Patent Application
20050084341
1. Field of the Invention
The present invention relates to machine tools for shaping a work piece, and more particularly to rotatable tools of the type provided with cutting inserts. Orientation of inserts on the tool is varied to avoid repetitive orientation which may promote vibrational harmonics during operation.
2. Description of the Related Art
Machining work pieces by rotary cutting tools may cause objectionable vibrational harmonics to occur. This results in chatter and other phenomena which may cause flaws in the machined product. It is not desirable to alter rotational speeds of a machine tool and rate of advance speeds of a cutting tool as such steps may interfere with optimal productivity. It is known to vary circumferential spacing of inserts and their pockets in a rotary cutting tool to break up harmonics which might otherwise occur. This approach is shown in U.S. Pat. No. 4,092,082, issued on May 30, 1978, to Severson, and U.S. Pat. No. 4,093,392, issued on Jun. 6, 1978, to Hopkins. It is also known to vary rake angles among inserts, as shown in U.S. Pat. No. 4,844,666, issued on Jul. 4, 1989, to Tsujimura et al., and U.S. Pat. No. 5,913,644, issued on Jun. 22, 1999, to DeRoche et al., of common ownership with the present application. The prior art does not show or suggest the novel combinations of insert orientation within a rotary cutting tool as claimed.
The present invention advances the art over prior known designs by introducing, in a rotary cutting tool on which cutting inserts are installed, irregularities of orientation of those inserts within a tool. Inserts may be varied in their circumferential spacing about the periphery of a cutting tool such as an end mill. Also, axial and radial rake angles of inserts may be varied from those of other inserts disposed about the peripheral face of the cutting tool.
In one embodiment of the invention, a rotary cutting tool displays both variable or irregular circumferential spacing of pockets about the peripheral face of the cutting tool, and also differing or variable rake angles among some inserts. The differing rake angles may be of axial rake, radial rake, or both.
In another embodiment of the invention, a rotary cutting tool has both variable axial rake and also variable radial rack angles among some inserts, but does not display variation in circumferential spacing.
It is, therefore, a feature of the invention to overcome harmonic vibration by varying orientation of pockets and of associated inserts within a rotary cutting tool using inserts.
In particular, it is a feature to combine different categories of variable orientation of inserts within a cutting tool.
It is a feature of the invention to provide improved elements and arrangements thereof by apparatus for the purposes described which is inexpensive, dependable, and fully effective in accomplishing its intended purposes.
These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
Various features and attendant advantages of the present invention will become more fully appreciated, as the same becomes better understood when considered in conjunction with the accompanying drawings, wherein:
Referring to the Drawings, wherein like reference characters represent like elements throughout the various Figures,
Rows refer to pockets 16 which are generally at the same vertical level when tool 10 is vertically oriented as seen in
One of three categories of orientational irregularity of the embodiment of
In the preferred embodiment, each pocket 16 is conventionally associated with flutes 24, 26, or 28. Therefore, it may be said that one flute 24, 26 or 28 is spaced apart from the others at irregular intervals, it necessarily following that pockets 16 and inserts 2 of any one row consequently also being irregularly spaced apart. In the embodiment of
Tool 10 also displays a second orientational irregularity, namely that at least one pocket 16 is arranged to hold an installed insert 16 at a first rake angle, and at least one other pocket 16 is arranged to hold another installed insert 16 at a different rake angle. In the embodiment of
Thus it will be seen that lead pockets 16 of different flutes 24, 26, 28 and hence columns display axial rake angles of greater negative magnitudes than the axial rake angles of some other pockets 16. More particularly, lead pockets 16 of different flutes 24, 26, 28 and thus of associated columns, and pockets 16 immediately adjacent to lead pockets 16 have similar axial rake angles of magnitude greater than those of the axial rake angles of other pockets 16.
Pockets 16 of the bottom or first row are lead pockets 16. It is preferred that lead pockets 16 be arranged such that their associated inserts 2 have the highest attainable axial rake, to reduce forces acting on the lead insert 2.
Tool 10 is also characterized by a third orientational irregularity of variation in radial rake angles among pockets 16. Notably, pockets 16 of the bottom two or first two rows within each flute 24, 26, or 28 are arranged to have radial rake angles of greater magnitude than those in the succeeding rows. This arrangement of radial rake angles has been found to be advantageous in smaller diameter cutting tools 10, for example, up to body diameter of two inches.
In tool 10, pockets 16 thus collectively display all three types of orientational irregularities.
Tool 10 of
Rake angles described herein may vary both as to magnitude and also as to whether they are positive or negative. Positive and negative angles may be selected to suit different applications. Variation in axial rake angles and in radial rake angles may comprise variation in magnitude, variation in positive orientation and negative orientation, or both.
In cutting tools having insert pockets formed along flutes, those pockets associated with any one flute will be understood to comprise a column of pockets even though the pockets may not be arrayed one above the other with respect to the rotational axis of the tool. In the same vein, pockets of different columns which are of even orientation along the rotational axis of the tool, regardless of whether they are associated with flutes, will be understood to comprise a row.
It should be noted that in the description of the Figures, it is to be understood that terms such as “forward,” “rearward,” “left,” “right,” “upwardly,” “downwardly,” and the like are words of convenience and are not to be construed as limiting (apart from the invention as claimed).
The documents, patents, and patent applications referred to herein are hereby incorporated by reference.
While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit. For example, it will be readily apparent that the invention, illustrated as pertaining to helical end mills, may be used with equal facility with other types of cutting tools, and description of the invention in relation to helical end mills is not to be construed as a limitation on the scope of the invention.
The same pockets 16 that vary in axial rake angles may be selected to also vary in radial rake angles. Alternatively, some pockets 16 may vary in axial rake angles while other pockets vary in radial rake angles. It is also possible to have some pockets vary in axial rake angles, other pockets to vary in radial rake angles, and still other pockets to vary in both axial rake angles and also in radial rake angles.
It is possible to provide a tool (not shown) according to the present invention which lacks flutes. Such a tool may instead, for example, have a chip gully or other chip disposal structure for each pocket or alternatively for several associated pockets, rather than having flutes per se.
