Method for adjusting container production plant

Abstract

The invention relates to a method for producing containers made of thermoplastic material by blow-molding or stretch blow-molding preforms, which are previously heated in a furnace and then placed in a mould consisting of two half-moulds, which delimit a molding cavity in which the preforms are blow-molded, the method may have a pre-blow-molding step, the heating step of the preform, the pre-blow-molding step and the blow-molding step being controlled by a control unit on the basis of so-called different control parameters, such as the heating temperature of the preform in the furnace, the blow-molding pressure in the mold and / or the pre-blow-molding pressure and / or the pre-blow-molding flow rate and / or the speed of the stretching rod; the method is characterized in that the method comprises a preliminary calibration step, and the calibration step at least comprises the following steps: producing a container based on a first control parameter so as to produce a container meeting requirements; measuring the thickness of the wall of the container at at least two different heights at the time of mold stripping corresponding to the production of the container based on the first control parameter, the measured values of the thickness corresponding to a reference thickness; recording the reference thickness in a storage unit; modifying each control parameter; after modifying each handling parameter, measuring the thickness of the wall of the container at at least two different heights upon demolding; for each modified control parameter, recording the thickness of the wall of the container during mold stripping in the storage unit; comparing the recorded measured thickness with the reference thickness or the theoretical thickness; and determining at least one control parameter causing a maximum change in the thickness of the wall of the container.

Description

Technical Field

[0001] This invention relates to the field of container manufacturing, for example, manufacturing containers such as bottles or vials from preforms made of thermoplastic materials (e.g., polyethylene terephthalate, PET) by blow molding or stretch blow molding. The object of this invention is to provide a method for forming containers from preforms by blow molding or stretch blow molding, and an apparatus for applying this method. Background Technology

[0002] In the field of container manufacturing, it is well known that these containers are produced using equipment that includes at least a heating unit and a forming unit, the forming unit being equipped with a series of molds having cavities for the container model to be formed, and corresponding injection molding mechanisms.

[0003] More specifically, the production of these containers comprises two main stages: a first stage, known as preform heating, in which a series of preforms are heated in a heating unit to a reference temperature at which they are in a plastic state, in which they can be shaped; and a second stage, known as forming, in which the heated preforms are transferred individually to molds in a blow molding unit, and pressurized fluid is injected into each preform through a corresponding injection mechanism (also known as a nozzle) to give the preform the final shape of the container. The pressurized fluid is typically a gas, such as air. Additionally, forming typically includes a stretching stage, which is achieved by applying a tensile force to the bottom of the preform in the mold using movable stretching rods, stretching the preform along its own axis, thereby helping to hold the preform in the center relative to the mold.

[0004] Furthermore, the production equipment for these containers typically includes a control console from which operators can manually adjust various parameters to control the heating and / or forming units. Regarding the heating unit, these parameters include, for example, heating power, machine cycle time to change the travel speed of the preform in the heating unit, ventilation power to ensure partial heat removal from the heating unit, and a preferred heating temperature profile. Regarding the forming unit, these parameters include, for example, pre-blow pressure, pre-blow initiation point, pre-blow flow rate, stretching speed, and blow pressure.

[0005] Before obtaining containers deemed compliant—that is, before obtaining containers that meet all quality standards predefined by the technical specifications—the production process requires multiple preliminary tests. This operation is cumbersome and time-consuming because every parameter of the equipment and method must be adjusted to ensure container compliance. Furthermore, this preliminary step must be performed for each container size. Container specifications can be defined, in particular, by the container's height, shape, volume, and material.

[0006] Therefore, the commissioning of the production method and the parameter setting of related equipment require the presence of an operator who is very familiar with the equipment, the method, and the types of preforms that can be easily introduced into the equipment to obtain containers that meet the desired specifications. This commissioning also takes a significant amount of time, which directly affects the output of the production line.

[0007] The obtained containers will then be evaluated to determine whether they meet standards; this process continues throughout the production phase. For example, to determine specifications, a quality criterion for judging container conformity could be the material distribution along the height of the container. It is well known that one of the parameters of the production method that affects this standard is the thermal conditioning of the preform as it passes through the heating unit.

[0008] If the material distribution standard is determined to be non-compliant, the operator must adjust different parameters to correct the defect during the heat conditioning phase, the forming phase, or both. Furthermore, the modifications performed should not lead to the occurrence of other defects or problems.

