A method and system for controlling the quality consistency of injection molded articles

Abstract

The application relates to a kind of injection molding product quality consistency control method and system, relate to injection molding process control field, it includes steps 100: the torque data of screw is collected;Step 101: in response to the torque data and preset reference torque, determine counterflow volume;Step 102: in response to the counterflow volume, determine packing pressure, and collect injection time;Step 103: when the injection time is greater than preset transition packing point, control preset injection device according to the packing pressure packing.This application has the effect of improving the consistency of injection molding product quality, reducing the situation that counterflow occurs in injection molding process and leads to the decline of injection quality.

Description

Technical Field

[0001] This invention relates to the field of injection molding process control, and in particular to a method and system for controlling the quality consistency of injection molded products. Background Technology

[0002] Injection molding is a processing method that involves heating and melting plastic raw materials, then injecting them under high pressure into a mold cavity, and finally cooling and solidifying them to obtain plastic products of a specific shape.

[0003] In a typical injection molding cycle, molten plastic is sequentially conveyed from the injection molding machine barrel into the mold cavity through the injection stage and the holding stage, completing the mold filling and shaping process of the product. The injection stage primarily delivers the melt from the screw tip to the mold cavity at a constant linear velocity until the screw reaches the preset V / P switching point, i.e., the injection-to-holding pressure node. Subsequently, in the holding stage, the system switches the injection pressure to a constant holding pressure, continuously replenishing material into the mold cavity for a set holding time to offset the volume loss caused by cooling shrinkage, thereby ensuring the dimensional stability and surface quality of the product.

[0004] When the screw is subjected to external interference during operation, the sealing performance of the check ring at the front end of the screw is easily reduced, which causes the melt to flow backward during injection and holding pressure. This leads to a reduction in the effective melt volume entering the mold cavity during injection molding, resulting in lighter injection molded products, incomplete filling, reduced dimensional accuracy, or even defects. Summary of the Invention

[0005] In order to improve the consistency of injection molded product quality and reduce the occurrence of backflow during the injection molding process that leads to a decline in injection molded quality, this invention provides a method and system for controlling the consistency of injection molded product quality.

[0006] In a first aspect, the present invention provides a method for controlling the quality consistency of injection molded products, which adopts the following technical solution:

[0007] A method for controlling the quality consistency of injection molded products, comprising:

[0008] Step 100: Collect the torque data of the screw;

[0009] Step 101: Determine the counterflow volume in response to the torque data and the preset reference torque;

[0010] Step 102: Determine the holding pressure in response to the counterflow volume and collect the injection time;

[0011] Step 103: When the injection time is greater than the preset holding pressure point, control the preset injection device to hold pressure according to the holding pressure.

[0012] By adopting the above technical solution, the screw torque is collected in real time during the injection stage. The reverse flow rate during the injection stage of the current cycle is quantified in real time by calculating the difference between the screw torque curve of the current cycle and the standard torque curve. Based on the quantified reverse flow volume, an appropriate holding pressure is selected during the holding pressure stage to compensate for the melt missing due to the reverse flow, thereby improving the consistency of injection molded product quality.

[0013] Optionally, the method for determining the countercurrent volume includes:

[0014] Step 104: Determine the reverse flow rate in response to the torque data and the preset reference torque;

[0015] Step 105: Determine the countercurrent volume in response to the countercurrent rate and the preset pressure holding point.

[0016] Optionally, the method for determining the holding pressure includes:

[0017] Step 106: Determine the correction coefficient in response to the counterflow volume and the preset mold cavity volume;

[0018] Step 107: Determine the holding pressure in response to the correction factor and the preset reference pressure.

[0019] Optionally, it also includes a method for adjusting the holding time, the method comprising:

[0020] Step 200: When the injection time is greater than the preset holding pressure point, update the torque data;

[0021] Step 201: Determine the holding volume in response to the torque data and the preset holding torque;

[0022] Step 202: Determine the holding pressure coefficient in response to the holding pressure volume and the preset mold cavity volume;

[0023] Step 203: Determine the holding time in response to the holding pressure coefficient and the preset reference time;

[0024] Step 204: Control the preset injection molding device to maintain pressure according to the holding pressure and holding time.

[0025] By adopting the above technical solution, during the holding pressure stage, the torque of the screw in the current cycle is continuously collected in real time, thereby quantifying the melt backflow situation in this stage. Based on the quantification result, the holding pressure time is dynamically adjusted, thereby achieving consistent control of melt filling quality and product weight in multi-mold production.

[0026] Optionally, the pressure holding time adjustment method further includes:

[0027] Step 205: Determine the rate of change in response to the pressure holding volume;

[0028] Step 206: Determine the compensation time in response to the rate of change;

[0029] Step 207: Calculate the sum of the compensation time and the pressure holding time, and define it as the pressure holding time.

