In CNC Turning, the tall error of point of a knife of lathe tool can affect the dimension precision of turning workpiece, this is in axis of a flight of stairs of turning high accuracy kind when the spare parts particularly apparent. Because of CNC Turning when, the feed dimension of cutting tool relies on set of numerical control program, and people often is used to axes of pair of turning a flight of stairs kind the spare parts uses a knife will big, small outside the circle is successive one knife car is become, such, to machining the spare parts of a flight of stairs with tall precision, if is big, small outside round tolerancepublic errand value is in IT7 class less than, people often can discover in to program true condition falls, small outside round dimension is in tolerancepublic errand less than, and big outside round dimension is incorrect however, contrary perhaps; Aperture of boring a flight of stairs is such also, by the point of a knife of cutting tool tall error causes this, with respect to cutting tool point of a knife tall error is opposite below the influence that machines precision of spare parts dimension makes an analysis. Graph the graph shows 1 treatment sketch map 1 times to be R for big round radius, roundlet radius is the spare parts of axis of a flight of stairs of R, wait when lathe tool point of a knife and line of workpiece circumgyrate axes tall when, the step dimension of turning is L; When lathe tool point of a knife under or when line of axle center of prep above work, want to satisfy the dimension requirement of big, small axis, the step measure that requires turning is L, l of apparent L ≠ , that is to say from big outside when the circle begins turning to be worth to set of numerical control program, small outside the circle did not achieve dimension requirement, put in the error apparently. Hypothesis is normal when point of a knife is tall, cutting tool nods cutting to Q from P, radial feed dimension is L, if point of a knife is H under height of line of work axle center, criterion actual cutting method became cutting tool to begin to M dot from N small outside round cutting, namely PQ=NM=L, with O right now the dot is the centre of a circle, OM makes a circle for radius, hand in OP to be nodded at T, so small outside round on size error is QT namely, set QT=d, the size of D can be gotten through the geometrical operation below. Foregone: PQ=NM=L; OS=h; OT=OM; ON=R; OQ=r, above of SM2)½={h2+[(R2-h2) ½-L]2}½=[R2+L2-2L(R2-h2)½]½ D=QT=OT-OQ=OM-r=[R2+L2-2L(R2-h2)½]½-r of ＋ of SN=(ON2-OS2)½=(R2-h2)½ SM=SN-MN-L=(R2-h2) ½-L OM=(OS2 is namely small outside the computation of D of round on size error is formulary, adopt this form but ration plan cipher out is small outside round on size error. Express tall error of 1 point of a knife to be worth H(mm) 0 of relation of H and D of value of on size error.
3 0.
4 0.
5 0.
6 0.
7 0.
8 0.
9 1.
0 D(µm) 2.
6 4.
6 7.
1 10.
3 14.
0 18.
3 23.
2 28.
6 watches H of value of tall error of 2 point of a knife and H(mm) 0 of relation of D of value of on size error.
1 0.
2 0.
3 0.
4 0.
5 0.
6 0.
7 0.
8 0.
9 1.
0 D(µm) 0.
4 1.
6 3.
6 6.
4 10.
0 14.
4 19.
6 25.
6 32.
4 40.
0 below the computation that passes specific example, will show the concern of D and H further. Be like the spare parts of axis of a flight of stairs of successive turning, big outside round diameter is 14mm, small outside round diameter is 10mm, so the impact that through going up type can get H and D (1) seeing a table. Be like the spare parts of axis of a flight of stairs of successive turning again, big outside round diameter is 100mm, small outside round diameter is 20mm, so the impact that through going up type can get H and D (2) seeing a table. From above two computation can see as a result, the axis of a flight of stairs to machining high accuracy (aperture) kind spare parts, the influence of tall error of point of a knife often cannot be ignored, especially two axes (aperture) the diameter differs bigger, the error with tall point of a knife is bigger also to the influence of dimension precision. CNC Milling