[0009] In this regard, to overcome this drawback, a method for adjusting the heating parameters of a furnace, particularly by adjusting the variation of the electric power of the radiation source according to the thickness of the wall of the formed container, has been considered. This is especially true in European Patent EP1998950.

[0010] Document EP1998950 proposes a solution that uses vertically arranged thickness sensors to control material distribution standards. If the standards are deemed non-compliant, the power of a heating lamp located at the same height as the sensors is adjusted accordingly. Other lamps are not affected, and their adjustments are not corrected. Therefore, the thermal conditioning of the preform is not fully controlled.

[0011] Furthermore, such changes in furnace heating parameters may alter the heat conditioning of the preforms during production, potentially leading to finished containers that do not meet customer specifications. This non-compliance increases production costs and may necessitate equipment downtime, further exacerbating production expenses.

[0012] Another known document, EP2352633, discloses a method and apparatus for blow molding a container. First, a preform made of thermoplastic material is heat-treated in a heated section along a transport path. Then, under blow molding pressure, the preform is formed into a container inside a blow mold. Once the container has been blow-molded, the thickness of its walls is measured at at least one vertical position. A predefined value for the wall thickness is transmitted to a controller as a desired value, and the measured wall thickness is transmitted to the controller as an actual value. Based on the difference between the desired and actual values, the controller predefines the amount of at least one parameter affecting the blow molding process. More specifically, the controller predefines the amount of at least one parameter affecting the supply of blow molding gas. This parameter is predefined based on a simulation model of the blow molding process applied in the controller.

[0013] For example, similar methods are disclosed in other documents such as patent applications FR3131555, FR3131556, FR3131557, and US2007 / 029707.

[0014] However, none of these solutions are sufficient because they do not allow operators to optimize the heating phase in a direct and rapid manner. The information currently available is insufficient to correct defects while preventing other problems (such as issues at other levels within the container).

[0015] Therefore, there is a need to optimize this production method by simplifying the operation of different steps and the parameter settings of the equipment. In particular, there is a need for better, more targeted control of the heat treatment stage of the preform along the height of the container in order to shorten the time required to obtain the first container that meets the new specifications. It is also essential to be able to quickly correct defects detected during container production, thereby effectively adjusting different parameters to avoid impacting the production process. Summary of the Invention

[0016] Therefore, one of the objectives of this invention is to remedy these disadvantages by providing a method that allows for the alteration of the thermal conditioning of the preform and / or the forming parameters of the container without stopping the production equipment, thereby maintaining the quality of the produced container.

[0017] Therefore, according to the present invention, a method for producing containers from thermoplastic materials by blow molding or stretch blow molding of a preform is proposed, wherein the preform is first heated in an oven and then placed in a mold consisting of two halves defining a molding cavity, the preform being blow molded in the mold, possibly including a pre-blow molding step, the heating step, the preform, and the blow molding step being controlled by a control unit based on different control parameters, such as: the heating temperature of the preform in the oven, the blow molding pressure and / or the pre-blow molding pressure and / or the pre-blow molding flow rate and / or the speed of the stretch rod, the method being significantly characterized in that the method includes a preliminary calibration step, the calibration step including at least the following steps:

[0018] - Produce containers based on the first control parameters to produce containers that meet the requirements;

[0019] - During demolding corresponding to container production based on the first control parameters, the thickness of the container wall is measured at at least two different heights, the measured thickness corresponding to a reference thickness;

[0020] - Record the reference thickness in the storage unit;

[0021] - Modify each control parameter;

[0022] - After modifying each control parameter, measure the thickness of the container wall at at least two different heights upon demolding;

[0023] - For each modified control parameter, the thickness of the container wall at the time of demolding is recorded in the storage unit;

[0024] - Compare the recorded measured thickness with the reference thickness or theoretical thickness;

[0025] - Identify at least one control parameter that causes the maximum change in the thickness of the container wall.

[0026] Following the initial calibration steps, the method includes at least the following steps:

[0027] a) Measure the thickness of the container wall at at least two different heights upon demolding;

[0028] b) Compare the measured thickness with a specified value determined for each height of the container;

[0029] c) If the deviation between the measured thickness and the determined specified value is greater than a determined threshold, then at least one control parameter is modified. The modified one or more control parameters are selected from at least one control parameter that causes the greatest change in the thickness of the container wall during the calibration step and / or selected by calculating the theoretical effect of the change of each parameter on the thickness—the theoretical effect of the change of each parameter defines the theoretical thickness—and then selecting one or more parameters that cause the smallest deviation between the measured thickness and the theoretical value.

