Method for controlling powder compacting apparatus and compacting apparatus

Abstract

There is provided a method for controlling a powder compacting apparatus including: a die having a hollow; an upper punch and a floating lower punch; a first actuator that pushes down the upper punch; a second actuator that controls a floating load of the floating lower punch; and a stopper that defines a pressurization stop position of the floating lower punch. The powder compacting apparatus is configured such that the first actuator is operated to push down the upper punch to pressurize powder charged into the cavity, and the second actuator is controlled to pressurize the powder such that a load acting on the powder during pressurization becomes a prescribed floating load required to compact the powder. The method includes reducing the floating load in a stepwise manner after completion of the pressurization.

Claims

1. A method for controlling a powder compacting apparatus including at least: a die having a hollow; an upper punch and a floating lower punch that slide in the hollow, the upper punch and the floating lower punch defining a cavity along with the die; a first actuator that pushes down the upper punch; a second actuator that controls a floating load of the floating lower punch; and a stopper that defines a pressurization stop position of the floating lower punch, the powder compacting apparatus configured such that the first actuator is operated to push down the upper punch to pressurize powder charged into the cavity, and the second actuator is controlled to pressurize the powder such that a load acting on the powder during pressurization becomes a prescribed floating load required to compact the powder, the method comprising reducing the floating load in a stepwise manner after completion of the pressurization.

2. The method for controlling the powder compacting apparatus according to claim 1, wherein each of both the first actuator and the second actuator is an electric servomotor.

3. A compacting apparatus comprising: an upper punch driven by a first actuator; a floating lower punch disposed below the upper punch, and the floating lower punch being driven by a second actuator to apply a prescribed pressure to an object along with the upper punch; and a stopper that defines a stop position of the floating lower punch, wherein the second actuator is configured to reduce a pressure applied to the object in a stepwise manner after the prescribed pressure is applied to the object.

4. A method for controlling a powder compacting apparatus including a die having a hollow; an upper punch and a floating lower punch that slide in the hollow, the upper punch and the floating lower punch defining a cavity along with the die; a first actuator that pushes down the upper punch; a second actuator that controls a floating load of the floating lower punch; and a stopper that defines a pressurization stop position of the floating lower punch, the method comprising: charging powder into the cavity; controlling the first actuator and the second actuator such that a load acting on the powder becomes a prescribed floating load; and reducing the floating load in a stepwise manner after application of the prescribed floating load.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

(2) FIG. 1 is a schematic view illustrating a state where powder has been charged into a cavity of a powder compacting apparatus to which a controlling method of the disclosure is applied;

(3) FIG. 2 is a schematic view illustrating a state where the controlling method of the disclosure is carried out to pressurize the powder, thereby forming a green compact;

(4) FIG. 3 is a schematic view illustrating a state where a floating lower punch reaches a stopper;

(5) FIG. 4 is a diagram illustrating an upper punch and floating lower punch displacements versus time graph and a load cell load versus time graph, both of which illustrate the controlling method of the disclosure; and

(6) FIG. 5 is a diagram illustrating an upper punch and floating lower punch displacements versus time graph and a load cell load versus time graph, both of which illustrate a conventional controlling method.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) Hereinafter, a method for controlling a powder compacting apparatus according to an example embodiment of the disclosure will be described with reference to the accompanying drawings.

(8) Method for Controlling Powder Compacting Apparatus According to Embodiment

(9) FIG. 1 is a schematic view illustrating a state where powder has been charged into a cavity of a powder compacting apparatus to which a controlling method of the disclosure is applied. FIG. 2 is a schematic view illustrating a state where the controlling method of the disclosure is carried out to pressurize the powder, thereby forming a green compact. FIG. 3 is a schematic view illustrating a state where a floating lower punch reaches a stopper. FIG. 4 is a diagram illustrating an upper punch and floating lower punch displacements versus time graph and a load cell load versus time graph, both of which illustrate the controlling method of the disclosure.

