structural designs
In terms of the transformation of the tool holder, it is necessary for the tool holder to provide critical support for complex component processing, in order to install a variety of types of tools. After removing the manual tool holder, it is also necessary to consider the actual production needs of CNC lathes and install corresponding automatic rotating CNC tool holders, fully ensuring the automation of tool holder positioning and multiple positioning, effectively enhancing the precision of part processing.
In terms of the structure of the slide box, the new structure can only be installed on the ball screw after the original structure is removed. The function of the structure generated during the processing operation is to pause the spindle rotation and maintain a smooth tool exchange. After the operation of structural modification is completed, the overall mechanical structure should be inspected strictly to grasp the transmission performance and spindle feed performance of the lathe, as well as the operating noise status, so that the lathe's operating performance meets the standards proposed by CNC machining.
4, Conclusion
This article mainly explores the design scheme of ordinary CNC transformation work, and conducts corresponding exploration in the selection and application of stepper motors and ball screw pairs. At the same time, it elaborates on the methods of longitudinal feed system, transverse feed system, and tool holder transformation design to ensure that key components can effectively operate in the equipment, achieve full play of motion performance, and ensure that the equipment has reliable accuracy, Promote the stable development of the CNC industry.