Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1988-10-28
1989-09-26
Dobeck, Benjamin
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
36447403, 409 99, G05B 1936
Patent
active
048703370
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a pick-feed method in the tracing of a rotating body. More particularly, the invention relates to a pick-feed method in which a pick-feed can be executed accurately every revolution with just one limit line in the direction of rotation.
2. Background Art
In tracer control, as shown in FIG. 6, a surface tracing method entails moving a stylus ST over a range X.sub.1 .about.X.sub.2, which is a tracing area, along the X axis or feed axis, moving the stylus up and down along the X axis or tracing axis in dependence upon the shape of a model MDL, thereby in effect causing the stylus to trace the model MDL so that a workpiece may be subjected to machining conforming to the shape of the model by means of a cutter, not shown.
In this surface tracing method, only the model profile above the feed axis (X axis) is traced, so that it is impossible to trace a model having an overhanging profile.
In a case where a cam or the head of a golf club is to be profiled, however, it is necessary to profile not just the surface on one side but both the front and back surfaces. When it is attempted to apply the above-described surface tracing method to tracing of both front and back surfaces, the stylus ST must be rotated by 180.degree. to shift it from front surface tracing to back surface tracing (see the dotted line in Fig. 7). However, the arrangement for performing tracing upon rotating the stylus by 180.degree. is complicated and undesirable for this reason.
A rotating body tracing method which does not require that the stylus be rotated has been proposed and put into use. According to this rotating body tracing method, tracer control is carried out by rotating the model MDL about a predetermined rotational axis, as shown in FIGS. 8(a), (b), and moving the stylus ST in contact with the model up and down in dependence upon model shape in the direction (Z-axis direction) of a line connecting the center O.sub.S of the stylus and the rotational center O.sub.M of the model.
The case shown in FIG. 8(a) represents a method of tracing the surface of the rotating body, and FIG. 8(b) shows a method of tracing the profile of the rotating body.
The case of FIG. 8(a) in which the surface of the rotating body is profiled will be described hereinbelow. However, the method will be similar for the case of FIG. 8(b) where the profile is profiled.
In this tracing of a rotating body, it is required that the stylus ST be pick-fed a predetermined amount each time in a direction orthogonal to the page each time the model MDL makes one revolution. In well-known 360.degree.-contouring tracing of a profile, if one limit line LL' (where +X.sub.L represents the X-axis coordinate) is set up, as shown in FIG. 9, then one revolution of tracing is realized, with application of pick-feed in the direction orthogonal to the page, by the stylus' crossing the limit line, namely X.sub.L , twice, wherein the present position of the stylus ST is monitored. The reason why a pick-feed can be performed every single revolution with just one limit line is that two points (PL, PL') having the same X-axis coordinate exist while the stylus is making one revolution.
In the tracing of a rotating body, however, the coordinate in the direction of rotation (the circumferential direction) is expressed by an angle and there is only one point having the same rotational angle in one revolution. Moreover, when the coordinate in the direction of rotation attains a value of 360.degree. starting from 0.degree., the coordinate returns to 0.degree. and then repeats the cycle of 0.degree. to 360.degree. in cyclic fashion.
In conventional rotating body tracing, therefore, control for effecting a pick-feed every revolution is difficult merely by setting one limit line (the rotational coordinate of which is .theta..sub.L) and comparing the present position .theta. and .theta..sub.L.
Accordingly, an object of the invention is to provide a pick-feed method in rotating body tracing in which a pick-feed can be made reliably every revolut
REFERENCES:
patent: 4620142 (1986-10-01), Yamazaki et al.
patent: 4688179 (1987-08-01), Yamazaki
patent: 4719578 (1988-01-01), Okitomo
patent: 4746251 (1988-05-01), Yoshikawa et al.
patent: 4747734 (1988-05-01), Ide et al.
Dobeck Benjamin
Fanuc Ltd.
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