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Difficulties and Countermeasures in Processing Large Blades

In the processing of blades, the processing of large blades is the most difficult. Mastering the measures to solve the processing difficulties of large blades will have a very positive effect not only on the large blades themselves, but also on the moving blades, stationary blades, guide vanes and final blades.

The difficulties in processing large blades include the following three aspects: milling the girdle; processing the blade root; and milling tie-bar holes.

1. Since the large blades are made of forgings, the profile part of the forgings is different from the value of the wheel. In this way, the profile pads poured out of the low melting point alloy cannot match each blade. During processing, the upper and lower pressure plates must be pressed tightly. Finally, the gap between the blade profile and the profile pad deforms the processed profile, causing unstable dimensional control at the shroud, resulting in scrapping.

2. The processing of blade roots is a difficult point in blade processing. Due to the complex shape lines and high precision requirements, it has always been a headache for operators. Especially the fork-shaped blade roots of large blades not only have their own accuracy problems, but also There is a problem of deformation caused by stress release. When the fork shape is processed, the disappearance of the tensile stress between each other causes the monotonicity of the shrinkage stress, which deforms the blade root. If the stress is very large, scrapping is inevitable, and the annual losses caused by this are not small. .

3. A large part of the reason why the processing of tie-bar holes is difficult is due to the uneven deformation of the blade roots, which causes the radiation lines to not coincide, causing the position of the tie-bar holes to change, thus producing waste products. On the other hand, due to the deformation of the profile lines, The gap between the molding line pad and the molding line and the severe deformation result in the inability to match.

1. Solutions to the difficulties encountered in milling process surrounding areas:

Based on the principle that two points determine a line and two lines determine a plane, a separate adjustable tooling is designed. Since three thimbles are used for positioning, the adjustable device is feasible.

Specific operation methods:

1. Put the large blade on, separate the left and right supports, pour low melting point alloy, and lock both parts 6 and 4.

2. When a gap is found, loosen parts 6 and 4 and adjust part 3 until there is no gap. Then lock parts 4 and 6 to restart processing.

3. Regardless of the gap on the left or right, line contact (with the profile line) can be ensured, thereby ensuring surface contact with the blade. In this way, there is no need to worry about deformation caused by the gap during processing.

4. The tooling is simple and easy to manufacture, easy to operate, and easy to use. Especially when applied to large blades with gaps between the profile line and the theoretical profile line, it can reduce the scrap rate (this process) by more than 80%.

2. Solutions to the difficulties encountered in leaf root processing:

Before the blade root is processed, the artificial aging method is used to remove as much stress as possible in the blade root. This has solved part of the problem – stress deformation to a certain extent. Facing the processing itself requires the operator. Use a dial indicator to calibrate the tools instead of using a dial indicator to calibrate the workpiece, so that the three knives are in the correct position. The process requires that the process is also divided into roughing and finishing during finishing, and the last knife is aligned, thus avoiding the need for fixation. Error caused by large area.

3. Solution to the difficult problem of milling tie-bead holes – shape correction:

Since the problem of blade root processing is solved, recycling is reduced, so that the positioning of the blade root is basically accurate when processing the tie hole. The remaining problem is how to solve the problem of the gap between the middle profile line and the profile line pad. When workers are processing, they generally use a pad method. However, due to the vibration of the machine during processing, the pad often falls off and is scrapped. At the same time, because this profile has a positioning function and cannot be raised or lowered at will, it can only be considered from the blade itself.

Before processing this process, the process should be processed with a process – shape calibration, that is, those molding lines that are different from the theoretical molding line are made to match the theoretical molding line using human or mechanical force. To this end, a set of calibration measuring tools is needed, that is, the air leakage of each section is checked through the measurement of the sample, and measures can be taken to distort it to the normal state using human or mechanical force.

By taking the above three solutions, the problem of large blade processing can be basically solved, and it provides a theoretical basis for the processing of other domestic blades and accumulates valuable experience.

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