TWI663043B - A method for online quality monitoring for molded part during injection molding - Google Patents

Abstract

An on-line real-time monitoring method for the quality of a finished product of an injection molding machine. The injection molding machine includes a plurality of machine pillars, a fixed template fixed to one end of the machine pillar, and a sliding plate capable of sliding along the machine pillars. The fixed template engages and separates the moving template. The method for online real-time monitoring of finished product quality includes an installation step, a measurement step, and a judgment step. The installation step is to set at least one strain sensor on any machine pillar. In the measuring step, the clamping force of the large column of the machine is measured by the strain sensor, and a clamping force monitoring curve is obtained. The judgment step is to judge whether the clamping force increase is generated from the clamping force monitoring curve, and to judge the quality of the finished product in real time from the clamping force increase value, and the clamping force increase value is positively related to the quality of the finished product.

Description

Online real-time monitoring method for finished product quality of injection molding machine

The invention relates to a quality monitoring method, in particular to an online quality monitoring method for the finished product of an injection molding machine.

The development of injection molding technology has a history of more than 100 years. It is one of the most important and popular mass production technologies in polymer material processing. Because injection molding has high efficiency, high precision and excellent molding characteristics that can produce complex geometric shapes, so Many products around the daily life are produced by injection molding, such as: electronic supplies, sports supplies, automobile and motorcycle components, biomedical supplies and optical lenses.

Due to the increasingly stringent requirements for injection molding quality, online injection molding quality prediction technology and instant feedback control technology have become important issues in the development of injection molding technology. At present, for all-electric injection molding machines, the mechanism motion control is quite accurate. However, with the requirements of precision injection molding technology, accurate machine motion control still cannot effectively overcome and improve the quality of the injection product. The abnormality caused by the variation in the quality of the melt glue is caused by the difficulty of the melt glue quality to be monitored online in real time, which affects the melt glue. There are quite a few factors for quality, including: the inherent variation of plastics, plasticization parameter design, injection molding parameter settings, and machine transport characteristics. When the quality of the melted adhesive varies, it will affect the quality of the injection product.

However, precise machine control can only ensure the stability, reproducibility, and immediate machine response of the process parameters, and does not improve the abnormal quality of the injection product caused by the difference in the quality of the melt glue.

In addition, for the quality of injection molding finished products, only visual inspection technology can be used to detect geometric shapes and surface defects. The essential physical properties cannot be effectively monitored online by relevant testing equipment. Therefore, when the quality of the injection product is abnormal, a lot of manpower, material resources and time are often wasted, and the abnormal quality of the injection molding cannot be detected online.

Therefore, an object of the present invention is to provide a real-time online monitoring method of the finished product quality of an injection molding machine capable of real-time online monitoring and finding that the injection molding quality is abnormal.

The method for real-time monitoring of the finished product quality of an injection molding machine according to the present invention includes an injection molding machine including a plurality of machine pillars arranged at intervals, a fixed template fixedly fixed to one end of the machine pillar, and an extension placed in the fixed template and used for A plastic filling tube, a screw for extruding the plastic in the material tube, and a moving template capable of sliding along the pillar of the machine to engage and separate with respect to the fixed template. The method for online real-time monitoring of finished product quality includes an installation step, a measurement step, and a judgment step. The installation step is to set at least one strain sensor on any machine pillar. In the measuring step, the clamping force of the large column of the machine is measured by the strain sensor, and a clamping force monitoring curve is obtained. The judging step is to judge whether the clamping force increase occurs from the clamping force monitoring curve, and to judge the quality of the finished product in real time from the clamping force increase value, wherein the incremental value of the clamping force is positively related to the quality of the finished product. .

Another technical means of the present invention is that in the judging step, the quality of the finished product refers to the weight of the finished product.

Another technical means of the present invention is that in the judging step, the incremental value of the clamping force has a correlation with the essential change of the melted glue formed after the plastic in the material tube is heated, and can pass the change of the essence of the melted glue. Immediately judge the quality of the finished product.