[0030] d) Repeat steps a) through c) until the deviation between the measured thickness and the determined specified value is less than the determined threshold.

[0031] Preferably, step c) includes at least the following steps:

[0032] - Define an optimal reference coefficient for each parameter, which is selected from the reference coefficients assigned to each thickness region of the container wall;

[0033] - Store the lower limit, upper limit, and range of each parameter;

[0034] - Calculate the adjustment of each parameter based on the predefined optimal reference coefficients;

[0035] - Calculate the theoretical correction value for each thickness region based on the calculated adjustments and range;

[0036] - Calculate the theoretical deviation of the container's thickness based on the theoretical correction values ​​calculated for each thickness region;

[0037] - Add the calculated theoretical deviation for each parameter; and

[0038] - Select at least one parameter that has the minimum cumulative deviation value.

[0039] In addition, prior to the step of selecting at least one parameter, the method includes a step of classifying the parameter based on the calculated theoretical deviation.

[0040] The parameters are graded in ascending order from the minimum cumulative deviation value to the maximum cumulative deviation value.

[0041] Preferably, after the adjustment calculation step and before the theoretical correction value calculation step, if the calculated adjustment is not within the upper and lower limits, an additional step of recalculating the adjustment is included.

[0042] In addition, the theoretical correction value that is calculated to be zero is excluded.

[0043] Furthermore, the theoretical deviations from the calculations are summed in absolute value form.

[0044] Preferably, the parameter selection step is performed after the new average thickness of each thickness region has been calculated and / or after the combination of deviations in each thickness region has changed.

[0045] In addition, the new average thickness for each thickness region is calculated at a predefined frequency.

[0046] Advantageously, the method according to the invention includes a modification step of predefined correction coefficients of the algorithm, such that the thickness measured after modifying one or more control parameters matches the theoretical thickness that should be obtained using the previously predefined coefficients.

[0047] According to a variant of the first embodiment, each control parameter is modified one by one during the calibration step.

[0048] According to a variant of the second embodiment, in the calibration step, each control parameter is modified simultaneously with at least one other control parameter.

[0049] In addition, during the calibration step, each control parameter is modified according to a predefined incremental value. Attached Figure Description

[0050] Further advantages and features of the method according to the invention will become clearer from the description of unique variant embodiments given by way of non-limiting example with reference to the accompanying drawings, wherein:

[0051] Figure 1 A schematic top view of a forming apparatus using the method according to the present invention.

[0052] Figure 2 To illustrate the supply Figure 1 A side view of the preform from the forming equipment.

[0053] Figure 3 To utilize Figure 1 A schematic diagram illustrating the different steps involved in container forming within a forming unit.

[0054] Figure 4 for Figure 1 A cross-sectional view of the heat treatment unit of the preform in the forming unit.

[0055] Figure 5 A schematic diagram illustrating the steps for measuring the wall thickness of a formed container at different heights.

[0056] Figure 6 The flowcharts are of different steps in the adjustment method of the container forming unit according to the present invention.

[0057] Figure 7 This is a flowchart illustrating different calibration steps of the adjustment method for the container forming unit according to the present invention. Detailed Implementation

[0058] In the following description of the method according to the invention for producing containers of thermoplastic material by blow molding or stretch blow molding of preforms, the same reference numerals denote the same elements. Different views are not necessarily drawn to scale.

[0059] In the subsequent description of this specification, elements having the same structure or similar function will be represented by the same reference numerals.

[0060] In the following description of this specification, the longitudinal, vertical, and transverse directions, as shown by the "L, V, T" three-dimensional coordinate system in the accompanying drawings, will be used in a non-limiting manner, wherein the longitudinal direction points along the direction of movement of the hollow body.

[0061] In the following text, the term "holding mechanism" refers to a gripping or supporting mechanism for hollow bodies that facilitates the transport of hollow bodies from one point to another.

[0062] Figure 1 The diagram shows a forming apparatus 1 for producing a final container 2 from a preform 3, made of a thermoplastic material such as recycled or non-recycled PET (polyethylene terephthalate) or PP (polypropylene). The preform 3 is typically made in advance by injection molding. These preforms 3 are usually cold when delivered to the inlet of the forming apparatus 1.

