Injection molding process stability monitoring analysis method and system thereof

Abstract

The invention provides a method for monitoring and analyzing the stability of an injection molding process. The method comprises the following steps: detecting an injection pressure value of injection molding equipment according to a set acquisition frequency; wherein the set acquisition frequency is set according to actual working condition requirements; determining a process capability index of the injection molding equipment according to the injection pressure value; judging whether the process capability index of the injection molding equipment is within a set threshold range or not, if yes, determining that the injection molding equipment is stable, and if not, generating an early warning instruction and executing early warning; according to the invention, the injection pressure of the injection molding equipment is continuously acquired for multiple times, the injection molding process capability index value is determined according to the acquired injection pressure value, and the influence of factors such as temperature and a mold is considered in the determination process, so that the stability of the current injection molding equipment can be accurately judged, frequent shutdown of injection molding production is effectively prevented, and the production efficiency is improved. And the production continuity and yield are ensured.

Description

Technical Field

[0001] The invention relates to a production analysis method and a system thereof, and in particular to an injection molding process stability monitoring and analysis method. Background Art

[0002] As one of the core processes in the plastics processing industry, the stability and reliability of injection molding have a decisive influence on product quality.

[0003] In the prior art, abnormal monitoring of injection molding is usually achieved by inspecting the quality of finished products. This method has a long monitoring cycle and may produce more waste. At the same time, relevant personnel need to handle it based on their own experience. The processing process is heavily dependent on personnel capabilities and has great uncontrollability. With the development of technology, although online monitoring methods have been gradually proposed, this method mainly relies on the parameters of the current production process. That is, if a parameter exceeds the set value, it needs to be repaired or maintained. However, this method has poor accuracy and is prone to frequent production stoppages, affecting production continuity and output.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an injection molding process stability monitoring and analysis method and system thereof, by repeatedly collecting the injection pressure of the injection molding equipment and determining the injection molding process capability index value based on the acquired injection pressure value, and taking into account the influence of factors such as temperature and mold in the determination process, so as to accurately judge the stability of the current injection molding equipment, effectively prevent frequent shutdowns of injection molding production, and ensure the continuity and output of production.

[0006] The present invention provides a method for monitoring and analyzing the stability of an injection molding process, comprising the following steps:

[0007] Detect the injection pressure value of the injection molding equipment according to the set acquisition frequency;

[0008] Determine the process capability index of the injection molding equipment by the injection pressure value;

[0009] Determine whether the process capability index of the injection molding equipment is within the set threshold range. If so, the injection molding equipment is stable. If not, generate an early warning instruction and execute the early warning.

[0010] Furthermore, the process capability indicators of the injection molding equipment determined by the injection pressure value specifically include:

[0011]

[0012] Among them, CMK represents the process capability index of injection molding equipment, U uplimIndicates the upper limit of the injection pressure of the injection molding equipment, U lolim represents the lower limit of the injection pressure of the injection molding equipment, Sd represents the standard deviation of the injection pressure of the injection molding equipment; n 1 It represents the adjustment coefficient of the standard deviation of the injection pressure of the injection molding equipment, and mean represents the mean value of the injection pressure of the injection molding equipment.

[0013] Furthermore, the injection pressure adjustment coefficient n of the injection molding equipment 1 Determined by the following method:

[0014] n 1 =β(1+δ t ·δ ma +δ mo );

[0015] Among them, β is the initial value of the adjustment coefficient related to the product, δ t is the temperature influence factor, δ ma is the influence factor of injection molding material, δ mo It is the mold influencing factor.

[0016] Furthermore, the injection pressure mean of the injection molding equipment is determined by the following method:

[0017]

[0018] Among them, x i is the injection pressure measurement value of the injection molding equipment for the i-th time, w i It represents the weight of the injection pressure measurement value of the i-th injection molding equipment, and n is the total number of measurements.

[0019] Furthermore, if the process capability index of the injection molding equipment is not within the threshold range, the early warning instructions generated specifically include:

[0020] When the process capability index of the injection molding equipment is greater than the third judgment threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is greater than the third judgment threshold within the set period is greater than r, an early warning instruction is generated, which is used to adjust the injection pressure upper limit value U uplim And the lower limit of injection pressure U lolim ;

[0021] When the process capability index of the injection molding equipment is less than the fourth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fourth determination threshold within a set period is greater than r, a warning instruction is generated, and the warning instruction is used to indicate that the injection molding process of the current injection molding equipment is unstable;

[0022] When the process capability index of the injection molding equipment is less than the fifth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fifth determination threshold within a set period is greater than r, an early warning instruction is generated, which is used to indicate that the injection molding equipment needs to be shut down immediately;

[0023] The first determination threshold and the second determination threshold constitute a threshold range of: [first determination threshold, second determination threshold];

[0024] The third determination threshold value>the second determination threshold value, and the fifth determination threshold value<the fourth determination threshold value<the first determination threshold value.

