JPH0359962B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a sizing method for sizing a powder molded product that has been pressure molded using a powder molding press and sintered.

(Prior Art) Molded products sintered after powder molding have variations in dimensions, so they are sized by applying pressure again using a sizing press to improve dimensional accuracy. In other words, various materials are mixed in the powder that is the raw material. For example, iron-based powder uses materials with different specific gravities such as iron powder (with variations in particle size), carbon, and zinc stearate. The powder is filled into a die attached to a powder molding press through a feeder, and the feeder is used to measure the filler in a squared manner, which causes variations in the amount of filling and also causes misfires due to sintering. In this case, the variation in the radial direction limited by the inner diameter of the die is small, but the variation in the height direction compressed by the movable upper and lower punches is large, and generally the height is 15 to 20 mm. In this case, there will be a variation of about ±0.2 mm from the specified dimension.
Therefore, in order to improve this dimensional accuracy, the sizing is performed by applying pressure again using the sizing press.

The sizing press for this is generally the second
As shown in the figure, the upper punch 4 is attached to the upper punch plate 3 and pressed by the upper hydraulic cylinder 1, and the lower punch 4 is attached to the lower punch plate 15 and supported by the lower hydraulic cylinder 11. A punch 16 and a die 6 attached to a die plate 7 that houses a sintered powder molded product 22 and cooperates with the upper punch 4 and the lower punch 16 to size the powder molded product 22. This is the main part of the press body.

Further, as a control circuit for the press body, an electromagnetic switching valve 23 for the upper hydraulic cylinder 1 and an electromagnetic switching valve 24 for the lower hydraulic cylinder 11 are each connected to a hydraulic power source 26.

In addition, numerals 2 and 12 are piston rods, 5 is a base, 8 is a guide rod, 9 is a core rod, 10 is a fixed plate, 13 is a yoke plate, and 14 is a connecting rod.

In the conventional sizing press, a stopper (not shown) is provided between the upper punch plate 3 and the lower punch plate 15, and when the height dimension of the powder molded product 22 reaches a specified dimension, the powder molding The load applied to the product 22 is received by the stopper.

However, if a large load is applied only to the stopper, the stopper and the mold will be distorted, so that it is not effective enough to obtain the desired accuracy. Therefore, the applicant of the present application previously proposed a new sizing press capable of solving these problems in Japanese Patent Application No. 89858/1983.

In this proposal, in the sizing press,
It is provided between the upper punch plate 3 and the lower punch plate 15 of the press body, and by measuring the distance, detects that the height of the powder molded product has reached the measured dimension and generates a detection signal. The length measurement sensor 17 and the electromagnetic switching valve 23 having a hydraulic circuit for controlling the upper hydraulic cylinder 1 are installed in parallel, and the sizing pressure that increases sequentially until the detection symbol is generated is supplied to the hydraulic circuit 23, and The gist of the present invention is to include a relief valve 25 (for example, a digital valve, a proportional solenoid valve, an electro-hydraulic servo valve, etc.) with a variable set pressure that acts on the hydraulic circuit 23 to stop the pressure increase upon receiving a detection signal. This is a sizing press for powder molding.

In addition, numerals 18 and 19 are mounting rods, 20 is a dock, 2
Reference numeral 1 indicates a switch, and when the upper punch 4 reaches the upper limit, the switch 21 becomes conductive and generates a control signal for taking out the powder molded product 22 knocked out on the die plate 7.

(Problem to be Solved by the Invention) However, in the previously proposed sizing press, the relief valve 2 operates to increase the pressing force, so the longer the dimensions of the powder molded product 22 before sizing, the greater the increase in the pressing force. 3 and 15 become susceptible to bending under a large load, and the spring back (the amount of return when released from the pressing force) also increases, so the dimensions are sized accordingly and a constant length is obtained. It had some serious flaws.

Therefore, an object of the present invention is to provide a method for sizing a powder molded product, which can size the molded product to a constant length even if the length of the molded product before sizing varies.

(Means for Solving the Problems) The gist of the present invention is to measure the dimensions of a molded product sintered after pressure molding using a powder molding press, and to calculate the compressed dimensions and the pressing force necessary for the compression using the measured values. Input the data into a computer in which the data is stored in advance and can set the sizing dimensions as desired, the computer calculates the necessary compression dimensions from the measured values and the sizing dimensions, and outputs the pressure force data necessary for the compression; This is a method for sizing a powder molded product, in which the output data is given to a control circuit of a sizing press filled with the molded product to perform sizing.

(Example) The present invention will be explained below based on the block diagram of FIG. First, a length measurement sensor 101 measures the length of the molded product, which is press-molded using a powder molding press (not shown) and then sintered.
This length measurement sensor 101 is made using, for example, Magnescale (trade name of Sony Magnescale Corporation).

The length measurement data a of the molded product is stored in the computer 10.
2, the necessary data b is input in advance to the computer 102 via the compression dimension/pressure force data input means 103 and stored therein. The data stored in the computer 102 is, for example, how many tons of pressurizing force is required to compress a molded product of what size to what mm? The computer 1 is configured to be able to
02 is configured to be able to calculate a compressed dimension by comparing desired sizing data c set by a sizing dimension setter and length measurement data a from the length measurement sensor 101.

Note that the above data a, b, and c can be entered via a keyboard or floppy disk, but it is also possible to directly enter the length measurement data a or set the sizing data c using a digital switch. can. Furthermore, the compression dimension-pressure force data is calculated based on theoretical values or actual measured locations. Therefore, when length measurement data a and sizing data c are input, the computer 102 outputs pressure data d necessary for compression molding the molded product to a predetermined sizing dimension, and this pressure data d is used for sizing. It is supplied to the control circuit of the press (for example, as a set pressure for the relief valve 25 in FIG. 2), and is molded to a constant sizing dimension. That is, for example, if the dimensions of the molded product before sizing are
If the size is 10.05-9.95mm (10±0.05mm) and the sizing dimension is set to 9.8mm, everything will be sized to 9.8mm even if there is some variation in density.

Furthermore, if there is a significant dimensional difference between the molded products before sizing, and if the molded products are smaller than the sizing dimensions or too large and will apply a load that will cause the press body to bend, the computer 102 will use the length measurement data a or The upper and lower limits may be determined based on the pressurizing force data d, and an alarm may be issued at the same time as a failure. In this application, the length measurement sensor 1 shown in FIG.
7 is unnecessary.

(Effects of the Invention) As is clear from the examples described above, according to the sizing dimensions of the present invention, powder molded products with different length dimensions are compression molded to a preset constant sizing dimension before sizing, and the sizing press machine body This has the effect of preventing excessive loads from being applied to the

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of an apparatus for carrying out the sizing method of the present invention, and FIG. 2 is an explanatory diagram of a sizing press machine to which the same method is applied.

Claims (1)

[Claims] 1. A computer that measures the dimensions of a molded product sintered after being pressure-molded using a powder molding press, stores the measured values in advance with data on the compressed dimensions and the pressure force necessary for the compression, and is capable of setting the sizing dimensions as desired. The computer calculates the necessary compression dimensions from the measured values and sizing dimensions, outputs the pressure data necessary for compression, and uses the output data to control the sizing press filled with the molded product. A sizing method for powder molded products that is sized by applying it to a circuit.