JPH01104500A - Automatic correcting device for forming condition of press - Google Patents

Abstract

PURPOSE:To prevent the generation of the defect of a product, and also, to improve the dimension accuracy by controlling the condition of the next forming cycle, based on a signal from a pressure detecting mechanism and a punch position detecting means provided on each punch driving mechanism. CONSTITUTION:From a computer 63, an operation condition of each punch such as a moving distance and moving speed, etc., of the punch and an operation timing and the work condition of a feeder are transmitted to an NC 61. At the time of executing a work, the operation is executed by a forming condition stored in the computer 63. In such a way, the generation of a defective is prevented, the dimension accuracy is improved, the productivity is improved and the quality can be stabilized.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to the control of an NG mechanical press for powder compaction, which compression-molds ceramic powder, metal powder, and other various powders into appropriate shapes, and particularly relates to the control of an NG mechanical press for powder compaction, which compresses and compacts ceramic powder, metal powder, and other various powders into appropriate shapes. Prevents fluctuations in molding pressure caused by variations in powder filling weight,
The present invention relates to an automatic molding condition correction device that can mold a molded product with a constant density.

[Conventional technology]

With an NC mechanical press that controls the punch position with an NC @ control device and forms the product, the variation in the thickness of the compact can be suppressed to less than ±10 μm, but the filling amount may vary due to changes in the properties such as the particle size distribution of the powder. The molding pressure changes by about ±10% due to the variation in the molding pressure, and the resulting change in the density of the molded product is also large, which changes the shrinkage rate during firing and causes dimensional errors in the fired product.

With conventional presses, when the frequency of molding outside the specified molding pressure range increases, molding is temporarily interrupted, and the operator uses key inputs such as filling depth based on skill and experience to make trial adjustments. Even if the molding pressure was exceeded, it was necessary to monitor the extent to which the molding pressure exceeded the range, so completely unmanned operation was not possible.

A known example of controlling the punch position and forming pressure (Japanese Patent Application Laid-open No. 1987-
13002, JP-A-60-54299, JP-A-59
-183998, etc.), but there is no mechanical press that can feed back the molding pressure, reset the filling depth, and independently operate the punch.

The purpose of the control device of Jikai 59-183998 powder molding press is to prevent cracks occurring during molding and vibrations during return, and the purpose is as follows.

It has a means for detecting the applied stress value or the difference in stress value when the powder molding press performs a pressing action, a means for comparing the stress value with a reference value, and a means for comparing the stress value and the stress value detected with respect to the reference value. The pressing action is controlled when the difference in stress values exceeds a predetermined value.

It also has means for detecting the amount of change in position of the press die or the difference in the amount of change, and performs comparison calculation control as described above. Then, it detects the stress value, stress value difference, and the difference in the amount of change and amount of change in position.
The driving action of the press is controlled when the difference between the reference value and the detected value exceeds a predetermined value.

That is, the aim is to control the press by detecting the stress generated in the press when performing a molding action or the dimension by which the press moves.

Jikai 60-54299 powder material pressing method and device detect the position and pressing force during actual pressing by setting the position and pressing force as reference values in advance, and then distinguishing between the actual value and the standard value. Depending on the size of the difference, the acceptance or rejection of the detailed material, that is, the molded body, is judged and allowed or rejected.

In other words, this disclosure provides an inspection means after molding the powder material in the means for pressing, and corresponds to a so-called inspection and sorting device in which various components act according to the detection signal. It is.

However, it would be effective to incorporate the inspection process after the press process into this press apparatus and shorten the molding operation time.

The automatic compact thickness correction device in the Jikai 59-13002 powder compacting machine moves the die up and down using a detector consisting of a differential transformer or potentiometer, etc., and outputs the filling depth H of the cavity from the control circuit. It is changed by

If the error with respect to the predetermined thickness Is is within a predetermined range, molding is continued as it is, and if it is thick, the die is lowered,
If it is thin, the die is raised to change the amount of raw material powder filled into the cavity, which is a concave part. Although it is based on the principle that the thickness of the compact is determined by the amount of filling, it does not take into account changes in pressure, displacement of the upper punch itself, displacement of the lower bunch itself, and changes in the diameter of the die.

It simply makes the dimensional difference between the contact surface of the lower punch and the upper surface of the die variable, and is an operating means that changes the dimension between the reference surfaces when the dimension is deviated from when moving up and down between the reference surfaces. .

The recent methods and products disclosed above as conventional examples are: (1) Detecting and controlling punch stress values and stress value differences.

