JP2545465B2 - Method for automatically setting upper and lower limits of molding conditions of molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for automatically setting upper and lower limit values of molding conditions used for automatically determining quality of a product in a molding machine such as an injection molding machine.

[Prior Art] When performing molding operations such as injection molding by automatic operation, it does not make any sense that the molded products become piles of defective products, so many molding operation conditions that determine the quality of products The settings are detailed. Then, the control device including a micro computer that controls the entire molding machine performs automatic operation by referring to the measurement information from various sensors based on preset molding operation condition values, and continuously executes the molded product. Mold. By the way, it is unavoidable in manufacturing that defective products are generated due to fluctuating operating conditions due to a sudden situation or the like. In this case, it is desirable to be able to automatically exclude defective products.

Therefore, along with the set values of the molding operation conditions described above, the upper limit value and the lower limit value are set in accordance with the respective set values, and the actual change of each molding operation condition value is measured while performing the automatic molding. However, the measured value is above
If it is within the lower limit, it is judged as a good product, and if it is out of the upper limit or the lower limit, it is judged as a defective product, and if a defective judgment is made, the molded product at that time is discharged normally when the mold is opened and taken out. A so-called "molding machine with a monitor function (or with a watching function or with an automatic inspection function)" that can be carried to a place other than a place is known.

Taking an injection molding machine as an example of monitor items, for example, a charge completion position, a position at which the injection primary pressure is switched to the secondary pressure (a so-called holding pressure switching position), and an injection screw tip position at the time of completion of the injection pressure holding stroke. (So-called amount of cushion) etc.
It has been used as an important monitor item since it has a strong correlation with the quality of molded products. By the way, recently, with the increasing complexity of molded products, the demand for higher precision, and the higher grade of resin used, the number of monitor items used to judge the quality of a molded product has increased, and the Depending on the molding machine, a large number of monitor items for counting 30 to 50 such as position, subdivided injection speed / injection pressure condition, charge condition, mold opening / closing condition, time of each stroke, etc. are provided. Then, for each monitor item, the upper and lower limit values are set together with the molding operation condition value described above.

Making full use of such a sophisticated monitor function is very useful for quality control. That is, for example, in order to grasp the correlation between molding conditions and quality, a printer is attached to the control device, and by this printer, each monitor item with the upper and lower limit values set on the horizontal axis is plotted on the vertical axis. Prints out the actual measured value of the monitor item for every one shot (or once every several shots) along with the shot number and time. Especially, for abnormal data that exceeds the upper and lower limit values, add an abnormal mark when printing. To On the other hand, the taken-out molded products are arranged in the order of the shot number, and by comparing them with the data printed out, the correlation between the abnormal condition (defective) of the molded product and the abnormal condition data can be examined. By adopting such a method, the quality of molded products (for example, from those closely related to the weight accuracy of molded products such as burrs and sink marks to defective surface appearance) even for products whose molding conditions are difficult to manage. It has become possible to clearly grasp the correlation between the allowable upper and lower limits of molding conditions and perform quantitative and concrete quality control.

[Problems to be solved by the invention] However, even with such a monitor function that is very useful in quality control, etc., 30 to 30
Setting the upper and lower limits for all 50 monitor items poses a problem for operators in the field.

The reason for the burden is to set the upper and lower limits with reference to the variations in the actual measurement data that have been printed out in advance, which is a task that requires a fairly high degree of judgment, and as the number of monitor items increases, it becomes more and more complicated and time-consuming. It will be costly.

It is difficult to set the upper and lower limits for all items, so even if you try to select only important items as monitor items,
Such a defect is likely to occur in the resin used in this product shape, so this is the item that should be monitored that has a causal relationship with it. ” Knowledge of injection molding in general and considerable experience required.

And the like.

