JPH09300418A - Method for setting point of judgement on quality of product in injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate fluctuation of setting points of judgement on quality of products and to facilitate its setting by a method wherein timing of injection operation when injection pressure becomes max. within section for judgement of quality set during molding a product of good quality and several points of time separated from the timing by a specified time are set as points for judgement on quality of the products. SOLUTION: In a CPU 25 for CNC of a control device 10, at first, an initial value 0 is set in a temporary max. injection pressure storing registor for detecting the max. injection pressure and as an index for refering to a sampling data storing file, set values for specifying the starting point and the end point of a section for judgement of quality to be an object of inspection of the max. injection pressure, are stored in an RAM 24. Then, in the CPU for CNC, the number of the points for judgement of the quality of the products are set by reading the value of the number of the front measuring points and the number of the back measuring points. Then, in the RAM 24, a storing file for setting comparative reference data is constructed. As the result, even when deviation is generated in generating timing for the max. injection pressure and the position of a screw, the quality of the product can be judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a product quality determination method in an injection molding machine.

[0002]

2. Description of the Related Art A change in the injection pressure for one injection process is sampled several times based on the elapsed time after the start of injection or the screw position, and the graphs are displayed in a superimposed manner to determine the pressure that affects the quality of the product. An operator determines the sampling timing or screw position that causes a change, and a product quality determination point setting method is known in which these sampling timings or screw positions are set as product quality determination points. Since the selection depends on the operator's judgment, that is, the operator's individuality, there is a problem that the setting of the product quality determination point varies.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art, eliminate the variation in the setting of the product quality determination point due to the individuality of the operator, and easily determine the product quality determination point at an appropriate timing. It is to provide a method for setting a product quality determination point in an injection molding machine that can be set.

[0004]

[Means for Solving the Problems] Since the injection pressure is larger at a position where the resistance applied to the resin is larger in the injection process, and the variation in the injection pressure between shots also becomes larger at this position, injection is performed near the position where the injection pressure is large. The quality of the product can be easily determined by using the product quality determination point based on the pressure. Therefore, the present invention detects the timing of the injection operation that maximizes the injection pressure within the quality determination section set during molding of a good product, and sets several points apart from the timing by a predetermined time as product quality determination points. The above object was achieved by setting.

Further, the screw position of the injection operation at which the injection pressure is maximum is detected within the quality judgment section set during the molding of the non-defective product, and several screw positions apart from the screw position by a predetermined distance are judged as product quality. The same purpose was achieved by setting points.

In short, the timing to be set as the product quality determination point may be a function of time or a function of the screw position. However, until the user gets tired, the setting criterion of the product quality determination point is the set quality determination. It is the timing at which the injection pressure becomes maximum in the section, or the screw position at that time.

More specifically, the injection pressure is sampled at a predetermined cycle during the molding of a good product, the sampling timing at which the injection pressure is maximized is detected within the set pass / fail judgment section, and only a predetermined time is passed from the sampling timing. The timing of the time function is set by setting some sampling timings that are distant as product quality determination points.

When the product quality determination point is set as a function of the screw position, the injection pressure and the screw position are sampled at a predetermined cycle during molding of a good product, and the injection pressure is maximized within the set quality determination section. The following screw positions are detected, and some screw positions apart from the screw position by a predetermined distance are set as product quality determination points.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of a control device 10 of an injection molding machine according to an embodiment for carrying out a product quality determination process to which a product quality determination point setting method of the present invention is applied.

The control unit 10 includes a CNC CPU 25, which is a numerical control microprocessor, and a PMC, which is a programmable machine controller microprocessor.
To detect the injection pressure and the screw back pressure from the pressure CPU on the side of the injection molding machine via the CPU 18 for servo control, the servo CPU 20 which is a microprocessor for servo control, and the A / D converter 16 to perform sampling processing. The CPU 17 has a pressure monitor CPU 17 and is capable of transmitting information between the microprocessors by selecting mutual input / output via the bus 22.

