Machining the spiral groove of the focusing cylind

2022-08-26
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Turning center machining focusing cylinder spiral groove

this paper analyzes the problems in the milling of cylinder parts' circumferential through wall spiral groove, and introduces how to realize normal machining from the improvement of fixture structure to programming and debugging

1 analysis of parts processing condition

the focusing cylinder (aluminum part) shown in Figure 1 is to process a straight arc building sound insulation measurement specification GBJ 75 (8) 4-shaped through wall groove and two-stage spiral through wall groove on the turned cylindrical blank. The wall thickness of the part is 4mm, and 4 milling cutters can be used to mill grooves directly, but it needs to be realized by using the additional fourth axis of the machining center or the c-axis function of the turning center. The turning center machine tool is selected in this paper

after processing with the simple fixture shown in Figure 2, it is found that because the groove is processed through the wall and the groove shape is long, simply using axial clamping will not meet the requirements of groove width due to clamping deformation during processing. In the middle section of the straight arc groove, the groove width can only reach 3.4mm, and the width of 4mm near the two ends of the groove cannot be guaranteed. Although the deformation of the chute is smaller, it can not meet the size requirements, and the height of the cylinder column has changed accordingly. The degree of deformation is proportional to the axial clamping force. If the clamping force is too small, it will also cause the relative rotation of the workpiece during milling. This fixture structure is only suitable for circumferential milling of shallow grooves, but not for milling of through wall grooves

Figure 1 focusing cylinder

Figure 2 axial clamping structure

improved design of fixture structure

centering fixture with inner wall positioning for cylindrical parts generally adopts elastic internal expansion clamping method, which can change the force application mode of axial clamping into radial force application mode, which is the best solution to prevent axial deformation and is suitable for the requirements of clamping and positioning of this part. However, the structural form of the standardized fixture is relatively complex. Referring to its working principle, the original fixture has been improved, the simplified structural form shown in Figure 3 has been adopted, and an elastic wedge sleeve matching with the mandrel in a cone has been added, which not only effectively ensures the processing quality requirements, but also reduces the manufacturing cost

Figure 3 elastic internal expansion clamping structure

in order to ensure the reliability of the fixture, the following considerations should be taken into the design and manufacture of the fixture:

· the elastic wedge sleeve and spindle should be ground according to the matching requirements, and the taper should not be too small

· the elastic wedge sleeve 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 moving distance of the front end of the elastic wedge sleeve is designed according to the calculated value of radial expansion and fit taper +1 ~ 2mm

· in order to facilitate wire cutting processing, the opening slots of the elastic wedge sleeve should be designed as an even number of 4 or 6

· since the spiral groove of the focusing cylinder is a through groove in the direction of wall thickness, a 0.2mm deep tool giving space can be pre machined on the outer circular surface of the wedge sleeve

· the spring is used to assist the pulling out of the elastic wedge sleeve. When unloading, only loosen the lock nut. When the workpiece and the elastic wedge sleeve are loose, the workpiece can be taken out. Loading and unloading the workpiece is simple and fast

3 design of parts processing program on turning center

when milling in turning center, the spindle should be converted to feed axis C, and the power head should be installed on the 11th tool position of the cutter head to realize the rotation movement of milling tools. The workpiece coordinate origin is set at the rotation center of the right end face of the workpiece, and the direction of each coordinate axis is shown in Figure 3, then the part processing program is designed as follows:

01235

g98 (feed per minute mode)

m24 (switch to milling mode)

G28 U0 W0

t1100 (change T11 tool)

G28 H0 (c-axis zero return orientation)

G0 g54 z-5 5 (feed to the starting point of straight arc groove)

m13 S3000 (start the power head)

g0 x62.5 (lower the knife to the vicinity of the outer surface of the workpiece)

m98 p1236 L9 (call the subroutine for 9 times)

g0 X100 (radial tool withdrawal)

m15 (close the power head)

g28 u0

g28 W0 (x, Z return to zero)

g28 H0 (c axis return to zero orientation)

m30

01236

g1u-13 F100m08 (cutting and cutting)

h180 F300 (milling straight arc groove)

g0 u13 (knife lifting)

w-7 (move to the starting point of another slot)

g1 u-13 F100 (lower the knife and cut in 0.5mm)

w-12 H-180. F300 (milling spiral groove)

g0 u13 (knife lifting)

z-12 5 (move to the starting point of another slot)

g1 u-13 F100 (lower the knife and cut in 0.5mm)

w-12 H-180. F300 (milling another spiral groove)

g0 u12 M09 (lift the knife, less 0.5mm)

z-5.5 (move to the Z position of the starting point of the straight arc slot)

g28 H0 (turn to the starting point of the straight arc slot, and prepare for the next layer)

m99 (return to the main program)

the above programs are written according to the program format requirements of FANUC Oi TB NC system. Because the tool used is small and limited to the power of the power head, the program is designed in the form of main and subroutine calls according to the cutting depth of each layer of 0.5mm. After milling three slots in each layer, the tool is raised and returned to the cutting position of the first slot before milling the next layer

using the programming form of subroutine call can better solve the problem of layered repeated processing, but the temperature range of checking the cooling speed is different from the same sequence size, which greatly simplifies the amount of program. However, the design of the initial depth and the amount of tool lifting each time is the key. As an important part of the instrument, the fixture of the electronic tensile testing machine in this procedure adopts incremental programming. After milling three grooves in each layer, lift up 0.5mm less. The height position of the first cutting should be calculated and determined outside the workpiece surface according to the tool lifting position after milling the last layer

4 conclusion

the fixture for milling through wall slots is different from the fixture requirements for milling shallow slots. The radial force application method of elastic internal expansion clamping is the best solution to prevent axial deformation. Fixture design does not necessarily adhere to standards, as long as you understand the principle, combined with the actual application, I hope that all operators can keep in mind the situation and simplify its structure, so as to meet the use requirements, operate simply and improve efficiency

the circumferential milling groove of cylindrical parts needs to be processed by turning center or machining center with additional rotation axis, but the milling function of turning center is usually low-power design, so its programming processing is different from that of machining center. As long as you master the programming rules and grasp the key points, you can design the correct program. (end)

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