The beneficial effect of the present invention is that, in addition to the clamping force that can monitor the production process, a strain sensor installed on the pillar of the machine can be used. In addition to changes, it can also be used as an indicator of the quality of the injection product, and can immediately detect and handle the abnormal quality of the injection product.

11‧‧‧machine pillar

12‧‧‧ fixed template

13‧‧‧ material tube

14‧‧‧ nozzle

15‧‧‧Screw

16‧‧‧Mobile template

2‧‧‧ Strain Sensor

3‧‧‧ pressure sensor

FIG. 1 is a schematic diagram illustrating a partial structure of a elbow-type injection molding machine in a preferred embodiment of an online real-time monitoring method of the finished product quality of the injection molding machine of the present invention; FIG. 2 is a graph illustrating the preferred implementation In the example, a single molding cycle machine large column clamping force measurement curve diagram; FIG. 3 is a schematic diagram illustrating the installation position of various sensors and the thickness measurement position of the finished product in the preferred embodiment; FIG. 4 is a curve The graph illustrates the trend of the curve of the average weight of the finished product and the average thickness of the finished product continuously injected by each plasticizing parameter; FIG. 5 is a graph illustrating the relationship between the pressure peak at different tube temperature settings and the quality of the finished product; and FIG. 6 is a graph illustrating the The relationship between the viscosity index of different tube temperature settings and the quality of the finished product; Figure 7 is a graph illustrating the relationship between the energy index of different tube temperature settings and the quality of the finished product; Figure 8 is a graph illustrating the different tube temperature settings (a) Incremental index of clamping force, and (b) Change in measurement time; Figure 9 is a graph illustrating the relationship between the peak pressure of different back pressure settings and the quality of the finished product; Figure 10 is a graph Describe the relationship between the viscosity index of different back pressure settings and the quality of the finished product; Figure 11 is a graph illustrating the relationship between the energy index of different back pressure settings and the quality of the finished product; Figure 12 is a graph illustrating the different back pressure settings (a ) Incremental clamping force index, and (b) measurement time change; Figure 13 is a graph illustrating the relationship between the pressure peak value of different screw speed settings and the quality of the finished product; Figure 14 is a graph illustrating the relationship between the viscosity index of different screw speed settings and the quality of the finished product; Figure 15 is a graph illustrating the The relationship between the energy index of different screw speed settings and the quality of the finished product; Figure 16 is a graph illustrating (a) the clamping force increase index and (b) the measurement time change of different screw speed settings; Figure 17 is a columnar shape The figure illustrates the correlation analysis result of the clamping force increase of the melt quality disturbance experiment with the quality of the finished product; Figure 18 is a bar graph illustrating the correlation analysis results of the melt tube quality setting of each melt quality index on the quality of the finished product; Figure 19 is a histogram illustrating the correlation analysis results of the quality index of the melt adhesive on the quality of the finished product in back pressure setting; Figure 20 is a histogram illustrating the correlation analysis of the quality index of the melt adhesive on the product quality by setting the screw speed Results; Figure 21 is a graph illustrating the relationship between the incremental clamping force index of the continuous molding compound and the weight and quality of the finished product; Figure 22 is a graph illustrating the pressure of the continuous molding compound experiment The relationship between the value index and the weight and quality of the finished product; FIG. 23 is a graph illustrating the relationship between the viscosity index of the continuous molding compound and the weight and quality of the finished product; and FIG. 24 is a graph illustrating the energy index of the continuous molding compound and the weight and quality of the finished product Relationship diagram; Figure 25 is a histogram illustrating the correlation analysis of the weight and quality of the finished product by each index of the continuous molding compound experiment; and Figure 26 is a graph illustrating the single clamping force increase and total clamping force increase And the change trend of the finished product weight curve.

The features and technical contents of the related patent application of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings.