[0063] In the following description of this specification, the general term "hollow body" will be used to refer indiscriminately to the preform, the container during the forming process, or the final container.

[0064] The equipment 1 includes multiple processing stations. Among the processing stations typically equipped on such equipment 1, a heating station 4 and a forming station 5 are shown here, the forming station being equipped with multiple forming units 6 mounted on the periphery of a turntable 7.

[0065] It is understood that equipment 1 may include other processing stations not shown here, such as filling stations, labeling stations, and capping stations.

[0066] Non-limitingly, this is equipment 1 for continuously forming container 2. Therefore, the hollow body is in constant motion from the time it enters equipment 1 as a preform 3 until it leaves the equipment as the final container 2. This allows for higher productivity in the production of container 2. For this purpose, equipment 1 includes a plurality of transport devices for the hollow bodies, the specific description of which is given below.

[0067] In a variant, the invention is applicable to devices that operate sequentially.

[0068] The device 1 includes a first conveyor wheel 8 at the entrance of the heating station 4, a second conveyor wheel 9 at the exit of the heating station 4, and a third conveyor wheel 10 between the second conveyor wheel 9 and the forming station 5. Finally, a fourth conveyor wheel 11 is positioned at the exit of the forming station 5 for conveying the hollow body (here, the final container 2) to the conveyor 12 (e.g., a conveyor belt or pneumatic conveyor).

[0069] Hollow body along Figure 1 The defined production path, shown in bold, travels through device 1.

[0070] Hollow bodies, in the form of preforms 3, arrive sequentially via ramp 13, which feeds material to the first conveyor wheel 8, thus forming the first transport device for the hollow bodies. The first conveyor wheel 8 is in the form of a disc 14, the periphery of which is equipped with multiple support grooves, each support groove constituting a holding mechanism 15 for the hollow body. Therefore, the holding mechanism 15 is mounted on the disc 14.

[0071] Reference Figure 1 The disc 14 is mounted and rotates counterclockwise around the vertical central axis "A". Therefore, the retaining mechanism 15 moves around axis "A" along a closed loop.

[0072] The hollow body (here, preform 3) is conveyed along the production path from ramp 13 to the entrance of heating station 4. As the hollow body is conveyed to heating station 4, holding mechanism 15 continues to move along the closed loop in an unloaded manner to return to the starting point of holding mechanism and load the next hollow body. Figure 1 The useful portions of the loop shown in bold form the open segments of the production path.

[0073] In a variant of the invention not shown, the holding mechanism of the first conveyor wheel is constituted by a hollow gripper.

[0074] The hollow body (still in the form of preform 3) is then conveyed through heating station 4 to heat it before blow molding or stretch blow molding operations. For this purpose, heating station 4 is equipped with heating devices such as lamps or diodes 16 that emit electromagnetic radiation to heat the material of preform 3, for example, emitting infrared radiation with a predefined power and spectrum, which interacts with the material of preform 3 to heat it. The power and spectrum are controlled by electronic control unit 17.

[0075] Obviously, lamp 16 can be replaced by any other heating device known to those skilled in the art, such as a VCEL diode emitting monochromatic or quasi-monochromatic electromagnetic radiation in the infrared band, or a microwave source, without departing from the scope of the invention.

[0076] Heating station 4 is also equipped with ventilation devices (not shown), such as fans or forced ventilation systems (also known as "airblades" in English). These ventilation devices participate in the temperature regulation of the hollow body. The ventilation devices include airflow control devices.

[0077] The parameters of each heating element are easily controlled to heat different parts of the hollow body to varying degrees. The parameters of each activated heating element, especially its height, are automatically controlled, for example, by an electronic control unit 17.

[0078] Each hollow body is carried by a rotating chuck (also called a turntable), which forms a holding mechanism 18 associated with the heating station 4. This holding mechanism 18 typically includes: a chuck (not shown) that is fitted around the neck of the hollow body; and a pinion that meshes with a fixed rack extending along the production path, thereby ensuring that the hollow body maintains a substantially uniform rotation during its heating process.

[0079] In this variant, each hollow body is driven to rotate by a separate electric motor. This rotation is controlled by an electronic control unit 17.

