Figure 1 Focusing tube
1. Analysis of parts processing conditions Figure 1 shows that the focusing cylinder (aluminum part) is a straight arc-shaped wall-penetrating groove and a two-stage spiral-through-wall groove processed on a car-shaped cylindrical blank. The wall thickness of the part is 4mm, and the Ø4 milling cutter can be used to directly layer the milling slot, but it needs to use the additional 4th axis of the machining center or the C-axis function of the turning center. This article uses the turning center machine tool. When using the simple jig shown in Fig. 2, it is found that because the groove is formed through the wall and the groove shape is long, the axial clamping pressure is simply adopted, and the requirements for the unwrinkled width cannot be guaranteed due to the compression deformation during the processing. The width of the groove in the middle of the straight arc groove can only reach 3.4mm, and the width of 4mm cannot be guaranteed near both ends of the groove. Although the chute deformation is smaller, but it can not meet the size requirements, the height of the cylinder column has also been changed, the degree of deformation is proportional to the size of the axial clamping force, clamping force too small can also cause milling Relative rotation of the workpiece. This jig structure is only suitable for the case of circumferential milling of shallow grooves, and is not suitable for milling through wall grooves.
Figure 2 axial clamping type clamping structure
Figure 3 Elastic inner expansion clamping structure
2 Improved design of clamp structure The centering fixture for the cylindrical part with inner wall positioning generally uses the elastic expansion clamping method, which can change the axial clamping pressure to the radial direction and prevent axial deformation. The best solution is to meet the requirements for the positioning of this part. However, the standardized fixture structure is more complex. Referring to its working principle, some improvements have been made to the original fixture. The simplified structure shown in Fig. 3 has been adopted. An elastic wedge sleeve with a tapered surface of the spindle has been added. It is effective. To ensure the processing quality requirements, but also reduce manufacturing costs. In order to ensure the reliability of the fixture, the fixture design and manufacturing should be considered as follows: The elastic wedge sleeve and the mandrel should be ground according to the matching requirements, and the taper should not be too small. Elastic wedges should be quenched to obtain hardness. The elastic wedge sleeve should be 0.2mm smaller than the inner hole size of the focusing cylinder workpiece in the free state. The axial movement distance of the front end of the elastic wedge sleeve is designed according to the radial expansion amount and the calculated value of the fitting taper of +1 to 2 mm. In order to facilitate the wire cutting process, the elastic wedge sleeve opening groove should be designed to be an even number of 4 or 6. Since the spiral groove of the focusing cylinder is a through groove in the wall thickness direction, a 0.2 mm deep knife space can be pre-machined on the outer surface of the wedge sleeve. The spring is used to assist the pull-out of the elastic wedge sleeve, and only the lock nut needs to be loosened when unloading the workpiece. When the workpiece and the elastic wedge sleeve are loose, the workpiece can be taken out and the loading and unloading of the workpiece is simple and quick. 3 Design of the part machining program on the turning center When machining the turning center, the spindle should be converted to the feed C axis, and the power head should be mounted on the No. 11 position of the cutter head to realize the rotary motion of the milling tool. The workpiece coordinate origin is set at the rotation center of the right end surface of the workpiece. The direction of each coordinate axis is as shown in Fig. 3. The part machining program is designed as follows: 01235 G98 (feed per minute mode) M24 (switch to milling mode) G28 U0 W0 T1100 (For T11 tools) G28 H0 (C axis zero return orientation) G0 G54 Z-5. 5 (Plunge to the starting point of arc groove) M13 S3000 (Starting the power head) G0 X62.5 (Lower knife to the outer surface of the workpiece) M98 P1236 L9 (Call subroutine 9 times) G0 X100 (Radial retraction) M15 (Turn off the power head) G28 U0 G28 W0 (X, Z return-to-zero) G28 H0 (C-axis zero return orientation) M30 01236 G1U-13. F100M08 (Lower knife cut in) H180. F300 (Milling straight slot) G0 U13. (Windle) W-7. (Move to the beginning of another slot) G1 U-13. F100 (Lower knife and cut in 0.5mm) W -12. H-180. F300 (Milling Spiral Groove) G0 U13. (Winching) Z-12. 5 (Move to the beginning of the other slot) G1 U-13. F100 (Knife down and cut in the 0.5mm) W-12 H-180. F300 (milling another spiral groove) G0 U12. M09 (tool pick, 0. 5 mm less) Z-5.5 (move to Z position at the start point of straight groove) G28 H0 (go to start point of straight groove , to prepare for the next layer) M99 (return to main program) The above program is based on FANUC-Oi-TB numerical control system Programs written format requirements. Due to the small tool used and limited to the power of the power head, the program cuts the depth by 0.5mm per layer and designs in the main and subroutine calls. After each layer has finished milling three slots, the knife is returned to the first slot under the knife. Then mill a layer. Adopting the programming form of the subroutine call can solve the problem of the program size of the layered repetitive processing and greatly simplify the program. However, the initial depth and the design of the amount of each tool are the key. This program uses incremental programming. After each layer has been milled three slots, it is less 0.5mm upward. The height of the first tool should be finished according to the last layer. The position of the rear knife is guaranteed to be determined externally on the surface of the workpiece. 4 Conclusions Milling through the wall slot fixture is different from the requirements of the milling shallow groove fixture, the use of elastic inner expansion clamping radial force, is the best solution to prevent axial deformation. Fixture design does not have to be rigidly adhered to standards, as long as the principle is understood, and its structure is simplified in light of actual application conditions, so as to meet the requirements of use, and to be able to operate simply and increase efficiency. The circumferential groove of a cylindrical part needs to be machined using a turning center or a machining center with an additional rotary axis. However, the milling function of a turning center is usually a low-power design. Therefore, the programming process is different from the machining center. As long as the programming rules are mastered, the key points are grasped. , you can design the correct program.
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