Also, if you try to quickly set the upper and lower limits of all monitor items, the upper and lower limits of momentum will be set roughly in the register, and the allowable range will become unacceptable, and you will win. The intended purpose of automatic inspection, which is to judge good / defective products by function, cannot be fulfilled.

Therefore, the technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art, and the purpose thereof is to perform an operation without special knowledge and experience of automatic inspection. It is an object of the present invention to provide a method for automatically setting upper and lower limit values of a molding condition of a molding machine that enables a worker (worker) to definitely perform a monitoring function to automatically perform a good / bad determination.

[Means for Solving the Problems] The above-described object of the present invention is to provide a control device including a micro-computer that drives and controls each part of the molding machine based on the set molding operation condition values and the measurement information from the sensors. In order to determine the quality of the molded product during continuous automatic operation, the control device compares the upper limit value and the lower limit value of the predetermined monitor item with the actual measurement value, and based on this comparison result, In the method for automatically setting the upper and lower limits of the molding conditions of the molding machine equipped with the function of determining the quality of the molded product, after starting the continuous automatic operation and ending the initial predetermined number of shots, each successive predetermined number of shots The measured value x of the monitor item is measured, and the variation range R (R = x max−x min) of the measured value x and the intermediate value Mi (Mi = x min + R / 2) of the measured value x are at least measured for each monitor item. Statistical calculation and the calculation The upper limit value and the lower limit value for each monitor item based on the result, the upper limit value and the lower limit value is an intermediate value Mi
It is achieved by automatically setting the same width from.

[Operation] When the continuous automatic operation is started, and the initial predetermined number of shots (for example, about 10 shots) that can be regarded as the operation state is stable after the initial transient / unstable period ends, the micro The control device composed of the computer stores the measured values x for all predetermined monitor items in a predetermined storage area for each successive shot of 10 shots or more (preferably about 100 shots). Then, when the sampling of the predetermined number of measured values x is completed, the control device statistically calculates a large number of measured values x for each monitor item based on a program written in advance, and the measured value x of each monitored item is calculated. Variation range R (x max-x min) and intermediate value Mi (x min + R / 2) of measured value x, or average value (Σx / n) of measured value x and standard deviation Is first calculated.

Next, the control device performs arithmetic processing on the calculated data in consideration of the preset correction value a, and determines the upper limit value and the lower limit value for each monitor item so that the upper limit value and the lower limit value have the same width from the intermediate value Mi. So that, for example, the upper limit value = Mi + a · R / 2 and the lower limit value = Mi−a · R / 2 are calculated, and this is fetched and stored in a predetermined storage area.

As described above, by automatically processing the reasonably calculated upper and lower limit values for all monitor items by statistically processing the actual measurement values of several 10 stable shots or more, automatic monitoring is performed. The (inspection) operation is executed reliably.

[Embodiment] The present invention will be described below with reference to an embodiment shown in FIGS. 1 to 6 in which the present invention is applied to an in-line screw type injection molding machine.

FIG. 1 is an explanatory diagram showing a schematic configuration of a main part of an injection molding machine. The upper left part of the figure shows the mold opening / closing mechanism system. In the illustrated part, 1 is a base, 2 is a fixed die plate fixed on the base, and 3 is a base 1.
The support boards 4 installed on the slide base 1a extended above are a plurality of tie bars installed between the fixed die plate 2 and the support board 3. A mold clamping cylinder (hydraulic cylinder) 5 serving as a mold opening / closing drive source is fixedly mounted on the support board 3, and a tip end of a piston rod 5a of the mold clamping cylinder 5 has a known toggle link mechanism 6 interposed therebetween. A movable die plate 7 inserted through the tie bar 4 is connected. Then, by moving the piston rod 5a forward and backward, the movable die plate 7 is moved relative to the fixed die plate 2.
It is designed to approach or retract.

