Method for tracking products in a ceramic tiles manufacturing process

Abstract

A method of tracing products (1) in a ceramic slab manufacturing process comprising: applying (S10) an identification pattern (3) to a surface of one of said products (1) and identifying said identification pattern (3) in one or more steps of said manufacturing process, characterized in that said identification pattern (3) is formed by an engobe (2) applied to a lower surface of said product.

Description

[0001] Method for tracking products in a ceramic tiles manufacturing process

[0002] The present invention relates to a method of tracing products in a ceramic slab manufacturing process. For example, the method refers to the tracing of ceramic slabs during the relevant manufacturing process for the monitoring and / or controlling of the parameters of said process. The invention furthermore concerns a method for producing ceramic slabs.

[0003] As is known, ceramic slabs, such as for example large slabs or tiles for covering walls and / or floors, are produced in manufacturing processes that comprise multiple steps, such as pressing, enameling, and firing, wherein each thereof has a determining impact upon the features of the finished product. For example, as described in WO 2023 / 170527, a slab firing process, at temperatures above 1000°C, involves material shrinkage and may result in dimensional and shape deformations.

[0004] In order therefore to correlate the features of the finished product with the parameters of the process, in such a way as to improve the yield of the process and / or the quality of the finished product, it may be useful to trace products during said process. To this end, JP H07129700 A and CN 116968446 A propose a tracing method which involves printing an identification code, such as a bar code, on one side of a product.

[0005] The firing of the slab may however result in degradation of the ink used to form the identification code. Therefore, in order to avoid the degradation of said ink, it is necessary to resort to ceramic inks which require specific printing heads. Such inks are however expensive and require delicate management both during storage and during printing. Furthermore, the heads themselves require careful and constant maintenance in order to prevent the nozzles from being blocked by the inks themselves.

[0006] One object of the present invention is to propose an alternative product tracing method. Such objects are achieved by the features of the invention as set out in the independent claim. The dependent claims outline preferred and / or particularly advantageous aspects of the invention. A first independent aspect of the invention provides a method for tracing products in a ceramic slab manufacturing process, comprising applying an identification pattern to a surface of said products and identifying said identification pattern in one or more steps of said manufacturing process. With the feature that said identification pattern is formed by an engobe that is applied to the lower surface of said product. In this way, the identification pattern is applied by means of a material that is normally used during the ceramic slab manufacturing process such that it is not necessary to install, manage and maintain additional machinery along the production line. Said engobe, in order to avoid excessive adhesion of the slab to the kiln rollers during the firing step, is in fact normally applied to the lower surface of the ceramic slabs before the firing step.

[0007] The engobe comprises one or more components selected from the group consisting of frit, clay, kaolin, zircon silicate, zircon oxide, feldspar, metal oxides, preferably tin and / or titanium oxides. Said engobe is preferably applied in liquid form, for example in the form of a preferably aqueous suspension of a mixture of said engobe. In the preferred embodiment, the engobe is white. The engobe may be applied in the form of a suspension, preferably an aqueous suspension.

[0008] It should be noted that for simplicity, throughout this application, the term “engobe” is used indiscriminately to signify the mixture of components, such as raw materials, suitable for forming an engobe after firing, and also the engobe itself.

[0009] In some embodiments, said identification pattern may cover a small part of the lower surface of the slab. The identification pattern may cover less than 50% of the lower surface of the slab, for example less than 30%.

[0010] Alternatively, according to the preferred embodiment, the identification pattern may cover a larger portion of the lower surface of the slab, for example more than 50% of the lower surface of the slab, preferably 80% or more of the lower surface of the slab. For example, the identification pattern may substantially cover the entire lower surface of the slab. In this way, it is possible to improve the readability of the identification pattern by virtue of its wide distribution upon the lower surface of the slab. In some embodiments, the method may comprise the application of an engobe layer to the lower surface of the slab. Said engobe layer may cover at least 50% of the lower surface of the slab, preferably at least 80% of the lower surface of the slab. The greater the portion of the lower surface of the slab covered by the engobe layer, the greater the effectiveness of said engobe during the manufacture of the slab in preventing adhesion of the slab to the kiln rollers. In some embodiments, said identification pattern may represent a minor portion of the engobe layer. In this case, the identification pattern may represent less than 50% of the engobe layer, for example less than 30% of the engobe layer. Alternatively, according to the preferred embodiment, the identification pattern represents a major part of the engobe layer, for example more than 50% of the engobe layer, preferably 80% or more of the engobe layer. For example, the identification pattern may substantially represent the entirety of the lower surface of the slab.

