Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1984-08-10
1986-03-11
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318565, 318568, G05B 1933
Patent
active
045756651
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
BACKGROUND OF INVENTION
The present invention relates to a tracer control method and, more particularly, to a tracer control method whereby a tracer machining inhibit area is set and tracer machining is performed while skipping the inhibit area.
A tracer appartus operates by calculating velocity commands along various axes by means of a tracer arithmetic circuit using a deflection value sensed by a tracer head, driving motors for the corresponding axes on the basis of the velocity commands along these axes to transport a tool relative to a workpiece, and repeating these operations to machine the workpiece into a shape identical to that of the model. In tracer control of this kind, the tracer head generally is made to trace the entire surface of the model to provide a machined object having a shape which is exactly the same as that of the model. There is now a requirement for tracer machining control whereby a portion of the model is skipped and both sides (or only one side) with respect to the skipped portion are traced. Such tracer machining control is well-suited for application to the machining of, say, a propeller having a boss and blades formed around the boss. The reason is that cutting solely the complicatedly shaped blade portions of a propeller under tracer control and applying NC control to cut the boss portion, which is difficult to trace because of its steep gradient, makes it possible to shorten machining time and improve the precision to which the boss portion is machined in comparison with tracer machining being applied to the entirety of the propeller.
In the prior art, if the portion desired to be skipped has, say, a concave configuration, the concave portion is flattened by being filled with clay or the like, the entire surface of the flattened model is traced to provide a machined object, and a concavity is subsequently formed in a predetermined portion of the machined object by NC control to provide the final article. With this method, however, fabricating the model is a troublesome operation. Moreover, since the skipped portion is machined to a flat shape by tracer control and is then machined into a concavity by NC control, forming the concave portion requires two operations, thereby lengthening machining time.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a tracer control method in which a model need not be remade, and in which the time required to obtain a final article can be shortened.
Another object of the present invention is to provide a tracer control method whereby a portion of a model, e.g., a portion which is difficult to trace, is skipped automatically, with tracer machining being applied to both sides, or to only one side, with respect to this portion.
The present invention provides a tracer control method which includes presetting a tracer machining inhibit area (skip area) and a safe level, monitoring a machine position at all times during tracer machining, inhibiting tracer machining when the machine position reaches the skip area and retracting the machine until the machine position coincides with the safe level, then transporting the machine in such a manner that the machine position moves along the safe level and passes the skip area, and resuming tracer machining after the skip area is passed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1, including 1(A) and 1(B), is a simplified view for describing the present invention;
FIG. 2 is a simplified view of a tracing machine tool to which the present invention can be applied; and
FIG. 3 is a block diagram illustrating an embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a simplified view for describing the present invention, in which (A) is a perspective view and (B) a sectional view. Formed at substantially the center of a model MDL is a projection PR. An area TMI containing the projection is a tracer machining inhibit area (skip area) in which tracer machining is unnecessary. Two areas TM, TM' on either side of the area
REFERENCES:
patent: 3611874 (1970-02-01), Larsen et al.
patent: 4489377 (1984-12-01), Mawyer et al.
Matsuura Hitoshi
Sakurai Hiroshi
Yamazaki Etsuo
Bergmann Saul M.
Fanuc Limited
Shoop Jr. William M.
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