[0025] Accordingly, the present invention also provides an injection molding process stability monitoring system, comprising:

[0026] Pressure sensor, used to detect the injection pressure of the injection molding equipment nozzle and output;

[0027] A processing unit, used for receiving a pressure signal output by the sensor, and determining a process capability index of the injection molding equipment according to the pressure signal;

[0028] The processing unit determines whether the process capability index of the injection molding equipment is within the set threshold range. If so, the injection molding equipment is stable. If not, the processing unit generates an early warning instruction.

[0029] The early warning module has an input end connected to the processing unit and is used to receive the early warning instruction output by the processing unit and execute the early warning.

[0030] Further, the processing unit determines the process capability index of the injection molding equipment according to the pressure signal, which specifically includes:

[0031]

[0032] Among them, CMK represents the process capability index of injection molding equipment, U uplim Indicates the upper limit of the injection pressure of the injection molding equipment, U lolim represents the lower limit of the injection pressure of the injection molding equipment, Sd represents the standard deviation of the injection pressure of the injection molding equipment; n 1 It represents the adjustment coefficient of the standard deviation of the injection pressure of the injection molding equipment, and mean represents the mean value of the injection pressure of the injection molding equipment;

[0033] Where: Injection pressure adjustment coefficient n of injection molding equipment 1 Determined by the following method:

[0034] n 1 =β(1+δ t ·δ ma +δ mo );

[0035] Among them, β is the initial value of the adjustment coefficient related to the product, δ t is the temperature influence factor, δ ma is the influence factor of injection molding material, δ mo It is the mold influencing factor.

[0036] Further, the processing unit determines whether the process capability index of the injection molding equipment is within a set threshold range and generates a warning instruction, specifically including:

[0037] When the process capability index of the injection molding equipment is greater than the third judgment threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is greater than the third judgment threshold within the set period is greater than r, an early warning instruction is generated, which is used to adjust the injection pressure upper limit value U uplim And the lower limit of injection pressure U lolim ;

[0038] When the process capability index of the injection molding equipment is less than the fourth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fourth determination threshold within a set period is greater than r, a warning instruction is generated, and the warning instruction is used to indicate that the injection molding process of the current injection molding equipment is unstable;

[0039] When the process capability index of the injection molding equipment is less than the fifth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fifth determination threshold within a set period is greater than r, an early warning instruction is generated, which is used to indicate that the injection molding equipment needs to be shut down immediately;

[0040] The first determination threshold and the second determination threshold constitute a threshold range of: [first determination threshold, second determination threshold];

[0041] The third determination threshold value>the second determination threshold value, and the fifth determination threshold value<the fourth determination threshold value<the first determination threshold value.

[0042] Furthermore, a temperature sensor is included, wherein the temperature sensor is used to detect the temperature of the current injection molding material and output it to the processing unit, and the processing unit determines the temperature influence factor δ according to the current temperature. t .

[0043] Beneficial effects of the present invention: Through the present invention, the injection pressure of the injection molding equipment is continuously collected for multiple times and the injection molding process capability index value is determined according to the acquired injection pressure value, and the influence of factors such as temperature and mold are taken into account in the determination process, so that the stability of the current injection molding equipment can be accurately judged, and the frequent shutdown of injection molding production can be effectively prevented, thereby ensuring the continuity and output of production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0045] Figure 1 It is a schematic diagram of the process of the present invention.

[0046] Figure 2 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below:

[0048] The present invention provides a method for monitoring and analyzing the stability of an injection molding process, comprising the following steps:

[0049] Detect the injection pressure value of the injection molding equipment according to the set acquisition frequency; wherein the set acquisition frequency is set according to the actual working condition requirements, such as collecting ten times in one minute, or collecting twenty times in one minute, etc.;

[0050] Determine the process capability index of the injection molding equipment by the injection pressure value;

[0051] It is determined whether the process capability index of the injection molding equipment is within the set threshold range. If so, the injection molding equipment is stable. If not, a warning instruction is generated and the warning is executed. Through the present invention, the injection molding process capability index value is determined by repeatedly collecting the injection pressure of the injection molding equipment continuously and according to the obtained injection pressure value, and the influence of factors such as temperature and mold are taken into account in the determination process, so that the stability of the current injection molding equipment can be accurately judged, and the frequent shutdown of the injection molding production can be effectively prevented, so as to ensure the continuity and output of production.

