Characteristics And Advantages Of Medium Wire Cutting Machine Tools

In daily life, we often hear about medium wire, slow wire, and fast wire. For people in the industry, it may be very simple, but for outsiders, how to distinguish between the three? This article briefly introduces the differences between the three. If you want to know more, please find more relevant information.
First of all, medium wire, slow wire, and fast wire all refer to wire cutting machines. Wire cutting electrical discharge machining (WEDM for short) belongs to the category of electrical machining. It was discovered by the former Soviet Union couple Lazarenko when they studied the phenomenon and cause of spark discharge corrosion damage to switch contacts. The instantaneous high temperature of the electric spark can melt, oxidize and corrode the local metal, thus creating and inventing the method of electrical discharge machining. According to the wire speed, the EDM wire cutting machine can be divided into three categories: high-speed reciprocating wire EDM wire cutting machine (Reciprocating type High Speed ​​Wire cut Electrical Discharge Machining commonly known as "fast wire cutting"), low-speed one-way walk Wire cut Electrical Discharge Machining (Low Speed ​​one-way walk Wire cut Electrical Discharge Machining commonly known as "slow wire cutting") and vertical self-rotating EDM wire cutting machine (Vertical Wire Electrical Discharge Machining machine tool With Rotation Wire). It can also be divided into single-column cross workbench type and double-column type (commonly known as gantry type) according to the workbench form.
Fast wire cutting refers to the molybdenum wire moving back and forth, which is more economical in molybdenum wire, but the accuracy is low, and it is generally used by domestic wire cutting machines.
Medium wire cutting is also a type of EDM wire cutting machine. The working principle is to use the continuously moving molybdenum wire (called electrode wire) as the electrode to perform pulse spark discharge on the workpiece to erode the metal and cut it into shape. Its wire speed and workpiece quality are between fast wire and slow wire, so it is called medium wire. To be precise, medium wire is an upgraded product of fast wire, so it can also be called: fast wire that can cut multiple times, so its processing speed is close to slow wire, and the processing quality is also close to slow wire. The wire speed is between 1 and 12 mm/s and can be adjusted as needed.
Slow wire wire cutting DK7632 Slow wire is a kind of English abbreviation of electric spark wire cutting (WEDM-LS). It uses a continuously moving thin metal wire (called electrode wire) as an electrode to perform pulse spark discharge to erode metal and cut and shape the workpiece. It is mainly used to process various complex and precise small workpieces. According to the different running speeds of the electrode wire, the electric spark wire cutting machine is usually divided into two categories: one is slow wire (also called low-speed wire electric spark wire cutting machine) The electrode wire moves in a low-speed unidirectional direction, the wire speed is generally less than 0.2 mm/s, the accuracy is up to 0.001 mm, and the surface quality is also close to the grinding level. The electrode wire is no longer used after discharge, and the work is stable, uniform, with little jitter and good processing quality. In addition, the use of advanced power supply technology has achieved high-speed processing, and the maximum productivity can reach 220mm2/min.
1. Characteristics of medium-wire wire cutting
The terms high-speed wire cutting and low-speed wire cutting (or fast wire cutting and slow wire cutting) are distinguished by the wire cutting speed of the electrode wire. Although the wire cutting speed of medium-wire cutting is between the two, the focus of its description is not the wire cutting speed. It is just referring to the previous terms, and figuratively calling this new type of machine tool, which is developed on the basis of high-speed wire cutting and has a processing effect close to that of low-speed wire cutting, medium-wire cutting; and it corresponds to the common names (previous terms) fast wire cutting and slow wire cutting.
In fact, in the current effective "special processing industry" standards, wire cutting machine types are no longer divided by wire cutting speed, but are divided into "unidirectional wire cutting type" and "reciprocating wire cutting type". For example, GB/T 7925-2005 Parameters of Wire EDM (Reciprocating Wire Cutting).
In this way, both fast wire cutting and medium wire cutting belong to reciprocating wire cutting. In ordinary descriptions, it is still possible to distinguish between fast wire cutting and medium wire cutting. Now, let's look at the characteristics of medium wire cutting.
(1) Multiple cutting can be achieved. The significant difference between medium wire cutting and fast wire cutting is that multiple cutting can be achieved. The purpose of multiple cutting is to improve the surface quality and meet the needs of processing workpieces, thereby expanding the scope of application. For example, after three cuttings, the surface roughness of the medium wire cutting machine tool reaches Ra≤1.2μm.
