Transient phenomenon of chip generation and its movement in hobbing (4th report, the relationship between the jamming of chips on the finished surface and the chip form in generating in flytool simulation tests)

The degradation of tooth surfaces and the abnormal tool wear sometimes occurs in dry hobbing. This paper investigates the transient phenomenon of chip formation and behavior in simulation tests of hobbing by using a high-speed video camera. The jamming of the chip between the tooth surface and the cutting edge causes scratches on the tooth surface and the chipping of a cutting edge so on. The figures of chips produced by hobbing are classified roughly into the "U", "J" and "I" types. This paper presents findings of the "J" and "I" type-chip movements in fiytool simulation tests. The "J" type-chip is removed with the two cutting edges both top and a side edge. In the "J" type-chip, a part of end side of the chip produced by the top cutting edge is often jammed into the finished surface by pushing from the chip at the side cutting edge. The "I" type-chip flows from the root to the tip side of the cutting tooth, and the pointed end of the chip is jammed into the space between the finished surface and the relief face of the cutting tooth, in down cut. In up cut, the chip flows to the root side of the rake face, and possibility of jamming is shown as well as the case of down cut.