TESTING PROCEDURES AND TESTING SYSTEM

Description

Subject area of ​​the invention

[0001] The present invention relates to a testing method and a corresponding testing system. Specifically, the present invention relates to a testing method and a corresponding testing system that are particularly suitable for verifying the properties of workpieces required in connection with the manufacture of beverage bottles and other similar containers. Examples of such items include so-called "preforms," ​​i.e., preforms or blanks from which beverage bottles are manufactured in a separate work process, as well as closures for the beverage bottles and all items required in the process of manufacturing beverage bottles. The present invention specifically relates to a method and a corresponding system for testing the preforms, in which an image of each preform is taken by means of a receiving device during transport and then checked by a testing device.

[0002] For the sake of completeness, it should be noted here that the term "preform," as used below, essentially refers to all items used in the manufacture of beverage bottles and similar containers, as well as all other similar items that are similar to conventional preforms in terms of production process, structure, and / or appearance. Examples of such items include syringes (for use in medical or laboratory settings), test tubes, cuvettes, etc. State of the art

[0003] In the production of containers, especially beverage bottles, preforms are generally manufactured first, which are then further processed into the finished containers. These preforms are typically made of plastic, primarily PET (polyethylene terephthalate). Other similar items, such as the syringes, test tubes, cuvettes, etc., described above, as well as plastic caps (closures) for beverage bottles, are manufactured in a similar manner.

[0004] Because manufacturing processes are energy-intensive and because production processes usually have to be stopped when defective preforms are discovered (resulting in higher costs), manufactured preforms and other preform-like items mentioned above are generally inspected for defects before being sent for further processing. Possible defects in manufactured preforms include, in particular, inaccurate dimensions, inaccurate shape, wall thicknesses that are too thin or too thick, pinholes, burn marks, the presence of foreign matter and / or bubbles, or defective color.

[0005] Furthermore, certain preforms, as well as the closures, feature a so-called barrier layer. In fact, the materials from which preforms are made are usually not completely impermeable. In other words, over time, ingredients can escape from the containers, which can lead to denaturation of the contents. For example, gas from carbonated beverages escapes through the walls of the PET bottle or through the contact point between the bottle and the closure, causing the beverage to develop a stale taste over time. Barrier layers are therefore applied to solve this problem and prevent the contents trapped in a container from escaping. Conversely, barrier layers are also used to prevent substances from penetrating the interior of the container.For example, an oxygen-impermeable barrier layer can be used to protect sensitive products inside the container from oxidation. Defects can also occur in this type of barrier layer, and these should be detected as reliably as possible.

[0006] Last but not least, many applications also require the accurate determination of the number of items to be inspected or inspected (including the number of defective and correct items). Since manual counting is very time-consuming, automated counting methods are used to precisely determine the number of required workpieces.

[0007] Various systems and methods for inspecting preforms and other similar items for such defects are known. In particular, inspection using digital scanning devices has become established. In this method, preforms are either moved past a scanning device so that one or more images of each preform can be taken, or the preforms to be inspected can remain stationary while the scanning device moves. In both cases, an electronic processing unit compares the resulting images with a reference image and determines whether the respective preform is free of defects or exhibits certain flaws. Non-compliant comparison values ​​lead to the elimination of the preform in question. The items can also be counted simultaneously.

[0008] A purely visual inspection of barrier layers does not yield satisfactory results, as these layers are usually transparent and therefore not visible, or not clearly visible, in daylight. Barrier layers in bottle closures also require special testing, as they are often inaccessible to conventional optical inspection due to the closure material. For this reason, infrared cameras, for example, are used to test barrier layers, enabling the detection of defects even in transparent or optically blocked layers.