[0080] The retaining mechanism 18 is carried by a closed chain, which is driven clockwise by a drive wheel 19 that is rotatably mounted about the vertical axis "B". Therefore, this chain of the moving retaining mechanism 18 constitutes a second transport device for the hollow body. Each retaining mechanism 18 is moved continuously along the closed loop, i.e., without interruption. Figure 1 The useful portions of the loop shown in bold form the open segments of the production path.

[0081] At the exit of heating station 4, the hollow body (here, the heated preform 3) is then transferred to the second conveyor wheel 9, which has a similar structure to the first conveyor wheel 8. This second conveyor wheel 9 constitutes the third transport device for the hollow body.

[0082] After the hollow body is transferred to the second transfer wheel 9, each holding mechanism 18 of the heating station 4 continues its path along the closed loop in an unloaded manner to return to the starting point of the holding mechanism and load a new hollow body.

[0083] The second transmission wheel 9 is presented in the form of a disc 20, the periphery of which is equipped with multiple support grooves, each support groove constituting a hollow holding mechanism 21. Therefore, the holding mechanism 21 is mounted on the disc 20.

[0084] See Figure 1 The disk 20 is mounted in a counterclockwise direction around the vertical central axis "C". Therefore, the retaining mechanism 21 moves around the axis "C" along a closed loop.

[0085] The hollow body is transferred along the production path from the outlet of the heating station 4 to the third transfer wheel 1. As the hollow body is conveyed to the third transfer wheel 1, the associated holding mechanism 23 continues to move along the closed loop in an unloaded manner to return to the starting point of the holding mechanism and load a new hollow body. Figure 1 The useful portions of the loop shown in bold form the open segments of the production path.

[0086] At the exit of the second conveyor wheel 9, the hollow body (here, the heated preform 3) is transferred to the third conveyor wheel 1. The third conveyor wheel 1 constitutes the fourth transport device for the hollow body.

[0087] Therefore, the third transmission wheel 10 is presented in the form of a central hub, around which are equipped a plurality of arms 22 radiating outwards. Each arm 22 has a clamp at its free end, which constitutes a holding mechanism 23 for the hollow body. See also Figure 1 The hub is mounted rotating clockwise around the vertical central axis "D". Therefore, the retaining mechanism 23 moves around axis "D" along a closed loop.

[0088] Arm 22 is easily pivotable about a vertical axis relative to the hub or extends in a telescopic manner to allow for changes in the spacing between the two hollow bodies.

[0089] Therefore, the hollow body is conveyed from the conveyor wheel 9 to the forming station 5 along the production path. When the hollow body is conveyed to the forming station 5, the associated holding mechanism 23 continues to move along the closed loop in an unloaded manner to return to the starting point of the holding mechanism and load a new hollow body. Figure 1 The useful portions of the loop shown in bold form the open segments of the production path.

[0090] As the hollow body is conveyed to forming station 5, each hollow body (in this case, in the form of a heated preform 3) is inserted into one of the forming units 6 of forming station 5. See also Figure 1 The molding unit 6 is driven to move continuously and regularly in a counterclockwise direction around the vertical axis "E" of the turntable 7. Therefore, the molding unit 6 moves around the axis "E" along a closed loop.

[0091] Therefore, during the forming of the hollow body, it is conveyed from the third conveyor wheel 10 to the fourth conveyor wheel 11. During the conveying of the hollow body, it is transformed into the final container 2 by the forming device shown in the schematic diagram below.

[0092] When container 2 is transferred to the fourth transfer wheel 11, the associated molding unit 6 continues its movement along the closed loop in an unloaded manner to return to the starting point of the molding unit and load a new hollow body. Figure 1The useful portions of the loop shown in bold form the open segments of the production path.

[0093] At the exit of forming station 5, the hollow body is transferred to the fourth conveyor wheel 11 in the form of the final container 2. The fourth conveyor wheel has the same structure as the conveyor wheel 10. The fourth conveyor wheel 11 constitutes the sixth transport device for the hollow body.

[0094] Therefore, the fourth conveyor wheel 11 is presented in the form of a disc 24, the outer periphery of which is equipped with multiple slots, each slot forming a hollow retaining mechanism 25. Thus, the retaining mechanism 25 is mounted on the disc 24.

[0095] See Figure 1 The disc 24 is mounted rotating clockwise around the vertical central axis "F". Therefore, the retaining mechanism 25 moves around axis "F along a closed loop.