The requirements of multiple cutting on the mechanical accuracy, repeat positioning accuracy, stability of the wire feeding system, performance of the pulse power supply, conductivity of the working fluid, and process database of multiple cutting are much higher than those of ordinary HSWEDM machine tools.
(2) Breakthroughs in pulse power supply. In order to achieve multiple cutting and ensure processing efficiency, the cutting speed during rough processing must be increased, which requires close cooperation with the pulse power supply.
To this end, according to the development of power electronics technology, the pulse power supply has been improved and the current limiting resistor has been eliminated. In this way, the performance of the pulse power supply is improved and energy is saved.
At present, the maximum cutting speed of the medium-speed wire cutting pulse power supply is close to 200mm2/min, and the average speed of multiple cutting (for example, three times) can reach about 60-80mm2/min; moreover, the effect of extremely low electrode wire loss is achieved. Therefore, some are called intelligent high-frequency pulse power supplies.
(3) Control system Medium-speed wire cutting mostly uses an industrial PC to form an integrated programming control system. Combined with the process database, the system can provide the best processing conditions to achieve high-speed processing, quality assurance, and simplified operation.
For example, after the user enters the processing conditions (material, thickness, etc.) and process parameters (surface roughness, etc.), the system can give appropriate electrical specifications (pulse width, pulse interval, no-load voltage, processing voltage, processing current, etc.), as well as servo feed speed, electrode wire speed, etc. for each processing, and make appropriate responses during processing.
Therefore, the control system requires close cooperation between the pulse power supply and the machine tool electrical system. Some people also call this type of machine tool "intelligent multi-speed wire cutting machine tool".
(4) Machine tool circuit In order to meet the different requirements of each cutting, the wire feeding speed of the electrode wire can be adjusted, and AC variable frequency speed regulation is a common method.
In this way, electronic logic circuits can be used instead of relay control circuits, which also facilitates the interface with the control system and facilitates the control of the wire feeding speed.
After the variable frequency speed regulation is adopted, the commutation impact of the wire feeding motor is also reduced, which is conducive to maintaining the stability of the electrode wire.
(5) Improvement of machine tool mechanical accuracy and others In order to ensure the effect of multiple cutting, the machine tool must have a high repeat positioning accuracy, which has certain requirements for the bed, guide rails, etc.
The measures taken include: designing a suitable structure, selecting suitable materials, using linear guide rails, and using gapless gear pairs or motor direct drag to eliminate gaps in the feed system, so as to maintain the accuracy and durability of the machine tool.
In terms of the stability of the electrode wire, various measures have also been taken.
In addition, new working fluids and new filtration systems have been developed to meet processing and environmental protection requirements.
2. Fast-wire Wire Cutting and Medium-wire Wire Cutting
The traditional "fast-wire Wire Cutting" is called "ordinary high-speed wire cutting" to distinguish it from the new machine tools that will appear in the future. For now, "medium-wire" is such a new machine tool.
(1) Fast-wire (ordinary high-speed wire cutting machine tools) will still have a large number of machines
Medium-wire Wire Cutting is a new type of machine developed in recent years; before, fast-wire cutting had experienced a heyday with an annual production and sales of tens of thousands of units, and this large number of machine tools will continue to be used. Moreover, due to the mature technology, low price, and advantages of high-efficiency and large-thickness processing of fast-wire cutting, it will still occupy a considerable market share.
Even if we take into account the machine tools that have been retired due to long-term use and the small number of machine tools that have been transformed with medium-wire technology, the absolute number of fast-wire cutting will still be a considerable number. Considering the long service life of machine tools, the number of fast-wire cutting will still have an absolute advantage for a considerable period of time.
(2) Fast wire cutting and medium wire cutting will coexist for a long time
At present, medium wire cutting has a strong promotion force and a good development momentum. It has practical value in processing some workpieces with small thickness, but if the workpiece is thick, it is more difficult to achieve reliable processing.
Since medium wire cutting inherits the advantages of high cost performance of fast wire cutting and good processing quality, although the price of the machine tool with better processing effect is higher, it will still be accepted by some users in need. Combined with the above discussion, it can be seen that fast wire cutting and medium wire cutting will coexist for a long time.
In addition, with the improvement of medium wire cutting technology, in terms of electrical control, some fast wire cutting will tend to merge with medium wire cutting. Fast wire cutting machine tools or popular machine tools that maintain cost performance advantages will learn from the available technology of medium wire cutting to improve performance.