Further, on the surfaces of the fixed die plate 2 and the movable die plate 7 which face each other, a fixed side die 8 and a movable side die 9 are provided.
And are installed. Then, during the mold closing process during the molding cycle, the toggle link mechanism 6 is extended by the forward movement of the piston rod 5a to move the movable die plate 7 forward so that the two dies 8 and 9 are brought into close contact with each other, and then, as is known, The toggle link mechanism 6 is urged to apply a predetermined mold clamping force. On the other hand, during the mold opening process in the molding cycle, the toggle link mechanism 6 is folded by retracting the piston rod 5a to retract the movable die plate 7 and separate the two molds 8 and 9. During this mold opening process, the product is taken out by a known eject mechanism (not shown) and a product (molded product) take-out means, and is placed on, for example, a belt conveyor. When it is done, the defective product taken out is conveyed to the defective product storage.

The upper right portion of FIG. 1 shows an injection mechanism system, in which 10 is a heating cylinder, 11 is a screw arranged in the heating cylinder 10 so as to be rotatable and forward and backward, and 12 is a heating cylinder 10. Nozzle attached to the tip of the, 13 is a band heater wound around the outer circumference of the heating cylinder 10 and the nozzle 12, 14 is a hopper for supplying the resin material to the rear of the screw 11, and 15 is a rotational drive source of the screw 11. A barrel motor (for example, on the right, an electromagnetic motor is used in this embodiment, but a hydraulic motor can also be used),
Reference numeral 16 is an injection cylinder (hydraulic cylinder) for controlling the forward / backward movement of the screw 11. As is known, the hopper 14
The resin material supplied from is melted while being kneaded and plasticized by the rotation of the screw 11 while being transferred to the tip side of the screw 11, and the molten resin is stored on the tip side of the screw 11, and thus the screw 11 is When the back pressure is controlled and the molten resin for one shot is stored on the tip side of the screw 11, the screw rotation is stopped. Then, after a lapse of a predetermined time, when the injection start timing is reached, the screw 11 is driven forward and the mold is clamped,
Molten resin is injected and filled into the cavity between 9.

20 is an injection pressure detection sensor consisting of a hydraulic pressure measuring head,
21 is an injection stroke detection sensor composed of an encoder, etc.
Reference numeral 22 is a screw rotation detection sensor including a rotary encoder, 23 is a temperature detection sensor including a thermocouple that detects the temperature of the heating cylinder 10, 24 is a mold opening / closing stroke detection sensor including an encoder, and 25 is a hydraulic pressure measurement head. In the mold clamping pressure detection sensor, the measurement information signals S1 to S6 of each of the sensors 20 to 25 and the measurement information signals from other sensors not shown are appropriately input-converted to the control device 30 described later as necessary. And sent out.

Reference numeral 30 is a control device for controlling the operation of the entire machine, which executes control of the entire molding process such as mold opening / closing operation, charge / injection operation and the like, and various arithmetic processing such as non-defective / defective product determination processing described later. The control device 30 is composed of a micro computer, and includes various I / O interfaces, a ROM storing main control programs and various fixed data, a RAM for reading and writing various flags and measurement data, and a CPU for controlling the entire control. It is equipped with and executes various processes according to various programs created in advance, but in the embodiment, for the sake of convenience of explanation, the control device 30 includes a molding condition setting storage unit.
The following description will be made on the assumption that functional units such as 31, a molding process control unit 32, a calculation processing unit 33, a measured value storage unit 34, an upper / lower limit value setting storage unit 35, a comparison calculation unit 36, and the like are provided.

The molding condition setting storage unit 31 stores various molding condition values input by the key input means 40 or other appropriate input means in a rewritable form after being subjected to arithmetic processing as necessary. The molding conditions include, for example, the relationship between the screw position and the screw rotation speed and back pressure during the charge stroke, the suck back control condition, and the injection start point (position).
To the holding pressure switching point (position), the subdivided injection speed condition, the subdivided secondary injection pressure (holding pressure) condition from the holding pressure switching time to the holding pressure end time, the band heater temperature of each part, Examples include mold closing stroke and speed, mold clamping force, mold opening stroke and speed, eject control conditions, product unloader control conditions, and the like.

