Overview: General CNC machine tools

Numerical Control Tools (Numerical Control Tools) is a new type of automatic machine tool that uses digital signals to control the position, angle, speed, force and other signals generated by the operation of the equipment and its processing through programmable automatic control. The computer information processing and control contents of CNC machine tools mainly include: basic CNC data input and output, linear and circular interpolation operations, tool compensation, gap compensation, pitch error compensation and position servo control. Some advanced CNC machines even have some intelligent functions, such as spiral interpolation, tool monitoring, online measurement, adaptive control, fault diagnosis, SoftKey menu, conversational programming, graphic simulation, etc. Most of the functions of CNC machine tools have strong requirements for real-time performance and a large amount of information processing. Therefore, many CNC machine tools use multi-microprocessor numerical control.

Generally, CNC machine tools are usually index-controlled lathes, CNC milling machines, CNC boring and milling machines, etc. Their following characteristics are very important for their automated manufacturing systems.

1, high flexibility

The CNC machine tool processes the parts according to the NC program. When the machined parts are changed, it is only necessary to replace the NC program and the required tools. There is no need for special process equipment such as molds, prototypes, and drill dies. CNC machine tools can quickly change from machining one part to another, with a short production preparation cycle and suitable for multi-variety and small batch production.

2, high degree of automation

The NC program is a collection of geometric and process information required to machine parts for CNC machines. The geometric information has a path, interpolation parameters, tool length and radius compensation; the process information includes tool, spindle speed, feed rate, coolant on/off, etc. During the cutting process, the relative movement of the tool and the workpiece is automatically realized, the cutting speed and the feed speed are automatically changed, the coolant is automatically turned on/off, and the CNC lathe is automatically indexed and changed. The operator's task is to load and unload the workpiece, change the tool, operate the button, monitor the machining process, and so on.

3. High processing precision and stable quality

Modern CNC machine tools are equipped with CNC numerical control devices and new servo systems, which have high control precision, generally reaching 1 rn, and high-precision CNC machine tools can reach 0.2 m. The feed servo system of CNC machine tools adopts closed-loop or semi-closed loop control to compensate for backlash and lead screw pitch error and tool wear, so CNC machine tools can achieve higher machining accuracy. For small and medium-sized CNC machine tools, the positioning accuracy is generally 0.03mm, and the repeat positioning accuracy can reach 0.01mm. The drive system and machine structure of CNC machine tools have high rigidity and stability, and the manufacturing precision is higher than that of ordinary machine tools. When the CNC machine has 3 to 5 axes linkage function, it can process various complex surfaces and achieve high precision. Since the automatic machining according to the numerical control program avoids the artificial operation error, the dimensional consistency of the same batch of processed parts is good, and the processing quality is stable.

4, high production efficiency

The machining time of the parts consists of maneuver time and auxiliary time. The maneuvering time and auxiliary time of CNC machine tools are significantly reduced compared with ordinary machine tools. The spindle speed range and feed speed range of CNC machine tools are larger than those of ordinary machine tools. The spindle speed range is usually 10~6000r/min, and the high-speed cutting process can reach 15000r/min. The upper limit of feed rate range can reach 10~12m/min. The cutting feed rate is even more than 30m / min, and the rapid moving speed exceeds 30 ~ 60m / min. The main motion and the feed motion are generally stepless speed change, and the most favorable cutting amount can be selected for each process, and the idle travel time is significantly reduced. The spindle motor and feed drive motor of CNC machine tools have larger drive capacity than ordinary machine tools of the same specification. The machine tool has high structural rigidity, and some CNC machine tools can perform powerful cutting, effectively reducing maneuver time.

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Pipette

A pipette, also known as a pipette gun, is a device used to quantitatively transfer liquids. When conducting research in analytical testing, a small or trace amount of liquid is generally removed with a pipette. Pipettes can be divided into gas piston pipettes (Air-displacement pipette) and external piston pipettes (Positive-displacement pipette) according to the principle. Gas piston pipettes are mainly used for standard pipetting, and external piston pipettes are mainly used to handle special liquids such as volatile, corrosive and viscous. Many people ignore the correct use of pipettes and some of the details.