The preferred embodiment of the method for online real-time monitoring of the finished product quality of the injection molding machine of the present invention is applied to an elbow-type injection molding machine. As shown in FIG. 1, the injection molding machine includes a plurality of machine columns 11 arranged at intervals. A fixed template 12 fixed on one end of the machine pillar 11, a material tube 13 extending into the fixed template 12 for filling plastic, a nozzle 14 located in front of the material tube 13, and a squeeze The plastic screw 15 in the material tube 13 and a moving template 16 capable of sliding along the machine pillar 11 and engaging and separating with respect to the fixed template 12.

The method for online real-time monitoring of finished product quality includes an installation step, a measurement step, and a judgment step. The installation step is to set at least one strain sensor 2 on any machine pillar 11. In this embodiment, a strain sensor 2 is installed on each of the machine pillars 11, and the installation position of each strain sensor 2 is about 1.5 times from the fixed template 12. Location of its diameter.

The measuring step is to measure the clamping force of the machine pillar 11 with the strain sensor 2 and obtain a clamping force monitoring curve. The judging step is to judge whether the clamping force increase occurs from the clamping force monitoring curve, and to judge the quality of the finished product in real time from the clamping force increase value, wherein the incremental value of the clamping force is positively related to the quality of the finished product. . Furthermore, in the judging step, the clamping force increase value has a correlation with the essential change of the melted glue formed after the plastic in the material tube 13 is heated, and the finished product can be judged immediately by the change of the melted glue's nature. Quality.

In detail, the present invention develops on-line injection molding product quality monitoring technology based on the characteristics of the extension curve of the machine pillar 11 during the injection molding process, and integrates the melt adhesive quality monitoring technology to explore the influence of the nature of the melt adhesive on the quality of the injection product. Because the polymer melt is a non-Newtonian fluid and has viscosity and compressibility, the melt filling process must be extruded through the screw 15 and flow through the nozzle 14 (runner system) and runner system in sequence. , Gate and fill cavity. Among them, the physical phenomenon represented by the pressure peak index is the maximum pressure value P _{peak that the} melt glue needs to act on the melt glue from filling to packing. In addition, because the viscosity represents the ease of flow of the melt, when the viscosity is large, it reflects the greater the resistance of the melt to fill, and the greater the pressure that must be driven to flow, so the nature of the viscosity of the melt during the flow can be defined as the viscosity quality index.

Similarly, the greater the viscosity of the melt, the greater the pressure required to drive its flow, and the greater the energy consumed, that is, the greater the work required by the screw 15 to act on the melt, so from an energy perspective, The energy index can be obtained by numerically integrating the change in the pressure history and the cross-sectional area of the screw 15 by the screw 15 pushing the melt glue in the material tube 13 and the movement stroke of the screw 15. The above-mentioned pressure peak index, viscosity quality index, and energy index are all related to the melt glue, and therefore belong to the quality characteristics of the melt glue. In the present invention, it will be used to explore the correlation between the nature of the melt glue and the quality of the finished product. It should be particularly noted that the definitions of the pressure peak index, the viscosity quality index and the energy index have been disclosed in the patent application No. 107104377 previously filed by the inventors, and will not be repeated here.

Because the melt glue will generate considerable pressure in the cavity during the injection process, the injection molding machine must provide sufficient clamping force so that the mold will not be stretched by the ambassador mold due to the cavity pressure and cause burrs on the finished product. As for the elbow-type injection molding machine, the clamping force is generated by the elastic restoring force of the extension deformation of the machine pillar 11. Therefore, a strain sensor 2 is installed on the surface of the machine pillar 11 to measure the The amount of clamping force can be obtained by the amount of strain.

During the plastic filling to the holding pressure stage, when the hot melt fills the cavity, the compression behavior will occur and the cavity pressure will increase instantly, which will cause the mold to support the mold. This is reflected in the measured clamping force monitoring curve, as shown in Figure 2. It can be clearly found in the figure that the clamping force has a significant increase feature during the injection to holding pressure process, which is called clamping force increment ( F _{Σ, increment} ). The present invention explores this feature and the quality of the finished product. Relevance and develop online quality monitoring methods for injection products.