[0030] By adopting the above technical solution, the changes in countercurrent can be obtained from the countercurrent situation during the pressure holding stage. This allows for a moderate extension of the pressure holding time to offset the effect of contraction when the countercurrent intensifies, and early termination of the pressure holding process to optimize cycle efficiency when the countercurrent slows down.

[0031] Secondly, this application provides a quality consistency control system for injection molded products, which adopts the following technical solution:

[0032] A quality consistency control system for injection molded products, comprising:

[0033] The data acquisition module is used to collect torque data and injection time.

[0034] A memory for storing the program of any of the above-mentioned methods for controlling the quality consistency of injection molded products;

[0035] The processor is the unit of memory that allows programs to be loaded and executed by the processor.

[0036] By adopting the above technical solution, the screw torque is collected in real time during the injection stage. The reverse flow rate during the injection stage of the current cycle is quantified in real time by calculating the difference between the screw torque curve of the current cycle and the standard torque curve. Based on the quantified reverse flow volume, an appropriate holding pressure is selected during the holding pressure stage to compensate for the melt missing due to the reverse flow, thereby improving the consistency of injection molded product quality.

[0037] In summary, this application includes at least one of the following beneficial technical effects:

[0038] The screw torque is collected in real time during the injection stage. The reverse flow rate during the injection stage of the current cycle is quantified in real time by calculating the difference between the screw torque curve of the current cycle and the standard torque curve. Based on the quantified reverse flow volume, an appropriate holding pressure is selected in the holding pressure stage to compensate for the melt missing due to the reverse flow, thereby improving the consistency of injection molded product quality.

[0039] During the holding pressure stage, the screw torque of the current cycle is continuously collected in real time to quantify the melt backflow situation in this stage. Based on the quantification result, the holding pressure time is dynamically adjusted to achieve consistent control of melt filling quality and product weight in multi-die production.

[0040] The changes in countercurrent can be obtained from the countercurrent situation during the pressure holding phase. Therefore, the pressure holding time can be appropriately extended when the countercurrent intensifies to offset the effect of contraction, and the pressure holding can be terminated in advance when the countercurrent slows down to optimize cycle efficiency. Attached Figure Description

[0041] Figure 1 This is a flowchart of a method for controlling the quality consistency of injection molded products;

[0042] Figure 2 This is a flowchart of the pressure holding time adjustment method. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] Reference Figure 1 A method for controlling the quality consistency of injection molded products, comprising:

[0045] Step 100: Collect the torque data of the screw.

[0046] Torque data refers to the real-time torque data curve of the screw. Torque data can be collected using the screw torque sensor built into the equipment. The method of collecting torque data is selected by the staff according to the actual situation, and will not be elaborated here.

[0047] Step 101: Determine the counterflow volume in response to the torque data and the preset reference torque.

[0048] The reference torque refers to the torque data curve during the injection stage when there is no backflow. The reference torque can be collected in advance by the staff, and the staff selects the reference torque according to the actual situation, which will not be elaborated here. Backflow volume refers to the volume of melt that flows back into the mold cavity during the injection stage. Generally, the backflow volume is calculated using a melt backflow prediction model. The calculation method for the backflow volume is selected by the staff according to the actual situation, which will not be elaborated here.

[0049] Step 102: Determine the holding pressure in response to the counterflow volume and collect the injection time.

[0050] Holding pressure refers to the pressure value that needs to be applied to the melt during the holding stage in the current production cycle. Generally, the holding pressure is calculated using a holding pressure correction model. The calculation method for holding pressure is selected by the staff according to the actual situation, and will not be elaborated here.

[0051] Injection molding equipment refers to the equipment used for injection molding. The selection of the injection molding equipment is made by the operator based on the actual situation and will not be elaborated upon here. Injection time refers to the duration of operation of the injection molding equipment. The injection time can be collected using a timer on the injection molding equipment. The method for collecting the injection time is selected by the operator based on the actual situation and will not be elaborated upon here.

[0052] Step 103: When the injection time is greater than the preset holding pressure point, control the preset injection device to hold pressure according to the holding pressure.

[0053] The transition point to the holding pressure stage refers to the point at which the injection molding machine switches from the injection stage to the holding pressure stage. This transition point is preset by the operator and selected based on actual conditions; details will not be elaborated here. If the injection time exceeds the transition point, it indicates that the injection molding unit has entered the holding pressure stage. At this point, pressure needs to be applied in a counter-current manner to compensate for the missing melt.