[0052] In this embodiment, the process capability index of the injection molding equipment is determined by the injection pressure value and specifically includes:

[0053]

[0054] Among them, CMK represents the process capability index of injection molding equipment, U uplim Indicates the upper limit of the injection pressure of the injection molding equipment, U lolim represents the lower limit of the injection pressure of the injection molding equipment, Sd represents the standard deviation of the injection pressure of the injection molding equipment; n 1 It represents the adjustment coefficient of the standard deviation of the injection pressure of the injection molding equipment, and mean represents the mean value of the injection pressure of the injection molding equipment.

[0055] Among them, the injection pressure adjustment coefficient n of the injection molding equipment 1 Determined by the following method:

[0056] n 1 =β(1+δ t ·δ ma +δ mo );

[0057] Among them, β is the initial value of the adjustment coefficient related to the product, δt is the temperature influence factor, δ ma is the influence factor of injection molding material, δ mo It is the mold influencing factor. Through the above method, the evaluation index is determined by a sequence of injection pressure values ​​of the injection molding material, so as to avoid the phenomenon of frequent shutdown caused by judging abnormalities through a single value of the index, and effectively ensure the continuity and output of production. Moreover, in the judgment process, the influence of temperature, material and mold factors is fully considered to ensure the accuracy of the final result. Among them, the temperature influencing factor is determined by looking up the corresponding relationship table through the real-time detected temperature value, and the corresponding relationship table is determined by prior experiments and other methods. The material influencing factor is determined according to the injection molding material. Plastic materials include polyethylene, polypropylene, polystyrene, etc. The influencing factors of different materials are different, and the injection molding temperatures of different materials are also different. The mold influencing factor can be determined in advance, and the corresponding value is determined by factors such as the number of historical maintenance times and service time.

[0058] In this embodiment, the injection pressure mean of the injection molding equipment is determined by the following method:

[0059]

[0060] Among them, x i is the injection pressure measurement value of the injection molding equipment for the i-th time, w i It represents the weight of the injection pressure measurement value of the i-th injection molding equipment, and n is the total number of measurements.

[0061] In this embodiment, if the process capability index of the injection molding equipment is not within the threshold range, the early warning instruction is generated specifically including:

[0062] When the process capability index of the injection molding equipment is greater than the third judgment threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is greater than the third judgment threshold within the set period is greater than r, an early warning instruction is generated, which is used to adjust the injection pressure upper limit value U uplim And the lower limit of injection pressure U lolim ;Through this process, the injection molding process capability indicators can be dynamically adjusted, thus ensuring the accuracy of subsequent early warnings;

[0063] When the process capability index of the injection molding equipment is less than the fourth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fourth determination threshold within the set period is greater than r, an early warning instruction is generated. The early warning instruction is used to indicate that the injection molding process of the current injection molding equipment is unstable; for example, the influence of temperature or the influence of the nozzle, etc. At this early warning level, the staff can be reminded to pay attention to the actual production process and adjust the corresponding parameters without stopping the machine for maintenance.

[0064] When the process capability index of the injection molding equipment is less than the fifth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fifth determination threshold within a set period is greater than r, an early warning instruction is generated, which is used to indicate that the injection molding equipment needs to be shut down immediately;

[0065] The first determination threshold and the second determination threshold constitute a threshold range of: [first determination threshold, second determination threshold];

[0066] The third judgment threshold value is greater than the second judgment threshold value, and the fifth judgment threshold value is less than the fourth judgment threshold value and less than the first judgment threshold value. The threshold range composed of the first judgment threshold value and the second judgment threshold value is a closed range, the second judgment threshold value is the upper limit value of the closed range, the first judgment threshold value is the lower limit value of the closed range, and there is a certain difference between the third judgment threshold value and the upper limit value, and there is a certain difference between the fourth judgment threshold value and the lower limit value, so as to maintain a certain margin, thereby avoiding frequent warnings and even shutdowns, and the difference is determined according to actual working conditions.

[0067] The value of m in the above description is generally set to 3-5 times, and the value of r is generally set to no less than 10 times.