[0011] In a first preferred embodiment, said identification pattern is substantially random. Said engobe is in fact preferably applied to the lower surface of a green slab by means of an engobing device such as to form a layer that covers the upper surface of the green slab. Said layer does not however necessarily cover the entire surface in a uniform manner and / or does not entirely cover said lower surface, thereby forming a substantially irregular pattern of random origin. In practice, the engobe forms a non-homogeneous layer upon the lower surface of the green slab, and said engobe layer, or rather the inhomogeneities thereof, forms the identification pattern. By tracing products by means of random identification patterns, the need to use devices that are capable of applying predefined patterns that may require special and onerous management and / or maintenance operations is avoided. Preferably, the engobing device, according to said first preferred embodiment, may comprise a coating roller, for example made of silicone, that is suitable for contacting the lower surface of the slab.

[0012] In a second preferred embodiment, said identification pattern is at least partially predetermined. Greater recognition of the pattern and greater variability of the pattern during manufacture may in this way be ensured. Said identification pattern, in some embodiment examples, may be entirely predetermined. According to said second preferred embodiment, said engobing device may comprise means for generating predetermined variations in said pattern. In this way, it is possible to use a single device for the application of the engobe, and for the creation of predetermined features of the pattern within the layer thereof, such as to be able to simplify management and maintenance operations and to limit the quantity of machinery on the production line. Said means may, for example, be configured to prevent the application of an engobe at one or more portions of the coating roller. Said portions may, for example, occupy certain positions along the longitudinal axis of said roller. In this way, it is possible to create engobe elements within the coating that are characteristic of a specific product. Said means may for example be in the form of one or more scrapers which may be actuated between an active position, in which they are in contact with the roller and remove the engobe from said roller in order to prevent the application thereof to the lower surface of the slab, and a passive position, in which they are not in contact with the roller and allow the engobe to be applied to the lower surface of the slab. In this way, therefore, the engobing device is capable of at least temporarily interrupting the application of the engobe at a certain portion of the lower surface, thus creating a predetermined and recognizable variation in the engobe layer. The identification pattern is in this way implemented by means of a device that is easy and inexpensive to manufacture. Advantageously, the engobing device may comprise a plurality of said means for generating variations within the identification pattern, preferably a plurality of said scrapers placed side by side along the longitudinal axis of the coating roller. In this way, it is possible to increase the variability and readability of the identification patterns.

[0013] In each of said preferred embodiments, the method may comprise the steps of: acquiring a digital copy of said identification pattern and comparing said digital copy with a reference copy of said identification pattern. This operation may be performed at each step of the manufacturing process where the product is to be traced. Preferably, said digital copy may be stored in a memory unit. Preferably, said memory unit may be connected to a control system, comprising an electronic computer, connected to one or more reading devices.

[0014] For example, during said comparison step, the method may include comparing a set of features of said digital copy with a corresponding set of features of the reference copy. For example, said features of said set may comprise the presence or absence of said engobe at determined locations in the digital copy and in the reference copy. For example, during said comparison step, the method may be configured to compare said digital copy with a plurality of said reference copies and identify a given product when a greater number of said features of said sets correspond to one another.

[0015] According to each of said first and second embodiments, said reference copy may be in the form of a first digital copy of said identification pattern, which first digital copy is acquired after the application of said engobe, for example immediately thereafter, and preferably stored in said memory unit.

[0016] Alternatively, according to the second preferred embodiment, said reference copy may be in the form of a digital model of said identification pattern, for example arranged to control said engobing device.

[0017] It should be noted that during said step of comparing the digital copy of the identification pattern and said reference copy, the control unit may be configured to identify an identification pattern by compensating for any differences between said digital copy and said reference copy. Said differences may be due, for example, to deformations in said identification pattern caused by the movement of the slab along the production line, to the firing step and / or to other causes relating to the slab manufacturing process. For example, in the preferred embodiments, said comparison step may include determining an index of similarity between the digital copy and the reference copy, expressed, for example, in terms of a percentage of correspondence where 100% represents total identicality between the two copies, and identifying the identification pattern when said index of similarity is higher than a threshold value, for example higher than 90% preferably, higher than 95%. In this way, it is possible to identify the product while also considering any possible deterioration of the engobe layer, and therefore of the identification pattern, due to the manufacturing process.

