Device for Instantaneous Stopping of the Cutting Process in Face Milling
Abstract Generated abstract
This paper describes a device developed at the Tomsk Polytechnic Institute for instantaneously stopping the cutting process during face milling in order to obtain high-quality chip roots for studying the stressed and deformed state of the chip-formation zone. The design uses an explosive charge to drive a piston and striker that rapidly displaces the specimen, shearing retaining keys and interrupting cutting at a selected cutter-tooth position. The apparatus includes adjustable supports, a timed electrical ignition contact linked to the machine spindle, and angular positioning to preserve the chip root during ejection. Tests with a single-tooth cutter on a vertical milling machine indicate the device’s intended applicability to chip-root acquisition at high cutting speeds.
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PROCEEDINGS
OF THE TOMSK ORDER OF THE RED BANNER OF LABOR
POLYTECHNIC INSTITUTE named after S. M. KIROV
Vol. 183 1968
A DEVICE FOR INSTANTANEOUS STOPPING OF THE CUTTING PROCESS IN FACE MILLING
G. L. KUFAREV, A. A. KOZLOV, V. V. OVCHARENKO, D. E. ZAITSEV
(Presented by the Joint Scientific Seminar of the Departments of Machine Tools and Metal Cutting
and Mechanical-Engineering Technology)
One of the most important tasks in the theory of metals is the study of the stressed and deformed state of the chip-formation zone. For this purpose it is necessary to obtain a high-quality chip root—an undistorted section of the chip together with the base material.
At present there are several different variants for the instantaneous termination of the cutting process. Existing designs [1] of devices have a common shortcoming—a comparatively long response time. Therefore these devices cannot be used at high cutting speeds. Recently several original designs of devices have appeared for instantaneous stopping of the cutting process in turning [2] by the explosive method, planing [Tomsk Polytechnic Institute], making it possible to obtain chip roots at high cutting speeds.
In the metal-cutting laboratory of TPI, an installation has been designed and manufactured for obtaining chip roots in face milling at high cutting speeds. The general view of the installation is shown in Fig. 1.
The operation of the device is based on the principle of using the force of an explosive wave. A main charge of pyroxylin powder “Sokol” is placed in the combustion chamber. To ignite the main charge, an igniter charge is required; black powder is used for this purpose. A constantan wire 0.05 mm in diameter is passed through the base of the cartridge. When a current at a voltage of 36 volts is passed through it, the wire burns out and ignites the powder.
A loaded cartridge case of caliber No. 12 is located in sleeve 8 and is pressed against it by rear cover 6. The latter is rigidly fastened to body 9 by bolts with nuts 5. When the powder explodes, the powder gases push the piston and the striker 10 secured in it. From the striker the blow is transmitted to specimen 17, resting on rolling supports 16. The impact force must be sufficient to shear two cast-iron keys 18. The amount of powder and the diameter of the keys are determined experimentally, depending on the machining conditions.
For constant pressing of the specimen against the keys being sheared, two plates 12 bear against its front end. The tension is produced by two screws not shown in Fig. 1. After the keys have been cut, the specimen moves to spring stop 20. To prevent the specimen from striking a tooth of the cutter (when it rebounds backward), retainer 13 is used.
The specimen is clamped by vertical and horizontal bearing supports 14. The clearances are adjusted by rotating racks 15.
During operation, the cutter tooth removes a chip of varying thickness along the entire arc of contact between the tool and the workpiece. Therefore, obtaining the chip roots at various positions of the cutter tooth is of definite interest. At a certain moment the electric circuit for igniting the charge is closed by a movable contact 21, fastened to the spindle of the machine.
Fig. 1. Device for instantaneous stopping of the cutting process in face milling
To prevent the chip root from breaking off from the cutter tooth when the specimen is knocked out, before the test the impact device and plate 4 with stand 19, in which the specimen is located, are turned through an angle $\alpha$, which depends on the angles $\psi$ and $\gamma$,
where $\psi$ is the angle fixing the instantaneous position of the cutter tooth along the arc of contact between the tool and the workpiece;
$\gamma$ is the rake angle of the cutter tooth.
Plate 4 turns on pin 26, fixed immovably in the base of the device 1. After turning, the plate is pressed to the base by clamps 2. Depending on the length of the specimen, the impact unit can be moved.
The device described above was tested during operation with a single-tooth cutter on a model 6H13P vertical milling machine.
LITERATURE
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L. N. Berdnikov. A device for obtaining a fixed zone of chip formation. Proceedings of the Leningrad Polytechnic Institute named after M. I. Kalinin, No. 250, 1965.
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E. D. Salomovich. An instrument for the instantaneous stopping of the cutting process at high speeds. Vestnik mashinostroeniya, No. 12, 1954.