The PMC CPU 18 is connected to the ROM 13 which stores a sequence program for controlling the sequence operation of the injection molding machine and the RAM 14 which is used for temporary storage of operation data. The CNC CPU 25 is connected to the entire injection molding machine. RO that stores the program to control automatically
M27 and RA used for temporary storage of operation data, etc.
M28 is connected.

Each of the servo CPU 20 and the pressure monitoring CPU 17 stores a ROM 21 storing a control program dedicated to servo control, a RAM 19 used for temporary storage of data, and a control program relating to injection pressure sampling processing and the like. The ROM 11 and the RAM 12 used for temporary storage of data are connected. Further, the servo CPU 20 has a clamp CPU, an injection controller, a screw driver,
A servo amplifier for driving a servo motor of each axis for an ejector or the like is connected, and an output from a position / speed detector attached to the servo motor of each axis is fed back to the servo CPU 20. The current position of each axis is determined by the servo CPU 2 based on the feedback pulse from the position / speed detector.
It is calculated by 0 and updated and stored in the current position storage register of each axis. In FIG. 1, the servo amplifier 15 for one axis
Although only the servo motor M and the position / speed detector P are shown, the configuration of each axis for clamping, injection, ejector, etc. is similar to this. However, it is not necessary to detect the current position for screw rotation,
Only the speed needs to be detected.

The interface 23 is an input / output interface for connecting to a host computer or the like.

A manual data input device 29 with a display is connected to the bus 22 via a CRT display circuit 26 so that a graph display screen and a function menu can be selected and various data can be input. A numeric keypad and various function keys are provided.

The non-volatile memory 24 is a memory for storing molding data which stores molding conditions relating to the injection molding operation, various set values, parameters, macro variables and the like.

Further, the control device 10 is disclosed in JP-A-6-1709.
07 has a known data sampling function, such as the temperature of the injection cylinder, the injection pressure, the injection speed, the injection / holding pressure switching position, the screw position, the cushion amount, etc. collected for each molding cycle by this data sampling function. In addition to molding data, molding data such as molding cycle time, required measurement time, required injection time, etc. are detected and stored in the sampling data storage file F1 of the non-volatile memory 24. Of these, the minimum required items in this embodiment are the injection pressure Pi and the screw Si position, as shown in FIG. Note that the item of i is an address, and the value of the address i is updated every time the sampling processing is performed in each predetermined cycle, and the injection pressure Pi and the value of the screw Si corresponding to that time are stored in the sampling data storage file. It will be written in F1.

With the above configuration, the PMC CPU 18 controls the sequence operation of the entire injection molding machine, and the CNC C
The PU 25 distributes the movement commands to the servo motors of the respective axes based on the operating program of the ROM 27, the molding conditions of the non-volatile memory 24, etc., and the servo CPU 20 detects the movement commands and the position / speed detection distributed to the respective axes. Based on the position and speed feedback signals detected by the detector, servo control such as position loop control, speed loop control, current loop control, etc. is performed in the same manner as in the past, so-called digital servo processing is executed, and servo of each axis is executed. Drive control of the motor.

FIG. 2 and FIG. 3 are flow charts showing the outline of the judgment point setting process for setting the product quality judgment point with reference to normal data regarding the injection pressure and the screw position at the time of molding the non-defective product. 4 to 6
6 is a flowchart showing an example of product quality determination processing for performing quality determination of a product using the set determination points.

The operator first carries out condition setting to stabilize the molding conditions, and then the CP for CNC of the control unit 10.
The determination point setting process of FIGS. 2 and 3 is executed by U25, and the non-volatile memory 24 stores the reference product quality determination point. Note that the data used at this time may be the latest data itself stored in the sampling data storage file F1, or may be an average value of the latest several times of sampling data, such as some statistical data. The data may be data that has been processed and stored again in the sampling data storage file F1.