[0009] Most known systems and methods are essentially based on the order and orientation of the objects to be inspected, as an image of each object in a desired position is to be created. However, there are also systems and methods in which the objects to be inspected cannot be examined in an ordered manner. Such systems and methods, as described, for example, in document CH 707 559 A2, are currently only known for checking color properties. Summary of the invention

[0010] It is therefore an object of the invention to propose a testing method and a testing system suitable for carrying out this testing method, in which the disadvantages of the known methods and systems described above are completely overcome or at least greatly reduced.

[0011] In particular, one object of the invention is to propose a testing method and the corresponding testing system that ensure reliable, fast, and very simple automatic quality testing of an entire series and the counting of the number of workpieces using a space-saving system. Furthermore, the installation of this system on existing manufacturing machines should also be very simple.

[0012] According to the present invention, these objectives are achieved in particular by the elements of the two independent claims. Further advantageous embodiments are also apparent from the dependent claims and the description.

[0013] In particular, these objectives of the invention are achieved by the following method for testing the workpieces, which consist of a base body on which a barrier layer is optionally applied at least partially and are intended for the production of containers, in particular beverage bottles, wherein the workpieces are transported by a transport device into a receiving vessel, and wherein an image of the workpieces is taken by means of a receiving device and transmitted to a processing device for testing, wherein the image is taken between leaving the transport device and being inserted into the receiving vessel, wherein the image is an optical coherence tomogram or a multispectral image, and wherein the image is processed by the processing device in such a way as tothat the condition of the base body and the condition of the barrier layer optionally applied at least partially to the base body are checked in order to detect the defective workpieces, wherein the condition of the base body includes its dimensions, shape, wall thickness and / or length of a injection point and the condition of the barrier layer includes the thickness of the barrier layer.

[0014] It should also be noted that there can be workpieces without a barrier layer. Furthermore, if a barrier layer is present, it can be located either on the outside (i.e., the surface facing outwards) or on the inside (i.e., the surface facing inwards) of the workpiece's base body. Finally, it is also conceivable that the barrier layer is located between two substrate layers of the base body (i.e., neither outside nor inside).

[0015] The advantage of this invention lies particularly in the fact that defective workpieces, namely preforms or closures, but also other similar objects, can be easily detected with regard to a whole range of defects, including defects in the barrier layer, and especially without the need for special alignment. Furthermore, hardly any modifications to existing production facilities are required.

[0016] However, it should be mentioned at this point that the present invention relates not only to the inventive testing method described above, but also to a corresponding testing system according to the independent apparatus claim.

[0017] The invention is illustrated by several embodiments. The individual technical features of one embodiment can also be used in combination with another embodiment, offering the advantages described. Therefore, the description of the technical features according to the invention is not limited to the respective embodiment. Brief description of the drawings

[0018] Embodiments of the present invention are described below by way of example. These examples are illustrated by the following accompanying figures: Figure 1 schematically shows a side view of a testing system according to a first embodiment of the present invention. Figure 2 This shows in Figure 1 Illustrated testing system in a perspective view from the front. Figure 3 schematically shows a side view of a testing system according to a second embodiment of the present invention. Figure 4 This shows in Figure 2 Illustrated testing system in a perspective view from the front. Figure 5a and 5b show a schematic representation of a possible image which occurs during the inspection of preforms by a receiving device in the testing system. Figure 1 or Figure 3 is made and evaluated by a processing unit. Figure 6 Figure 1 schematically shows a perspective view from the front of a testing system according to a further variant of the second embodiment of the present invention. Figure 7 shows a schematic representation of a possible image which occurs during the inspection of preforms by a receiving device in the testing system. Figure 6 is made and evaluated by a processing unit. Figure 8 Figure 1 schematically shows a perspective view from the front of a testing system according to yet another variant of the second embodiment of the present invention. Figure 9 shows a schematic representation of a possible image which occurs during the inspection of preforms by a receiving device in the testing system. Figure 8 is made and evaluated by a processing unit. Detailed description of the embodiments

[0019] In Figure 1 and Figure 2A first embodiment of a testing system 1 according to a first embodiment of the present invention is schematically illustrated. As already mentioned several times, the testing system according to the invention can advantageously be used for testing preforms for the production of plastic beverage bottles. For the sake of simplicity, the following description will always refer to the testing of preforms, unless specific reference is made to the particularities of testing other workpieces. However, it is self-evident that the described elements of the testing system and the testing method according to the invention also apply to the testing or counting of all other corresponding workpieces (e.g., closures).