[0068] Accordingly, the present invention also provides an injection molding process stability monitoring system, comprising:

[0069] The pressure sensor is used to detect the injection pressure of the injection molding equipment nozzle and output it; the pressure sensor is implemented by using an existing high temperature resistant pressure sensor, such as a sensor device based on sapphire or titanium alloy, such as the UV805 series pressure sensor;

[0070] A processing unit, used to receive the pressure signal output by the sensor, and determine the process capability index of the injection molding equipment according to the pressure signal; wherein the processing unit is implemented by an existing processor, chip or working condition machine, etc.;

[0071] The processing unit determines whether the process capability index of the injection molding equipment is within the set threshold range. If so, the injection molding equipment is stable. If not, the processing unit generates an early warning instruction.

[0072] The early warning module, whose input end is connected to the processing unit, is used to receive the early warning instruction output by the processing unit and execute the early warning. The early warning module can adopt the existing sound and light alarm, or can adopt the combination of display and sound and light alarm.

[0073] In this embodiment, the processing unit determines the process capability index of the injection molding equipment according to the pressure signal, specifically including:

[0074]

[0075] Among them, CMK represents the process capability index of injection molding equipment, U uplim Indicates the upper limit of the injection pressure of the injection molding equipment, U lolim represents the lower limit of the injection pressure of the injection molding equipment, Sd represents the standard deviation of the injection pressure of the injection molding equipment; n 1 It represents the adjustment coefficient of the standard deviation of the injection pressure of the injection molding equipment, and mean represents the mean value of the injection pressure of the injection molding equipment;

[0076] Where: Injection pressure adjustment coefficient n of injection molding equipment 1 Determined by the following method:

[0077] n 1 =β(1+δ t ·δ ma +δ mo );

[0078] Among them, β is the initial value of the adjustment coefficient related to the product, δ t is the temperature influence factor, δ ma is the influence factor of injection molding material, δ mo It is the mold influencing factor.

[0079] In this embodiment, the processing unit determines whether the process capability index of the injection molding equipment is within the set threshold range and generates a warning instruction specifically including:

[0080] When the process capability index of the injection molding equipment is greater than the third judgment threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is greater than the third judgment threshold within the set period is greater than r, an early warning instruction is generated, which is used to adjust the injection pressure upper limit value U uplim And the lower limit of injection pressure U lolim ;

[0081] When the process capability index of the injection molding equipment is less than the fourth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fourth determination threshold within a set period is greater than r, a warning instruction is generated, and the warning instruction is used to indicate that the injection molding process of the current injection molding equipment is unstable;

[0082] When the process capability index of the injection molding equipment is less than the fifth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fifth determination threshold within a set period is greater than r, an early warning instruction is generated, which is used to indicate that the injection molding equipment needs to be shut down immediately;

[0083] The first determination threshold and the second determination threshold constitute a threshold range of: [first determination threshold, second determination threshold];

[0084] The third determination threshold value>the second determination threshold value, and the fifth determination threshold value<the fourth determination threshold value<the first determination threshold value.

[0085] In this embodiment, a temperature sensor is also included, and the temperature sensor is used to detect the temperature of the current injection material and output it to the processing unit. The processing unit determines the temperature influence factor δ according to the current temperature. t The temperature influence factor is determined by searching the pre-established corresponding relationship table between temperature and temperature influence factor through the real-time detected temperature value.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for monitoring and analyzing the stability of an injection molding process, characterized in that: The steps include: Detect the injection pressure value of the injection molding equipment according to the set acquisition frequency; Determine the process capability index of the injection molding equipment by the injection pressure value; Determine whether the process capability index of the injection molding equipment is within the set threshold range. If so, the injection molding equipment is stable. If not, generate an early warning instruction and execute the early warning.

2. The method for monitoring and analyzing the stability of the injection molding process according to claim 1, characterized in that: The process capability indicators of injection molding equipment determined by the injection pressure value include: Among them, CMK represents the process capability index of injection molding equipment, U uplim Indicates the upper limit of the injection pressure of the injection molding equipment, U lolim It represents the lower limit of the injection pressure of the injection molding equipment, Sd represents the standard deviation of the injection pressure of the injection molding equipment; n1 represents the adjustment coefficient of the standard deviation of the injection pressure of the injection molding equipment, and mean represents the mean value of the injection pressure of the injection molding equipment.

3. The method for monitoring and analyzing the stability of the injection molding process according to claim 2, characterized in that: The injection pressure adjustment coefficient n1 of the injection molding equipment is determined by the following method: n1=β(1+δ t ·d ma +d mo ); Among them, β is the initial value of the adjustment coefficient related to the product, δ t is the temperature influence factor, δ ma is the influence factor of injection molding material, δ mo Is the mold influencing factor.