The CPU for the CNC which has started the discrimination point setting processing
First, 25 sets an initial value 0 to the temporary maximum injection pressure storage register Pmax used to detect the maximum injection pressure (step a1), and sets the index i for searching the sampling data storage file F1 to the set value k. Is stored (step a2).

This set value k is a set value for specifying the start point of the pass / fail judgment section which is the target of detection of the maximum injection pressure, and is paired with a set value m described later for specifying the end point of the pass / fail judgment section. ing. Since the set values k and m are values corresponding to the addresses of the sampling data storage file F1, in this embodiment, the product quality determination section is basically set by a function of the elapsed time after the start of the injection operation. become. That is, if the sampling period is τ, the pass / fail judgment section in which the maximum injection pressure is detected is the range of the elapsed time after the start of injection from k · τ to m · τ. Of course, a configuration in which the pass / fail judgment section is set depending on the screw position may be applied. An example of setting the pass / fail judgment section is shown in FIGS. 10 and 11.

C for CNC in which set value k is stored in index i
The PU 25 then reads the injection pressure Pi at the time of sampling corresponding to the address i and the injection screw position Si at that time from the sampling data storage file F1 as shown in FIG. 8 (step a3). Then, the magnitude relationship between the injection pressure Pi and the current value of the temporary maximum injection pressure storage register Pmax is compared (step a4), and the injection pressure Pi is determined.
Is larger than the value of the temporary maximum injection pressure storage register Pmax, the injection pressure Pi is updated and stored in the temporary maximum injection pressure storage register Pmax (step a5), and at the same time, the value of Si is stored in the screw position storage register Smax ( In step a6), the current value of the index i is stored in the address storage register Max (step a7). Injection pressure Pi
Is equal to or less than the value of the temporary maximum injection pressure storage register Pmax, the processing of steps a5 to a7 is not executed, and the values of the registers Pmax, Smax, Max are held as they are without being updated.

Next, the CPU 25 for CNC increments the value of the index i by 1 (step a8), and based on the updated value of the index i until the value of the index i exceeds the set value m (step a9). Then, in the same manner as described above, step a3
Or, the processing of step a9 is repeatedly executed to detect and store the screw position Smax corresponding to the timing when the injection pressure becomes the maximum in the pass / fail judgment section and the address value Max corresponding to this.

Next, the CNC CPU 25 determines whether or not the number of product quality determination points has already been set (step a10). If not set, the operator waits for a setting input operation, and the operator inputs it. The value of the previous measurement point and the value of the subsequent measurement point are read, and the respective values are stored in the previous measurement point storage register Bp and the subsequent measurement point storage register Ap (step a11).

The pre-measurement point storage register Bp is a register for storing the number of product quality determination points set at a point before the maximum injection pressure is achieved, and the post-measurement point storage register Ap is the maximum. It is a register for storing the number of product quality determination points set for the subsequent time points when the injection pressure is achieved as a reference, and the operator can set any natural number or 0 to each register. .

For example, when 4 is set as the number of pre-measurement points and 0 is set as the number of post-measurement points, a total of 5 points, that is, 4 points when the maximum injection pressure is achieved and before the maximum injection pressure is set, are set as the product quality determination points. In addition, when 0 is set as the number of previous measurement points and 4 is set as the number of subsequent measurement points, a total of 5 points, that is, 4 points at the time when the maximum injection pressure is achieved and after that point, are set as the product quality determination points. Furthermore, when 4 is set for both the front measurement point and the rear measurement point, a total of 9 points, that is, 4 points when the maximum injection pressure is achieved, 4 points before the maximum injection pressure, and 4 points after the maximum injection pressure is achieved, are judged as good or bad. It will be set as a point. When both the number of pre-measurement points and the number of post-measurement points are set to 0, only one point when the maximum injection pressure is achieved is set as the product quality determination point. Both FIG. 10 and FIG. 11 are examples when the number of front measurement points is set to 4 and the number of rear measurement points is set to 0.