[0020] The plastic preforms 2 (e.g., made of PET) produced in a conventional manufacturing machine or system are transported by the transport device 3 to a receiving vessel 4. This transport is essentially random. By this term, we mean an arrangement of the preforms that arises "naturally," i.e., without prior ordering or sorting. Of course, it is also conceivable that the preforms 2 are ordered during transport by the transport device 3, i.e., that they have a predetermined orientation upon exiting the transport device 3. The present invention naturally also unfolds its advantages in such a case.

[0021] Furthermore, it is conceivable that the preforms 2, after leaving the transport device 3, are not transferred to a receiving vessel 4, but to another transport device. This is not part of the claimed invention. However, the further method also works in the same way in this alternative case. The transport device 3 in the Figure 1 and 2 The diagram shows a conventional conveyor belt with a drive roller 3a, which is driven by a drive unit (not shown). However, it is of course possible to use a different suitable transport device instead of a conveyor belt, for example a vacuum conveying system or a gripping device.

[0022] After leaving the transport device 3, the transported preforms 2 enter a receiving container 4, as shown schematically. This receiving container 4 can be a simple cardboard box, which is closed and carried away by the operator after being filled, or a more complex receiving container that can be used automatically or semi-automatically for packaging and storing the preforms 2. Instead of the receiving container 2, another conveyor belt, a so-called cooling belt, or another similar device can be used. This is particularly useful when the inspected preforms 2 require further inspection and / or treatment.

[0023] As shown by the Figure 1 and 2As can be clearly seen, the preforms 2 are disordered during transport on the transport device 3 and during insertion into the receiving vessel 4. In other words, the preforms 2 are brought directly from the manufacturing machine onto the transport device 3 without any alignment or ordering and transported in this state until they reach the receiving vessel 4. However, if, as mentioned above, the preforms 2 emerge from the manufacturing machine in an ordered manner, it is also possible that they will be transported in this ordered manner on the transport device 3. The present invention would clearly function perfectly well even in such a situation, but it is by no means dependent on such alignment or ordering.

[0024] On the right side in Figure 1 or in Figure 2A recording device 6 is shown. This could, for example, be a conventional digital (or even analog) camera. According to the invention, however, the recording device 6 is a device that enables the recording of so-called optical coherence tomograms or the recording of so-called multispectral images. Such a device (e.g., a multispectral camera) is used according to the invention for testing the properties of the barrier layer in the preforms. .

[0025] Optical coherence tomography (OCT) is an imaging technique that uses an interferometer to measure the distance of scattering materials with low coherence length light. The object under investigation is scanned point by point. Specifically, this OCT technology allows the visualization of surface topography and internal structures. Broadband superluminescent diodes and laser light sources in the near-infrared wavelength range between 600 and 1700 nm are used as light sources. Low-coherence light in the aforementioned wavelength range is shone into the object being examined, and the backscattered light is analyzed. These images allow for the calculation of volume information (i.e., tridimensional information), which can be used, for example, to determine the thickness of a barrier layer.

[0026] Multispectral images are typically digital image data composed of multiple spectral channels. Specifically, they contain information about reflected or emitted electromagnetic radiation of different wavelengths. To achieve this, the same images are captured with responses to different colors, from which a unified image is later assembled. Such multispectral images are particularly well-suited for determining the thickness of the barrier layer, among other applications.