[0096] Therefore, the hollow body is conveyed along the production path from the exit of forming station 5 to conveyor 12. As the hollow body is transferred to conveyor 12, the associated holding mechanism 25 continues its movement along the closed loop in an unloaded manner to return to the starting point of the holding mechanism and load a new hollow body. Figure 1 The useful portions of the loop shown in bold form the open segments of the production path.

[0097] In a variant of the invention not shown, the holding mechanism of the fourth transfer wheel is constituted by clamps.

[0098] Therefore, refer to Figure 3 Each hollow body undergoes different processing steps during its journey along the production path, especially the heating step in heating station 4 and the subsequent forming step in forming station 5.

[0099] Typically, this forming equipment 1 can easily produce final containers 2 of different sizes. For this purpose, the forming unit 6, located at the forming station 5, is equipped with interchangeable molds. Therefore, the shape of the final container produced can be modified.

[0100] Depending on the specifications of the final container selected, equipment 1 will be supplied with preforms 3 having suitable inherent properties.

[0101] like Figure 2As shown, the preform 3 has a cylindrical body 26, the tubular wall 27 of which is closed at one axial end by a bottom 28, and the body is extended at the other end by a similarly tubular neck 29. The neck 29 is typically injection molded, thus giving the neck its final shape, while the body 26 of the preform 3 is designed to undergo relatively large deformation during the molding process to form the final container 2. The preform 3 is here made of recycled or non-recycled "PET" or "PP" material, meaning that the preform 3 is made by molding a single thermoplastic material having a defined composition.

[0102] Among the properties that are prone to change from batch to batch of preform, attention should be paid to, for example, the thickness of the wall 27 of preform 3, or the absorption rate of infrared radiation by the thermoplastic material.

[0103] This invention proposes a control method for a hollow body forming device 1. This method enables automatic adjustment of the processing parameters of the processing station based on measurements taken directly on the container at the outlet of the forming station, such as... Figure 5 As illustrated schematically, it can be observed that the thickness of the container is measured at at least two different heights using any suitable method known to those skilled in the art, such as an interferometric sensor.

[0104] Therefore, the method according to the invention involves measuring the thickness of the container wall at at least two different heights during demolding (step 100); then comparing the measured thickness with a specified value determined for each height of the container (step 200); if the deviation between the measured thickness and the specified value is greater than a determined threshold, then modifying at least one control parameter (step 300), said one or more control parameters being selected at least by calculating the theoretical effect of the change of each parameter on the thickness and then selecting one or more parameters that cause the smallest deviation between the measured thickness and the theoretical value; repeating the above steps until the deviation between the measured thickness and the specified value is less than the determined threshold.

[0105] More specifically, refer to Figure 6 The modification step (300) of at least one control parameter includes at least the following steps:

[0106] - Define (310) the optimal reference coefficients for the thickness regions of each wall of the container for each parameter;

[0107] -Store (320) the lower limit, upper limit, and range of each parameter;

[0108] - Calculate the adjustment of each parameter (330) based on the predefined optimal reference coefficient;

[0109] -If the calculated adjustment is not within the lower or upper limit, the adjustment may be recalculated (340);

[0110] -Calculate the theoretical correction value (350) for each thickness zone based on the range and calculation adjustments;

[0111] - Calculate the theoretical deviation (360) of the container thickness based on the theoretical correction value calculated for each thickness region.

[0112] - Add the calculated theoretical deviation (370) for each parameter; and

[0113] - Select at least one parameter (380) with the minimum cumulative deviation value.

[0114] Prior to the step of selecting at least one parameter, the procedure includes classifying the parameters according to the calculated theoretical deviation. The parameters are classified in ascending order from the minimum cumulative deviation value to the maximum cumulative deviation value.

[0115] Preferably, theoretical correction values ​​that are calculated to be zero are excluded, and the calculated theoretical deviations are added together in absolute form.

[0116] Advantageously, the parameter selection step is performed after the new average thickness of each thickness region is calculated and / or after the combination of deviations in each thickness region changes. In this way, the adjustment according to the invention enables the real-time correction of possible deviations without stopping the production equipment, thereby maintaining the quality of the produced containers. The new average thickness of each thickness region is calculated at a predefined frequency. For example, for every m bottles removed from the mold and whose thickness has been measured, the new average thickness of each thickness region is calculated, where m is an integer contained between 30 and 80. For example, m equals 50. However, it is obvious that m can be any integer without exceeding the scope of the invention.