In this embodiment, the injection pressure and the screw position are sampled every predetermined period τ, so that the product quality determination point is determined by the time function (not the elapsed time after the start of injection). In the case of setting, the time difference between the closest product quality determination points necessarily coincides with τ.
Further, when the product quality determination point is set as a function of the screw position (not the absolute screw position), the advancing speed of the injection screw in the injection process is not uniform, so that the product quality determination points between the closest product quality determination points There is not necessarily a causal relationship between each of the screw position differences.

After the values of the pre-measurement point number Bp and the post-measurement point number Ap are specified, the CNC CPU 25 sets an initial value [-Bp] to the index j for generating the comparison reference data setting storage file F2. (Step a12), an initial value [Max-Bp] is set to the index i for searching the sampling data storage file F1 (step a1).
3) Corresponding to the value of the index j, the injection pressure Pi at the address i in the sampling data storage file F1 and the screw position Smax corresponding to the maximum injection pressure detection time from the screw position at the address i of the sampling data storage file F1. The value obtained by subtracting Si [Smax-Si] is stored (step a14).

Thereafter, the CNC CPU 25 sequentially increments the values of the indexes j and i by 1 until the value of the index j exceeds the value of the set value Ap of the subsequent measurement points (step a17) (step a15). , Step a16), and similarly to the above, the processing of steps a14 to a17 is repeatedly executed to build the comparison reference data setting storage file F2 in the nonvolatile memory 24.

FIG. 9 shows an outline of the structure of the comparison reference data setting storage file F2. As described above, this file is a file that stores reference data regarding the injection pressure and the screw position for each product quality determination point according to the settings of the pre-measurement point number Bp and the post-measurement point number Ap. As is clear from the description of steps a12 to a17, the injection pressure P (Max-Bp) is at the first address [-Bp] of the comparison reference data setting storage file F2, that is, the maximum injection pressure Max. Injection pressure data P (Max-B) past Bp · τ from the time of τ
p) will be stored. Further, since the absolute position of the injection screw at the time of Max when the maximum injection pressure is achieved is S (Max), if the screw position at the time of maximum injection pressure is taken as the zero reference, Bp. Of course, the screw position at a time point past by τ is [Smax-S (Max-Bp)]. In this embodiment, the most advanced position of the screw is set as the origin of the mechanical coordinate system, so at least as long as the injection screw continues to advance before and after the maximum injection pressure is achieved,
The value of Sj is always negative in the section where the value of j is [-Bp] to 0, and the value of Sj is always positive in the section where the value of j is 0 to AP. The product quality judgment point is based on when the maximum injection pressure is reached [-
Bp] · τ, and the first product quality determination point set based on the screw position is [Smax-S] based on the screw position when the maximum injection pressure is achieved.
(Max-Bp)], and the reference value of the normal injection pressure corresponding to these is P (Max-Bp).

Similarly, the product quality judgment points of the time functions concerning the second, third, ...: Product quality judgment points on the basis of the screw position: The relationship between the standard values of the normal injection pressures corresponding to them is shown in FIG. 9 and as shown below: Time: Screw position: Pressure reference value [(-Bp + 1) · τ]: [Smax-S (Max-Bp + 1)]: [P (Max-Bp + 1)] [ (-Bp + 2) ・ τ]: [Smax-S (Max-Bp + 2)]: [P (Max-Bp + 2)] ・ ・ ・ [0]: [0]: [P (Max)]・ ・ ・ [(Ap-1) ・ τ]: [Smax-S (Max + Ap-1)]: [P (Max + Ap-1)] [Ap ・ τ]: [Smax-S (Max + AP )]: [P (Max + Ap)] Needless to say, in FIG. 9 and in the above, the time at which the value of the item of the time function becomes 0 and at the same time the value of the item of the function of the screw position becomes 0 is the timing for achieving the maximum injection pressure.

