Thu Jun 09 09:41:19 CST 2022
When a wire cutting machine is delivered to the household, the "machining performance" of the machine tool is basically finalized, and the structure of the molybdenum wire positioning "guidance system" guide wheel assembly determines the quality of the wire cutting surface to a certain extent.
From the analysis of the working principle and working environment of the guide wheel assembly, we can have actual reference value for keeping the wire cutting machine in a good state of machining surface roughness.
Let’s start with the structure of the guide wheel assembly. Whether it is a fast wire feeder or a middle wire feeder modified on the basis of the fast wire feeder structure, the guide wheel assembly is divided into two parts: “main pulley assembly” and “auxiliary guide wheel assembly”.
Whether it is the main pulley assembly or the auxiliary pulley assembly, it is composed of the following main components:
Guide roller sleeve, guide roller, bearing, sleeve, nut.
We know that the idler shaft and the inner ring of the bearing run together at high speed during work, reaching several thousand revolutions per minute. Especially for fast wire, the processing environment of the middle wire is to dissolve the wire cutting fluid mixed with various discharge impurities. the elements of.
Although the auxiliary guide wheel assembly does not play a decisive role in the "positioning" of the molybdenum wire, it ensures the smoothness of the wire in the entire wire running system. The tension system of the wire traveling in the elephant is more "restrained" by the pulley assembly. It is manifested in the broken wire due to non-discharge factors during processing, the "jump stitch" on the processing surface, and the reversing trace of the wire drum.
The "absolute positioning" coordinate of our molybdenum wire in the processing area is the positioning of the guide wheel assembly on the end of the upper and lower wire arms. The machining track sent by the control system is the only "position signal" of the molybdenum wire relative to the machine table, and the machining track is theoretically calculated to be "zero deviation". The guide wheel assembly affects the molybdenum wire in actual work, so that the actual molybdenum wire trajectory can be "dynamically" displaced along the fixed position of the guide wheel in the axial and radial directions of the guide wheel installation. This is an important reason that affects the final result of the surface roughness of wire cutting, especially on the middle wire, this "dynamic" displacement affects the effect of multiple cuts in many ways - that is, the surface roughness.
As a wire cutting technician, replace the guide wheel and bearing so that the working accuracy of the assembled guide wheel assembly is within the range required by the machine tool, that is, the molybdenum wire space is within 0.005MM along the axial and radial directions of the guide wheel. It is not simple to say. It is difficult to say, the key is that we need to have a deep understanding of which human factors will affect the actual result of the assembly during the process of replacing bearings and guide wheels, and which are caused by the quality factors of the guide wheels and the bearing itself.
Let's talk about the guide wheel first, the quality check of the bearing itself. In the past, our domestic wire cutting factories had professional production of guide wheel components, and the specifications, styles and quality were controlled according to the national standard. Now it is generally entrusted to domestic professional manufacturers in this area to produce, and the quality is guaranteed. Like the "Xieye" brand guide wheel produced by "Wuxi Xieye Machinery Factory", which is currently produced for most domestic wire cutting manufacturers. It is produced according to the national standard "JB/T6565-1993.JB/T3720-1993. The main product accuracy of the guide wheel is what we see on the guide wheel packaging: V-groove R is less than 0.04MM. Radial Jump is less than 0.004MM. Axial Jump is less than 0.004MM. According to the material of the working position, there are: steel guide wheel, gemstone guide wheel, ceramic guide wheel. There are also various kinds of "waterproof guide wheels" made in recent years based on functions. "Surface" Ceramicized Aluminium Idler Pulleys".
According to the introduction of the patent for the invention of this "waterproof guide wheel": the principle of action: the device includes a guide wheel, a guide wheel shaft, a bearing, and a composite seat. An annular groove is also arranged on the small shaft of the guide wheel in the groove along the radial direction, and an annular boss is arranged at the adjacent end of the composite seat and the guide wheel, forming a matching gap with the annular groove and the annular groove respectively. When the machine tool is working, the splashed working fluid will enter the annular groove along the boss, and then flow out from the lower part along the annular groove, and will not enter the bearing, which effectively protects the bearing and improves the working accuracy of the guide wheel device. and service life.
The aluminum alloy guide wheel with ceramic surface is made of composite material. The inertia of aluminum alloy is small. The surface of the guide wheel is coated with a layer of ceramics to utilize the wear resistance of ceramics. The guide wheel of this structure gives full play to the achievements of high technology to meet the practical application needs of the guide wheel.
According to the introduction of the patent. A layer of aluminum oxide ceramic oxide film is grown in-situ on the whole surface of the aluminum alloy guide wheel by using the micro-arc oxidation process, and the surface hardness of the surface ceramicized aluminum alloy guide wheel is Hv1300-Hv1800. The surface ceramic aluminum alloy guide wheel has high hardness, friction and wear resistance, high dielectric strength and acid and alkali corrosion resistance, which is very suitable for the working conditions of the wire EDM guide wheel.
The working life of the guide wheel is greatly affected by the quality of the molybdenum wire and the material of the processing cutting parts. Most of the failure of the guide wheel is caused by the damage of the V-shaped groove.
For example, the roughness of the molybdenum wire itself is poor, the contact with the V-groove of the guide wheel is poor, and the friction force is large. When processing aluminum alloy, tungsten carbide, etc., the damage of the guide wheel is faster, and it is also necessary to replace different ones on the same wire cutting machine. Molybdenum wire cutting "wire diameter size" will also increase the positioning failure of the V-groove of the guide wheel, causing reversing sliding friction between the molybdenum wire and the guide wheel. Of course there are other factors. But the above is the main reason.
The working life of the guide pulley is longer than the working life cycle of the bearing. If conditions permit, place the working V-groove of the guide wheel under the projector and observe the working V-groove of the guide wheel. Generally, it will be replaced in three to four months according to the actual situation. The relative replacement of the middle wire is two to three months, which is related to the specific processing material, and the aluminum alloy is cut. Tungsten steel is shorter. It is also related to the properties of the wire cutting fluid used. According to the actual processing statistics, the water-soluble cutting fluid has a greater impact on the guide wheel than the oil-based emulsion.