4. The method for monitoring and analyzing the stability of the injection molding process according to claim 2, characterized in that: The mean injection pressure of the injection molding equipment is determined by the following method: Among them, x i is the injection pressure measurement value of the injection molding equipment for the i-th time, w i It represents the weight of the injection pressure measurement value of the i-th injection molding equipment, and n is the total number of measurements.

5. The method for monitoring and analyzing the stability of the injection molding process according to claim 2, characterized in that: If the process capability index of the injection molding equipment is not within the threshold range, the warning instructions generated include: When the process capability index of the injection molding equipment is greater than the third judgment threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is greater than the third judgment threshold within the set period is greater than r, an early warning instruction is generated, which is used to adjust the injection pressure upper limit value U uplim And the lower limit of injection pressure U lolim ; When the process capability index of the injection molding equipment is less than the fourth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fourth determination threshold within a set period is greater than r, a warning instruction is generated, and the warning instruction is used to indicate that the injection molding process of the current injection molding equipment is unstable; When the process capability index of the injection molding equipment is less than the fifth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fifth determination threshold within a set period is greater than r, an early warning instruction is generated, which is used to indicate that the injection molding equipment needs to be shut down immediately; The first determination threshold and the second determination threshold constitute a threshold range of: [first determination threshold, second determination threshold]; The third determination threshold value>the second determination threshold value, and the fifth determination threshold value<the fourth determination threshold value<the first determination threshold value.

6. An injection molding process stability monitoring system, characterized in that: include: Pressure sensor, used to detect the injection pressure of the injection molding equipment nozzle and output; A processing unit, used for receiving a pressure signal output by the sensor, and determining a process capability index of the injection molding equipment according to the pressure signal; The processing unit determines whether the process capability index of the injection molding equipment is within the set threshold range. If so, the injection molding equipment is stable. If not, the processing unit generates an early warning instruction. The early warning module has an input end connected to the processing unit and is used to receive the early warning instruction output by the processing unit and execute the early warning.

7. The injection molding process stability monitoring system according to claim 6, characterized in that: The processing unit determines the process capability index of the injection molding equipment according to the pressure signal, specifically including: Among them, CMK represents the process capability index of injection molding equipment, U uplim Indicates the upper limit of the injection pressure of the injection molding equipment, U lolim It represents the lower limit of the injection pressure of the injection molding equipment, Sd represents the standard deviation of the injection pressure of the injection molding equipment; n1 represents the adjustment coefficient of the standard deviation of the injection pressure of the injection molding equipment, and mean represents the mean value of the injection pressure of the injection molding equipment; Among them: The injection pressure adjustment coefficient n1 of the injection molding equipment is determined by the following method: n1=β(1+δ t ·d ma +d mo ); Among them, β is the initial value of the adjustment coefficient related to the product, δ t is the temperature influence factor, δ ma is the influence factor of injection molding material, δ mo Is the mold influencing factor.

8. The injection molding process stability monitoring system according to claim 7, characterized in that: The processing unit determines whether the process capability index of the injection molding equipment is within the set threshold range and generates an early warning instruction, specifically including: When the process capability index of the injection molding equipment is greater than the third judgment threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is greater than the third judgment threshold within the set period is greater than r, an early warning instruction is generated, which is used to adjust the injection pressure upper limit value U uplim And the lower limit of injection pressure U lolim ; When the process capability index of the injection molding equipment is less than the fourth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fourth determination threshold within a set period is greater than r, a warning instruction is generated, and the warning instruction is used to indicate that the injection molding process of the current injection molding equipment is unstable; When the process capability index of the injection molding equipment is less than the fifth determination threshold for m consecutive times or the cumulative number of times that the process capability index of the injection molding equipment is less than the fifth determination threshold within a set period is greater than r, an early warning instruction is generated, which is used to indicate that the injection molding equipment needs to be shut down immediately; The first determination threshold and the second determination threshold constitute a threshold range of: [first determination threshold, second determination threshold]; The third determination threshold value>the second determination threshold value, and the fifth determination threshold value<the fourth determination threshold value<the first determination threshold value.

9. The injection molding process stability monitoring system according to claim 7, characterized in that: The temperature sensor is used to detect the temperature of the current injection material and output it to the processing unit. The processing unit determines the temperature influence factor δ according to the current temperature. t .

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