FIGS. 4 to 6 are flowcharts showing an example of the product quality determination processing for performing the quality determination of the product using the set product quality determination points. This processing is one molding in the continuous molding operation. It is repeatedly executed by the CPU 25 for CNC every time the injection process of the cycle is completed, that is, every time the sampling process regarding the injection pressure is completed.

This product quality determination process is different from the conventional one in that the quality of the product is determined based on the time when the maximum injection pressure in the quality determination section in the injection process is detected. In other words, due to some reason the injection operation is delayed or advanced, or the measured amount of resin fluctuates, causing a time or screw position deviation in the timing of maximum injection pressure. In this case, the data to be compared can be automatically shifted accordingly, and the quality of the product can be determined by comparing the detection data of the injection process and the reference data suitable for this. That is. In the prior art, since the timing of product quality determination is set with reference to the absolute elapsed time with respect to the injection start time or the absolute position of the injection screw,
When the above-mentioned deviation occurs, normal pass / fail determination may not be performed.

The CP for the CNC that has started the product quality determination process
U25 refers to the sampling data of the immediately preceding injection process stored in the sampling data storage file F1,
The timing when the injection pressure becomes maximum in the immediately preceding injection process, that is, the injection process in which the product that is the object of quality determination is molded, by performing the same processing as steps a1 to a9 of FIG. The screw position Smax corresponding to and the address value Max corresponding to the screw position Smax are detected (steps b1 to b9).

Next, the CPU 25 for CNC initializes the defect detection flag Fx to 0 (step b10), and determines whether the time is selected as the product quality determination point or the screw position reference is selected (step b1).
1). This selection information is stored in the non-volatile memory 24, and can be switched appropriately according to the operator's judgment.

When the time is selected as the product non-defective point, the CNC CPU 25 first sets an initial value [-Bp] to the index j for searching the comparison reference data setting storage file F2 (step b12). ), An initial value [Max-Bp] is set to the index i for searching the sampling data storage file F1 (step b13). Next, while the injection pressure Pi is read from the sampling data storage file F1 in correspondence with the value of the index i, the injection pressure Pj serving as the discrimination reference is read from the comparison reference data setting storage file F2 (step b14), and the injection pressure P is read.
It is determined whether i is within the range allowed by the reference injection pressure Pj (step b15). Then, if an abnormality is detected in the determination processing in step b15, the CPU 25 for CNC sets 1 to the defect detection flag Fx (step b16), and if no abnormality is detected, the initial value is 0.
Hold as is.

Thereafter, until the value of the index j reaches the value of Ap (step b19), the CPU 25 for CNC uses the index j.
Then, the value of the index i is sequentially incremented by 1 (steps b17, b18), and the processes of steps b14 to b19 are repeatedly executed as described above.

Therefore, in this embodiment, if even one injection pressure Pi whose difference from the reference injection pressure Pj exceeds the allowable value ε is detected, the product molded in the injection process is regarded as a defective product. Will be. Of course, instead of the defect detection flag Fx, the counter Fx is used, and the value of the counter Fx is incremented by 1 each time an abnormality is detected in the determination processing of step b15, and the determination result of step b19 becomes true. At that time, the quality of the product may be determined by referring to the value of the counter Fx. More specifically, the quality of the product is determined by whether or not the value of the counter Fx exceeds the set value when the result of the determination in step b19 becomes true. The maximum value is Bp + Ap + 1. In short, the value should not exceed the set total number of product quality determination points. For example, the set value is Bp + Ap−α (where 0 ≦ α ≦ Bp + Ap)
By setting as, it is possible to automatically adjust the set value to be compared in accordance with the setting state of the number of front measurement points Bp and the number of rear measurement points Ap.

