Powder molding press method of green compact for cutting insert, and powder molding press device
A powder molding press method of a green compact for a cutting insert including: filling a molding space with raw material powder in a state where a lower punch is inserted from below into a hole portion of a die; performing preliminary molding by inserting an upper punch for preliminary molding including a preliminary molding surface having a shape different from a shape obtained by inverting the upper surface of the green compact for a cutting insert in a plane symmetry into the molding space from above such that a thick portion between the upper and lower surfaces in the direction of the insert center line is filled with more raw material powder than a thin portion therebetween, relative to a state before the step of performing the preliminary molding; and inserting an upper punch for final molding into the molding space from above to powder-molding-press the raw material powder.
1. A powder molding press method of a green compact to be sintered to obtain a cutting insert including an upper and lower surfaces substantially perpendicular to an insert center line of the cutting insert and a side surface disposed around the upper and lower surfaces and having different thicknesses between the upper and lower surfaces locally, the insert center line pass through a center of the insert and parallel to a thickness direction of the insert, the method comprising the steps of:
inserting from below a lower punch having a lower-surface molding-surface as an upper end surface into a hole portion of a die having a side-surface molding-surface as an inner peripheral surface,
filling a molding space formed by the lower-surface molding-surface and the side-surface molding-surface with a raw material powder of the green compact, the lower-surface molding-surface and the side-surface molding-surface being configured to mold a lower surface and a side surface of the green compact, respectively;
performing a preliminary molding by inserting a first upper punch for preliminary molding including a preliminary molding-surface as a lower end surface into the molding space from above, the preliminary molding-surface having a shape different from a shape obtained by inverting a shape of the upper surface of the cutting insert in plane symmetry and being configured to preliminary mold the upper surface of the raw material powder filled in the molding space, more raw material powder being filled in thick portions than thin portions between the preliminary molding-surface and the lower-surface molding-surface by performing the preliminary molding, wherein the preliminary molding-surface of the first upper punch is provided with an inclined surface protruding downward toward one of the thin portions, and the thick portions are filled with more raw material powder than the thin portions by the insertion of the first upper punch by guiding the raw material powder from the thin portions to the thick portions by the inclined surface, each of the thick portions and the thin portions being arranged alternately along the side surface of the green compact; and
inserting a second upper punch for final molding having an upper-surface molding-surface into the molding space from above, the upper-surface molding-surface is configured to mold the upper surface of the raw material powder after the step of performing a preliminary molding, and the raw material powder after the step of performing a preliminary molding being pressed and molded into the green compact that have a substantially same shape as the cutting insert, wherein
in the thin portions, a downward protrusion amount of the preliminary molding-surface of the first upper punch is larger than a downward protrusion amount of the upper-surface molding-surface of the second upper punch.
2. The powder molding press method of claim 1 , wherein
directions of downward protrusions and recesses in the preliminary molding-surface are opposite to directions of downward protrusions and recesses in a shape obtained by inverting the upper surface of the green compact in plane symmetry,
the preliminary molding-surface of the first upper punch is provided with an inclined surface protruding downward toward one of the thick portions from one of the thin portions, and extent of compression in the thin portions in the step of performing a preliminary molding is less than extent of compression in the thick portions, and
the powder molding press method further comprises the step of refilling a space above the raw material powder after the step of performing the preliminary molding with a refilling raw material powder in such way that the thick portions are filled with more raw material powder and the refilling raw material powder as a total than the thin portions, wherein the thick portions are refilled with more refilling raw material powder than the thin portions by compressing the raw material powder in the step of performing a preliminary molding by the inclined surface,
a space above the raw material in the thin portions after the step of performing the preliminary molding is smaller than a space above the raw material in the thick portions after the step of performing the preliminary molding
the raw material powder molded in the step of performing a preliminary molding and the refilling raw material powder refilled in the step of refilling are pressed and molded into the green compact.