[0117] It can be observed that if, after n corrections to the selected parameter (where n is a predefined number greater than or equal to 1), the deviation between the measured thickness and the determined specified value exceeds a determined threshold, a new parameter is selected. The selected new parameter i+1 corresponds to the grading parameter i+1.

[0118] Furthermore, advantageously, the optimal reference coefficient assigned to each thickness region of the container wall is variable, and this reference coefficient is calculated each time the parameters are modified. The calculation of the optimal reference coefficient assigned to each thickness region of the container wall is obtained by calculating the actual impact of adjustments on each thickness region of the container wall.

[0119] Preferably, the calculation includes at least the following steps:

[0120] - The offset of the blow molding and / or heating parameters is calculated by multiplying the initial coefficient by the thickness drift;

[0121] - Determine the new coefficients based on the offset applied to the parameters and the actual impact on the material distribution measurement for each thickness region.

[0122] It can be observed that this variable optimal reference coefficient allows these coefficients to be customized according to the environment, machine, resin of the preform, etc.

[0123] The parameters consist of heating unit parameters, such as heating power at a defined height of the preform and / or machine cycle time that changes the travel speed of the preform in the heating unit and / or ventilation power that ensures some of the heat is dissipated from the heating unit and / or a preferred heating temperature profile, and / or the parameters consist of forming unit parameters, such as pre-blow molding pressure value and / or pre-blow molding start point and / or pre-blow molding flow rate and / or tension bar speed and / or blow molding pressure.

[0124] Particularly advantageously, to enable rapid and efficient parameter setting in the adjustment method according to the invention, the method advantageously includes a parameter pre-selection step from a GUI (i.e., abbreviation for "Graphical User Interface"), wherein one or more parameters are associated with a predefined production configuration. For this purpose, the device includes at least a display screen (touchscreen or non-touchscreen, not shown) connected to the device's control unit.

[0125] For example, a GUI includes at least three predefined production configurations: so-called method configurations, so-called application configurations, and so-called option configurations.

[0126] The method configuration includes at least three sub-configurations: namely, the so-called HR sub-configuration, the so-called CHP sub-configuration, and the so-called STD sub-configuration, wherein one or more parameters are associated with each sub-configuration.

[0127] The application configuration includes at least three sub-configurations: namely, the so-called non-gas product sub-configuration, the so-called carbonic product sub-configuration, and the so-called other product sub-configuration, wherein one or more parameters are associated with each sub-configuration.

[0128] The option configuration includes at least three sub-configurations: a so-called box-shaped bottom sub-configuration, a so-called reusable sub-configuration, and a so-called petal-shaped bottom sub-configuration, wherein one or more parameters are associated with each sub-configuration.

[0129] Obviously, the GUI may include other predefined configurations and / or sub-configurations without exceeding the scope of this invention.

[0130] Additionally, refer to Figure 7 According to a fundamental feature of the adjustment method of the present invention, the method includes a so-called calibration step, which includes the following steps.

[0131] The calibration step includes a first production step (400) of producing a container that meets the requirements from predefined first control parameters. In a second step (410), at the time of demolding corresponding to the container production based on the first control parameters, the thickness of the container wall is measured at at least two different heights, the measured thickness corresponding to a so-called reference thickness, and then in step (420), the reference thickness is recorded in a storage unit not shown in the figure.

[0132] Subsequently, each control parameter is modified in step (430). According to the first embodiment, each control parameter is modified one by one. In the second embodiment, each control parameter is modified simultaneously with at least one other control parameter. Additionally, in this calibration step, each control parameter is modified according to a predefined incremental value.

[0133] Subsequently, in step (440), after modifying each control parameter, the thickness of the container wall is measured at at least two different heights upon demolding, and steps (410) to (440) are repeated until all parameters have been modified at least once. Therefore, for each modified control parameter, the thickness of the container wall at demolding is recorded (step 420) in the storage unit.

[0134] In step (450), the recorded measured thickness is then compared with the reference thickness, and finally, in step (460), at least one control parameter that causes the maximum change in the thickness of the container wall is determined.

[0135] According to one embodiment variant, in the thickness comparison step (450), the recorded measured thickness is compared with a so-called theoretical thickness, which is obtained by calculating the theoretical effect of the change of each parameter on the thickness, as described above.

[0136] Finally, it is clear that the examples described above are merely illustrative and should not be considered as limiting the scope of application of this invention under any circumstances.