The value of the injection pressure Pi read in the process of step b14 which is firstly executed, that is, the value of the injection pressure P (Max-Bp) is determined from the maximum injection pressure detection time Max · τ in the injection step. Is also the value of the injection pressure detected by Bp · τ in the past, and is the reference pressure Pj read first from the comparison reference data setting storage file F2, that is, Bp · There is a one-to-one correspondence with the injection pressure at the time of molding a good product, which is detected by τ in the past. For example, if Bp · τ = 0.5 seconds, the detected injection pressure Pi detected 0.5 seconds before the maximum injection pressure at the injection step is always the maximum injection during good product molding. The reference injection pressure Pj is detected 0.5 seconds before the pressure is reached,
No matter how the detection time point of the maximum injection pressure based on the injection start time point shifts during the continuous molding operation, this correspondence does not change. The same applies to the relationship between the detected value Pi of the second or subsequent product quality determination point and the pressure reference value Pj of the second or subsequent product, which is t seconds before the time when the maximum injection pressure is achieved in the injection process. It is said that the detected injection pressure Pi detected at or after t seconds) is always compared with the reference injection pressure Pj detected at t seconds before (or after t seconds) from the time when the maximum injection pressure is achieved at the time of molding a good product. That is.

On the other hand, when the screw position is selected as the product non-defective point, the CNC CPU 25 first sets an initial value [-Bp] to the index j for searching the comparison reference data setting storage file F2. (Step b2
0), the index j from the comparison reference data setting storage file F2
The position Sj of the product quality determination point corresponding to is read (step b21).

However, as described above, the moving speed of the screw may vary in various ways depending on the injection situation. Therefore, the time relationship based on the maximum injection pressure detection time is set as in steps b12 and b13. Even if they are matched, it is not possible to match the screw positions based on the detection of the maximum injection pressure in the relationship between the sampling data at the time of molding a good product and the sampling data at the injection step. The indexes j and i are merely for comparing the injection pressures as a function of time with respect to the time when the maximum injection pressure is reached.

Therefore, the CNC CPU 25, which has read the screw position Sj of the product quality determination point set with reference to the maximum injection pressure detection position during molding of a good product, first determines the screw absolute position corresponding to this in the injection process. The injection pressure P of the injection process corresponding to the screw position is obtained based on the data in the sampling data storage file F1 (step b22). For example, Sj =
1 mm, in short, if the reference injection pressure Pj is stored in the comparison reference data setting storage file F2 corresponding to a position 1 mm before the screw position at the time of achieving the maximum injection pressure during molding of a good product, first, 1 more than the absolute screw position when the maximum injection pressure in the injection process is reached
The absolute screw position before mm is obtained on the sampling data storage file F1, and the value of the injection pressure P of the injection process corresponding to the position 1 mm before the absolute screw position at the time when the maximum injection pressure of the injection process is achieved. Is estimated based on the sampling data storage file F1.

This processing can be achieved by the algorithm shown in FIG. Hereinafter, this process will be briefly described.

First, it goes without saying that the screw absolute position Sx of the injection step corresponding to the screw position Sj of the product quality determination point set with the maximum injection pressure detection position during molding of a good product as the zero reference is Smax-Sj. (Step c1). However, since the value of Smax-Sj = Sx is a calculated value, there is no guarantee that the data of the screw absolute position that completely matches this value is recorded in the sampling data storage file F1. Therefore, the CNC CPU 25 once initializes the value of the index i to 0 (step c2), and stores two addresses i and i that store the screw absolute positions before and after the screw absolute position Sx on the sampling data storage file F1. -1 is detected (step c3 to step c5).

As described above, the most advanced position of the screw is the origin of the machine coordinate system, and the screw moves (advance) in the negative direction at the time of injection. Therefore, when Si ≦ Sx is satisfied for the first time in the process of step c4. , The screw absolute position Sx is sandwiched between the screw absolute position Si and the screw absolute position Si-1 in the relationship of Si ≦ Sx <Si−1.