The molding process control unit 32, based on the molding process control program created in advance and the setting condition value stored in the molding condition setting storage unit 31, the information from the sensors 20 to 25 and the like built in the control device 30. The corresponding drive source is drive-controlled through the driver group 41 while referring to the clocked time information from the clock, and a series of molding steps are executed.
In FIG. 1, the drive signal D1 of the driver group 41 is the control valve.
Drive control of the mold clamping cylinder 5 via 42, drive signal
D2 drives and controls the electric heat source of the band heater 13, drive signal D3 drives and controls the motor 15, and drive signal D4 controls the valve.
The injection cylinder 16 is drive-controlled via 43, and other drive signals drive-control an appropriate drive source (not shown).

In the measured value storage section 34, all measured values x of monitor items, which are prerequisites for executing an automatic inspection (monitor) operation during continuous automatic operation, are distributed over a predetermined number of consecutive shots. Captured in the recording area. The monitor items that can be taken in are roughly classified into time monitoring items, position monitoring items, rotation speed monitoring items, speed monitoring items, pressure monitoring items, temperature monitoring items, power monitoring items, and the like. A considerable portion overlaps with this, and a factor closely related to the quality of the molded product is preset as a monitor item (for example, refer to the monitor item shown in FIG. 4). In this embodiment, the number of the monitor items is about 30 to 50, and the information from the sensors 20 to 25 and the clock information from the clock built in the control device 30 are converted as necessary. Sequentially stored. The monitor items can be set by the operator by selectively inputting them.

When the data stored in the actual measurement value storage section 34 reaches a predetermined number of sampling shots, the arithmetic processing section 33 statistically calculates the actual measurement value x for each monitor item to obtain a variation range R (x max−x min) and the intermediate value Mi (x min + R / 2) between the measured value x and / or the average value (Σx / n) of the measured value x and the standard deviation Is calculated first, and then the upper and lower limits of each monitor item are calculated by the above calculation result and the correction coefficient (correction value) a set as will be described later. Upper limit value = Mi + a.R / 2 Lower limit value = Mi−a · R / 2 or upper limit value = + a · 3σ / 2 lower limit value = −a · 3σ / 2. The upper limit value and the lower limit value for each monitor item calculated in this way are transferred to and stored in the above-described upper / lower limit value setting storage unit 35. Here, the intermediate value Mi of the actual measurement value x used in the present embodiment is as described above.
Mi = x min + R / 2, which is the measured value x
It is always located at the center of the data width of the group. Therefore, the upper limit value = Mi + a · R / 2 and the lower limit value = Mi−a · R / 2 calculated and set using the intermediate value Mi are the allowable range of the same width from the center of the data width of the measured value x group. Will be prescribed. For this reason, the upper and lower limits are Mi + aR / 2, Mi-
When a / R / 2 is used, the allowable setting range for the quality judgment can be grasped easily and surely, and the quality judgment is well-balanced between the upper limit value side and the lower limit value side. .

The comparison calculation unit 36 compares the data stored in the upper / lower limit value setting storage unit 35 with the actual measurement value data in the latest shot (for example, transferred from the actual measurement value storage unit 34),
It is determined whether or not the measured value is within the upper / lower limit value range (within an allowable range), and if the measured value is out of the upper / lower limit value range, the molding process control unit 32 is notified of this fact, Under the control of the product take-out machine by the molding process control unit 32, the molded product by the latest shot is conveyed as a defective product to a predetermined defective product storage.

In FIG. 1, reference numeral 44 is a display device composed of a color CRT display or the like, and 45 is a printer such as a dot printer, and the processing results of the control device 30 are output to the output devices 44 and 45 as needed. . Reference numeral 46 denotes an external memory such as a magnetic disk device, which exchanges information with the control device 30 as needed.