[0027] A person skilled in the art will readily be aware of other recording devices that can be used instead of the conventional digital camera, or instead of a device for generating optical coherence tomograms or a multispectral camera. However, this is not the subject of the invention. The recording device 6 is connected to a processing device (not shown).

[0028] The preforms 2, which are generally transported in a disordered manner on the transport device 3, also leave this transport device 3 in a disordered manner and then fall (due to the force of gravity) into the receiving vessel 4. At this moment, i.e., precisely between leaving the transport device 3 and falling into the receiving vessel 4, the receiving device 6 takes an image of the falling preforms 2 and transmits it to the processing device for inspection. Depending on the selection of the receiving device 6, either an optical coherence tomogram or a multispectral image is acquired. Combinations of these different images are also conceivable.It is also conceivable to take a series of images instead of a single one, so that the image in which at least a representative number of the preforms to be tested have the optimal position can be selected for evaluation. The total number of preforms can then be deduced from this representative number.

[0029] Instead of or in addition to checking the preforms, their number can also be determined. For this, the captured images are also evaluated by the evaluation unit, using different algorithms. In this way, a very precise and simple count can be achieved.

[0030] Behind the falling preforms 2 (as seen from the receiving device 6) during the Figure 1 and 2In the first embodiment shown, a screen or display device 5 is provided, the function of which will be explained later. However, it is also possible to implement this first embodiment of the present invention without the screen 5.

[0031] In Figure 3 and Figure 4 A schematic diagram illustrates a system 1 for testing preforms according to a second embodiment of the present invention. Identical parts and devices that correspond to those of the first embodiment and have the same function are numbered with the same reference numerals.

[0032] The preforms 2, which are transported in a generally disordered manner on the transport device 3, also leave this transport device 3 in a disordered manner and then land on a plate 5', over which they can slide (particularly due to the action of gravity) to be inserted into the receiving vessel 4. While sliding on the plate 5', the preforms 2 are still disordered, but all lie in the plane of the plate 5'. During this sliding on the plate 5', i.e., between leaving the transport device 3 and falling into the receiving vessel 4, the receiving device 6 takes an image (i.e., a photograph, an optical coherence tomogram, or a multispectral image) of the passing preforms 2 and transmits it to the processing device for inspection.It is also conceivable to take a series of several images instead of a single image, so that the image taken in which the preforms 2 to be tested have the optimal position can be selected for evaluation.

[0033] In the Figures 5a and 5b A purely schematic illustration depicts a system according to the first or second embodiment of the invention. Images of several preforms can be identified in this illustration. The background of the illustration can be seen in Figure 5a the screen 5 and in Figure 5bThe plate 5' can be seen. In Figures 5a and 5b, the images of preforms bear the reference number 7 (instead of 2) so that they can be distinguished from the "real" preforms. That is, the preforms numbered 7 represent those preforms that are representative of all preforms. The preforms 7 are located in an area in front of the screen 5 that is suitable for obtaining images suitable for evaluation with the processing device. This area is defined, for example, by a distance to the recording device 6.

[0034] In the exemplary image according to Figure 5aIt can be seen that the preforms 7 are disordered. In this sense, the image of certain preforms 7 may be incomplete, as they are wholly or partially obscured by other preforms 7. Furthermore, it can be seen that some preforms 7 in the image are positioned at an angle to the image screen 5 (or to the plane perpendicular to the viewing direction of the camera 6), meaning that only a portion of their surface is visible in the image. In the extreme case, it is conceivable that a preform 7 in free fall could be located directly in the viewing direction of the camera 6. In this situation, the corresponding image would only show the head or base of the preform.

[0035] As in Figure 5bAs can be seen, in the case of a plate 5', all preforms 7 lie in the same plane, i.e., in the plane of the plate 5', so that they are always at an optimal angle to the recording device 6. This ensures that a large number of recorded images of the preforms 7 can be used for evaluation.

[0036] The screen 5 can be made of different materials, for example, plastic or textile. The panel 5' can also be made of many materials, for example, plastic, glass, or metal, or even a combination of materials.