Naturally, the screw absolute position Si and the screw absolute position Si-1 are recorded in the sampling data storage file F1, and the injection pressures Pi and Pi-1 corresponding to these positions are also stored in the sampling data storage file F1. As recorded above, the CP for CNC
U25 reads these data from the sampling data storage file F1 (step c6), [difference between screw absolute position Si and screw absolute position Si-1].
[Injection pressure Pi] according to the ratio of [difference between screw absolute position Si and screw absolute position Sx]
And the injection pressure Pi-1] are proportionally distributed, and the injection pressure P of the screw absolute position Sx corresponding to the product quality determination point is estimated (step c7).

In this way, the CPU for CNC which has obtained the injection pressure P of the injection step corresponding to the product quality determination point Sj
25 is the comparison reference data setting storage file F2 to Sj
The reference injection pressure Pj corresponding to is read (step b2
3) It is determined whether the estimated injection pressure P is within the range allowed by the reference injection pressure Pj (step b24). When an abnormality is detected in the determination process of step b24, the CPU 25 for CNC sets 1 to the defect detection flag Fx.
Is set (step b25), and if no abnormality is detected, the initial value 0 is held as it is.

Thereafter, until the value of the index j reaches the value of Ap (step b27), the CPU 25 for CNC uses the index j.
Value is sequentially incremented by 1 (step b2
6), the processing from step b21 to step b27 is repeatedly executed.

Therefore, in this embodiment, if any one of the estimated injection pressures P whose difference from the reference injection pressure Pj exceeds the allowable value ε is detected, the product molded in the injection process is regarded as a defective product. Will be done. As in the case where time is selected when setting the product quality determination point, it is possible to perform quality determination using the value of the counter.

As described above, when the screw position is selected in setting the product quality determination point, the product quality determination point is set before and after the position where the maximum injection pressure is generated in each injection process. Therefore, even if the screw position is deviated in each molding cycle due to a difference in the measuring state or the like, accurate pass / fail determination can be performed.

Whether the time or the screw position is selected at the time of setting the product quality determination point is arbitrary, and may be determined according to the characteristics of the mold or resin each time.

In the product quality determination process shown in FIGS. 4 to 6, the sampling data time and screw position detected in the immediately preceding injection step are made to correspond to the time and screw position of the comparison reference data setting storage file F2. In a broad sense, the product quality determination process itself is also a part of the process for setting the product quality determination point.

In the above-mentioned embodiment, the comparison judgment of the product quality judgment is made based on the point where the maximum injection pressure occurs in the set section as a reference. However, as a simple method, the product is judged based on the sampling time. You may make the comparison judgment of the quality judgment. In this case, in the process shown in FIGS. 2 and 3 for setting the product quality determination point, the processes of steps a12 and a15 are not necessary, and the process of step a17 is i> Max +
It may be determined whether Ap has occurred, and in step a14, the injection pressure Pi and the screw position Si may be stored in the comparison reference data file F2 corresponding to the index i. That is, the set sections (Max-Bp) to (M
ax + Ap) at the time of sampling i · τ each injection pressure Pi,
It suffices if the screw position Si is stored.

Further, the processing of FIG. 4 is not necessary in the product quality determination processing, and the processing of steps b12 and b17 is not necessary in the processing of FIG. 5, and the file F1 is not used in steps b14 and b15. , F2, it is determined whether the difference between the injection pressures Pi read from the injection pressure Pi is equal to or less than the set allowable amount ε, and in step b19, it is determined whether the index i exceeds Max + Ap. It may be determined whether the injection pressure at each sampling time is within the allowable range with respect to the reference injection pressure.