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

When the operator selects a mode for automatically calculating the upper limit value and the lower limit value for each monitor item, which is a prerequisite for the monitor function (automatic inspection function) to be exerted by the operator. For example, the display device 44 displays the monitor upper / lower limit value automatic setting screen as shown in FIG.

In FIG. 2, a window for designating the output mode of the printer 45 during sampling of the actual measurement values, which is the basic data of the statistical calculation process, is displayed on the left side portion of the display screen 50, and if print output is desired, the cursor is displayed. To the “ON” display and select it. Similarly, move the cursor to select "Print all monitor (measured) data", "Print every arbitrary number of shots" or "Print only defective data (when defective judgment is made)" When "Print every few shots" is selected, a specific numerical value is keyed in. If "Print all monitor data" or "Print every arbitrary number of shots" is selected, "Defective data mark (to identify this as defective data)"
Is selected.

In the center part of the display screen 50, a window display for performing initial setting for automatically calculating the upper limit value and the lower limit value for each monitor item is made, and when calculating the upper and lower limit values, Naturally, "ON" is selected. In addition, how many times the actually measured values for each monitor item, which are the prerequisites for calculating the upper and lower limit values, are sampled are set by keying in a numerical value on the "statistical shot number" display section. It is desirable to select several tens of shots or more in order to improve the accuracy of the statistical calculation to be described later, and FIG. 2 shows the case where 100 shots are selected, and only the statistical calculation is performed. If the calculation result is not automatically set in the setting data for automatic inspection, the mode of "Start only statistical calculation" is selected, the statistical calculation is executed, and the calculation result is calculated based on this calculation result. When the upper / lower limit values are automatically set, the mode of “interlocked with automatic setting of upper / lower limit values” is selected.

On the upper right portion of the display screen 50, a window display of the initial setting items for calculating the above-mentioned upper and lower limit values is made, and the upper and lower limit values are represented by the variation range R of the measured value x and the intermediate value Mi. When calculating, the calculated value “R” is designated and selected, and when calculating the upper and lower limit values by the average value and the standard deviation σ of the measured value x, the count value “3σ” is designated and selected. . Further, the correction coefficient a used in the above formulas for calculating the upper and lower limit values is, for example, "1.10" or "1.20".
Input is set as follows. The correction coefficient a is determined in consideration of the degree of difficulty of the required quality of the molded product,
When high accuracy is required, it is set to a relatively small value, and when required accuracy is rough, it is set to a relatively large value. Normally, a value of 1.00 or more is set. In the embodiment, the count value and the correction coefficient a are commonly input and set for all monitor items, but are indicated by a chain double-dashed line at the lower right of the display screen of FIG. As shown in the enclosed area, the count value “R” or “3σ” may be selected and the correction coefficient a may be set for each monitor item.

Now, on the monitor upper / lower limit value automatic setting screen of FIG. 2, the printer mode is turned “ON” to select the desired print output mode, and the statistical calculation mode is turned “ON” to input the statistical shot number. At the same time, a mode “in conjunction with automatic setting of upper / lower limit values” is selected, and either one of the above-mentioned count value “R” or “3σ” used for calculating the upper / lower limit values is selected. It is assumed that the correction coefficient a is set while being selected. In this state, the control device 30
When the automatic continuous operation of the injection molding machine is started under the control of, and the predetermined number (for example, about 10 shots) of the initial number of shots is counted from the initial number of shots, the controller 30 makes an initial transient. It is considered that the unstable operation is over and the operating condition is stable, and the actual measurement value x of all the preset monitor items is stored in the actual measurement value storage unit 34 for each subsequent continuous automatic operation. Incorporate.