[0037] For securing or correctly positioning the screen 5 or panel 5', special fastening devices can be provided (not shown), for example, racks or hanging hooks. In particular, it is possible and advantageous to provide such fastening devices with which the panel 5' can be attached directly to the transport device 3.

[0038] In Figures 3 and 4 A light source 8 is also visible behind the plate 5'. It is practical if the light source 8 is positioned so that the preforms 2 sliding on the plate 5' are illuminated through the transparent area of ​​the plate 5'. Thanks to the light source 8, the preforms 1 can always be illuminated from behind with respect to the receiving device 6. Such a light source 8 is also conceivable for an embodiment with a screen 5.

[0039] However, it should be noted that in a testing system for inspecting closures or other opaque or semi-opaque (i.e., non-transparent) workpieces and other objects, a light source (not illustrated) should be provided above the plate 5' so that the workpieces to be inspected can also be illuminated from above and not only from below. Of course, several such lights can be used, and it is also possible to partially or completely omit the rear illumination (i.e., the light source 8).

[0040] The acquired images (an optical coherence tomogram or a multispectral image) are transmitted from the acquisition unit 6 to the processing unit. This processing unit then evaluates the images to check the preforms.

[0041] When inspecting preforms for defects (for example, inspecting for defective dimensions, shapes, wall thicknesses, the presence of pinholes, burns, foreign matter, bubbles, excessively long injection points (so-called gates), etc.), one or more preforms 7 are first identified in the respective image being evaluated. These preforms were oriented during the image capture in such a way that their entire length is visible as completely as possible. These preforms 7 can then be compared, for example, with a reference image of a correct preform to check the quality of the preform 7 under inspection with respect to the desired parameter(s). According to the invention, the preforms that are correctly positioned with respect to their location, angular position, overlapping parts, etc., are automatically detected in the captured image so that they can be compared with a reference image.

[0042] In the case of the first embodiment with an image screen 5, for example, those preforms 7 are identified which, during free fall and image capture, were oriented at such an angle to the image screen 5 that their entire length can be seen as completely as possible in the image. Specifically, this means that those preforms 7 are to be identified whose longitudinal axis (at the moment the image is captured) is as parallel as possible to the image screen 5. Figure 5a For example, preforms 7 could be selected which bear the reference numbers.

[0043] In the case of the second embodiment with a plate 5', for example, those preforms 7 are identified which are completely captured by the image, that is, which lie entirely within the image area and are not covered by other preforms. Deviations from the reference image with respect to one or more parameters could directly indicate defects in the preform series. Instead of a reference image in the strict sense, however, it is also conceivable to use certain characteristic reference measurements, which are then compared with the corresponding measurements of the recorded preforms under test.

[0044] This procedure may not allow all preforms 7 to be inspected, as statistically, some preforms 2 may be positioned during their slide between the transport device 3 and the receiving vessel 4 in such a way that their image cannot be properly evaluated as described. In extreme cases, it is also conceivable that not a single image of preforms 2 in a recording is oriented in such a way that its evaluation by the processing device is possible. However, these disadvantages can surprisingly be accepted, as it has been found that the same defects often occur in an entire series (or in a part of the series), so that inspecting a certain number of preforms 7 is quite sufficient to draw relevant conclusions about the quality of the entire series.It is particularly important to note that this method allows for continuous inspection, leading to significantly more accurate results compared to trial inspections. Furthermore, this continuous inspection enables the detection of non-defective parts within a production run, meaning that only defective parts need to be rejected – something not possible with trial inspections.

[0045] In this context, it is quite conceivable that the evaluation of each image is used directly to draw conclusions about the characteristics of an entire preform series. On the other hand, it is also quite possible that several captured images are evaluated first before a conclusion is drawn about the characteristics of the entire series.

