Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
1998-11-09
2001-05-01
Martin, David (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S600000, C700S188000
Reexamination Certificate
active
06225772
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement for a numerical control device and an acceleration/deceleration control method for numerical control.
2. Description of the Related Art
Pre-interpolation acceleration/deceleration control and post-interpolation acceleration/deceleration control are known in cases in which tool feed speeds are accelerated or decelerated during transition from the currently executed tool feed step to the subsequent tool feed step on the basis of a tool feed speed specified in advance for each tool feed step by means of tool feed speed values (expressed, for example, in mm/min units), which are given by the amount of movement (tool feed distance) to be made per unit time.
However, in turning, tapping and other type of machining, tool feed rate (for example, mm/rev) for each tool feed step, which is commanded in terms of feed distance per a single rotation of or unit angle of the spindle (hereinafter referred to as an amount of movement per unit angle of the spindle) and rotational speed of the spindle (for example, rev/mm), which substantially represents an angular speed of the spindle, are specified so that the tool is fed according to the rotational speed of the spindle. Consequently, a tool feed speed (for example, in mm/min) expressed as the amount of movement per unit time cannot be provided as part of machining data in a program. As a result, the aforementioned pre-interpolation acceleration/deceleration control based on the tool feed speed expressed as the amount of movement per unit time cannot be applied to turning, tapping, or other types of machining.
In some conventional numerical control devices, the tool feed speed (for example, in mm/min), expressed as the amount of movement per unit time at each tool feed step, is calculated on the basis of the tool feed rate (for example, in mm/rev) at each tool feed step, expressed as the amount of movement per unit rotation angle of the spindle, and on the basis of the current value (for example, in rev/min) of the rotational speed, substantially expressed as the angular speed of the spindle; and this tool feed speed is used for carrying out the post-interpolation acceleration/deceleration control of the tool feed speed at the currently executed tool feed step, which is expressed as the amount of movement per unit time.
However, according to such post-interpolation acceleration/deceleration control, acceleration/deceleration control is carried out after interpolation, thus creating shape errors in the work.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to prevent the above-described drawbacks of prior art and to provide a pre-interpolation acceleration/deceleration control method and a numerical control device capable of performing precision machining without creating shape errors in the work even when the rotation angle of the spindle varies in cases in which tools are caused to feed in a manner dependent on the rotational speed of the spindle, as in turning, tapping, or the like.
In the present invention, the numerical control device for controlling a tool feed speed on the basis of a tool feed speed expressed as the amount of tool movement per unit rotation angle of the spindle comprises means for sensing the actual feed speed of the spindle; command conversion means for achieving conversion to a tool feed speed, expressed as the amount of movement per unit time, on the basis of an instructed tool feed speed and the actual rotation angle of the spindle sensed by the aforementioned sensing means, and obtaining a speed command for a tool; and means for performing pre-interpolation acceleration/deceleration control on the basis of the current tool feed speed converted by said conversion means and expressed as the amount of movement per unit time, and a subsequent tool feed speed expressed as the amount of movement per unit time, wherein performing of pre-interpolation acceleration/deceleration control on the basis of the tool feed speed which was converted to the amount of movement per unit time allows pre-interpolation acceleration/deceleration control to be performed even in execution of a machining program in which the tool feed speed is defined as the amount of movement per unit rotation angle of the spindle.
According to the present invention, even when a tool feed rate for each tool feed step is commanded in terms of the amount of movement per unit rotation angle of the spindle, a tool feed speed for each tool feed step, which is expressed as the amount of movement per unit time, is automatically calculated based on the actual rotational speed of the spindle, and a tool feed speed expressed as the amount of movement per unit time, which is to be designated for the subsequent tool feed step, is also calculated in advance on the basis of the actual rotational speed of the spindle, thereby making it possible to adequately implement pre-interpolation acceleration/deceleration control of tool feed and to effectively prevent shape errors from developing during cutting even when the rotation angle of the spindle varies in cases in which tools are caused to feed in a manner dependent on the rotational speed of the spindle, as in turning, tapping, or the like.
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Aizawa Nobuaki
Miyajima Hidehiro
Fanuc Ltd.
Martin David
Staas & Halsey , LLP
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