In addition, the present invention also explores the impact of melt quality variation on the quality of the finished product through the incremental clamping force characteristics and related melt quality indicators. Therefore, the correlation analysis is used to discuss the impact of plasticization parameters on the quality of the melt and the quality of the finished product. Sexual strength. The general correlation analysis uses r to represent the strength of the correlation between the two physical quantities x and y, as follows:

The range of correlation coefficient is 1 r Between -1, r> 0 is a positive correlation, r <0 is a negative correlation, and the magnitude is the correlation strength. When r 0.7 is strongly correlated, 0.7> r 0.3 is medium correlation; r <0.3 is weak correlation.

The present invention is based on the existing injection machine and sensing technology, and is used to monitor the quality of injection molding products on the injection molding process development line. The experiment uses a 100-ton all-electric injection molding machine manufactured by Japan Fanuc Corporation. The basic specifications of the machine As shown in Table 1, the experimental plastics used PA-756 and PA-756H produced by CHI-MEI and two different types of ABS. The recommended molding parameters of the materials are shown in Table 2.

In the present invention, various sensors are used to collect relevant molding process information and calculate the quality of the finished product. Therefore, a pressure sensor is installed in the nozzle 14 and the cavity. In addition, when the quality of the melt adhesive is changed, it is expected to have different degrees of impact on the injection molded products and reflect different degrees of the die support effect. Therefore, a strain sensor 2 is installed on the large pillar 11 of the injection molding machine to monitor the large pillar of the injection molding process. Elongation changes, the overall measurement system and the sensors used in the experiment are shown in Figure 1 and Table 3, and the sensor installation position is shown in Figure 3, including two pressure sensors 3 (cavity pressure installed in the cavity) sensor (CPa-CP _b ) and four strain-strain sensors 2 (tie-bar strain sensor (SGa-SG _d )) installed on the machine pillar 11, and the quality of the finished product can be the weight of the finished product, the geometric size of the finished product, and the finished product The amount of warpage, mechanical strength of the finished product, etc., the quality of the injection finished product discussed in the present invention is mainly based on the weight and thickness of the finished product, in which the thickness measurement position of the finished product is at positions A1, A2, B1, and B2 in FIG. 3.

It should be particularly noted that, in FIG. 3, the numbers 0, 20.5, 40, 75, and 100 are the specifications of the mold, not the numbers of the components.

Because the plasticizing quality of the melt adhesive will affect the quality of the injection product during the molding process, the present invention discusses three process parameters that are expected to affect the plasticizing quality of the melt adhesive during the plasticization stage, including: tube temperature, back pressure and screw speed, and The influence of the quality variation of the plasticized melt on the quality of the injection products was discussed with the relevant melt quality indicators. In the present invention, the weight and thickness of the finished product are selected as the focus of discussion and defined as the quality of the finished product. Therefore, the correlation between the weight of the finished product and the thickness of the finished product is discussed first. FIG. 4 is a trend chart of the average weight of the finished product and the average thickness of the finished product continuously injected with various plasticization parameters. According to the correlation analysis, it can be known that the correlation between the two can reach a maximum of 0.99. Therefore, the present invention will discuss the quality of the finished product through the weight of the finished product.

First, the effect of the temperature of the tube on the plasticizing quality of the melt adhesive was tested. In the melt glue disturbance experiment, PA756 was used as the plastic. Table 4 shows the parameters of the variable tube temperature setting experiment.

When the tube temperature is set to increase, the specific volume is increased, and the mass per unit volume of the melted adhesive is reduced. Therefore, the initial viscosity of the melted plastic is expected to decrease and increase the fluidity. Because the melt glue has a certain volume flow rate during the injection filling stage, when the temperature rises, the same volume is filled into the cavity, and the resulting mass is lower. Therefore, the pressure difference and energy required to drive the melt glue filling process are small. The pressure peak, viscosity index and energy index obtained by nozzle monitoring decrease with the increase of the material temperature, as shown in (a) of each of the figures 5 to 7, where the pressure The peak force changes at 22 MPa and 14 MPa at the system and the nozzle, respectively. The occurrence time is close to the time of injection and cutting (that is, before the end of filling). However, when the melt temperature rises, the gate solidification time is prolonged and the melt is compressible. The property also increases accordingly, so more melt glue is filled into the cavity during the holding pressure stage to compensate for the volume shrinkage, so that the pressure peak of the cavity pressure curve occurs during the holding pressure stage and increases accordingly, which results in a significant improvement in the weight and quality of the finished product. It is about 0.09g, so all the indexes obtained in the mold cavity monitoring increase with the increase of the melt temperature, as shown in (b) of each of the graphs of Fig. 5 to Fig. 7.

