Electricity: motive power systems – Positional servo systems
Reexamination Certificate
2003-07-25
2004-11-09
Duda, Rina (Department: 2837)
Electricity: motive power systems
Positional servo systems
C318S567000, C318S568100, C318S570000, C318S578000, C318S569000, C318S600000, C700S159000, C700S192000, C700S193000, C082S019000, C082S157000, C082S158000, C082S118000
Reexamination Certificate
active
06815917
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an automatically operated lathe and method for controlling the same.
BACKGROUND ART
A turning machine tool capable of performing an automatic turning process (referred generically to as an automatically operated lathe in this specification) may automatically carry out various turning processes in sequence or, if necessary, simultaneously, by causing a feed motion of various tools carried on a tool rest relative to a bar-shaped or disk-shaped workpiece to be machined, which is securely held in a spindle. Recently, an automatically operated lathe of a type (so called an electronic-cam type) controlling a relative feed motion between a workpiece or spindle and a tool or tool rest by a machining command using a cam-reference data for successively directing tool positions as a function of cam rotation angles has been provided.
In the electronic-cam type automatically operated lathe, an electric operating command following a predetermined cam curve is used, in place of a mechanical operation of a cam used in a traditional cam-installed automatic lathe, to automatically control a relative feed motion between the spindle and the tool rest. Accordingly, the electronic-cam type automatically operated lathe is capable of advantageously performing a relatively simple machining sequence in a short time, due to respective motions of tools carried on plural tool rests, which follow individual cam curves in a way similar to the conventional cam-installed automatic lathe. In particular, according to such an electronic-cam system, it is not necessary to provide many types of mechanical cams corresponding to the configurations of machined products, and it is possible to significantly reduce time and labor required for an initial set-up, which permits various kinds of products to be manufactured in very high productivity in comparison with the conventional cam-installed automatic lathe.
Also, in the electronic-cam type automatically operated lathe, even when the machine structure thereof is provided with a plurality of control axes along which the spindle and the tool rest are relatively operated, it is possible to prepare cam diagrams for the respective control axes on a common reference (i.e., a cam rotation angle), which advantageously makes it easier to program a synchronizing command of the control axes. Moreover, the operation of the control axes is individually and freely controllable, so that, in the case where various machining processes are successibly performed by using plural tools, it is made easier to operate the tools so as to overlap in time, and thereby, it is possible to significantly reduce the time required for the entire machining process (i.e., one machining cycle) of the workpiece to be machined.
In the above-described electronic-cam type automatically operated lathe, the cam rotation angle as a reference for preparing the cam diagrams may be defined on the basis of a rotational frequency of the spindle. That is, a predetermined rotational frequency of the spindle is defined to correspond to a single rotation (360 degrees) of the cam, and tool positions are successively directed correspondingly to the rotational frequencies of the spindle, so as to control the operation of the respective control axes. According to this structure, it is possible to individually control the operation of the plural control axes on the basis of a common reference defined by the rotational frequency of the spindle that is a mechanically operative component of the automatically operated lathe.
However, in this structure, the operation of the control axes cannot be controlled during a period when the spindle does not rotate. Therefore, it is difficult, in the automatically operated lathe performing an electronic-cam control on the basis of the rotational frequency of the spindle, to carry out, for example, a secondary process (e.g., a cutting process by a rotary tool) during a period when the spindle does not rotate, which can be carried out by a conventional multifunctional numerically-controlled (NC) lathe. Also, when the compensation of the tool position to be directed, i.e., a tool offset, should be commanded due to, for example, a tool edge wearing or a tool changing, it is required to prepare the cam diagram in which the tool position is shifted in a desired offset value. In this case, the rotational frequency of the spindle corresponding to a cam single rotation is not changed, so that the cutting feed speed of the tool relative to a workpiece to be machined is varied, which may result in changing the roughness of a machined surface.
Contrary to this, in the conventional NC lathe, since a relative feed motion between a spindle and a tool rest is controlled to continuously move a tool toward a designated position on the basis of an elapsed time under the designation of a feed speed in the desired control axis, it is possible to command a tool offset without varying the cutting feed speed of the tool. However, a time required for one machining cycle is somewhat readily varied due to the way of arranging a machining program and the selection of the numerical value of input data, so that an operator's skill is necessary to efficiently program, for example, a synchronization command between plural control axes or a superposition command between axes-systems in a multi-axes, multi-path NC lathe.
Furthermore, in the case where various machining process are successively performed by using plural tools in the conventional NC lathe, it is generally difficult, from a viewpoint of machine and control structure, to perform a machining process of one tool until another tool reaches a stand-by position after finishing the machining process thereof, and thereby, the time required for one machining cycle inevitably includes the idle time of tools. In this respect, the electronic-cam type automatically operated lathe is capable of easily eliminating the idle time of tools as already described and, therefore, of effectively reducing the time required for one machining cycle in comparison with the conventional NC lathe.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an automatically operated lathe which makes it possible to effectively reduce a time required for one machining cycle in comparison with a conventional NC lathe, and which includes multi-functional properties capable of performing a secondary process during a period when a spindle does not rotate, as well as to provide a method for controlling such an automatically operated lathe.
Another object of the present invention is to provide an automatically operated lathe which makes it possible to easily program a synchronization command between plural control axes and to command a tool offset without varying the cutting feed speed of the tool, as well as to provide a method for controlling such an automatically operated lathe.
To achieve the above object, the present invention provides in one aspect thereof a method for controlling an automatically operated lathe provided with at least one spindle and at least one tool rest, comprising providing each of a plurality of transfer position data required in a sequence of machining programs in connection with the at least one spindle and the at least one tool rest in a form of either one of two types of transfer position data, one of which is a cam-reference data directing a transfer position as a function of a cam rotation quantity and the other of which is a time-reference data directing a transfer position as a function of an elapsed time; and processing each of the plural transfer position data provided in the form of either one of the cam-reference data and the time-reference data, to control a relative feed motion between the at least one spindle and the at least one tool rest in the sequence of machining programs.
In the preferred embodiment, the method for controlling is provided, wherein the at least one spindle and the at least one tool rest are capable of performing a relative feed motion along a plurality of contr
Citizen Watch Co. Ltd.
Duda Rina
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
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