Cutting by use of rotating axially moving tool – With control means energized in response to activator... – To control infeed
Patent
1995-02-15
1997-02-04
Bishop, Steven C.
Cutting by use of rotating axially moving tool
With control means energized in response to activator...
To control infeed
36447402, 36447417, 408 3, 408 6, B23B 3908, B23B 4900
Patent
active
055991424
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a drilling control apparatus for drilling holes using a numerically controlled machine tool.
BACKGROUND ART
A numerically controlled machine tool drills holes by controlling RPMs of a spindle and a feed axis so that the RPM of the spindle and an amount of feed commanded on a machining program as cutting conditions coincide with an actual RPM of the spindle and an actual amount of feed.
Incidentally, a tip configuration of a drill is gradually changed while drilling operation is repeated. Although proper cutting conditions are also sequentially changed accordingly, unless the conditions are positively changed on the machining program, drilling is carried out with a given amount of feed. Consequently, a load on the drill is gradually changed and holes may be defectively drilled or sometimes the drill may be broken.
Further, even if a load on a drill is very small, since an amount of feed is given, sometimes a drilling efficiency may be deteriorated.
To cope with this problem, there have been conventionally proposed adaptive control methods of preventing an unnecessary load from being applied on a drill.
For example, the applicant proposed in Japanese Patent Application Laid-Open No. 4-240011 an arrangement that a load sensor is disposed in an arbor mounted on a spindle to sense a load torque of a drill and when a detecting signal of the sensor is greater than a set load level, the drill is retracted once and drilling operation is continued again after changing an amount of feed.
In the conventional method, however, since an object to be controlled is a cutting feed speed (F) commanded by a program and the load torque of the drill is indirectly controlled by controlling the cutting feed speed F, it cannot be always said that a load on the drill is properly controlled.
Further, a load torque imposed on a drill is greatly varied by factors such as a depth of a drilled hole, and an amount of chips produced between a drill groove and the inner wall of the drilled hole. In the above conventional method, since an upper limit is set to the load torque and the cutting feed speed F affecting the load torque is positively changed, sometimes the load torque is too abruptly varied and the drill may be broken before the abnormal torque is sensed and the drill is retracted.
On the contrary, when a load is set to a sufficiently low level, the cutting feed speed F must be made small accordingly. As a result, a longer time is needed to drill holes and a drilling efficiency is deteriorated.
Further, since a command of the cutting feed speed F is automatically changed, it is difficult for the operator to get a correct value of the cutting feed speed F at any given time.
DISCLOSURE OF THE INVENTION
Taking the above into consideration, an object of the present invention is to provide a drilling control apparatus capable of properly controlling a load on a drill.
To solve the above problem, in accordance with the present invention, there is provided a drilling control apparatus for drilling holes using a numerically controlled machine tool, which comprises cutting reaction force estimate unit for estimating a cutting reaction force in an axis direction generated between a drill and a workpiece, cutting reaction force monitor unit means for monitoring whether or not a cutting reaction force estimated by the cutting reaction force estimate unit follows a predetermined command pattern, and feed axis torque control unit for controlling a torque of a feed axis of the drill to cause the estimated cutting reaction force to follow the command pattern when the estimated cutting reaction force does not follow the command pattern.
The cutting reaction force estimate unit estimates a cutting reaction force in the axis direction generated between the drill and the workpiece. The cutting reaction force monitor unit monitors whether the cutting reaction force estimated by the cutting reaction force estimate unit follows a predetermined command pattern. When the estimated cutting reaction fo
REFERENCES:
patent: 4451187 (1984-05-01), Ishikawa et al.
patent: 5116168 (1992-05-01), Aihara
Fujimoto Akihiko
Nagatomi Takashi
Sato Naoki
Bishop Steven C.
Fanuc Ltd.
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