If you observe the incremental change of the clamping force, you can find that it increases with the increase of the material temperature, and the development trend is the same as the weight and quality of the finished product, as shown in Figure 8 (a). The reason is that when the material temperature increases, the pressure is maintained. During the phase, more melt glue is filled into the cavity to compensate for the shrinkage of the melt volume of the cavity, which results in a significant increase in cavity pressure and a greater support effect, which is reflected in the significant increase in clamping force. Quality trends are the same. In addition, when observing the change of the measurement time, it can be found that when the temperature of the material tube changes, the specific volume of the melted adhesive changes, but because the back pressure setting and the screw speed are constant, the screw back resistance is the same during the plasticization stage, so the measurement time slightly increases. About 0.06 seconds, there is no significant change, as shown in Figure 8 (b).

Then, the influence of back pressure on the plasticizing quality of the melt adhesive is tested. Table 5 shows the parameters of the variable plastic back pressure setting experiment.

In terms of the PVT properties of polymer materials, when the pressure increases, the specific volume decreases, the density increases, and the mass per unit volume of the melt adhesive increases. Therefore, when the back pressure is increased, it is expected to increase the viscosity of the melt and reduce the fluidity. During the filling stage of the melt with a constant volume flow rate, when the back pressure is increased, the mass of the same volume into the cavity is increased, so The pressure difference and energy that drive the flow of the glue filling are relatively increased and cause the pressure peak, viscosity index and energy index monitored in the system and the nozzle to increase as the back pressure increases, as shown in (a) of each of the figures 9 to 11 As shown in the figure, the peak pressure changes at 9MPa and 8MPa at the system and the nozzle, respectively, and the time of occurrence is close to the cut-off time. This phenomenon coincides with the previous experiment.

In terms of the cavity position, although the material temperature is the same and the gate solidification time is expected to be the same, the amount of melt adhesive that can compensate for volume shrinkage during the holding stage is the same for different back pressure settings. However, due to the melt density and viscosity of the filling stage The back pressure increases and increases, so the quality of the melt adhesive flowing into the cavity increases. Therefore, the peak pressure, viscosity index and energy index obtained by monitoring will increase, and the weight and quality of the finished product will increase slightly by about 0.03g, as shown in Figure 9 to Figure As shown in (b) of each figure in Figure 11; if you observe the incremental change in clamping force, you can find that it increases with increasing back pressure, and the development trend is the same as the weight and quality of the finished product, as shown in Figure 12 (a), because During the process of filling the cavity with the melt, the mass of the melt filled into the cavity increases as the back pressure increases. Therefore, the larger support effect is reflected in the larger column extension and the increase in clamping force. The results agree with the previous experiment. In addition, when observing the change of the measurement time, it can be found that when the back pressure increases, because the melt back resistance of the plasticizing phase increases, the measurement time significantly increases by about 1.1 seconds, as shown in FIG. 12 (b).