(10) A powder compacting apparatus 10 illustrated in the drawings mainly includes a die 1 having a hollow 1a, a third actuator 2 that slides the die 1 (in a direction X3), an upper punch 3 that slides in the hollow 1a, a first actuator 4 that slides the upper punch 3 (in a direction X1), a stationary lower punch 6 that is partially disposed in the hollow 1a, a floating lower punch 5 that slides in the stationary lower punch 6, a second actuator 7 that slides the floating lower punch 5 (in a direction X2), and a stopper 8 on which the stationary lower punch 6 is disposed, the stopper 8 defining a descending limit of the floating lower punch 5.

(11) Each of the first actuator 4, the second actuator 7, and the third actuator 2 is constituted by an electric servomotor.

(12) In the powder compacting apparatus 10, during float compacting, a control for causing the floating lower punch 5 to descend (in the direction X2) while the upper punch 3 is descending (in the direction X1) is executed, so that a floating load is applied to powder F due to the descending of the floating lower punch 5. When the descending speed of the upper punch 3 is reduced, the floating lower punch 5 is controlled such that the descending speed of the floating lower punch 5 is also reduced in accordance with the reduction in the descending speed of the upper punch 3.

(13) This control is feasible because each of the first actuator 4 and the second actuator 7 is constituted by a servo actuator (an electric servomotor).

(14) The die 1 is also caused to descend (in the direction X3) by the third actuator 2 (the electric servomotor) while the floating lower punch 5 and the upper punch 3 are descending. With this configuration, when the powder F is gradually compacted from the vicinity of the upper punch 3 to produce a green compact C (see FIG. 3), it is possible to inhibit the generation of a density distribution in which the density of the green compact C decreases with increasing proximity to the upper punch 3 (i.e., a density distribution in which the density of the green compact C becomes lower as the distance to the upper punch 3 decreases in the green compact C).

(15) As illustrated in FIG. 1, a cavity is defined by an inner peripheral surface of the die 1, which defines the hollow 1a, an upper surface of the floating lower punch 5, and an upper surface of the stationary lower punch 6. The powder F to be compacted is charged into the cavity.

(16) Next, as illustrated in FIG. 2, the powder F is pressed downward while the upper punch 3 is descending to apply a pressing force P to the powder F. While the upper punch 3 is descending, the floating lower punch 5 is also caused to descend, thereby applying a floating load P to the powder F. The descending control of the upper punch 3, the floating lower punch 5, and the die 1 is executed while the floating load P acts on the powder F.

(17) Upon completion of the pressurization, the green compact C having a prescribed shape is obtained, as illustrated in FIG. 3.

(18) The pressurization of the powder F proceeds. After the completion of the pressurization, the floating load is reduced as illustrated in FIG. 4.

(19) During the reduction of the floating load, a load (a load cell load) to be applied to a load cell mounted in the floating lower punch is reduced in a stepwise manner.

(20) Specifically, as illustrated in FIG. 4, the floating load (the load cell load) that is maintained at about 250 kN at the time of completion of the pressurization is reduced to a low load of 25 kN. At this point, the reduction in the load is temporarily stopped.

(21) Next, the load cell load is reduced to zero from 25 kN.

(22) As in the controlling method illustrated in FIG. 4, because the floating load is reduced in a stepwise manner after the pressurization is completed, the floating lower punch-system components (e.g. the actuator that drives the floating lower punch, and a connecting member that connects the floating lower punch to the actuator) no longer attempt to stretch downward, and the floating lower punch is no longer pulled until the motion stops. As a result, it is possible to avoid damages to the floating lower punch components due to an attempt of the floating lower punch-system components to stretch downward and pulling of the floating lower punch.

(23) Because sharp reduction in the floating load can be avoided, damages to the apparatus due to sharp reduction in the floating load can be avoided.

(24) While the embodiment of the disclosure has been described in detail with reference to the drawings, the specific configuration is not limited to the foregoing embodiment, and the disclosure is intended to cover various design changes or the like within the scope of the disclosure.