In the product quality determination processing based on the screw position shown in FIGS. 6 and 7, Max-Bp is set as the index i in step b20, the screw position Si is read from the file F2 in step b21, and step b22 is performed. Then, the injection pressure Pi of the file F1 corresponding to the screw position Si is obtained. That is, in the process of FIG. 7, the process of step c1 is not performed, and the index k is updated in step c2 instead of the index i, for example, until the screw position Sk in the file F1 becomes smaller than the screw position Si read in step b21. Meanwhile, the same processing as that in steps c3 to c5 (Sk <Si in the processing in step c4) is performed. When it becomes smaller, Sk, Pk, Sk-1 and Pk-1 are read from the file F1 (step c
6), and in step c7, P = Pi-{(S
k-Si) / (Sk-Sk-1)}. (Pi-Pi-1) is performed to obtain the injection pressure P corresponding to the screw position Si. Then, Pi is read from the file F2 (processing corresponding to step b22), it is determined that the difference between the injection pressures P and Pi is equal to or less than the set allowable value ε (processing corresponding to step b24), and when the allowable value ε is exceeded. Only the defect detection flag Fx is set to "1" (processing corresponding to step b25), the index i is incremented (processing corresponding to step b26), and it is determined whether the index i exceeds Max + Ap (corresponding to step b27). Process), if not exceeded, the process returns to step b21, and if exceeded, the product quality determination process ends.

[0056]

According to the present invention, several product quality determination points are set before and after the timing of the injection operation at which the injection pressure has the largest variation within the quality determination section. Therefore, it is possible to easily avoid the variation of the setting due to the individual difference of the operator and to set the optimum product quality determination point.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a control device of an injection molding machine according to an embodiment for carrying out product quality determination processing to which a product quality determination point setting method of the present invention is applied.

FIG. 2 is a flowchart showing an outline of discrimination point setting processing.

FIG. 3 is a continuation of the flowchart showing the outline of the discrimination point setting process.

FIG. 4 is a flowchart showing an example of product quality determination processing.

FIG. 5 is a continuation of the flowchart showing an example of product quality determination processing.

FIG. 6 is a continuation of the flowchart showing an example of product quality determination processing.

FIG. 7 is a flowchart showing a part of product quality determination processing.

FIG. 8 is a conceptual diagram showing a sampling data storage file.

FIG. 9 is a conceptual diagram showing a comparison reference data setting storage file.

FIG. 10 is a diagram showing an example of setting a quality determination section.

FIG. 11 is a diagram showing an example of setting a quality determination section.

[Explanation of symbols]

 Reference Signs List 10 control device 11 ROM 12 RAM 13 ROM 14 RAM 15 servo amplifier 16 A / D converter 17 pressure monitor CPU 18 PMC CPU 19 RAM 20 servo CPU 21 ROM 22 bus 23 interface 24 nonvolatile memory 25 CNC CPU 26 CRT Display circuit 27 ROM 28 RAM 29 Manual data input device with display

Claims (4)

[Claims] 1. The timing of the injection operation that maximizes the injection pressure is detected within the pass / fail judgment section set during molding of a good product, and several points apart from the timing by a predetermined time are set as product pass / fail judgment points. A method for setting a product quality determination point in an injection molding machine, characterized by: 2. The screw position of the injection operation that maximizes the injection pressure is detected within the pass / fail judgment section set during molding of a good product, and several screw positions apart from the screw position by a predetermined distance are judged as product pass / fail. A product quality determination point setting method in an injection molding machine characterized by setting points. 3. An injection pressure is sampled at a predetermined cycle during molding of a non-defective product, a sampling timing at which the injection pressure is maximum is detected within a set pass / fail judgment section, and some are separated from the sampling timing by a predetermined time. A method for setting a product quality determination point in an injection molding machine, wherein the sampling timing of is set as a product quality determination point. 4. The injection pressure and the screw position are sampled at a predetermined cycle during molding of a good product, and the screw position where the injection pressure is maximum is detected within the set pass / fail judgment section, and the screw position is separated from the screw position by a predetermined distance. A method for setting a product quality determination point in an injection molding machine, characterized by setting several screw positions as product quality determination points.