Next, the effect of screw speed on the plasticizing quality of the melt adhesive is tested. Table 6 shows the parameters of the variable screw speed setting experiment. When the screw speed increases, the melt adhesive is expected to undergo a greater shear effect during the plasticizing stage. Due to the shear thinning behavior of the thermoplastic polymer material, the melt viscosity decreases as the shear rate increases. The average material temperature is expected It rises, but the plasticizing time is significantly shortened. In other words, when the plasticizing screw rotates and retracts, the more front-end melt glue undergoes the shearing effect, the shorter the time and the temperature rise is not obvious, which only slightly affects the quality of the melt glue. Impact and therefore monitoring in the system and nozzle The obtained pressure peak, viscosity index, and energy index all decrease slightly with the increase of the screw speed, as shown in (a) of each of the graphs 13 to 15, where the pressure peak changes only 4 MPa and 4 MPa at the system and the nozzle, respectively. 3 MPa means that when the screw speed increases, only the average temperature of the melt is slightly increased, so the viscosity is slightly reduced, and the pressure difference and energy required to fill the melt are slightly reduced.

As far as the cavity pressure is concerned, the relevant monitoring indicators only increase slightly with the increase of the screw speed, and the weight and quality of the finished product also increase only slightly by about 0.01g, as shown in (b) of each of the figures 13 to 15, Because the melt temperature has not increased significantly, the amount of melt that can be compensated for the mold cavity during the holding pressure stage is limited; as far as the incremental change in clamping force is concerned, because the weight and quality of the finished product has only increased slightly, the incremental increase in clamping force is also only small. The increase is as shown in Fig. 16 (a), and the measurement time is significantly shortened by about 6.2 seconds as the screw speed increases, as shown in Fig. 16 (b).

According to the foregoing experimental results, it can be understood that the three main parameter settings such as the tube temperature, back pressure and screw speed during the plasticization stage affect the initial quality of the melt adhesive, and through the curve change, it can be clearly observed that the quality variation of the melt adhesive does indeed affect the weight and quality of the finished product. Different degrees of influence, however, the relationship between the quality monitoring indicators of finished products and the quality monitoring indicators of melt adhesives on the weight and quality of finished products has not yet been clarified, so the following content will explore the correlation between related quality indicators and finished product quality for different sensing locations.

The finished product quality index of the incremental clamping force characteristics has a strong positive correlation with the finished product weight and thickness in three different melt quality disturbance experiments. As shown in Figure 17, due to the incremental clamping force characteristics occurring in the mold cavity, the supporting mold is generated. At the moment, at this moment, the melt glue fills the mold cavity and compresses, which results in the mold support effect. The mold cavity pressure reaches a maximum value, and the mold support effect also actually causes different degrees of clamping force increase characteristics. The correlation coefficient obtained in the pressure experiment is 0.96 ~ 0.99, so it is quite strong. In contrast, although the correlation coefficient obtained in the screw speed experiment is 0.76 ~ 0.89, it is not as high as the other two. It is presumed that the weight of the finished product does not change. Big cause, but also above strong correlation. Therefore, when the weight and thickness of the finished product varies, it can be detected in real time through the incremental clamping force feature, so it is feasible and industrially useful as an indicator of the quality of the finished product that is injected online.

Further explore the correlation between the quality of the melt glue and the quality of the finished product, and observe that the correlation between the quality index of the melt glue and the weight of the finished product is quite strong at different sensing positions. However, in terms of the effect of the temperature setting of the material tube on the quality of the product, the material tube Increasing temperature reduces the initial viscosity of the melt, so the melt's fluidity increases, and the pressure and energy required to drive the melt's flow decrease. In addition, as the gate solidification time also increases, more melt can be filled during the holding stage. The mold cavity increases the weight and thickness of the finished product, so the correlation between the pressure peak, melt viscosity index and energy index and the quality of the finished product is -0.95 ~ -1 at the system and nozzle, and 0.99 ~ 1 at the cavity. As shown in FIG. 18, the correlation coefficients are all strong.

In terms of the effect of back pressure setting on the quality of the finished product, the increase in back pressure increases the initial viscosity and density of the melt, and the pressure and energy required to drive the flow of the melt increase. Therefore, the quality of the melt filling the cavity in the same flow time It is increased to increase the weight and thickness of the finished product. Therefore, the correlation between the pressure peak, melt viscosity index and energy index and the quality of the finished product is 0.92 ~ 1 in the system, nozzle and mold cavity, which are all positively correlated, as shown in the figure. 19 is shown.

