Electricity: motive power systems – Positional servo systems
Reexamination Certificate
2003-07-29
2004-11-02
Duda, Rina (Department: 2837)
Electricity: motive power systems
Positional servo systems
C318S567000, C318S568100, C318S570000, C318S569000, C318S600000, C700S159000, C700S192000, C700S193000, C082S019000, C082S118000, C082S157000, C082S158000
Reexamination Certificate
active
06812664
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 (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 successively 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. Contrary to this, 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 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 corresponding 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 (normally, the rotational frequency of the drive source 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, the rotational frequency of the spindle may be varied, in general, due to a machining load applied to the spindle by, e.g., a cutting force during the machining process. In particular, in the structure wherein a drive force from a spindle drive source is transmitted to the spindle through a transmission mechanism such as a belt/pulley, the rotational frequency of the spindle drive source tends to become different from the actual rotational frequency of the spindle, when a slip is caused in the transmission mechanism by the machining load. In this case, in an electronic-cam control on the basis of the rotational frequency of the spindle drive source, the spindle and the tool rest are operated to perform the relative feed motion in accordance with the rotational frequency of the spindle drive source irrespective of the actual machining progress of the workpiece, which may cause deterioration of the machining accuracy.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an automatically operated lathe capable of controlling a relative feed motion between a spindle and a tool rest in an electronic-cam system, and capable of exerting multifunctional properties for 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 capable of controlling a relative feed motion between a spindle and a tool rest in an electronic-cam system, and capable of performing a high precision machining without being influenced from the variation of the rotational frequency of the spindle, 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 a cam-reference data directing a transfer position as a function of a cam rotation quantity; providing a plurality of pulse-train generating sources, each of which generates any pulse train; designating, with regard to each of the plurality of transfer position data, a pulse-train generating source for generating a pulse train defining the cam rotation quantity as one component of the cam-reference data, the pulse-train generating source being selected from the plurality of pulse-train generating sources; and processing each of the plurality of transfer position data provided in the form of the cam-reference data by using the pulse train generated through the pulse-train generating source as designated, 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 control axes, and wherein the step of designating the pulse-train generating source includes designating the pulse-train generating source with regard to each of the plurality of transfer position data in relation to each of the plurality of control axes.
In the preferred embodiment, the method for controlling is provided, further comp
Citizen Watch Co. Ltd.
Duda Rina
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
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