While storing the measured value x in the measured value storage unit 34,
When it is recognized that the number of sampling shots set by the shot counter has been reached, the arithmetic processing unit 33
Performs statistical calculation processing on the actual measurement value x of the total number of sampling shots for each monitor item as described above. In the embodiment, all of the variation range R of the actual measurement value x, the intermediate value Mi of the actual measurement value x, the average value of the actual measurement value x, and the standard deviation σ of the actual measurement value x are calculated. The upper and lower limit values are calculated as described above based on the calculation result and the correction coefficient a. FIG. 3 schematically shows the work area of the arithmetic processing unit 33 in which such arithmetic processing is performed.

The upper / lower limit values obtained as described above are transferred and stored in the upper / lower limit value setting storage unit 35 as described above,
In addition, this data is stored in the external memory 46 described above as needed.
Is also transferred and stored. The actual measurement value data during the above-mentioned statistical (sampling shot) period is displayed on the display device 44 in the form as shown in FIG. 4, for example, and printed out as necessary. In the figure, max and min are initial values that are automatically set by the control device 30 for convenience, and are not the maximum and minimum values of the results of comparing the data. In addition, "○
“/ ×” indicates, for example, the setting of whether or not to perform the maximum / minimum statistical processing.

Then, as described above, the data taken in the upper / lower limit value setting storage unit 35 is each monitor item (molding condition measured value) in the monitor operation (automatic inspection) during continuous automatic operation.
Is used as a value indicating the allowable range of the above, and the monitor operation by the control device 30 is executed as described above. Note that FIG. 5 schematically shows a work area for this monitor operation, and the “number of defects” in the same figure indicates the counting contents of the defect counter up to the present.

FIG. 6 shows an example of an upper / lower limit value automatic calculation processing flow executed by the control device 30. When the upper / lower limit automatic setting is instructed after the numerical value or mode set or selected on the display screen 50 of FIG. 2 is input, after the initial setting step S1 shown in FIG. Start continuous automatic operation of injection molding machine and proceed to step S3.
In step S3, it is judged whether or not the preset initial number of shots has been reached. If YES, the process proceeds to step S4, and if NO, the step remains. At step S4, measured values x for all monitor items are sampled for each shot, and the process proceeds to step S5. In step S5, it is judged whether or not the set number of sampling shots has been reached, and YES
If so, proceed to step S6, and if NO, return to step S4. In step S6, the sampled actual measurement value x is statistically calculated as described above for each monitor item to obtain the actual measurement value x.
Variation range R, the intermediate value Mi of the actual measurement value x, the average value of the actual measurement value x, and the standard deviation σ of the actual measurement value x are calculated, and the process proceeds to step S7. In step S7, it is asked whether or not the variation range R of the actual measurement value x is used for calculating the upper and lower limits. The process of calculating the lower limit value is performed and the process proceeds to step S10. If NO, the process of calculating the upper and lower limit values is performed by the above formula using the average value of the measured value x and the like and the process proceeds to step S10. At step S10, the upper and lower limit values are automatically set, and a series of automatic upper and lower limit value calculation / setting processing flow ends.

[Effects of the Invention] As described above, according to the present invention, the operator at the site allows up and down fluctuations in the factors that cause defects due to the shape of individual molded products and the characteristics of the resin used and corresponding molding conditions (monitor items). Even if you do not have a high degree of knowledge about the range and a good judgment (if you are an operator who has knowledge about the quality judgment of molded products), the upper and lower limit values reasonably calculated from the measured statistical data Since it is automatically entered and set, the monitoring function makes sure that the good / bad determination can be made automatically. Further, the intermediate value Mi defined by Mi = x min + R / 2 is obtained, and the upper limit value and the lower limit value for each monitor item are automatically set so that the upper limit value and the lower limit value have the same width from the intermediate value Mi. Therefore, the allowable setting range for the quality judgment can be grasped easily and surely, and the quality judgment is well balanced between the upper limit side and the lower limit side. Further, the value of the correction coefficient (correction value) a is adjusted according to the judgment based on the production control factor that does not appear in the statistics, for example, the strictness of the inspection standard of the product delivery destination to perform quality control / cost control. Can be thorough.

