Boots – shoes – and leggings
Patent
1982-06-14
1986-02-18
Ruggiero, Joseph F.
Boots, shoes, and leggings
82 2B, 82 5, 318571, 408 11, G06F 1546
Patent
active
045716870
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a screw cutting control system which permits enhancement of screw cutting accuracy through utilization of a numerically-controlled machine tool.
In performing screw cutting using a numerically-controlled machine tool, it is customary in the prior art to carry out the following sequence with a fixed cycle. First, a tap 1 is positioned by a quick feed to a predetermined position in the X-Y plane of a workpiece 2 as shown in FIG. 1(A). Then, positioning of the tap 1 in the Z axis direction is effected by a quick feed while driving a spindle in a forward direction as shown in FIG. 1(B), after which, as shown in FIG. 1(C), the tap 1 is fed in the direction of the arrow at a feed rate dependent on the revolving speed of the spindle and the lead or pitch of the tap 1 while driving the spindle in the forward direction, thus performing screw cutting.
Upon completion of screw cutting of a predetermined quantity, i.e., depth, the rotation and feed of the spindle are stopped. However, the inertia of a spindle motor (not shown) is larger than the inertia of a feed motor (not shown) and even if stop commands are simultaneously applied, they do not stop at the same time but the spindle motor stops after the feed motor stops. Further, even after the feed is stopped, the tap 1 retains thrust if the spindle rotates and, accordingly, the tap 1 is coupled with the spindle through a tapper, or tap holder (not illustrated) for example, a tapper like those manufactured by Tapmatic Corporation. Next, as shown in FIG. 1(D), the spindle is reversed and, at the same time, the tap 1 is fed in the direction of the arrow at a feed rate dependent on the revolving speed of the spindle and the lead of the tap and when the tap 1 gets out of the workpiece 2, the tap 1 is returned by quick feed to a predetermined position as shown in FIG. 1(E).
Screw cutting by the above-described sequence has been accompanied by the following disadvantage. First, during screw cutting, the tap 1 must be fed by the feed motor. The feeding causes vibration which make it difficult to obtain a high degree of screw cutting accuracy. Second, when a stop instruction is received to stop the rotation and feed of the spindle after completion of a predetermined quantity or depth of screw cutting, the tap 1 is moved forward by the inertia force of the spindle motor to continue screw cutting even after the application of the stop instruction, therefore, it is difficult to obtain tapped holes of a designed fixed depth.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the above-described defects, improve the screw cutting accuracy and simplify control.
According to the present invention, the tap is held so as to be movable in the axial direction of the spindle. A tapper, which does not transmit the rotation of the spindle to the tap in the case where the amount of movement of the tap exceeds a predetermined range, is engaged with the spindle. During screw cutting, the feed by the feed motor is stopped prior to completion of the screw cutting and the screw cutting is completed by the trust of the tap resulting from its rotation transmitted from the spindle via the tapper. Accordingly, screw cutting accuracy can be enhanced. Moreover, since the sequence of screw cutting is commanded by one block of command data, control can be simplified.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1(A) to 1(E) are diagrams of the sequence of conventional screw cutting;
FIGS. 2(A) to 2(C) are sectional views of a tool for use in an embodiment of the present invention;
FIGS. 3(A) to 3(F) are diagrams of the sequence of screw cutting in the embodiment of the present invention;
FIG. 4 is a sectional view illustrating the state of the tool during cutting;
FIG. 5 is a block diagram illustrating the embodiment of the present invention; and
FIG. 6 is a diagram of the movement of a spindle.
DESCRIPTION OF THE PREFERRED EMBODIMENT
For a detailed description of the present invention, an embodiment will hereina
REFERENCES:
patent: 3854837 (1974-12-01), Kreithen et al.
patent: 4079235 (1978-03-01), Froyd et al.
patent: 4096770 (1978-06-01), Tanner
patent: 4338556 (1982-07-01), Hetzel
patent: 4342528 (1982-08-01), Nozu et al.
Fukuyama Hiroomi
Isobe Shin-ichi
Fujitsu Fanuc Limited
Ruggiero Joseph F.
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