Research on Precision Prediction System of CNC Lathe Machining

Interactive visual forecasting. Experiments verify the validity of this model.

1 Formation Mechanism of Turning Diameter Size The machining accuracy includes dimensional accuracy and shape accuracy. The basic size of turning machining is diameter. If the instantaneous diameter of the workpiece can be found. The instantaneous diameter is sampled separately in the axial direction of the hook. Then, according to the specific accuracy evaluation index, the data structure is reorganized, and the accuracy prediction can be realized. In this paper, only the accuracy of the inch and the accuracy of the shape of the shape are used as an example to give the forecast result of the precision sweat price. 1 When the process dimension chain simplifies the turning process, the working edge that participates in the cutting is a straight line or a curve, and; The key factor of the 3 ring-shaped workpiece inch is the position of the work towel and the art heart. For the convenience of research, the tool tip is abstracted as a tangent point, and the distance from the tangent point to the center of the process is the instantaneous radius of the workpiece. 4. Since the distance between the tangent point and the process center is through the tool slide rail machine tool small axis fixture and workpiece, etc. The machined process system is formed by the relationship of motion and dynamics. The machine tool, the tool holder and the workpiece form the final size of the workpiece. Therefore, it is necessary to consider the motion error and the force deformation error.

I heard that I analyzed the process dimension chain. The radius makes the analysis and calculation very difficult, if not impossible, when forming the workpiece. In order to facilitate the detection and analysis, the process dimension chain can be divided into several groups, namely the workpiece spindle bed and the tool holder. By establishing their respective coordinate systems, a closed fund project is formed. This research project was awarded the 865940 ring by the National Natural Science Foundation of China 50075014863. .

1.2 Process system coordinate system setting In the turning process, in order to determine the position of the workpiece, the process coordinate system is used to extract the edge of the process coordinate system. The general process center line is the point on the two coordinate planes of the workpiece reference. The process center coincides with the workpiece geometry centerline. The rest of the coordinate system is introduced through the main reference plane of the process system. In order to judge the installation error of the workpiece and the fixture, the coordinate system of the main reference plane passing through the spindle is taken as the spindle coordinate system. The static adjustment error during tool installation and the movement of the tool on the guide rail are described by B. Relative to the dynamic adjustment error of the spindle coordinate system, the blade of the tool holder coordinate system is introduced by the main reference of the tool. To study the mutual relationship between the coordinate systems, the ideal spindle coordinate system is taken as the reference coordinate system with the edge 0,1.

1.3 The instantaneous method of forming the workpiece surface also includes the thermal deformation error of the process system. By detecting and identifying the above error, the distance between the tool tip point, that is, the point of the tangent point relative to the actual process center, that is, the instantaneous radius of the workpiece can be obtained.

The vector relationship of 1 can be obtained from the tangent point relative to the process coordinate system. Here, from the Han, the sink is the rotation coordinate matrix of the process coordinate system spindle coordinate system and the tool holder coordinate system.

The motion vector of the tool nose point at any time relative to the center of the spindle rotation has measurability, which can be controlled by dynamically adjusting the micro feed of the tool holder. =, 5, is the installation vector of the process system, and its physical meaning is The motion vector of the process center relative to the center of the spindle during machining at any time has measurability, which can be controlled by dynamically adjusting the machining parameters to reduce the force and deformation of the process system; the vector equation reflects the workpiece on the 0-side projection. The size of the cross section and its variation can be used to predict the diameter and roundness error; the projection of the 2 magic plane reflects the dimension and its variation in the longitudinal section of the workpiece, which can be used to predict the axial dimension of the straight line between the stepped axes of the busbar. Axis and cylindricity errors. Therefore, Equation 2 is called the accuracy prediction model. In order to monitor the machining accuracy in real time, this model is referenced in an open CNC system, and the machining accuracy is ensured by monitoring the installation error vector and adjusting the error vector.

