Gear cutting – milling – or planing – Milling – Process
Reexamination Certificate
2001-12-21
2004-11-30
Cadugan, Erica (Department: 3722)
Gear cutting, milling, or planing
Milling
Process
C409S084000, C409S196000, C700S188000, C700S174000, C700S171000
Reexamination Certificate
active
06824336
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
1. Field of the Invention
The present invention relates to a method and a system for controlling a numerical control cutting machine for cutting a work.
2. Description of Related Art
It is common for cutting operation such as numerically controlled cutting operation to feed a rotating cutting tool on a cutting surface of a metal work along a specified path. During the cutting operation, the rotating cutting tool possibly encounters a change in cutting load. In order, for example, to cut an object work having a number of free curved surfaces such as a metal mold for press-forming a body component of a vehicle, it is popular to use a ball end mill as a three-dimensional rotating cutting tool. Even this ball end mill is apt to be so often applied with load in excess.
In order for the rotating cutting tool to be free from being applied with cutting load in excess, it is conventionally practiced to control a relative feed speed of the rotating cutting tool according to a change in cutting load that is detected during cutting. It has been proposed in, for example, Japanese Unexamined Publication No. 61-30355 to prevent cutting edges of a rotating cutting tool from being damaged due to an excessive cutting load. This is realized by starting adaptive control in response to detection of contact of the rotating cutting tool with an object work and reducing a tool feed speed at a start of the adaptive control.
It is advantageous to protection of a rotating cutting tool from being applied with cutting load in excess to vary the tool feed speed according to cutting load during cutting operation. However, although the cutting load is detected by monitoring a load current on a main spindle motor, the load current is affected by various factors, so that it is hard to regard the load current as representing true cutting load and, in consequence, it is hard to securely protect the rotating cutting tool from being applied with cutting load in excess. Further, regarding the NC machining systems, cutting is performed under the control of program telling a cutting procedure, a tool path, cutting conditions and the like. This makes it hard to change control variables according to a change in load current during cutting. Therefore, in order to prevent the rotating cutting tool from being damaged, it is essential to set a constant tool feed speed so as to fit part of an object work where the rotating cutting tool is applied with heaviest cutting load. In this case, the rotating cutting tool is fed at a comparatively low tool feed speed even over part of the object work where the rotating cutting tool is applied with light cutting load.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for controlling a numerical control cutting machine which can prolong service life of a rotating cutting tool by preventing the rotating cutting tool from being applied with loaded in excess.
It is another object of the present invention to provide a method for controlling a numerical control cutting machine that can save cutting time.
The aforesaid objects of the present invention is achieved by a cutting machine control method of controlling a numerical control cutting machine equipped with a rotating cutting tool, such as a ball end mill, for cutting a surface of a work.
According to an aspect of the present invention, the cutting machine control determines a required stock-removal volume to be removed from an object work along a tool path on the basis of a blank configuration of the object work and variably controls a tool feed speed of the rotating cutting tool along the tool path according to the required stock-removal volume so that the rotating cutting tool removes a predetermined stock-removal volume of material from the object work per unit time.
Because the stock-removal volume of rotating cutting tool per unit time is substantially proportional to cutting load applied to a rotating cutting tool, it is not too much to say that observing a stock-removal volume of the rotating cutting tool per unit time is equivalent to observing a cutting load indirectly. As the cutting machine control of the invention controls a tool feed speed so that a stock-removal volume becomes a specified or target stock-removal volume, when the target stock-removal volume is appropriately established, the rotating cutting tool is prevented from being applied with a cutting load in excess. This contributes to a long service life of the rotating cutting tool. That is, to bring a stock-removal volume per unit time to the predetermined stock-removal volume implies a change in tool feed speed according to a required stock-removal volume from a work along a tool path. Therefore, each cutting edge of the rotating cutting tool is prevented from being applied with a cutting load in excess by decreasing a tool feed speed for part of the work that has a large required stock-removal volume. In addition, the rotating cutting tool is fed at an increased tool feed speed for part of the work that has a small necessary stock-removal volume, this contributes to making a cutting time for the entire pan of a work as short as possible.
According to another aspect of the present invention, the cutting machine control determines a required stock-removal volume to be removed from an object work along a tool path on the basis of a blank configuration of the object work and variably controls a tool feed speed of the rotating cutting tool along the tool path according to the required stock-removal volume so that the rotating cutting tool removes a predetermined stock-removal volume of material from the object work per one revolution.
Because the stock-removal volume of cutting edge per one revolution is substantially proportional to cutting load applied to a cutting edge, it is not too much to say that observing a stock-removal volume of one cutting edge per one revolution is equivalent to observing a cutting load applied to the cutting edge indirectly. When controlling fir tool feed speed of the rotating cutting tool so that the cutting edge removes the specified stock-removal volume per one revolution, there occurs no significant difference in cutting load applied to one cutting edge irrespective of differences in the number of cutting edge and/or speed of rotation of the of the rotating cutting tool. Therefore, each catting edge of the rotating cutting tool is prevented from being applied with a cutting load in excess irrespective of the number of cutting edges and speed of rotation of the rotating cutting tool. This contributes to a long service life of the rotating cutting tool In addition, the rotating cutting tool is fed at an increased tool feed speed for part of the work that has a small necessary stock-removal volume, it is prevented that a cutting time for the entire work is made long.
The required stock-removal volume may be determined for each of a plurality of component path sections into which the whole length of the tool path is divided. In this event, the rotating cutting tool is fed at a constant tool feed speed along the component path section so that the rotating cutting tool removes the required stock removal volume from the object work for the component path section when the rotating cutting tool cuts the object work along each the component path section with the predetermined stock-removal rate per unit time.
The rotating cutting tool is fed at a constant tool feed speed over each component path section but not over the entire tool path. The rotating cutting tool is slowed down for a component path section along where the required stock removal volume is large and speeded up for a component path section where the required stock removal volume is small. This contributes to making a cutting time for the entire part of a work as short as possible.
In the case where an end mill or end mills are used, when the end mill is fed to approach a cutting surface of the object work at a tool feed angle with respect to the cutting surface in the component path section, the
Hosoda Tsuyoshi
Izutsu Yukio
Nishimoto Mitsuki
Ohta Atsushi
Brooks & Kushman P.C.
Cadugan Erica
Mazda Motor Corporation
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