■ Detect and control the position and position difference of the punch.

There is also combined control with ■.

■ The press force of the punch is detected, and molded products are inspected or rejected based on the difference between the preset standard value and the actual press force.

■ Detect the thickness after molding and move the die up and down to change the amount supplied to the cavity.
It can be summarized as a technique called ゛.

[Problem that the invention seeks to solve]

Conventional presses for powder molding have the following problems.

If the molding pressure fluctuates due to changes in the properties such as the particle size distribution of the powder, it is necessary to temporarily stop molding and reset the filling depth, which setting depends on the operator's intuition and experience. Therefore, the adjustment time varies greatly depending on the level of skill, which causes a decrease in productivity.

The purpose of the present invention is to automatically and rationally reset data such as filling depth by feeding back the molding load during molding to the next molding cycle and setting the filling depth etc. appropriate to the properties of the powder. An object of the present invention is to provide an automatic molding pressure correction device that calculates and sets molding conditions.

(Means for Solving the Problems) In order to solve the first problem, the present invention has the following configuration. That is, an upper punch having an electric motor such as a servo motor or a pulse motor, a speed reducer, and a link mechanism. Drive mechanism and electric motor such as servo motor or pulse motor,
a lower first punch having a speed reducer, a link mechanism, and a lower first punch driving member that moves in substantially the same direction and the same distance as the lower first punch;
A punch drive mechanism, a lower second punch drive mechanism having an electric motor such as a servo motor or a pulse motor, a speed reducer, and a precision guide, a molding pressure detection means consisting of a load cell installed on the drive side member of each punch, and a load cell amplifier. , a punch position detection control means consisting of a linear encoder and an amplification converter connected to the driving side member of each punch, storage of operating conditions of each punch, creation of operating data and NC program, reception of data from forming pressure detection means, The control system consists of a computer, NC control device, and sequencer that judge the quality of the forming load, calculate the filling depth for the next forming cycle, send operating data to the NC, and monitor the operating status of the press. It is.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a front view of a press according to an embodiment of the present invention;
The figure is a cross-sectional view taken along line A-A in FIG. FIG. 3 is a configuration diagram of the control system of the present invention. FIG. 4 is a control flowchart. FIG. 5 is a diagram showing the density and molding pressure characteristics of the powder used in the experiment, FIG. 6 is a diagram showing the relationship between filling depth and molding pressure, and FIG. 7 is a chart of each punch operation.

In FIGS. 1 and 2, the upper punch 41 is fixed to the lower end of the upper punch holder 40, and the mount base of the load cell 39 is loaded on the upper end of the upper punch holder 40.
It is held by a linear bearing 43. Further, the lower part of the upper punch holder 40 is connected to a linear encoder 44 attached to the frame 16 via a connecting part 54. The load cell 39 is installed inside the load cell box 38. The load cell box 38 is connected to a bracket 49 via a linear guide 42 attached to a side plate. The speed reducer 34 is fixed to the frame 50, a motor 33 is connected to the input shaft side, a shaft 35 is connected to the output shaft side, and the shaft 35 is connected to a link 36. The link 36 is connected to the link 37 via a pin 47, and the link 37 is connected to the load cell box 38 via a pin 48.

The lower first bunch 13 and the lower second punch 28 are attached to the mold base 51
It is arranged so that it faces the upper punch 41 with the upper punch 41 in between.

The lower first punch 13 is fixed on the lower first punch holder 12, and the lower first punch holder 12 is fixed on the tie plate 11. The upper end of the lower first punch holder 12 is connected to a linear encoder 32 attached to the frame 16 via a connecting part 52. tie plate ll
Both ends are connected to two rods 10, respectively. The rod 10 is attached to both ends of the load cell box frame 7 via linear guides 14 so as to be vertically movable, and is loaded on the load cell 9. Reducer 2 is frame 1
A motor 1 is connected to the input shaft side, a shaft 3 is connected to the output shaft side, and a link 4 is connected to the shaft 3. The link 4 is connected to a link 6 via a pin 5, and the link 6 is connected to a load cell box frame 7 via a pin 46.