[0018] Advantageously, said identification of said identification pattern may be performed by means of reading devices, which in the preferred embodiment may comprise cameras. In particular, both the reference copy and the digital copy may be acquired by means of said reading devices.

[0019] Preferably, the process of manufacturing a slab from ceramic material comprises at least the steps of forming a green slab comprising a ceramic mixture, i.e., a raw material that is suitable, after firing, for forming the ceramic material, and a step of firing said green slab in order to obtain a slab of ceramic material. Said engobe is applied after said forming step and before said firing step.

[0020] Said forming step preferably comprises compacting said mixture in powder or granular form in order to obtain a compacted body. Said compaction may take place within discontinuous presses or within continuous compactors. In some embodiments, during compaction, the lower and / or upper surface of the slab may be provided with a relief by means of an embossing pad or belt.

[0021] The slab manufacturing process may comprise one or more steps for decorating the upper surface of the slab, i.e., the surface opposite the lower surface having the identification pattern. The process may comprise a step of applying one or more opaque enamel layers. Said layers of opaque enamel may define the final decoration for the slab, or else form the background for the decoration of the slab. Furthermore, the opaque enamel may have the purpose of waterproofing the surface of the compacted body and of covering the color of the body. The process may involve the application of a decoration, for example a predetermined design, preferably by means of a printing technique, advantageously ink-jet printing by means of piezoelectric heads. Preferably, the decoration may be printed onto said opaque enamel. The process may comprise a step of applying one or more layers of transparent enamel, preferably on top of said opaque enamel and / or said printed decoration.

[0022] The firing step preferably takes place within a continuous roller kiln. The firing step may take place according to a firing cycle which comprises a step of heating up to a maximum temperature and a cooling step. Said maximum temperature is preferably higher than 1000°C. Said process may comprise, after said firing step, one or more finishing steps, for example grinding, lapping, polishing, or brushing.

[0023] Advantageously, said manufacturing process, after said firing step, comprises a selection and / or quality control step. In this case, it is preferable for one of said steps for identifying said identification pattern to be performed near to said selection and / or quality control step, for example immediately beforehand.

[0024] It should be noted that the process for manufacturing ceramic slabs is described, for example, in WO 2023 / 170527, WO 2023 / 047260 and WO 2022 / 324399, which are incorporated herein in the entirety thereof by reference.

[0025] In some embodiments, said first digital copy may be acquired after said firing step. In this way it is possible to reduce any errors during the identification step that could be caused by deformations in the identification pattern before and / or during said firing step.

[0026] In other embodiments, said first digital copy of the identification pattern may be acquired before said firing step. In this way, the tracing method allows a product to be traced during a greater number of steps of the manufacturing process.

[0027] It should be noted that said engobing device, in having means for forming said identification pattern as described above, may constitute an independent aspect of the invention. In particular, a second aspect of the invention may relate to an engobing device that is suitable for depositing an engobe layer on a lower surface of a ceramic slab according to a pattern, preferably a random pattern, and comprising means for generating predetermined variations in said pattern. Said engobing device preferably comprises a coating roller preferably made of silicone. Said means may, for example, be configured to prevent the application of an engobe at one or more portions of the coating roller. Said portions may, for example, occupy certain positions along the longitudinal axis of said roller. Said means may for example be in the form of one or more scrapers which may be actuated between an active position, in which they are in contact with the roller and remove the engobe from said roller in order to prevent the application thereof to the lower surface of the slab, and a passive position, in which they are not in contact with the roller and allow the engobe to be applied to the lower surface of the slab. In this way, therefore, the engobing device is capable of at least temporarily interrupting the application of the engobe at a certain portion of the lower surface, thus creating a predetermined and recognizable variation in the engobe layer. Advantageously, the engobing device may comprise a plurality of said means for generating variations within the identification pattern, preferably a plurality of said scrapers placed side by side along the longitudinal axis of the coating roller.