In terms of the effect of the screw speed setting on the quality of the finished product, the increase of the screw speed slightly increases the initial average temperature of the melt, and the melt viscosity decreases slightly, so the impact on the quality of the melt is not significant, resulting in a slight increase in the weight of the finished product, but due to changes The trend is not obvious, so the correlation coefficient between the pressure peak, the melt viscosity index and the energy index and the quality of the finished product are in the system and the nozzle The location is -0.61 ~ -0.77, showing a negative medium-strong correlation, and the mold cavity is 0.73 ~ 0.99 showing a positive medium-strong correlation, as shown in Figure 20.

Based on the above discussion, the melt quality index of the system and the nozzle is consistent with the initial melt viscosity variation, so it can actually reflect the initial melt state, not the quality of the finished product. In contrast, the melt quality index at the cavity location is consistent with the quality variation of the finished product, so it can actually reflect the quality status of the finished product, not the melt quality. In addition, the incremental clamping force characteristics are consistent with the quality status of the finished product, so it can actually be used as an indicator of the quality of online injection molding finished products.

From the foregoing experiments, the influence of plasticization parameters on the quality of the melt adhesive and the quality of the finished product can be clearly understood, and the quality of the injection finished product can be successfully monitored through the incremental clamping force feature. Next, two different molding quality disturbance methods are applied to verify the online injection molding. Feasibility of quality monitoring methods.

The following experiment uses a mixing method to observe whether the influence of the melt quality variation on the quality of the finished product can be correctly reflected in the clamping force increase feature to achieve the purpose of monitoring the quality of the finished product. Therefore, the experiment uses two types of ABS for the experiment. It is mixed in advance before feeding. The experiment process starts with 100% by weight PA756 injection, and each group increases by 20% by weight PA756H until the sixth group is completely replaced with 100% PA756H. Each group of plastic is about 800g. The experimental process parameters are shown in Table 7, where the V / P position is set to 15mm.

The experimental results show that because PA756H has lower viscosity and better melt fluidity, under the same process conditions, the weight of the injection product increases as the melt viscosity decreases. Therefore, when the mixing ratio increases, the weight of the product increases. And it is successfully reflected in the increase of total clamping force and single clamping force. The trends of the finished product quality monitoring index and the finished product weight and quality are the same, as shown in Figure 21.

By observing the pressure peak, viscosity index and energy index through the system and the nozzle position, the performance of the melt quality index can successfully reflect that the initial melt quality changes with the variation of the mixing ratio, and the development trend is exactly the opposite of the quality of the finished product. The changes in the quality index of the melt adhesive monitored by the system and the nozzle are reflected in the initial quality of the melt adhesive rather than the quality of the finished product. In contrast, the performance of all melt adhesive quality indicators observed at the cavity position can successfully reflect the effects of different mixing ratios. As a result, the quality of the finished product changes, and the development trend is exactly the same as the quality of the finished product. Therefore, the change in the quality index of the melt adhesive monitored at the cavity position is reflected in the final quality characteristic of the finished product, and it is the same as the development trend of the finished product quality index of the clamping force increase As shown in Fig. 22 to Fig. 24, and the correlation between various quality indicators relative to the weight characteristics of the finished product is shown in Fig. 25, and it can be clearly found that the correlation between the quality index of the finished product with an increase in clamping force and the weight and quality of the finished product is quite strong. Therefore, feasibility and practicability have been confirmed through this experiment, and the melt quality index is slightly lower than the energy index by one. But between the weight of the finished quality substantially all exhibit strong correlation, and therefore be used to determined the initial melt quality of the finished product quality impact.

In addition, the following experiments are performed with the V / P position set to 15mm as a reference for continuous experiments, and the V / P position set value is changed by a factor of 5 (such as: 5, 10, 15 ...) to form 1 mold After that, it will be changed back to the reference value, so as to observe whether the quality variation of the finished product can be correctly reflected in the incremental force of the clamping force to achieve the purpose of monitoring the quality of the finished product. The experimental process parameters are shown in Table 7. Change the V / P position setting. The value principle is also explained in the table.

