The way of the knife: As shown in Figure 1, the spiral feed is adopted, that is, the tool rotates half an arc in the X and Y planes (reverse), and the pitch increases or decreases by 0.5 pitch in the Z direction. This reduces the vibration during the infeed, improves the tool life and the quality of the thread surface, and allows the machined thread to have a half-buckle smooth transition.
Feeding mode: Radial feed is divided into 3 depths of cut, and the side feed mode in thread turning is used, as shown in Figure 2. In order to fully reduce the radial force during machining, avoid vibration and improve tool life. It should be noted that in the first and second cutting depths, the axial offsets t1 and t2 with respect to the third cutting depth position are determined by calculation to ensure that they are not located outside the thread contour. Causes the thread to be overcut. Here, t1=0.10 and t2=0.05.
Cooling method: internal cooling. Because it is a blind hole, it can be fully cooled while using internal cooling to remove iron filings.
Cutting parameter selection: cutting speed Vc=81m/min, then speed N=1000 Vc/(D2×p)=1000×81/(14×3.14)=1842r/min; feed rate fz=0.075mm/Z, then The feed speed at the cutting edge of the milling cutter is F1=fz×N×Z=0.075×6×1842=828mm/min. The centering feed rate of the milling cutter should be given during programming F2=F1(D0-D2)/D0=828 ×(16-14)/16=103 mm/min. In addition, in order to avoid the vibration during cutting, each time the cutting is performed with a semicircular arc, the feed is F2 = 50 mm/min.
4 Programming
According to the determined processing methods and parameters, the program can be programmed as follows. The numerical control system is Siemens 840D. This program is only used as a subroutine for machining a threaded hole.
G90 G17
S1842 M3
G0 X0.000 Y0.000 Z2.000
G91
G0 Z-18.750
(1st deep cutting)
Z-0.10 (axial offset t1)
G41 G1 X0.000 Y7.000 F828
G3 X0.000 Y-14.815 Z0.750 I0.000 J-7.408 F50
G3 X0.000 Y0.000 Z1.500 I0.000 J7.815 F103
G3 X0.000 Y14.685 Z0.750 I0.000 J7.408
G40 G1 X0.000 Y-7.000
(2nd deep cutting)
Z0.15 (axial offset t2)
G42 G1 X0.000 Y7.000 F828
G2 X0.000 Y-14.9 Z-0.750 I0.000 J-7.45 F50
G2 X0.000 Y0.000 Z-1.500 I0.000 J7.9 F10
G2 X0.000 Y14.865 Z-0.750 I0.000 J7.45
G40 G1 X0.000 Y-7.000
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