A speed reducer 18 is installed at the rear of the load cell box 7. A motor 17 is connected to the input shaft side of the reducer 18, and a pulley 19 is connected to the output shaft side. Boo IJ 19
is connected to a pulley 21 via a belt 20. The ball screw 23 is rotatably attached to the load cell pock frame 7 with a bearing 22, and a pulley 2 is attached to the lower end.
1 is fixed, and a nut 24 is attached to the upper end so as to be movable in the vertical direction. A nut 24 is fixed to the lower end of a load cell box 25 holding a load cell 26. The load cell box 25 is connected to the load cell box frame 7 via a linear guide 29 so that it can only move up and down. The lower second punch 28 is attached to the lower second punch holder 2
7, and the lower end is loaded on the load cell 26. The lower second punch holder 27 passes through the tie plate 11 and the lower first punch holder 12, and the tie plate 1
It is guided to be movable in the vertical direction by a linear bearing 30 fixed to 1. Further, the upper end of the lower second punch holder 27 is connected to a linear encoder 31 attached to the load cell box frame 7 via a connecting component 53.

The die 45 is detachably attached to the mold base 51. A feeder 55 whose sliding portion is made of Teflon is placed on the mold base 51, and an air cylinder 56 connected to the feeder 55 is fixed.

In FIG. 3, the control system includes an NC 61, a sequencer 62, a computer 63, a servo motor 72, a linear encoder 65, a load cell 67, and the like.

Next, the operation of the above configuration will be explained.

The operation of each punch and feeder is controlled by the NC6 shown in Figure 3.
1 and sequencer 62. computer 63
The operating conditions of each punch, such as the moving distance and moving speed, as well as the feeder operating timing and working time, are transmitted to the NC 61, and at the same time the signal to start automatic operation is input, the rotation of the motor and the air cylinder are controlled via the sequencer 62. 56 and informs the computer 63 of the work status.

After confirming that there are no mechanical problems during the initial inspection and that there is powder in the hopper (not shown) of the powder feeding device,
Turn on the power to the control system. Set the origin position of each punch in manual mode of NC61.What is the origin position of NC61?
This is the position where the coordinate value of each axis is O, and the top surface of the die and the punch surface are made to match, and that position is set as the origin of each punch.0 Next, the operation mode of the NC 61 is switched to automatic (DNC) mode. When the molded body base and the number of pieces to be molded are input to the computer 63, the molding conditions are read out from the memory of the computer 63, the molding conditions etc. are displayed on the CRT 64, and after confirmation, the computer 63 is used to input the operation execution. After inputting the operation execution, the computer 63 sends five cycles of operation data to the NC 61 through the R3-232G, and the NC 61 issues commands to the servo drive circuit 71 and the sequencer 62 based on the operation order of the received operation data. First, each punch moves to the powder feeding starting position. The powder feeding start position is a position where the upper punch 41 allows the feeder 55 to pass, and a position where the upper surface of the die and the punch surface of the lower first punch 13 and the lower second punch 28 coincide. When each punch reaches the powder feeding start position, the NC 61 issues a powder feeding start command to the sequencer 62, and the sequencer 62 opens a forwarding solenoid valve (not shown) of the air cylinder 56 to advance the feeder 55. When the feeder starts moving forward, the lower first punch 13 and the lower second punch 28 descend to the filling depth position.

When the feeder 55 reaches its forward limit, a forward limit switch (not shown) is activated. When the forward limit switch signal is sent to the sequencer 62, the sequencer 62 closes the forward solenoid valve of the air cylinder 56, opens the backward solenoid valve (not shown), and moves the feeder 55 backward. When the feeder 55 reaches the intermediate point, the intermediate point limit switch (
(not shown) is activated. When the signal from the midpoint limit switch is sent to the sequencer 62, the sequencer 62 closes the backward solenoid valve of the air cylinder 56, opens the forward solenoid valve, and moves the feeder 55 backward. The feeder reciprocates between the forward limit and the intermediate point until a powder feeding stop command is issued from the NC61.

When the predetermined powder feeding time has passed, the NC 61 activates the sequencer 62.
A command to stop powder feeding is issued. The sequencer 62 is the feeder 55
At any position, the forward solenoid valve of the air cylinder 56 is closed, the backward solenoid valve is opened, and the feeder 55 is moved backward. When the feeder reaches the waiting position, a waiting position limit switch (not shown) is activated, and the signal is sent to the sequencer 6.
2, and the sequencer 62 sends a punch enable signal to the NC 61. An enable signal is also sent to computer 63, and computer 63 begins sampling the forming load for each punch. The NC 61 sends a command to the servo drive circuit 71 to rotate the motor 69 based on the operation data of the molding conditions. The amount of rotation of the motor 69 is controlled while being compared with pulses fed back from a linear encoder 65 connected to the punch holder.

