The purpose of this paper is to automate part measurement in machining centers and perform in-line measurement by installing probes in machining centers. Using the interactive interface of the microcomputer, the automation of the measurement and the automatic generation of the measurement program are realized. The calculation of the measurement results is corrected in the program, which makes the complex comprehensive error compensation operation possible due to the initial impossibility.
System structure, working principle and workflow of touch probes:
A complete machining center online control system usually consists of the following parts:
1. Machining center. The basis of machining and inspection is that the workpiece allows the required basic motion, and the accuracy of the transmission components directly affects the accuracy of machining and inspection.
2. Numerical control system. The numerical control system generally adopts the programming of input storage, numerical control addition operation, interpolation operation and various machine tool control functions.
3. Servo system. An important part of the CNC machine tool is to control the feed position of the CNC machine tool and the speed (or position) control of the axis.
4. Measuring system. The touch-trigger probe, signal transmission system and data acquisition system are important components of the online control system of CNC machine tools, which directly affect the accuracy of online control. A CNC machine tool is both a machine tool and a measuring machine.
5. Computer system. The online control system uses a computer to collect and process the measurement data, generate the numerical control program, and communicate with the numerical control machine tool.
On-line control system of machining center is an important part of modern advanced manufacturing system such as flexible manufacturing system. To establish an online computer-aided machining center, first assist the main detection programming in the computer system, automatically detect the communication interface between the main program and the machining center through the rs-232 cluster, and use the control program to test the movement trajectory of the head. The measurement activity when the measuring part is in contact, the trigger signal of each digitizing touch probe under test can well trigger the interface with the system Computer Numerical Control (CNC) parts are specially designed for signal converters, machine tools and the converted transmission record coordinate points trigger signal of the control system.
After receiving the signal, the machine stops working, and transmits the coordinates of the measuring point to the computer through the serial communication interface rs-232; then the next measuring action is programmed. Under the control of the computer software of the control system, the measurement results of the system can be calculated, and the data processing operations can be compensated and corrected.
There are 3 positioning posts symmetrically distributed at 120° on the same horizontal plane inside the touch-trigger probe, and each positioning post is supported by two supporting balls below it, which constitute a pair of contact pairs (two contact points). ).
When the three pairs of balls are in uniform contact, the measuring head is set to zero. When the steel ball comes into contact with the part under test, a contact force is generated under which the head support moves or deflects; at this time, at least one contact point of the steel ball pair 3 separates, resulting in an initially closed series connection The circuit breaks and triggers the trigger signal.
When the measuring head is separated from the measured part, the contact force disappears and the measuring head returns to its original position under the action of the readjusted spring. First trigger the signal level and digital transmission of the signal processing interface computer numerical control (CNC) signal level and digital transmission in the system through the measured transmission signal (infrared, electromagnetic disaster, radio wave transmission or transmission control interface to the interface unit (usually)).
After receiving the trigger signal from the touch probe, the numerical control system stops the movement of the machine, and locks the three coordinate values of the ball center at this time through the probe positioning system to determine the coordinates of the contact point between the ball and the workpiece; then we continue to the next paragraph. Therefore, positioning, automatic detection and control can be performed anywhere in space.