Cutting by use of rotating axially moving tool – Including means to cause tool to progressively vibrate...
Patent
1996-12-11
1998-07-21
Howell, Daniel W.
Cutting by use of rotating axially moving tool
Including means to cause tool to progressively vibrate...
82 13, 408 69, 408 91, 409 75, 409162, B23B 2722
Patent
active
057825858
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a precision drilling machine for drilling noncircular bores according to the introductory part of patent claim 1.
Such precision drilling machines are known, for example from DE 38 18 827 C; EP 0 430 984 B; and DE 43 12 937 A.
In connection with said drills, the drilling spindle with the rotating bit, or only the drilling bit is periodically deflected as required when drilling the form of the bore to be drilled. Practically, any desired shape of bores can be drilled with said devices. Any shape of a bore is limited only by the technically possible kinetic dynamics of the drilling spindle or the drilling bit support.
Devices, in connection with which the drilling spindle or the entire drilling head is adjusted, only permit relatively low numbers of revolutions because of the relatively large masses to be moved.
Devices, in connection with which only a support of the drilling bit is deflected within the drilling head, can operate with comparatively higher numbers of revolution. In the last-mentioned case, the support of the drilling bit, however, has only relatively little rigidity, which impairs the quality of the work.
Based on the facts outlined above, the invention deals with the problem of drilling noncircular bores with high working quality and with the high rotary speeds required for economical operation, in a superior way and at more favorable cost than previously possible.
Said problem is solved with a design having the characteristic features of patent claim 1.
Deviating from the state of the art heretofore, the workpiece and not the drilling bit or its support, or the spindle, is periodically deflected for drilling a non-circular drilling form in connection with said solution. This results in a simplification in that the periodic motion of deflection needs not to be superimposed on a rotational motion, but rather represents the only form of motion for such workpiece.
The device according to the invention is particularly suitable for drilling bores with an oval round shape. In this case, the workpiece only has to run through one motion period with one rotation of the drilling bit. This is explained in greater detail in the following by reference to a diagram. On the other hand, with each deflection of the drilling bit the latter would have to run through two periods, i.e., twice the number of periods during each rotation, which means that the rotary speed applied in the work operation has to be kept in economically unfavorably low ranges, taking into account the limits in kinetic dynamics. For obtaining a bore with an oval basic shape, in connection with which practically any oval, noncircular shapes are achievable up to the circumferential zone, through which the long oval axis extends, the tool has to oscillate translatorily only in one direction.
According to claim 2, the deflection of the tool is controlled according to the given actual position of the drilling bit, in that a defined value of deflection is associated, for example in an electronic memory, with each actual position, such value being in each case transmitted to the deflecting device of the workpiece as the control quantity. Furthermore, usefully, the given actual position is also taken into account by a position control circuit.
In case the bores should additionally extend conically in the longitudinal direction, the drilling spindle can be supported in a deflectable way. Systems suitable for such deflectability are known per se.
Schematic diagrams for a better understanding of the invention are shown in the drawing, in which:
FIG. 1 shows a schematic, perspective representation of a device according to the invention;
FIG. 2 shows a schematic representation of the patterns of motion of the drilling bit and a workpiece worked by said bit.
With a precision drilling machine 1, a drilling bit 3 rigidly mounted on a spindle 2 rotates on a circular working path in the bore 4 of a piston serving as the workpiece 5.
The workpiece 5 is rigidly chucked in a holder 6.
The spindle 2 is countersupported in a tip 7. Hig
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patent: 5201618 (1993-04-01), Malarz et al.
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Bhargava Adesh
Howell Daniel W.
Mahle GmbH
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