Cutting by use of rotating axially moving tool – With control means energized in response to activator...
Patent
1990-03-26
1991-11-05
Howell, Daniel W.
Cutting by use of rotating axially moving tool
With control means energized in response to activator...
10139R, 36447402, B23G 144
Patent
active
050627449
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for confirming the movement of a tap when tapping a thread by employing a spindle directly rotated by a built-in spindle motor in synchronization with a Z-axis motor driving the spindle in the forward and rearward directions along a central axis thereof, in a machine tool, namely, when rigid tapping, more particularly to an apparatus by which a rapid and precise tapping is effected.
BACKGROUND ART
Conventionally a tap is rotated and moved linearly by a spindle motor for rotating the spindle and a Z-axis motor for moving the spindle linearly along an axis thereof, i.e., a direction Z. The spindle is rotated at a set speed corresponding to the pitch of a thread to be cut when a workpiece is tapped by a tap attached to the spindle of a machine tool. In this operation, the motors are affected by load fluctuations during the tapping process, depending on the output of each motor, and thus a thread having a constant pitch is not always formed. Therefore, an error of the pitch of the thread to be tapped is absorbed by a floating tapper tap system, i.e., a system wherein a spring is incorporated to force the tap along the axis of the spindle.
The above-mentioned floating tapper tap system, however, is not always suitable for high speed tapping with a high accuracy, and the products must be inspected for defects, and thus the production efficiency is lowered.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the present invention is to determine whether or not a tapping is too fast for a motor to follow up, and to reduce the number of defective products to thereby achieve a highly effective tapping while both motors are synchronously controlled.
In accordance with the present invention, there is provided an apparatus for confirming the movement of a tap when rigid tapping with a machine tool having a built-in spindle motor for directly driving a spindle to rotate and a Z-axis motor for driving the spindle to move linearly along an axis of the spindle, comprising a detecting means for detecting a rotation of the spindle, a spindle control means for outputting a signal for controlling a rotation of the spindle motor according to a signal output from the detecting means, a Z-axis control means for outputting a signal for controlling a rotation of the Z-axis motor, a synchronous control means for outputting a synchronous signal to the spindle control means and the Z-axis control means, respectively, and a judgement means for judging an ability of the spindle motor to follow up, by comparing a prescribed reference signal with a signal of a rotational error of the spindle calculated by the spindle control means, using the synchronous signal from the synchronous control means and the signal from the detecting means.
A power limit against a load is lower in a built-in spindle motor for directly driving the spindle than in a Z-axis motor for driving the spindle by way of a ball screw shaft, etc., to move linearly along a direction Z. Accordingly, a rigid tapping cannot be effected at an acceleration or deceleration greater than the power limit of the spindle motor, even though both motors are synchronously controlled by the synchronous control means to maintain the pitch of a thread tapped in a workpiece at a constant value. The follow-up ability of the built-in spindle motor is judged by the judgement means by comparing the reference value with a difference between a rotational speed of the spindle motor required for the synchronous control and an actual rotational speed of the spindle driven by the spindle motor and detected by the detecting means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural view of an apparatus for confirming a movement of a tap when rigid tapping according to the present invention; and
FIG. 2 is a diagram for explaining the process of a tapping operation.
BEST MODE OF CARRYING OUT THE INVENTION
The present invention is described in more detail in the following and in accordance with the embodiments shown in the a
REFERENCES:
patent: 4692071 (1987-09-01), Hirota
patent: 4813821 (1989-03-01), Hirota
patent: 4879660 (1989-11-01), Asakura et al.
Nakamura Kosei
Numai Kazuhisa
Fanuc Ltd.
Howell Daniel W.
LandOfFree
Apparatus for confirming movement of tap when rigid tapping does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for confirming movement of tap when rigid tapping, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for confirming movement of tap when rigid tapping will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-495438