[Brief description of drawings]

Each of the drawings relates to one embodiment of the present invention, FIG. 1 is an explanatory view showing a schematic configuration of a main part of an injection molding machine, and FIG. 2 is a monitor upper / lower limit value automatic setting screen on a display screen of a display device. FIG. 3 is an explanatory view showing an example of a mode, FIG. 3 is an explanatory view schematically showing a work area of a control device in which arithmetic processing for calculating upper and lower limits is performed, and FIG. 4 is an actual measurement during a sampling shot period. Explanatory drawing which shows an example of the display form of a display device of value data,
FIG. 5 is an explanatory diagram schematically showing a work area of the control device in which the monitoring process is performed, and FIG. 6 is an explanatory diagram showing an example of an upper / lower limit value automatic calculation process flow executed by the control device. 1 ... Base, 2 ... Fixed die plate, 3 ... Support board, 4 ... Tie bar, 5 ... Mold clamping cylinder, 6 ... Toggle link mechanism, 7 ... Movable die plate, 8 ... Fixed side metal Mold, 9 ... Movable mold, 10 ... Heating cylinder, 11 ...
Screen, 12 ... Nozzle, 13 ... Band heater, 14 ...
… Hopper, 15 …… Motor, 16 …… Injection cylinder, 20…
… Injection pressure detection sensor, 21 …… Injection stroke sensor,
22 …… Screw rotation detection sensor, 23 …… Temperature detection sensor, 24 …… Mold opening / closing stroke detection sensor, 25 …… Clamping pressure detection sensor, 30 …… Control device, 31 …… Molding condition setting storage unit, 32… … Molding process control unit, 33 …… Computational processing unit,
34 …… Measured value storage, 35 Upper / lower limit setting storage, 36 ……
Comparison calculation unit, 40 ... key input means, 41 ... driver group,
42,43 …… Control valve, 44 …… Display device, 45 …… Printer, 4
6 …… External memory, 50 …… Display screen, 51 …… Cursor.

Claims (5)

(57) [Claims] 1. A control device comprising a microcomputer for driving and controlling each part of a molding machine on the basis of set molding operation condition values and measurement information from each sensor, the control device being in continuous automatic operation. In order to determine the quality of the molded product in, a molding machine equipped with a function of comparing the upper limit value and the lower limit value of a predetermined monitor item with the measured value and determining the quality of the molded product based on the comparison result. ,
After the continuous automatic operation is started and the initial predetermined number of shots is finished, the actual measurement value x of each monitor item is measured for each subsequent predetermined number of shots, and the variation range R ( R = x max−x min) and at least the intermediate value Mi (Mi = x min + R / 2) of the measured value x is statistically calculated, and the upper limit value and the lower limit value for each monitor item are set to the upper limit value based on the calculation result. Also, a method for automatically setting upper and lower limits of molding conditions of a molding machine, wherein the lower limit is automatically set to have the same width from the intermediate value Mi. 2. A semi-fixed correction value is included in a formula when setting and calculating an upper limit value and a lower limit value for each monitor item based on the statistical calculation result according to claim 1. A method for automatically setting upper and lower limits of molding conditions of a molding machine. 3. The upper limit value and the lower limit value for each monitor item, where the correction value is a, according to claim 2, wherein the upper limit value is Mi + a.R / 2 and the lower limit value is Mi-a.R /. A method for automatically setting the upper and lower limits of the molding conditions of the molding machine, which is determined by 2. 4. The correction value a according to claim 2, wherein:
A method for automatically setting the upper and lower limits of molding conditions for a molding machine, which can be variably set for each monitor item. 5. A method for automatically setting upper and lower limit values of a molding condition of a molding machine according to claim 1, wherein the number of shots for performing the statistical calculation can be variably set.