Introduction to the cutting accuracy of low-speed wire-cutting machine tools

Low-speed wire cutting is to use continuously moving fine metal wire (called electrode wire) as an electrode to perform pulse spark discharge to remove metal and cut the workpiece. It is mainly used to process all kinds of complex and precise small workpieces. According to the different running speeds of the electrode wires, wire EDM machine tools are usually divided into two categories: one is the slow wire (also called low-speed wire EDM wire cutting). Machine tool) The electrode wire moves in one direction at a low speed. Generally, the wire speed is lower than 0.2m/s, the accuracy is up to 0.001mm, and the surface quality is close to the grinding level.

The cutting precision of low-speed wire-cutting machine tools is increasing day by day

(1) Multi-cutting technology Multi-cutting technology is a fundamental means to improve the machining accuracy and surface quality of low-speed wire EDM. It is a scientific integration of design and manufacturing technology, numerical control technology, intelligent technology, pulse power technology, precision transmission and control technology. Generally, it is formed by cutting once, cutting twice to improve accuracy, and cutting more than three times to improve surface quality. In order to achieve a high-quality surface, the number of multiple cuts was as high as 7-9 times, but now it only needs 3 to 4 times.

(2) Continuous optimization of corner processing technology. Due to the hysteresis of the electrode wire when cutting corners, corners will collapse. In order to improve the accuracy of corner cutting, researchers have adopted more dynamic corner processing strategies. Such as: changing the wire walking path; changing the processing speed (thin plate); automatically adjusting the water pressure; controlling the processing energy, etc. By adopting a comprehensive corner control strategy, the corner shape error during rough machining is reduced by 70%, and the matching accuracy of up to 5 points can be cut at a time.

(3) Adopting technology to improve flatness. High-precision finishing circuits are all technologies to improve flatness, which are considered to be of great significance to the processing of thick parts.

(4) The structure of the machine tool is more precise. In order to ensure high-precision processing, many technical measures are adopted to improve the accuracy of the main machine: ①Control the temperature. The use of a water temperature cooling device makes the internal temperature of the machine tool the same as the water temperature, reducing the thermal deformation of the machine tool. ②Using linear motors. High responsiveness, precision positioning can achieve 0.1μm equivalent control, feed without vibration, no noise, increase the discharge frequency, maintain stable discharge, and cut Ry5μm twice. ③Using ceramic and polymer artificial granite parts, its thermal inertia is 25 times larger than that of cast iron, which reduces the influence of temperature changes on cutting accuracy. ④Using a fixed workbench and a movable column structure to increase the load-bearing capacity of the workbench, and is not affected by water immersion processing and changes in the weight of the workpiece. ⑤Adopt immersion processing to reduce the thermal deformation of the workpiece. ⑥Motor servo, closed-loop electrode wire tension control. ⑦High-precision tool setting: voltage-modulated tool setting power supply is adopted. The accuracy of tool setting can reach ±0.005mm, without damaging the workpiece, regardless of whether it is wet or dry.

(5) Filament cutting In order to carry out the micro-finishing of small fillets, narrow slits, narrow grooves and fine parts, various manufacturing companies have spent great efforts on the research of filament cutting technology. At present, the world's major electrical processing machine manufacturers can use electrode wires of 0.02 to 0.03 mm for cutting.