[0054] The screw torque is collected in real time during the injection stage. By calculating the difference between the screw torque curve of the current cycle and the standard torque curve, the reverse flow rate of the injection stage in the current cycle is quantified in real time. Based on the quantified reverse flow volume, an appropriate holding pressure is selected in the holding pressure stage to compensate for the melt missing due to the reverse flow, thereby improving the consistency of injection molded product quality.

[0055] Methods for determining the countercurrent volume include:

[0056] Step 104: Determine the reverse flow rate in response to the torque data and the preset reference torque.

[0057] The melt flow rate prediction model includes calculation steps for calculating the flow rate from torque data and calculation steps for calculating the flow volume from the flow rate. The flow rate refers to the velocity of the melt flowing in reverse. The calculation step for calculating the flow rate from torque data can be performed using formula Q. back =k1*(dT F / dt-dT0 / dt), where Q back This refers to the required countercurrent rate. k1 is a proportionality coefficient related to the screw geometry and melt rheological properties. k1 is selected by the operator based on the actual situation and will not be elaborated here. T F The torque data mentioned above refers to T0, which is the reference torque.

[0058] Step 105: Determine the countercurrent volume in response to the countercurrent rate and the preset pressure holding point.

[0059] The calculation steps for calculating the countercurrent volume from the countercurrent rate can be performed by integrating the countercurrent rate from the start of the injection stage to the holding pressure point to calculate the countercurrent volume during the injection stage. The calculation method for calculating the countercurrent volume from the countercurrent rate can be selected by the staff according to the actual situation, and will not be elaborated here.

[0060] Methods for determining the holding pressure include:

[0061] Step 106: Determine the correction coefficient in response to the reverse flow volume and the preset mold cavity volume.

[0062] The holding pressure correction model includes calculation steps for the correction coefficient based on the backflow volume and calculation steps for the holding pressure based on the correction coefficient. The mold cavity volume refers to the volume of the cavity inside the mold of the product being injected by the injection molding machine. The mold cavity volume can be initially set by the operator, and the operator selects the appropriate volume based on actual conditions; this will not be elaborated upon here. The correction coefficient is the coefficient value used to correct the holding pressure. A larger backflow volume requires a larger correction coefficient. The calculation steps for the correction coefficient based on the backflow volume generally use the formula k2 = 1 + V. F / (V) m *k3), where k2 is the required correction coefficient, V F For the countercurrent volume mentioned above, V m The volume of the mold cavity is given above, and k3 is the material compression coefficient. k3 is selected by the staff according to the actual situation, and will not be elaborated here.

[0063] Step 107: Determine the holding pressure in response to the correction factor and the preset reference pressure.

[0064] The reference pressure refers to the pressure applied to the melt during the holding stage when there is no backflow. The reference pressure can be preset by the operator, and the operator selects the reference pressure according to the actual situation, which will not be elaborated here. The calculation steps for calculating the holding pressure using the correction factor generally adopt the formula P=P0*k2, where P is the required holding pressure and P0 is the aforementioned reference pressure.

[0065] Reference Figure 2 The methods for adjusting the pressure holding time include:

[0066] Step 200: When the injection time is greater than the preset holding pressure point, update the torque data.

[0067] The pressure conditions differ between the injection and holding phases. Torque data is re-acquired after entering the holding phase to assess the backflow of the melt.

[0068] Step 201: Determine the holding volume in response to the torque data and the preset holding torque.

[0069] Holding torque refers to the torque data curve during the holding stage when there is no backflow. The holding torque can be collected in advance by the operator, who selects the appropriate torque based on the actual situation; details will not be elaborated here. Holding volume refers to the volume of melt flowing backwards within the mold cavity during the holding stage. It is generally calculated using a holding melt backflow prediction model, which includes steps to calculate the holding rate from the torque data and to calculate the holding volume from the holding rate.

[0070] The step of calculating the pressure holding rate from torque data generally uses formula Q. back1 = (dT) F1 / dt-dT1 / dt), where Q back1 That is, the required holding pressure rate, T F1 For the torque data mentioned above, T1 is the holding torque mentioned above. The step of calculating the holding volume from the holding rate generally uses the formula V. p =k4*A,V p This refers to the required holding volume, where k4 is the pressure compensation coefficient, determined based on the material compressibility and the rigidity of the mold cavity structure. k4 is selected by the operator according to the actual situation and will not be elaborated upon here. A represents the holding rate Q. back1 The integral value A obtained by integration is calculated using a method that is common knowledge to those in the field and will not be elaborated here.

[0071] Step 202: Determine the pressure holding coefficient in response to the pressure holding volume and the preset mold cavity volume.

[0072] The pressure holding factor is a coefficient used to correct for the pressure holding time. The larger the pressure holding volume, the larger the pressure holding factor should be. It is generally calculated using the formula k5 = 1 + V. p *k6 / V m Where k5 is the required pressure holding coefficient, and k6 is the volume compensation weight. k6 is selected by the staff according to the actual situation, and will not be elaborated here.