Claims

1. A method for producing containers of thermoplastic material by blow molding or stretch blow molding of a preform, wherein the preform is first heated in an oven and then placed in a mold consisting of two halves defining a molding cavity, the preform being blow molded in the mold, possibly including a pre-blow molding step, the heating step, the preform heating step, and the blow molding step being controlled by a control unit based on different control parameters, such as: the heating temperature of the preform in the oven, the blow molding pressure and / or the pre-blow molding pressure and / or the pre-blow molding flow rate and / or the speed of the stretch rod, characterized in that... The method includes a preliminary calibration step, which includes at least the following steps: -i) Produce containers based on the first control parameters to produce containers that meet the requirements; -ii) When demolding a container produced based on the first control parameter, the thickness of the container wall is measured at at least two different heights, the measured thickness corresponding to a reference thickness; -iii) Record the reference thickness in the storage unit; -iv) Modify each control parameter; -v) After modifying each control parameter, measure the thickness of the container wall at at least two different heights upon demolding; -vi) For each modified control parameter, record the measured thickness of the container wall at the time of demolding in the storage unit; -vii) Compare the recorded measured thickness with the reference thickness or theoretical thickness; -viii) Determine at least one control parameter that causes the maximum change in the thickness of the container wall.

2. The method according to claim 1, characterized in that, Following the initial calibration steps, the method includes at least the following steps: a) Measure the thickness of the container wall at at least two different heights upon demolding; b) Compare the measured thickness with a specified value determined for each height of the container; c) If the deviation between the measured thickness and the determined specified value is greater than a determined threshold, then at least one control parameter is modified. The modified one or more control parameters are selected from at least one control parameter that causes the greatest change in the thickness of the container wall during the calibration step and / or selected by calculating the theoretical effect of the change of each parameter on the thickness—the theoretical effect of the change of each parameter defines the theoretical thickness—and then selecting one or more parameters that cause the smallest deviation between the measured thickness and the theoretical value. d) Repeat steps a) through c) until the deviation between the measured thickness and the determined specified value is less than the determined threshold.

3. The method according to claim 2, characterized in that, Step c) includes at least the following steps: - Define an optimal reference coefficient for each parameter, which is selected from the reference coefficients assigned to each thickness region of the container wall; - Store the lower limit, upper limit, and range of each parameter; - Calculate the adjustment of each parameter based on the predefined optimal reference coefficients; - Calculate the theoretical correction value for each thickness region based on the calculated adjustments and range; - Calculate the theoretical deviation of the container's thickness based on the theoretical correction values ​​calculated for each thickness region; - Add the calculated theoretical deviation for each parameter; and - Select at least one parameter that has the minimum cumulative deviation value.

4. The method according to claim 3, characterized in that, Prior to the step of selecting at least one parameter, the method includes a step of classifying the parameter based on the calculated theoretical deviation.

5. The method according to claim 4, characterized in that, The parameters are graded in ascending order from the minimum cumulative deviation value to the maximum cumulative deviation value.

6. The method according to any one of claims 3 to 5, characterized in that, If the calculated adjustment is not within the upper and lower limits after the adjustment calculation step and before the theoretical correction value calculation step, the method includes an additional step of recalculating the adjustment.

7. The method according to any one of claims 3 to 6, characterized in that, Theoretical correction values ​​that are calculated to be zero are excluded.

8. The method according to any one of claims 3 to 7, characterized in that, The theoretical deviations from the calculations are summed in absolute form.

9. The method according to any one of claims 3 to 8, characterized in that, The parameter selection step is performed after the new average thickness for each thickness region has been calculated and / or after the combination of deviations for each thickness region has changed.

10. The method according to claim 9, characterized in that, The new average thickness for each thickness region is calculated at a predefined frequency.

11. The method according to any one of claims 3 to 10, characterized in that, The method includes a modification step of predefined correction coefficients of the algorithm, such that the thickness measured after modifying one or more control parameters matches the theoretical thickness that should be obtained using the previously predefined coefficients.

12. The method according to any one of claims 1 to 11, characterized in that, In the calibration process, each control parameter is modified one by one.

13. The method according to any one of claims 1 to 11, characterized in that, In the calibration step, each control parameter is modified simultaneously with at least one other control parameter.

14. The method according to any one of claims 1 to 13, characterized in that, In the calibration step, each control parameter is modified according to a predefined incremental value.

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