[0046] According to the invention, it is also possible to offer the receiving device 6, the corresponding processing device, the image screen 5 or the plate 5', and the corresponding fastening means together as a kit. In this case, these elements could be easily installed and commissioned by a person without specific training on a conventional preform manufacturing machine or system. Thanks to this possibility, no modifications to the manufacturing machine itself would be necessary.

[0047] In Figures 6 to 9 A second and a third variant of the system according to the second embodiment of the present invention are shown. The systems according to these two variants of the present invention differ from the system described in the Figures 3 and 4This is illustrated only by the fact that the plate 5', over which the preforms 2 slide after leaving the transport device 3 and before entering the receiving vessel 4, is not flat. For this reason, the elements in the Figures 6 to 9 the same reference symbols as the elements in the Figures 1 to 4 .

[0048] Specifically, plate 5' in the system according to the second variant of the invention ( Figure 6 and 7 ) so curved that it is channel- or trough-shaped. As in Figure 6As can be clearly seen, the plate 5' has a shape that allows all preforms 2 coming from the transport device 3 to accumulate in the center of the plate 5' as they slide and exit the plate 5' at the center of the lower edge. In this way, the position or focus of the receiving device 6 can be adjusted so that the images of the sliding preforms 2 can be optimally captured. Furthermore, thanks to the curved shape of the plate 5', the sliding preforms 2 are partially sorted; that is, they are inevitably oriented so that their longitudinal axes are parallel to the direction of travel. This also contributes to optimizing the capture and evaluation of the images of the preforms 2 to be inspected. However, the preforms are still somewhat disordered, meaning that different distances may exist or that the preforms may have their tops facing in opposite directions.

[0049] Of course, it is also conceivable that the curvature of the plate is arranged or formed differently than shown in Figure 6 This is shown. However, a specialist will know how the curvature of plate 5' can be adapted to the specific needs.

[0050] In particular, it is also conceivable that not the entire 5' plate has a curvature. Such a variant is found in the Figures 8 and 9 shown. In contrast to the variant shown in Figure 6 and 7 As shown, the plate has 5' in Figure 8 a curved area 5a and a flat area 5b. In this variant, the advantages of the systems according to the first embodiment ( Figure 1 and 2 ) and the second embodiment ( Figures 3 and 4) of the present invention. In this variant, it is therefore particularly advantageous to provide two receiving devices 6, each of which makes images of preforms 2 in one of the two areas 5a and 5b of the plate 5'. However, such a dual arrangement is also possible in the other cases.

[0051] Furthermore, it would be possible in yet another embodiment ,However, although this is not part of the claimed invention, it is possible for images of the preforms 2 to be taken by the receiving device 6 not only after they have left the transport device 3 (i.e., while the preforms 2 are in free fall), but also beforehand, i.e., while the preforms 2 are still being transported on the transport device 3. For this purpose, the receiving device 6 can be arranged above the transport device 3 so that it is directed towards the top of the transport device 3. Images of the preforms 2 transported on the transport device 3 can then be taken by making the transport device 3 completely or partially transparent, so that sufficient illumination of the preforms 2 is possible.The images of the preforms 2 recorded in this way correspond essentially to the images recorded during free fall with or without screen 5 or to the images recorded during sliding on the plate 5', so that the subsequent evaluation can be carried out in the same way.

[0052] It should be noted here that the present invention is not limited to the described embodiment. It will be readily apparent to a person skilled in the art that further developments and modifications within the scope of the protected invention are easily possible. For example, system elements can be replaced as needed with other elements that perform the same (or similar) functions. Additional devices and / or elements can also be provided; for instance, multiple image acquisition units can be provided, allowing the preforms 2 to be inspected to be photographed from different sides. However, such measures and modifications must fall within the scope of protection of the invention, which is defined by the following claims.