[0028] Further features and advantages of the invention will become apparent from the following non-limiting examples given by way of example with the aid of the figures shown in the accompanying drawings.

[0029] Fig. 1 schematically shows a few steps in a manufacturing process for a ceramic slab that comprises a slab tracing method.

[0030] Fig. 2 shows an enlargement of the detail F2 in Fig. 1.

[0031] Fig. 3 A and 3B show lower surfaces of a slab produced according to the process of Fig. 1 at two different moments in the process.

[0032] Fig. 4 shows an enlargement of the detail F2 in Fig. 1, in a second embodiment.

[0033] Fig. 5 is a top view of Fig. 4.

[0034] Fig. 6 shows the lower surface of a slab produced according to the process of the second embodiment.

[0035] Fig. 1 shows the flow diagram of a ceramic slab manufacturing process 1 extending along a direction of advancement A of the slabs 1; the terms “downstream” and “upstream” will be used hereinafter in reference to said advancement step. The process comprises a step SI of compacting the powders P of a ceramic mixture into the form of a slab and a step S2 of drying said slab in order to remove moisture from said mixture. The process comprises a step of enameling and decorating said slab, comprising: a first step of applying an opaque enamel S3 to the upper surface of the slab; a step of ink-jet printing S4 a decoration on the enameled surface. The method therefore provides for a step S5 of firing the enameled and decorated slab, for example at a temperature above 1200°C. Once the firing step S5 is completed, the method comprises one or more finishing steps, for example a grinding step S6, an upper surface smoothing step S7 and a slab selection step S8.

[0036] Fig. 1 shows that in the vicinity of printing step S4, for example downstream thereof, and in any case upstream of the firing step S5, a step S10 is provided for the application of an engobe 2 to the lower surface of the slab. Said engobe application step S10 is performed by means of an engobing device 10, shown schematically in Fig. 2, comprising a silicone coating roller 11 and a collection tank 12 of the engobe 2, which tank is arranged below the coating roller 11. The collection tank receives the engobe from a supply circuit that is not shown. The engobing device 10 is arranged below a slab conveyor 13, for example a belt conveyor, such that the coating roller 11 may come into contact with the lower surface of the slab 1, thereby leaving the engobe 2 thereupon. The engobe 2 is in the form of an aqueous suspension and comprises a mixture of frit and kaolin.

[0037] As shown in Fig. 3 A, the engobe 2, applied to the lower surface of the slab 1, forms an engobe layer 3 which covers said lower surface in an irregular and non-predetermined manner. By virtue of such randomness, the engobe layer 3 forms a unique identification pattern 4 for each slab.

[0038] Fig. 1 shows a system 20 for identifying slabs 1 during the process, which system comprises at least one control unit 21, for example a personal computer, to which a memory unit 22 and a plurality of reading devices 23, 24 are connected, in particular optical image acquisition devices, preferably cameras.

[0039] In particular, the identification system 20 comprises a first reading device 23, which is arranged downstream of the engobing device 10 and is suitable for acquiring a first digital copy 5 of the identification pattern 4 of the slab 1 as it moves along in the direction of advancement. Said first digital copy of the identification pattern 3 is stored in the memory unit 22. Possibly, said first digital copy 5 of the identification pattern 4 is associated with other slab data, such as the product, production batch, dimensional data, copy acquisition time, etc. The identification system 20 therefore comprises a plurality of second reading devices 24 arranged at other steps of the process, for example at the end of the firing step S5, upstream of the grinding S6, smoothing S7 and selection S8 steps. Each of said second reading devices is suitable for acquiring a second digital copy 6, shown in Fig. 3B, of the identification pattern 4 of the slab 1 as it moves along in the direction of advancement. Said second digital copy 6 of the identification pattern 4 is compared to the first digital copy 5 stored in the memory unit. Said comparison is performed, for example, by means of a program loaded into the control unit 21. In this way it is possible, for example, to correlate any defect identified during the selection S8 with a determined moment in time when the firing S5 took place, and with parameters of said firing that may have influenced the generation of the defect.

[0040] Fig. 3 shows that the comparison between the first digital copy 5 and the second digital copy 6 takes place by identifying and comparing a set of features 7 of the respective identification patterns 3.

[0041] Fig. 4, 5 and 6 show a second embodiment, which differs from the first embodiment shown in Fig. 1 to 3, in that the engobing device 10’ is configured to form identification patterns 3 which are at least partially predetermined.

