Process arrangement of five-axis milling of square steel blades

Leaves can basically be divided into three parts: root, body and crown.

Generally, square steel blades have single T or double T-shaped blade roots, with at least two or more blade root grooves, as well as the inlet and outlet side planes and the inner back radial plane;

The blade body is composed of several profile lines, which are divided into four parts: inner arc, back arc, steam inlet edge, and steam outlet edge;

The uppermost part is the blade crown. Like the blade root, the two sides and the inner and back radial surfaces must also be processed; the area where the profile and the blade root and blade intersect is transitioned by a rounded corner, which is called a turn. catch.

When preparing a blade, the first thing to consider is the formulation of a process plan. Based on the structural characteristics of the product as well as the accuracy level and technical requirements, the most stable clamping method and the most reasonable processing method are determined, such as the high-pressure of a combined cycle unit. For moving blades, the most demanding requirements should be the size of the two sides and the pitch between the inner radial surfaces, as well as the position between the blade root and the blade crown. The most basic clamping method is one clamp and one top. However, in order to ensure the consistency of the process datum, the positioning process boss and center hole are first processed on the vertical machining center, and then the entire process is carried out based on the processed positioning datum. Processing of blades. In order to ensure the accuracy of both sides and pitch, these parts are processed with the same precision milling cutter, and online measurement is used. The two sides of the blade root or blade crown are processed first, measured online, and the tool length is adjusted. Align the two sides, and then use the adjusted tool length to process the inner radial surface of the corresponding part to ensure the pitch requirements.

The entire process is arranged as follows:

1. On the five-axis vertical machine tool, in one clamping process, the clamping process boss of the square steel is first processed, and then the center drill is used to process the center holes for positioning at both ends. This fully ensures the consistency of all process benchmarks;

2. Position the process boss and the center hole, and clamp it on the five-axis machine tool by pressing one end and tightening the other;

3. After the clamping is firm, first clear up the entire wasteland to remove a large area of margin;

4. Rough machine the two sides of the tip of the tailstock and the inner back radial surface, then use a fine milling cutter to finish machining the two sides at a slightly larger amount, measure online, compare it with the nominal size after the increased amount, and adjust the tool length accordingly. Then process until the two sides are accurate; then use the last adjusted tool length to finely mill the inner back radial surface of the tailstock side;

5. Repeat the above steps and the method of online measurement and adjustment of the knife length to accurately determine the two sides of the drive end clamp and the inner radial surface of the part;

6. Then rough mill the profile and transfer the two transition fillets, leaving a margin of 0.5 to 1MM on one side;

7. Then rough and fine mill to process the blade root groove and steam seal as well as each chamfer and process groove;

8. Rotary machining and fine milling of the profile, as well as two transfers; if the margin is large, you can also add one step of semi-finishing;

9. Finally, mill out the blade top and blade root bottom surface, and use a keyway milling cutter to drill out the semicircular groove on the blade root bottom surface to complete the processing of all parts.

For large-area land reclamation, rough milling of both sides, radial surfaces and rough milling profiles, the same φ40MMR6 rough milling fillet blade is used. The blade is a φ12MM round blade, with low speed and large feed. method for processing. The fine milling cutter for fine milling both sides and the radial surface is a φ63MM insert cutter, using an R0.5 square shoulder insert. The fine milling cutter for fine milling the profile is a φ20MMR4 insert cutter, using a φ8MM round insert. The transfer part uses a 4° taper ball nose cutter. As for the rest of the root groove and other parts, solid carbide end mills are used. According to different groove widths, different diameters and R angles are selected, as well as different processing parameters.

The initial process plan is to process all parts on a five-axis machine, regardless of rough and finish machining, and place the process boss on the side of the blade crown. Then when clamping, the blade crown is pressed at the fixture and the blade root is It was placed at the tip of the tailstock, and a large number of vibration patterns appeared in the inner and back radial surfaces of the blade root processed in this way. No matter how the processing parameters were adjusted, the results were not ideal, and the longer the blade, the more serious the vibration patterns were. Later, the process plan was changed. The process boss is placed at the blade root and pressed tightly against the blade crown side, which solves the problem of radial vibration marks. Another problem that troubled us was the processing of the semicircular groove on the bottom surface of the blade root. Because it was not perpendicular to the radial surface, the left and right position tolerance requirements could not be guaranteed. For this, a lot of time and blanks were wasted. In the end, after communicating with the craftsmen, we had to Put the semicircular groove on the three-axis equipment to make it.

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