Each punch performs forming by moving up and down within the die based on operational data, and extrudes the formed object onto the upper surface of the die.

This completes one cycle of molding. As shown in the control flowchart of FIG. 4, at this point the computer 63 stops sampling the molding load, compares the maximum molding load or maximum molding pressure with a predetermined molding load or molding pressure, and determines the predetermined molding load or molding pressure. If it is outside the range, it is rejected as a defective product by a molded body removal device (not shown).

Comparison of molding load or molding pressure is performed separately for the lower first punch side and the lower second punch side, but there is no significant difference in the accuracy of defective product determination even if the comparison is made for the upper punch side all at once. N
When C61 finishes this one cycle of molding, the feeder 5
5 is advanced and the molded body is moved onto the mold base 51 with the tip of the feeder 55. At the same time, powder is fed and molded in the same manner as described above, and the computer 63 judges whether the molding load or molding pressure is acceptable. , the molded body is manufactured for 5 cycles. When the five cycles of molding are completed, the computer 63 resets the filling depth based on the molding load or molding pressure for the five cycles.

The reset method can be used for cases where the relationship between molding pressure and filling depth shown in FIG. In some cases, it is an existing product stored in In the case of a new product, it is calculated from the relationship between the density of the molded body and the molding pressure shown in FIG. The density and molding pressure of a compact can be expressed by a quadratic curve, and the density of a compact is the ratio of the filling depth to the thickness of the compact multiplied by the density of the powder during filling. Calculated using formula (2). Equation (1) is a characteristic relational expression between the density of the molded body and the molding pressure, where P is the molding pressure, d is the density of the molded body, Po is the target molding pressure, and P is 5.
This is the average molding pressure during cycle molding. , is the filling depth at that time, ! ! is the filling depth to be reset. A
, B, and C are coefficients of the quadratic curve.

The correction to formula (1) P-AXd" +BXd+ is performed on both the lower first punch side and the lower second punch side, and the filling depth and the molding pressure at that filling depth are stored in the memory of the computer 63. This resetting After doing this five times, the relational expression between the filling depth and molding pressure is calculated for each of the lower first punch side and the lower second punch side using the least squares method, and the coefficients of the relational expression are stored in the memory of the computer 63. After that, reset the settings based on the relationship between filling depth and molding pressure.

In the case of an existing product, the relational expression between the filling depth and the molding pressure stored in the memory of the computer 63 is translated in parallel so that the average value of the molding pressure for 5 cycles and the filling depth are satisfied.

Calculate the filling depth from the target molding pressure using the parallel-shifted relational expression. Alternatively, it is also possible to calculate using a formula similar to (Formula 2) depending on the properties of the powder. This calculation is performed for each of the lower first punch side and the lower second punch side. The calculated filling depth and the molding pressure at that filling depth are stored in the memory of the computer 63, and after 500 moldings, the molding pressure is
A new relational expression between filling depth and molding pressure is calculated using the square method.

After the computer 63 finishes calculating the filling depth, the computer 63 creates 5 cycles of operation data based on the filling depth to be reset, and sends it to the NC via RS-232C.
61, and the NC 61 molds the powder based on the newly received operation data.

When the computer 63 has finished molding the input number of pieces, it waits for the next command (to continue molding or stop the program), and displays this on the CRT 64. In the example, after 5 cycles of molding, the filling depth was reset.
Although the relational expression between the filling depth and the molding pressure was calculated every 00 moldings, the frequency may be changed depending on the powder manufacturing status or the fluctuation status of the powder size distribution. In the example, the filling depth was reset based on the forming pressure of each punch on the lower punch side, but it is also possible to reset the filling depth by making it proportional to the compression ratio of each punch side using the forming pressure of the upper punch. Therefore, there is not much difference in the accuracy of the correction.

Next, the initial setting of molding conditions will be explained. The basic settings are to set the distance between the upper punch and the lower punch so that the thickness of the molded product matches the target value, and to set the forming load on the upper punch side to be the sum of the forming load on the lower first punch side and the forming load on the lower second punch side. The movement amount and movement pattern of each punch are set to be approximately equal to the load. The molding pressure on the lower first punch side and the lower second punch side may need to be slightly different depending on the shape of the molded product and the shrinkage condition during firing, and the filling depth also depends on the movement of powder during compression. Depending on the situation, it may be necessary to set different compression ratios. FIG. 7 is an operation chart of each punch when forming a concave rectangular molded body. In this molded body, by making the molding pressure applied by each punch approximately equal, it was possible to prevent deformation after firing and improve dimensional accuracy. In the operation chart of FIG. 7, when the compression ratio was 2.21 on the lower first punch side and 2.67 on the lower second punch side, no cracks occurred (and the molding pressure of each punch could be made equal).

