The pressure of the fuel injection nozzle of the internal combustion engine is as high as 2000 BAR, so the machining accuracy is extremely high, including the manufacturing precision of the machine tool and the effective and reliable monitoring of the state of the tool during machining.
The Robert Bosch company in BAMBERG, Germany, invented the fuel injection pump in the 20th century. No matter what kind of supercharging system (such as pump/injector or diesel intake system), the fuel must be compressed and then enter. Nozzle body. There is a micro-hole in the nozzle body. When the working state of each cylinder is in the compression stroke, the micro-holes will be opened or closed through the nozzle needle, and the gap between the nozzle needle and the nozzle body is only a few micrometers.
After the workpiece has been drilled, it needs to be ground. In order to avoid elastic bending deformation when grinding the elongated workpiece, the grinding process should not be too long. This requires the workpiece to meet the design requirements after the initial machining. Just polish it.
When machining the nozzle body, the Bosch company initially machined the hole with a drill and a reamer on the MIKRON disc-type automatic machine before grinding. MIKRON machines (especially Swiss-made machines) are well known to many precision machine tool builders and users. In the precision manufacturing industry, in addition to the extremely high precision of machine tools, the tools used also have the characteristics of high manufacturing precision and extremely small geometrical dimensions.
For many years, MIKRON machines have been using NORDMAN tool monitors from HüRTH. This device is an effective tool that has been found so far to monitor difficult-to-detect parts (eg, monitoring of micro-hole machining processes with diameters less than 0.1 mm). Here, in order to measure the sound waves generated during the processing of the workpiece and the tool, the jet beam of the cooling lubricant is used as a conductor of the acoustic wave, and is received by the liquid acoustic detector. When measuring the active power, it can be digitally measured via the signal bus according to the driving condition of the spindle, or three-phase analog measurement on the tool monitor.
Bosch mainly monitors the active power of the machine tool by arranging the cooling lubricant nozzles close to the machining tool, making it difficult to install additional mechanical probes for tool monitoring in tight spaces. .
The measured active power curve of the machine tool axis is usually given in the form of linear upper and lower limits (ie envelope curves). The lower limit is always below the sharp tool measurement curve, while the upper limit is always above the sharp tool measurement curve. At Bosch, it is hoped that the measurement curve will always be in a narrow, uniform range. However, this does not only depend on whether the tool is sharp or not. During the cutting process, some minor damage to the tool, or other sudden changes, will cause the measurement curve to change. Since there is a certain width requirement between the upper and lower limits of the envelope curve, it is necessary to compensate for the portion of the measurement curve that changes due to tool wear. This compensation value is calculated by averaging the measurement curves obtained when machining more than 8 workpieces. Thereafter, the measured curve of the workpiece will be judged by the compensated envelope curve. During the cutting process, the tool will wear continuously, so the envelope curve needs to be compensated at any time to adapt to the wear of the tool, so this curve is usually called the “slip curveâ€.
The operator of MIKRON disc-type automatic machine tool OTTOHALAMA describes the manufacturing process of the nozzle body: usually, in addition to monitoring the damage of the drill bit, we can also control the pre-machining amount within 0.02MM through the NORDMAN system, and also detect the drill bit. Is the wear even? When the measurement is just started, if the distribution of the measured values ​​is obviously dispersed, it means that the bit wear is increased and the bearing of the machine tool shaft is defective. If the dispersion of the measured curve value is too large, the upper and lower limits of the envelope curve will fluctuate.
In the machining process of MIKRON's DICO-18 machine, when the new tool is replaced, the measurement curve of the tool monitor will swing from left to right. In addition, the curve value measured when machining with a sharp new tool is generally biased. low. Therefore, every time the tool wears and replaces, the slip envelope curve needs to set a new threshold by re-learning, and compare the collected machining measurement data with the threshold set by self-learning at any time. Here, The envelope curve previously measured without changing the sharp tool is generally adjusted downward. For a single processing station, this "adaptive learning" process can be set via the "menu", but for convenience, an operation key with a number of stations is also set on the right side of the tool monitor. . When in a certain processing station, the envelope curve can be adjusted and set by observing the measured curve of the processed hole and observing the button of the corresponding station while observing, Then restart the process.
On MIKRON's DICO-18 machine, the wear of the machining tool can also be observed by measuring the dispersion of the curve. The dispersion value of the active power measurement curve should be controlled within a certain range, which is obtained by processing a certain amount of workpiece measurement data, and a trend graph can be drawn on the tool monitor.
Although the range of the envelope curve set by the active power measurement curve is very narrow, occasionally this may occur when the drill bit diameter is small (eg less than 1 MM), although the drill bit is slightly damaged, but the active power measurement is Not recognized. At this time, it is necessary to use an acoustic emission liquid acoustic detector, which works on the principle that when a slight breakage occurs on the metal solid material of the workpiece or the tool, a special, click-like noise is emitted, thereby A propagable acoustic wave is formed inside the solid material, and then propagated as an acoustic waveguide through the cooling lubricating medium used in the processing, and finally received by the acoustic emission liquid sound detector. The fluid-transmitted sound wave has the characteristics of large propagation frequency range, small interference loss, and small signal distortion. On the MIKRON disc-type automatic machine, all the stations can be monitored by measuring the active power, including the machining of precision workpieces with a tapered valve seat diameter reduced from 0.8MM to 0.4MM. However, only the acoustic emission liquid acoustic detector attached to the machine tool can measure and monitor the change of the acoustic frequency caused by the micro-damage of the tool tip during machining. Of course, this measurement and monitoring is also difficult, because the diameter of the 4MM is quite large for the processing of the micro hole, that is, the drilling frequency of the drill using this diameter is already quite high.
In the processing of the tapered valve seat, in order to monitor the damage of the drill tip, there are two methods to choose: one is to install the oil jet jet inverter; the other is to install the acoustic reflection sensor.
Process monitoring is a complex and difficult task. Through adaptive learning, the monitor can draw real-time curves of AE, power and other parameters changes during processing. In addition to various types of sensors and monitors, software and data processing technologies are also crucial, and this problem can only be effectively solved through close cooperation between machine tool manufacturers and users.
Diamond-tech Engineered Flooring
Gray Floors,Dark Grey Wood Floors,Gray Hardwood Floors,Light Grey Wood Floor
Jiangsu Sunyo Flooring Co., Ltd , https://www.woodmapflooring.com