Causes and solutions to dimensional deviations of workpieces processed by CNC lathes

We all should know that CNC lathes are equipped with control devices such as CNC systems and servo control systems, as well as actuators such as high-precision feed systems and tool magazines, forming a new type of processing equipment. In terms of processing form, its processing form is different from any other processing machine tools. Generally speaking, CNC lathe is an efficient and high-precision processing equipment that integrates automatic processing and compound centralized processing. However, there are many reasons that affect the accuracy and processing efficiency of CNC lathes. Here is a brief introduction to the causes of dimensional deviations of CNC lathes and corresponding solutions, for user reference only.

In order to understand the causes of workpiece dimensional deviations, we need to knowCNC latheIt mainly consists of a control system, servo drive device, mechanical feed device, servo motor, workbench position and feedback measurement device. When processing a workpiece, the digital operation of the CNC system first sends a control signal to the servo drive device, then drives the servo motor to rotate, and then transmits it to the workbench through the mechanical feed device, causing relative movement between the workpiece and the tool. At the same time, the position detection feedback device converts the actual relative motion between the workpiece and the tool into an electrical signal, and then feeds it back to the CNC device. The CNC device then compares the command displacement with the actual feedback displacement, so that the processing meets the design requirements of the processing program. However, when a CNC lathe actually processes a workpiece, it often happens that the relative motion between the workpiece and the tool does not completely follow the command value, resulting in the size of the machined part not meeting the design. In this way, dimensional deviation of the workpiece to be processed will occur. Typically, there are several reasons for this failure:

1. The actual indexing value of the servo motor is inconsistent with the commanded indexing value, resulting in dimensional deviation of the workpiece being processed.

2. The actual indexing value of the servo motor is consistent with the commanded indexing value, but the actual relative motion of the workpiece to be processed and the tool does not meet the corresponding requirements.

3. Zero return position deviation of CNC lathe transmission system.

4. Pulse loss or external interference, as well as mechanical failure lead to deviation of the workpiece being processed.

The solution to the dimensional deviation of workpieces processed by CNC lathes is as follows:

CNC lathes are usually equipped with electronic control devices of CNC systems and servo control systems. These systems usually have error compensation functions, so software compensation is an effective and direct method to prevent and solve dimensional deviations in processed workpieces. This mainly includes two methods: cutter compensation and interpolation algorithms, as follows:

1. Methods of using tools to compensate

The tool compensation method mainly compensates through the tool to prevent excessive dimensional deviation of the workpiece. This method is a commonly used and effective compensation method. However, in order to compensate the tool, the trajectory transition type of the front and rear sections must first be determined. There are four transition forms between arcs and straight lines, namely, straight lines meet straight lines, straight lines meet arcs, arcs meet straight lines, and arcs meet arcs. According to the difference between the vector angle of the two program trajectories and the tool compensation direction, the tool radius compensation of the program segment transition is divided into three transition modes: shortening, expansion and insertion.

2. Use interpolation algorithm for compensation

The data value of the CNC system of a CNC lathe can only be the coordinate values ​​of the starting point and end point of a trajectory, so the data points should be densely processed between the starting point and the end point, also known as interpolation processing. Through this interpolation process, the cutting trajectory of the tool during the entire machining process can be controlled in real time, reducing the impact of large programs on the machining dimensions of the workpiece due to some unpredictable reasons, thereby achieving high-precision machining operations of the workpiece.