Claims

1. Testing method for testing workpieces (2) consisting of a basic body, to which a barrier layer is optionally applied at least partially, and which are intended for the manufacture of containers, in particular beverage bottles, whereby the workpieces (2) are transported into a receiving vessel (4) by means of a transport device (3), and whereby an image of the workpieces (2) is generated by means of a capturing device (6) and is transmitted to a processing device for testing, the image of the workpieces (6) is taken between the workpieces leaving the transport device (3) and being introduced into the receiving vessel (4), the image is an optical coherence tomography image or a multispectral image, and whereby the image is processed by the processing device in such a way that the quality of the basic body and the quality of the optionally at least partially applied barrier layer on the workpieces (2) are tested in order to detect defective workpieces (2) whereby the quality of the basic body comprises its dimensions, shape, wall thickness and / or length of an injection point, and the quality of the barrier layer comprises the thickness of the barrier layer.

2. Testing method according to claim 1, characterized in that the imaging of the workpieces (2) is carried out in front of a projection screen (5) or a plate (5').

3. Testing method according to one of the preceding claims, characterized in that after leaving the transport device (3) the workpieces (2) are led into the receiving vessel (4) in free fall or slide over the plate (5') in such a way that they are introduced into the receiving vessel (4).

4. Testing method according to one of the preceding claims, characterized in that a plurality of images are evaluated in order to draw conclusions about a defective series of workpieces (2).

5. Testing method according to one of the preceding claims, characterized in that when making the image the workpieces (2) are illuminated by at least one illuminating body (8), and in that the at least one illuminating body is positioned in such a way that the workpieces (2) are illuminated from the rear or from above in relation to the capturing device (6).

6. Testing method according to claim 2, characterized in that at least one portion of the plate (5) <sic. 5')> is curved in at least one direction.

7. Testing method according to the preceding claim, characterized in that the plate (5') is curved in such a way that at least one channel for the sliding workpieces (2) is formed in the plate (5').

8. Testing method according to one of the preceding claims, characterized in that the workpiece (2) is a preform or a cap.

9. Testing system for testing of workpieces (2), which consist of a basic body, to which a barrier layer is optionally applied at least partially, and are intended for the manufacture of containers, in particular beverage bottles, comprising a transport device (3) for transporting of workpieces (2) into a receiving vessel (4), a processing device for testing and a capturing device (6) for making an image of the workpieces (2) and transmitting this image to the processing device for testing, whereby the imaging of the workpieces (6) is performed between the workpieces leaving the transport device (3) and being introduced into the receiving vessel (4), the image is an optical coherence tomography image or a multispectral image, and the processing device is moreover designed such that the image is processed by the processing device in such a way that the quality of the basic body and the quality of the barrier layer optionally applied at least partially to the basic body of the workpieces (2) are checked in order to detect the defective workpieces (2), whereby the quality of the basic body comprises its dimensions, shape, wall thickness and / or length of an injection point, and the quality of the barrier layer comprises the thickness of the barrier layer.

10. Testing system according to claim 9, characterized in that an projection screen (5) or a plate (5') is provided so that the imaging of the workpieces (2) in front of the projection screen (5) is feasible.

11. Testing system according to claim 10, characterized in that after leaving the transport device (3) workpieces (2) are able to slide over the plate (5') in such a way that they are able to be introduced into the receiving vessel (4).

12. Testing system according to one of the claims 9 to 11, characterized in that an illuminating body (8) is provided, by means of which the workpieces (2) are able to be illuminated during creation of the image, whereby the at least one illuminating body (8) is positioned in such a way that the workpieces (2) are able to be illuminated from behind or from above in relation to the capturing device (6).

13. Testing system according to one of the claims 9 to 12, characterized in that at least a portion of the plate (5') is curved in at least one direction.

14. Testing system according to claim 13, characterized in that the plate (5) is curved in such a way that at least one channel for the sliding workpieces (2) is formed in the plate (5').

15. Testing system according to one of the claims 9 to 14, characterized in that the workpiece (2) is a preform or a cap.