[0042] Fig. 4 and 5 show the engobing device 10’ of this second embodiment which differs from the device shown in Fig. 2 in that it comprises a plurality of scrapers 14 arranged side by side along the longitudinal axis of the coating roller 11. Said scrapers 14 may be actuated, for example by means of electric actuators 15, between an active position, in which they are in contact with the coating roller 11 and remove the engobe 2 from said roller in order to prevent the application thereof to the lower surface of the slab 1, and a passive position, in which they are not in contact with the roller 11 and allow the engobe 2 to be applied to the lower surface of the slab 1. In the example shown, the engobing device 10’ is connected to the identification system 20 and is controlled by the control unit 21. As shown, in Fig. 6 the identification pattern 3 comprises predetermined features that are represented by strips of a predetermined length that are devoid of an engobe 2.

[0043] The present invention is in no way limited to the embodiments described above, but said invention may be implemented according to different variants without thereby departing from the scope of the present invention.

[0044] The invention is further defined by each of the following points:

[0045] 1. A method of tracing products (1) in a ceramic slab manufacturing process comprising: applying (S10) an identification pattern (3) to a surface of one of said products (1) and identifying said identification pattern (3) in one or more steps of said manufacturing process, characterized in that said identification pattern (3) is formed by an engobe (2) that is applied to a lower surface of said product.

[0046] 2. The method according to point 1, wherein the method comprises a step of acquiring a first digital copy (5) of said identification pattern.

[0047] 3. The method according to point 2, wherein said pattern identification step comprises the sub-steps of: acquiring a second digital copy (6) of said identification pattern; comparing said second digital copy (6) and said first digital copy (5).

[0048] 4. The method according to 3, wherein said comparison step provides for determining an index of similarity between the second digital copy and the first digital copy and identifying the identification pattern when said index of similarity is higher than a threshold value.

[0049] 5. The method according to point 4, wherein said index of similarity is expressed in terms of percentage of correspondence where 100% represents total identicality between the two copies.

[0050] 6. The method according to point 5, wherein said threshold value is higher than 90%, preferably higher than 95%. 7. The method according to any one of points 2 to 6, wherein said acquisition is performed by means of cameras.

[0051] 8. The method according to any one of the preceding points, wherein said identification pattern (3) is random.

[0052] 9. The method according to any one of points 1 to 7, wherein said identification pattern (3) is at least partially predetermined.

[0053] 10. The method according to any one of the preceding points, wherein said engobe (2) is applied by means of an engobing device (10, 10’), preferably comprising a coating roller (11) that is suitable for contacting the lower surface of said product for the application of the engobe (2).

[0054] 11. The method according to point 10, wherein said engobing device (10’) comprises means (14) for generating predetermined variations in said pattern (3).

[0055] 12. The method according to point 11, wherein said means (14) are configured to prevent the application of the engobe (2) at one or more portions of said lower surface of the slab.

[0056] 13. The method according to point 12, wherein said means comprise one or more scrapers (14) which may be actuated between an active position, in which they are in contact with the coating roller and remove the engobe from said roller in order to prevent the application thereof to the lower surface of the slab, and a passive position, in which they are not in contact with the roller and allow the engobe to be applied to the lower surface of the slab.

[0057] 14. The method according to point 13, comprising a plurality of said scrapers (14) placed side by side along the longitudinal axis of the coating roller (11).

[0058] 15. A process for producing ceramic slabs (1) comprising the tracing method according to any one of the preceding points. 16. The process according to point 15, characterized in that it comprises a firing step, and in that a step of acquiring a first digital copy of said identification pattern is carried out prior to said firing step.

[0059] 17. The process according to point 15, characterized in that it comprises a firing step (S5), and in that a step of acquiring a first digital copy of said identification pattern is carried out after said firing step.

[0060] 18. The process according to any one of points 15 to 17, wherein said identification pattern is applied prior to said firing step (S5).

[0061] 19. The process according to any one of points 15 to 17, comprising a step of acquiring a second digital copy of said identification pattern is carried out after said firing step.

[0062] 20. An engobing device (10, 10’), preferably comprising a coating roller (11) that is suitable for contacting the lower surface of said product for the application of the engobe (2), the device comprising means (14) for generating predetermined variations in said pattern (3).