Through the establishment of the coordinate system, the tool point point tangent point is determined in the tool holder coordinate system 6 and 7, and the point moves to the point under the action of the tool post feed vector, 5. In the spindle coordinate system, the spindle center 6 is determined, and the process center is defined in the process coordinate system 6 especially 0. It can be seen from the vector relationship of 1 that the vector in the process coordinate system is the workpiece at any time. The radius vector can be obtained from the instantaneous chain center, which is called the instantaneous size chain vector, which is the basic idea of ​​instantaneously finding the diameter of the workpiece.

In actual machining, due to the influence of error, the actual coordinate system deviates from the ideal reference coordinate system, which is now the translation and rotation of the relative ideal coordinate system, thus introducing the installation error of the relevant error tool, which is now 0 point relative, point initial coordinate The change and the rotation of the tool holder coordinate system; 0 vector vector with the tool holder feed vector 0 motion will be introduced 2 process system error modeling according to the process system error component to the tool holder coordinate system spindle coordinate system motion error process system force deformation The system error such as error is measured and identified, and the motion vector equation 2 is substituted to predict the machining accuracy of the workpiece.

2.1 Calibration and Modeling of Motion Error of Tool Holder Coordinate System Determine the motion error of the relatively ideal spindle during the movement of the tool holder. 1 can know the motion law of the tool holder coordinate system to determine the tool holder coordinate system. To this end, the parallelity error of the longitudinal slide relative to the ideal spindle motion and the parallelism error of the slide movement to the spindle centerline are reflected to reflect the error motion of the slide relative to the main axis. 1 affects the position and attitude of the tool holder coordinate system.

Therefore, the coordinate origin of a machine tool holder coordinate system is obtained, and the error of the sitting rail of 6 is obtained; 0 embodies the length of the spindle coordinate system relative to the reference coordinate system, and the machining radius of the current process is the deformation deformation of the tool holder. I want to ask for it. The error component of the relative reference coordinate system during the movement of the slide is determined by 1.

2.2 Calibration of the spindle coordinate system motion error and modeling The motion error of the spindle is used to calibrate the actual spindle coordinate system. Here, measure the radial runout of the centerline of the spindle taper by pressing several 8342.196. In this way, the mathematical model of the spindle motion error of the machine tool is reflected by the experimental results. (4) The actual ten-digit position of the shaft is the standard of the zero-scale. The calibration and construction of the force distortion error of the 2.3 coordinate system. The mold must calculate the process system force deformation to determine the process baseline. Here, the static deformation method is used to solve the rigidity of the process system based on the initial calibration of the chuck of the machine chuck and the rigidity of the tool holder. Through the finite element analysis of the process system, the force deformation error of the process system is calculated.

Through the cutting force experiment and cutting force prediction, through the finite element analysis and data processing of the process system, the deformation of the process system in the current process is obtained, and the position of the original coordinate point of the process coordinate system in the reference coordinate system is obtained. The processing precision prediction visualization realizes two parts of forecasting and comprehensive error impact prediction. The former is used to analyze the influence trend on the machining accuracy when the tool coordinate system or the spindle coordinate system produces the error motion, and gives the comparison between the actual machining result and the ideal shape of the workpiece. 2. Convenient craftsman analysis affects the machining accuracy. s reason. The latter is used to predict the influence of the comprehensive error of the process system on the machining accuracy. The evaluation index 3 of the roundness of the workpiece diameter can be given in real time, so as to guide the process personnel to optimize the machining, the number, the high processing quality and the machining efficiency. In order to test the reliability of the virtual machining workpiece accuracy prediction model, the actual processing and virtual machining comparison experiments. Machining conditions The geometric parameters of the turning tool are the front angle and the back angle. The main bias, the radius of the tool nose arc, 1. The tool material is D1 14.1 for the comparison of the secondary processing results. Among them, 1 忭 axis 1 7-1 is the actual machining workpiece diameter, and the team is the virtual machining workpiece diameter. It can be seen from 1 that the theoretical calculation and the measured value are small and the prediction result is compared with the experimental scallop trend, and the relative error is controlled within 10.

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Cuckoo Clock S

(Finish)