Gear cutting – milling – or planing – Milling – Process
Patent
1990-01-19
1991-07-30
Briggs, William
Gear cutting, milling, or planing
Milling
Process
408 1R, 408 13, B23C 900, B23B 3500
Patent
active
050355546
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to methods and apparatus for automatically obtaining an indication of the radius of a circle described by the tool tip, that is the cutting edge of a boring tool, for example, when driven by a machine tool.
The determination of the radius or diameter described by a boring head tool tip is not at present carried out as an unmanned operation and in-process on a CNC boring or milling machine tool.
Instead, tool setting is carried out manually using a tool setting machine separate from the CNC machine tool. Generally fixed radius boring bars with a small range of radius adjustment are used. Usually, a new tool tip is secured in a boring bar and an operator manually rotates the boring head to find the maximum deflection of a displacement sensor by trial and error. This maximum deflection determines the described radius of the tool tip. The operator then adjusts the boring head to set the radius to the correct value.
According to a first aspect of the present invention there is provided a method for use in obtaining an indication of the radius of a circle described by the tip of a tool when driven by a machine tool comprising
mounting a tool for rotation parallel to the maximum curvature of an arcuate surface,
bringing the tip of the tool into contact with the arcuate surface at least in two successive positions 180.degree. apart with respect to the centre of rotation of the tip while varying the distance between the said centre of rotation and either the tip or the centre of arc of the surface if necessary to allow contact in the two positions to occur if the centre of arc is not coincident with the said centre of rotation, and
obtaining an indication of any change in the said distance, to allow the radius described by the tool tip to be derived from the radius of the arcuate surface and the said change in the said distance.
The method is most accurate when the centre of rotation of the tip and the centre of arc are coincident the change in the said distance is then zero and the radius described by the tool is equal to the radius of the arcuate surface However the method is intended for use when the two centres are nominally coincident but it becomes inaccurate when the centres are too far apart.
An advantage of the invention is that it allows the radius of a boring tool to be set unmanned and on the machine tool or at any other location as required The invention differs from previous usage in that the diameter described by the tool tip itself is determined.
According to a second aspect of the invention there is provided apparatus for use in the method of the first aspect, comprising
an arcuate surface mounted for rotation with an axle,
spring means mounted between the arcuate surface and the axle,
engagement means for causing the arcuate surface to rotate when engaged by the tip of a rotating tool, and
measuring means for providing a signal representative of deflection by the spring means.
In operation the tool tip is brought into contact with the arcuate surface and is rotated until the engagement means is engaged. The tool tip is then rotated through at least a further 180.degree. and causes the arcuate surface to rotate with it. The radius of the circle described by the tool tip is then derived from the radius of the arcuate surface and the output of the measuring means, at least, at two points 180.degree. apart, as the tool tip and the surface rotate together.
The spring means may comprise a planar spring, and the measuring means may then include strain gauges mounted on the planar spring to provide deflection signals over an infinite number of contact positions as the tool tip and the arcuate surface rotate together. The engagement means may comprise a projection on the arcuate surface which allows the tool tip when rotated, to engage the projection and rotate the arcuate surface as the tool is rotated.
Since the arcuate surface can be concave or convex, the radius of a tool set for internal or external boring can be determined.
According to a third aspect of the invention th
REFERENCES:
patent: 3492894 (1970-02-01), Hann et al.
patent: 4016470 (1977-04-01), Gabor et al.
patent: 4400118 (1983-08-01), Yamakage
patent: 4417490 (1983-11-01), Mochizuki
patent: 4451892 (1984-05-01), McMurtry
patent: 4513646 (1985-04-01), McMurtry
patent: 4648757 (1987-03-01), Plummer
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