[0073] Step 203: Determine the holding time in response to the holding pressure coefficient and the preset reference time.

[0074] The baseline duration refers to the duration of the pressure holding phase when there is no backflow. The baseline duration can be preset by staff, and is selected based on actual conditions; details will not be elaborated here. The pressure holding duration refers to the duration required to maintain pressure during the current production cycle, generally expressed by the formula t. P =t P0 *k5 calculates and determines the holding time, where t P That is, the required holding time, t P0 This refers to the aforementioned baseline duration.

[0075] Step 204: Control the preset injection molding device to maintain pressure according to the holding pressure and holding time.

[0076] During the holding pressure stage, the screw torque of the current cycle is continuously collected in real time to quantify the melt backflow situation in this stage. Based on the quantification result, the holding pressure time is dynamically adjusted to achieve consistent control of melt filling quality and product weight in multi-stage production.

[0077] The pressure holding time adjustment method also includes:

[0078] Step 205: Determine the rate of change in response to the pressure holding volume.

[0079] The rate of change refers to the speed at which the countercurrent volume of the melt changes during the holding pressure stage in the current production cycle, and is generally expressed by the formula v. p =dV p / dt is used to determine the rate of change, where v p That is, the required rate of change, V p This refers to the pressure-holding volume mentioned above.

[0080] Step 206: Determine the compensation time in response to the rate of change.

[0081] Compensation time refers to the holding time that needs to be adjusted to account for the countercurrent volume change of the melt during the holding phase. A positive rate of change indicates intensified countercurrent, requiring an increase in holding time. Conversely, a negative rate of change indicates a slowing countercurrent trend, allowing the holding phase to end earlier. The formula t is generally used. 补 =k7*v p Calculate and determine the compensation time, where t 补 This refers to the required compensation time, and k7 is the rate compensation coefficient. k7 is selected by the staff based on the actual situation, and will not be elaborated here.

[0082] Step 207: Calculate the sum of the compensation time and the pressure holding time, and define it as the pressure holding time.

[0083] The changes in countercurrent can be obtained from the countercurrent situation during the pressure holding phase. Therefore, the pressure holding time can be appropriately extended when the countercurrent intensifies to offset the effect of contraction, and the pressure holding can be terminated in advance when the countercurrent slows down to optimize cycle efficiency.

[0084] Based on the same inventive concept, embodiments of the present invention provide a quality consistency control system for injection molded products, comprising:

[0085] The data acquisition module is used to collect torque data and injection time.

[0086] A memory for storing the program of any of the above-mentioned methods for controlling the quality consistency of injection molded products;

[0087] The processor is the unit of memory that allows programs to be loaded and executed by the processor.

[0088] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0089] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method of controlling the quality consistency of an injection molded article, characterized by, The method comprises: Step 100: collecting torque data of the screw; Step 101: determining a reverse flow volume in response to the torque data and a preset reference torque; Step 102: determining a holding pressure in response to the reverse flow volume and collecting an injection time; Step 103: when the injection time is greater than a preset switch-holding pressure point, controlling a preset injection device to hold pressure at the holding pressure; The method further comprises a holding time adjustment method, which comprises: Step 200: when the injection time is greater than a preset switch-holding pressure point, updating the torque data; Step 201: determining a holding volume in response to the torque data and a preset holding torque; Step 202: determining a holding coefficient in response to the holding volume and a preset cavity volume; Step 203: determining a holding time length in response to the holding coefficient and a preset reference time length; Step 204: controlling a preset injection device to hold pressure at the holding pressure and the holding time length.

2. The method of claim 1, wherein The method for determining the reverse flow volume comprises: Step 104: determining a reverse flow rate in response to the torque data and a preset reference torque; Step 105: determining a reverse flow volume in response to the reverse flow rate and a preset switch-holding pressure point.

3. The method of claim 1, wherein The method for determining the holding pressure comprises: Step 106: determining a correction coefficient in response to the reverse flow volume and a preset cavity volume; Step 107: determining a holding pressure in response to the correction coefficient and a preset reference pressure.

4. The method of claim 1, wherein The holding time adjustment method further comprises: Step 205: determining a change rate in response to the holding volume; Step 206: determining a compensation time in response to the change rate; Step 207: calculating a sum of the compensation time and the holding time length, and defining the sum as the holding time length.

5. A system for controlling the quality consistency of injection molded articles, characterized in that, The method comprises: An acquisition module for collecting torque data and injection time; A memory for storing a program of an injection product quality consistency control method according to any one of claims 1 to 4; A processor, and the program in the memory can be loaded and executed by the processor.

Images