The initial setting largely depends on experience, but the approximate filling depth can be calculated from the relationship between the density of the compact and the compacting pressure shown in Figure 5.
After testing several types of molding patterns, the CRT64
It is possible to easily set the forming pattern by looking at the changes in the forming load of each punch displayed on the screen. Fine adjustments to the filling depth and molding end position can be made after several trial runs.

As described above, since the filling depth is corrected by the molding pressure feedpack, a molded product with the desired dimensions and density can be obtained continuously without having to adjust it.
For example, even if the properties of the powder change due to changes in the humidity in the air during molding, automatic correction can quickly respond and process the change.

〔Effect of the invention〕

As explained above, the following effects can be obtained by the present invention.

a. Since the position of each punch is monitored and controlled by a linear encoder connected to the punch hole and the punch hole, the only difference in the thickness of the molded product is the springback amount due to the difference in molding pressure, and the accuracy is less than ±10 μm. Can be molded.

b. Since the drive unit of the lower second punch is installed on the load cell box frame of the lower first punch,
The punch and the lower second punch can move completely in parallel, and there is no cracking due to poor synchronization between the lower first punch and the lower second punch when extruding the molded product.

C3 Since each punch can be driven and controlled independently, a molding pattern suitable for the properties of the powder and the shape of the molded product can be set.

d. All settings for the position and movement of each punch are made using the computer keyboard, so they are accurate and reproducible.
It can be done in a short time regardless of the skill level of the worker,
Productivity improves.

e. Since the molding pressure is fed back to the molding conditions such as the filling depth, if the particle size distribution of the powder fluctuates, it can be automatically adjusted to the specified molding pressure, allowing unattended molding operation and improving the molding process. It is possible to reduce fluctuations in molding density and improve quality.

f. There is no mechanical adjustment mechanism like a mechanical press,
Due to its simple structure, maintenance and inspection are easy.

[Brief explanation of the drawing]

FIG. 1 is a front view of an NC mechanical press according to an embodiment of the present invention, FIG. 2 is a sectional view of FIG. 1, and FIG. 3 is a configuration diagram of a control system. Figure 4 shows a flowchart of the present invention, Figure 5 shows the characteristic relationship between the density of the powder used in the implementation and the molding pressure, and Figure 6 shows the relationship between the filling depth and the molding pressure. FIG. 7 is an operation chart of each punch. 1...Motor, 2...Reducer, 3, 5...Axle, 4
, 6... Link, 7... Load cell box frame, 8... Linear guide, 9... Load cell, 10...
・Rod, 11...Tie plate, 12...Lower 1st
Punch holder, 13...Lower first punch, 14...Linear bearing, 15.16...Frame, 17...Motor, 18...Reducer, 19°21...Pulley, 20.
... Belt, 22... Bearing, 23... Ball screw, 24... Nut, 25... Load cell box, 26... Load cell, 27... Lower first punch holder, 28... Lower 1st punch, 29... linear guide,
30...Linear bearing, 31...Linear encoder, 3
2... Linear encoder, 33... Motor, 34...
...reducer, 35...axis, 36.37...link,
3rd...Load cell box, 39...Load cell, 40...Upper punch holder, 41...Upper punch, 4
2...Linear guide, 43...Linear bearing, 44...Linear encoder, 45...Dice, 47.48...
Bin, 49... Bracket, 50... Frame, 5
1... Mold base, 52° 53.54... Connection jig, 55... Feeder, 56... Air cylinder, 60
...CRT, 61...NC, 62...Sequencer, 63...Computer, 64...CRT. 65... Linear encoder, 66... Amplification converter,
67...Load cell, 68...Load cell amplifier,
69...Motor, 70...Tachogenerator, 71
...Servo drive circuit, 72...Punch.

Claims (1)

[Claims] The NC-controlled mechanical press has an upper punch drive mechanism, a lower first punch drive mechanism, and a lower second punch drive mechanism, and each punch drive mechanism is equipped with a pressure detection means and a punch position detection means, and the pressure An automatic molding condition correction device for a press comprising a control device that receives signals from a detection means and a punch position detection means, calculates conditions for the next molding cycle, and issues operation signals to each punch.