Correlation analysis of heavy vertical injection molding machine parts and products filling pressure

Date：2014/10/31 16:50:17

        The use of vertical injection molding machine producing plastic products, piece weight is to evaluate the reproducibility of the most important indicators of its products. Affect the product piece weight is mainly three processes: clamping process, preparation process and the filling process. In the case of clamping stable and can meet the requirements, the preparation process determine the repeatability of each is filled with molten plastic density distribution, and determines the filling process is repeatable every time filling plastic volume. Clearly, the repeatability and reproducibility of the density distribution of the filling volume determines the piece weight repeatability. Currently it is generally controlled by three aspects of the product piece weight: ① control motor speed and backpressure sol motor (or proportional pressure valve) torque (or pressure) to ensure preparation of density; ② control the speed and distance of the filling process (or time) to ensure that the volume of injection; ③ control the pressure and dwell time to make up the surface of the cooling produced by the contraction of plastic products.
         Further, the preparation process by controlling the pressure and density distribution of the distance to ensure reproducibility; the filling process by controlling the speed - distance, pressure - time to ensure the filling volume repeatability. Clearly, both the control content inconsistency exists, the content of control may be to improve product inconsistency repetitive piece weight disorders. Thus, by analyzing the experimental measurements of pressure and product filling process PcsWgt relevance, and as a basis made ​​more concise, effectively improve the reproducibility of the product piece weight control program, the pressure control throughout the filling process, has made it good control effect.
1 Experimental
1.1 Design
         The purpose of the experiment is to collect data, filling pressure and the product piece weight correlation analysis. Therefore, the experiment needs to simultaneously record two types of data, one for each pressure curve filling process, the other for the corresponding product piece weight. Wherein the pressure detected by the pressure sensor, through the A / D converter is recorded by the controller output, sampled once every 2ms. The product piece weight as measured by precision electronic scales.
1.2 materials, instrumentation and parameters
         Materials: ABS, Taiwan Chi Mei Corporation;
         Equipment: Zhenxiong JM55EA Full-induced electric vertical injection molding machine;
         Mold: a mold eight cameras with precision gear molds;
         Process parameters: the filling rate of 50mm / s, the filling distance of 39mm, a sol of the motor speed 525r / min;
         Sensing elements: a load sensor (200kN, 0 ~ 10V);
         Data acquisition: 12 A / D converter;
         Measuring instruments: a precision electronic scales (accuracy 0.01g), Japan Sunbeam Corporation.
1.3 Data Consolidation
         The method of recording data according to the above experiment, the continuous production of two times, respectively, to obtain 22 sets of data, as shown in Table 1. With the area between the pressure curve and the horizontal axis represents the pressure every filling process, with each product piece weight correspondence. Production between the two spaced apart.
2 Analysis
2.1 Correlation Analysis Method
         Correlation reflects the non-deterministic relationship between variables.
2.2 Correlation analysis results
         Correlation analysis using the above methods of experimental data analysis, correlation coefficients of the first group of experimental data is 0.859, the correlation coefficient of the second group of experimental data is 0.882. Obviously, vertical injection molding machine filling pressure and the product piece weight correlation is very high. Description filling pressure is closely related with the product piece weight, precise control of pressure filling process, improve its reproducibility, we can improve the product piece weight repeatability.
3 Pressure Control Applications
         The most important evaluation vertical injection molding machine is a heavy product repeatability, through experiments and analysis the author reveals a strong correlation between the pressure vertical injection molding machine products, piece weight and filling process. Therefore, I changed the filling control method now widely used for speed control in the whole process of implementation of the filling pressure control. Inner inverter speed control, the outer motion control card based pressure control. The common method of controlling the speed of the filling process into two stages: in the implementation of multi-target distance within a speed control, both the speed - distance control; in a certain period of time after the implementation of multi-stage pressure control, both the pressure - time control. That is, as the horizontal distance encoder as the detection element filling process speed, and speed setting value, the internal inverter operation, to speed the filling process is controlled so that the actual speed of setting a good fit value. The pressure control method in time for the abscissa, in filling the full implementation of the pressure control, it is applied as a load sensor detects the pressure element filling process, the feedback output value compare with the reference pressure curve, the application of advanced PID algorithm, the whole process of filling pressure control, the output good track reference pressure curve to obtain a good result. Wherein the reference pressure curve is commissioning the machine several times to the satisfaction of the curve, automatically recorded by the controller down.
         With the above pressure control method and speed control method for product piece weight repeatability experiment, the results shown in Table 2.
         Speed ​​control, including two sets of data, corresponding to the first group of high filling rate (60mm / s), piece weight repeat the error of 1.5%; Group 2 corresponds to the low filling rate (30mm / s), piece weight repeat the error of 0.7%. Pressure control also includes two sets of data, the first group corresponds to the low filling pressure reference curve, piece weight repeat error of 0.4%; Group 2 high filling pressure corresponding reference curve, piece weight repeat error of 0.38%.
         Therefore, this method is effective to improve the vertical injection molding machine pouring product piece weight repeatability, while under different reference pressure curves can get repetitive error of about 0.4%, significantly better than pieces of speed control weight repeatability.
4 Conclusion
         Vertical injection molding machine injection the most important evaluation of products is a heavy repeatability, the author reveals through experiments and analysis of vertical injection molding machine has a strong correlation between the pressure piece weight and filling process products and apply it to the actual control to go, the whole process of filling pressure control, was significantly better than the speed control product piece weight repeatability. At the same time, I also noticed that part of Japan's FANUC company's all-electric vertical injection molding machine also uses a full pressure control program. These are instructions on the vertical injection molding machine for the entire filling process pressure control is a control method for injection molding products, worthy of promotion.

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