Indexing failure of the hottest m6420b hob grinder

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The indexing failure of m6420b hob grinder and Its Countermeasures

m6420b hob grinder is a product of Wuhan machine tool factory in the 1970s. The equipment has been overhauled and debugged for many times. During the debugging process, it is found that the indexing disc sometimes does not work in place, sometimes some parts may produce spark due to vibration and friction, and sometimes there is no action at all. The direct harm of inadequate or excessive indexing is the phenomenon of cutting, resulting in personal and equipment accidents

according to the hydraulic schematic diagram of the machine tool, the working principle of the indexing plate can be seen:

the pressure oil from the oil pump passes through the workbench pilot valve → indexing and non indexing control valve → indexing control box. The pressure oil entering the indexing control box is divided into three routes:

1) enters the upper chamber of the indexing cylinder through two valves D and C

2) enter the right chamber of valve C, push out the valve rod of valve C, and loosen the indexing locking mechanism. At the same time, as the C valve moves to the left, the pressure oil enters the lower chamber of the indexing cylinder to raise the indexing cylinder and complete the indexing

3) enter the left chamber of valve D through one-way throttle valve K to move valve d to the right, and pressure oil enters the left chamber of valve C to reset valve C and lock the indexing locking mechanism

the adjustment of one-way throttle valve K is the key to whether normal indexing can be achieved, because valve D is reversed and the locking mechanism is locked. The time before valve D is reversed is the indexing time. However, this time shall not be too long, otherwise the indexing is excessive

therefore, the following countermeasures are taken:

1 In the original equipment, K valve is sealed by steel ball, with poor guiding and sealing performance. The following structure is changed (see Figure 1)

figure 1K valve transformation diagram

2 In the original equipment, the one-way valve g acts as a sequence valve, that is, after the indexing cylinder is reset downward, the pressure oil passes through the upper chamber of the indexing cylinder → valve g → the left chamber of the worktable reversing valve to realize the reversing of the worktable reversing valve. However, since the spring of valve G is too weak, so that valve g cannot play the role of sequence valve, the spring should be appropriately thickened

3. The return oil of the indexing reversing valve (valve d) shall be returned through the left end of the pilot valve of the console control box. The poor return oil is an important reason for inaccurate indexing. Therefore, the groove of the pilot valve shoulder should be properly increased (but not too large, otherwise the oil will not be sealed)

4. During commissioning and use, we also found that the oil viscosity has a great impact on the sensitivity of indexing, especially when the oil cylinder speed of the workbench is large. After repeated tests, it is more suitable to use 20hydraulic oil in winter and 30hydraulic oil in summer. Especially in winter, the oil should be heated to about 20 ℃ before the equipment is used

after taking the above 18. Different force value units (n, KGF, GF) measures, after repeated tests, it will be accepted in the second half of the year, and the expected effect has been achieved

another reliable method is to transform the whole system of the equipment: the standard valve and electrical proximity switch are used as basic components, and the proximity switch can be installed on a guide rod with adjustable position. During commissioning, the proximity switch shall be positioned at the best position according to the actual situation. The sensing distance of the proximity switch shall be ≤ 5mm. A suitable set can be installed at the end of the cylinder piston rod for sensing. See Figure 2 for the system improvement schematic diagram

Figure 2 system improvement schematic diagram

electrical transmission schematic diagram can be designed according to the equipment action sequence and trigger conditions listed in the system improvement truth table

by using these trigger conditions, the electrical interlocking can be realized, so as to ensure the reliability of the graduation of m6420b hob grinder and the system that often encounters the phenomenon of good and bad operation of the instrument. System improvement truth table


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