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Figure 1 Rudder Parts Diagram The rudder (Figure 1) is one of the important parts of the ship. Its symmetrical keyway has both dimensional accuracy requirements and shape-position tolerances, and its keyway is up to 575mm. How to effectively process its keyways has plagued many companies. For a long time, the C630 and C650 machine tools have been used for cantilever milling in actual machining. After manual processing, they are then researched and formulated. It is not only labor-intensive and takes a long time (processing time is as long as 1 month), but also requires high operator demand. The quality is difficult to guarantee. For this purpose, we designed a special milling and keyway machine to better solve the processing of the rudder keyway. 1 Design plan The key technology adopted for keyway processing: Roughly mill the keyway with a Ø30mm coarse-tooth end mill, then use a Ø30mm fine-tooth end mill to finish-mill the side of the keyway, and then use a flying knife to mill the bottom of the keyway. Finally, the side of the keyway is prepared (this step is used to determine if it is to be used according to the test conditions).
Rudder Keyway cutting parameter table Cutting parameters Roughing Finishing Side cutting Milling Cutting speed (r/mm) 150 180 150 Feed (mm/tooth) 0.15 0.10 Depth of cut (mm) 3.5 0.5 0.25 Milling, end mills The flying knife has been cutting continuously. When the cutting teeth periodically cut into the metal, the cutting force is periodically changed from cutting to cutting. The rudder part material is ZB55. After normalizing, the hardness of the substrate is 220 to 280 HB. The milling force is larger than that of ordinary carbon steel. The keyway is too long, the overhang of the cantilever milling head is long, and the rigidity of the cantilever system is not easily improved from the structure. In order to give full play to the cutting performance of the end mill and improve the production efficiency, it is particularly important to select the appropriate cutting speed, feed amount, cutting depth and cutter diameter. Otherwise, the cutting power is increased, the load of the milling motor is overloaded, and a boring car occurs and the tool device is damaged. For the sake of safety, we have added a factor of insurance based on the conventional recommended cutting parameters. At the same time, the cutting speed and feed rate are controlled by a variable frequency motor to achieve stepless speed regulation, so that in the actual milling process, different tools and work steps are selected according to different materials, and the cutting depth, feed per tooth, and cutting are reasonably selected. speed. Regarding the choice of cutter diameter, considering the rigidity of the boom milling, try to use a small-diameter cutter. Because the diameter is too large, the cutting torque is increased and cutting vibration is easily caused. If the diameter is too small, the milling cutter is poor in rigidity and the production efficiency is low. When designing, choose Ø30mm end milling cutter as power parameter design basis. The machining of the above rudder keyway is intended to use the cutting parameters shown in the following table. Because the keyway is on the inner wall of the tapered hole and the bottom surface is a tapered surface, the feed direction of milling should be consistent with the direction of the busbar of the tapered hole, and the included angle with the centerline of the rudder part cone bore is equal to half of the taper angle of the rudder taper. By rotating and translating the center of the workpiece to adapt to the milling feed direction, the manual feed in the vertical direction is complemented by the high-precision raster readings to ensure the width of the keyways and the mutual position. 
1. Cycloid reducer 2. Ball screw 3, 9. Adjusting screw
4. Gear reducer 5. Vertically move the handwheel 6. Rotary milling head
7. Milling cutter 8. Vertical carriage 10. Dial 11. Horizontal handwheel
12. Drag the plate 13. Move the handwheel in the longitudinal direction 14. Change the handle
Fig. 2 Schematic diagram of the machine tool structure (overhead view) 2 The main structure and operation of the special machine Fig. 2 is a schematic diagram of the structure of the milling and key slot machine tool. It consists of four parts: longitudinal feed, transverse depth of cut, vertical feed and main motion mechanism. The longitudinal feed mechanism implements a longitudinal automatic milling cutter, and a cycloidal pin gear reducer 1 (BWY-23-2.2kW) pushes the rotary milling head 6 longitudinally through a pair of gear transmission ball screw pairs 2. In order to facilitate the adjustment of the machine tool and protect the frequency converter, a pair of double slip gears are added to achieve manual and maneuvering conversion by changing the handle 14 . The frequency range set by the inverter is 35~50Hz, and the speed range of the automatic knife is 30~325mm/min. The depth cut mechanism controls the depth of the keyway, and the vertical feed mechanism ensures the width of the keyway. Both are achieved manually by a screw nut, a laterally moving hand wheel 11, and a vertically moving hand wheel 5. Due to the dimensional accuracy of the keyway width of H8, the precision of the key reading is ensured by the vertical grating reading. The keyway depth is determined by the horizontal handwheel scale ring. Both horizontal and vertical carriages are provided with adjustment screws 3 and 9 which are locked during processing to eliminate gaps. The main movement mechanism realizes the rotary motion of the milling cutter. It is transmitted from the gear reducer 4 (TCJY132F-335-3) to the transmission shaft through the elastic coil pin coupling, and transmitted to the main shaft through a pair of bevel gears (the ratio of gears is 1:1). . Because the keyway is 90H8 wide and the milling cutter is Ø30mm, the reducer, milling headstock, etc. are tightly coupled to the vertical carriage and move with vertical feed. To mill symmetrical keyways, the headstock of the milling cutter must be rotated and positioned 180°. The speed reducer motor is frequency-converted to make the spindle speed adjustable from 60 to 320r/min. The specific operation process is: clamping the workpiece correction, roughing one end keyway, rotating the work table to install the workpiece and moving, eliminating the gap in each part and locking, rotating the spindle box spindle 180 °, roughing the other end of the keyway. To change the fine tooth end mill, finish the side of the keyway, move the other side of the keyway of the fixed dragging plate vertically, and similarly change the symmetrical side of the milling keyway. The actual milling process shows that the side milling speed of the finishing milling should be lower than the predetermined speed to meet the requirements of the side roughness. The special plane design satisfies the processing requirements of the rudder parts, and the bottom of the keyway does not need to be ploughed to reach the user's requirements, which is better than the design. 3 Design and Operation Precautions The cantilever is long, and the milling process is an interrupted cutting process. The mechanical impact causes the cutting force to fluctuate. Therefore, the rigidity of the structure of each part, the diameter of the tool, and the choice of cutting parameters should be fully considered in the design process. . During operation, the manual carriage and vertical feed must lock the moving carriage to eliminate gaps. The ZG55 has poor cutting performance, a large cutting load, a good rigidity of the clamping mechanism of the workpiece, a large clamping force, and a stable workpiece during the milling process. If the workpiece is loose, the machining surface will be rough and the milling cutter will chip. In severe cases, the cutter body, workpiece or machine tool will be damaged. The direction of rotation of the milling and the direction of longitudinal feed should be chosen so that the radial resistance of the milling cutter is as downward as possible, so as to avoid gaps between the lateral carriage and the bed due to changes in the radial resistance of the milling cutter.
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