[0063] 21. The device according to point 20, wherein said means (14) are configured to prevent the application of the engobe at one or more portions of said roller.

[0064] 22. The device according to point 21, wherein said means comprise one or more scrapers which may be actuated between an active position, in which they are in contact with the roller and remove the engobe from said roller in order to prevent the application thereof to the lower surface of the slab, and a passive position, in which they are not in contact with the roller and allow the engobe to be applied to the lower surface of the slab.

[0065] 23. The device according to point 22, comprising a plurality of said scrapers placed side by side along the longitudinal axis of the coating roller.

Claims

Claims1. A method of tracing products (1) in a ceramic slab manufacturing process comprising: applying (S10) an identification pattern (3) to a surface of one of said products (1) and identifying said identification pattern (3) in one or more steps of said manufacturing process, characterized in that said identification pattern (3) is formed by an engobe (2) that is applied to a lower surface of said product.

2. The method according to claim 1, wherein the method comprises a step of acquiring a first digital copy (5) of said identification pattern.

3. The method according to claim 2, wherein said pattern identification step comprises the sub-steps of: acquiring a second digital copy (6) of said identification pattern; comparing said second digital copy (6) and said first digital copy (5).

4. The method according to claim 3, wherein said comparison step provides for determining an index of similarity between the second digital copy and the first digital copy and identifying the identification pattern when said index of similarity is higher than a threshold value.

5. The method according to claim 4, wherein said index of similarity is expressed in terms of percentage of correspondence where 100% represents total identicality between the two copies.

6. The method according to claim 5, wherein said threshold value is higher than 90%, preferably higher than 95%.

7. The method according to any one of claims 2 to 6, wherein said acquisition is performed by means of cameras.

8. The method according to any one of the preceding claims, wherein said identification pattern (3) is random.

9. The method according to any one of claims 1 to 7, wherein said identification pattern (3) is at least partially predetermined.

10. The method according to any one of the preceding claims, wherein said engobe (2) is applied by means of an engobing device (10, 10’), preferably comprising a coating roller (11) that is suitable for contacting the lower surface of said product for the application of the engobe (2).

11. The method according to claim 10, wherein said engobing device (10’) comprises means (14) for generating predetermined variations in said pattern (3).

12. The method according to claim 10, wherein said means (14) are configured to prevent the application of the engobe (2) at one or more portions of said lower surface of the slab.

13. The method according to claim 12, wherein said means comprise one or more scrapers (14) which may be actuated between an active position, in which they are in contact with the coating roller and remove the engobe from said roller in order to prevent the application thereof to the lower surface of the slab, and a passive position, in which they are not in contact with the roller and allow the engobe to be applied to the lower surface of the slab.

14. The method according to claim 13, comprising a plurality of said scrapers (14) placed side by side along the longitudinal axis of the coating roller (11).

15. A process for producing ceramic slabs (1) comprising the tracing method according to any one of the preceding claims.

16. The process according to claim 15, characterized in that it comprises a firing step, and in that a step of acquiring a first digital copy of said identification pattern is carried out prior to said firing step.

17. The process according to claim 15, characterized in that it comprises a firing step (S5), and in that a step of acquiring a first digital copy of said identification pattern is carried out after said firing step.

18. The process according to any one of claims 15 to 17, wherein said identification pattern is applied prior to said firing step (S5).

19. The process according to any one of claims 15 to 17, comprising a step of acquiring a second digital copy of said identification pattern is carried out after said firing step.

20. An engobing device (10, 10’), preferably comprising a coating roller (11) that is suitable for contacting the lower surface of said product for the application of the engobe (2), the device comprising means (14) for generating predetermined variations in said pattern (3).

21. The device according to claim 20, wherein said means (14) are configured to prevent the application of the engobe at one or more portions of said roller.

22. The device according to claim 21, wherein said means comprise one or more scrapers which may be actuated between an active position, in which they are in contact with the roller and remove the engobe from said roller in order to prevent the application thereof to the lower surface of the slab, and a passive position, in which they are not in contact with the roller and allow the engobe to be applied to the lower surface of the slab.

23. The device according to claim 22, comprising a plurality of said scrapers placed side by side along the longitudinal axis of the coating roller.

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