The experimental results are shown in Fig. 26. The change trend of the single clamping force increase, the total clamping force increase, and the finished product weight curve can be clearly found in the figure. It has consistency. When the V / P position is set to 15mm, the total clamping force is about 544kN, the average value of the total clamping force increase is 3.010kN, the total distance is 0.306kN, and the average weight of the finished product is 4.815g. The total distance is only 0.010g, so the degree of change in the quality of the finished product is quite small. In contrast, when changing the different V / P position settings, it can be found that when the amount of change is 0.2mm, the single clamping force increase and the total clamping force are Increment can all produce a response and successfully discover the quality variation of the finished product. The same experimental results can be found in the other larger and different V / P position setting value changes. Therefore, this experiment proves once again the quality of the finished product developed by the online injection. The monitoring method can successfully monitor the quality variation of the micro-finished product.

The quality of traditional injection molding finished products is mainly measured offline. The abnormal quality of the finished product is often not detected immediately. In recent years, due to the development of sensing technology, the common injection molding quality monitoring technologies are mostly based on the cavity pressure curve. However, in practical industrial applications, since each mold must be equipped with a cavity pressure sensor, in addition to increasing the cost of the mold, its practicality and convenience cannot make it universally available. Because the variation in the quality of the melt glue will cause the quality of the finished product to change and be reflected in the incremental performance of the clamping force at different degrees, the present invention successfully develops an online injection molding product quality monitoring method based on the characteristics of the clamping force curve, and passes the relevant melt glue The quality monitoring index explores the influence of melt quality variation on finished product quality to verify the feasibility of the finished product quality monitoring method.

In summary, the quality variation of the melt glue will affect the quality of the injection product and is reflected in the expression of the clamping force increase at different degrees. The development trend of the clamping force increase characteristic is the same as the change in the weight and quality of the finished product, and the correlation is 0.96, so it can be successful. Carry out on-line injection product quality monitoring. In the verification experiments, it can be successfully found that whether the quality of the melt is changed or the process parameters are changed slightly, the stability of the process parameters will change the quality of the finished product, and the clamping force increase feature is used to successfully monitor the variation of the quality of the finished product. The invention utilizes a strain sensor installed on the large pillar of the machine, in addition to monitoring the change in clamping force during the production process, and can also be used as an indicator of the quality of the injection product. Immediately find the abnormal quality of the finished product and process it online, so it can really achieve the purpose of the invention.

However, the above are only the preferred embodiments of the present invention. When the scope of implementation of the present invention cannot be limited by this, that is, the simple equivalent changes and modifications made according to the scope of the patent application and the description of the invention, All are still within the scope of the invention patent.

Claims (2)

An on-line real-time monitoring method for the quality of a finished product of an injection molding machine. The injection molding machine includes a plurality of machine pillars arranged at intervals, a fixed template fixedly fixed to one end of the machine pillar, and an extension placed in the fixed template and used for filling. A plastic tube, a screw for squeezing the plastic in the tube, and a mobile template capable of sliding along the machine column to engage and separate with respect to the fixed template. The quality of the finished product is monitored in real time. It includes the following steps: an installation step, setting at least one strain sensor on any machine pillar; a measurement step, using the strain sensor to measure the clamping force of the machine pillar, and obtaining a mold clamping A force monitoring curve; and a judging step, the clamping force monitoring curve is used to judge whether a clamping force increase is generated, and the clamping force increase value is used to judge the quality of the finished product in real time, wherein the clamping force increase value and the The quality of the finished product is positively related, and the quality of the finished product refers to the weight of the finished product. According to the method for online real-time monitoring of the finished product quality of the injection molding machine as described in item 1 of the scope of the patent application, in the judging step, the incremental value of the clamping force and the nature of the molten glue formed after the plastic in the material tube is heated The change is relevant, and the quality of the finished product can be judged in real time through the change of the nature of the melt glue.