Instrumented tools through functionalized additive manufacturing

Description

TECHNICAL FIELD AND PRIOR TECHNOLOGY

[0001] This application relates to the field of industrial tooling, machine tools, material shaping, and mechanical parts in general. It concerns more specifically the field of molds, particularly plastics molds for shaping polymer materials.

[0002] In a material shaping process using a mold, it is useful to be able to know precisely the thermal cycle (temperature, rate of rise and fall) to which the molded material is subjected at the level of the receiving surface.

[0003] To achieve this, one may want to integrate one or more sensors into the mold, particularly temperature sensors, for example in the form of thermocouples, which are inserted into the structure of the mold by drilling.

[0004] The number of holes drilled, and consequently the number of thermocouples that can be integrated, is generally limited because the holes tend to weaken the mold structure.

[0005] On the other hand, because drilling can usually only be done in a straight line, the possibilities for arranging the sensor are generally limited.

[0006] Furthermore, the integration of thermocouples by drilling requires taking precautions in order not to alter certain sensitive parts and in particular not to deform the receiving surface.

[0007] The document US9440397B1 presents an embodiment of an object formed from an assembly of a plurality of layers and the possibility of an integrated sensor.

[0008] The WO2013021195A2 document provides for a tool consisting of a plurality of layers arranged to protect control circuits and components from excessive temperatures.

[0009] The problem therefore arises of creating an improved instrumented mold with respect to the disadvantages mentioned above. DESCRIPTION OF THE INVENTION

[0010] According to one aspect, the present application relates to a mold having at least one cavity on which a material is intended to be placed to take the shape of that cavity and having a material reception surface, the mold being formed of an assembly of a plurality of layers, said mold integrating, in said assembly of layers, one or more sensors.

[0011] A layered mold allows sensors to be integrated without drilling, the sensor(s) being able to be integrated, particularly from the design stage, in an inter-layer housing or between two layers or on at least one layer.

[0012] The sensors may include at least one temperature sensor and / or at least one pressure sensor. Such sensors can be used to monitor the progress of a molding process and to adjust process parameters based on the measurements collected by the sensor(s). These sensors can also be used to monitor the mold structure.

[0013] According to one embodiment, one or more sensors may be integrated into a zone called the "detection zone" of a flexible support, the detection zone being arranged between at least one first layer and at least one second layer, the first layer being placed on top of the second layer. The one or more sensors may be arranged below the material receiving surface. Such a flexible support allows for the instrumentation of a complex topographic mold, particularly at its material receiving surface.

[0014] Advantageously, the support can be made of polymer material.

[0015] According to one possible implementation, one or more of these sensors can be formed at least partially from a conductive or semiconductive ink. This allows for the creation of sensors with a limited footprint that can be easily inserted into the interlayer space. They are placed as close as possible to the material receiving surface at a distance roughly corresponding to the thickness of a layer, and which may depend on the phenomena to be observed.

[0016] Advantageously, the flexible support includes at least one so-called "connection zone" incorporating one or more conductive tracks connected to said one or more sensors, said connection zone forming a non-zero angle α with said detection zone. Typically, said connection zone extends against a lateral face of said second layer.

[0017] The flexibility of the support facilitates the connection and transfer of measurement signals to another part of the mold or even outside the mold.

[0018] This connection area can extend to below the base of the mold, particularly when a connection is to be established between the sensor(s) and an electronic device located below the mold.

[0019] The assembly may include a base having a cavity to accommodate an electronic circuit, said connection area further extending below said base and being arranged so as to connect at least one of said conductive tracks (to a conductive element of said electronic circuit).

[0020] The electronic circuit may be equipped with at least one control stage for one or more regulating valves of a fluidic network, the fluidic network being equipped with one or more channels extending into the layer assembly.

[0021] In another embodiment, the sensor(s) can be integrated into a layer of the assembly, for example, on the top face of a layer. If the sensor is located on a layer, it can be in the form of a device printed or screen-printed onto that layer. The sensor can then be advantageously positioned and manufactured on the surface of the layer without necessarily requiring machining of the layer.

[0022] In another respect, the present application concerns a method for manufacturing a mold comprising steps consisting of: provide a set of elementary parts each forming a layer, assemble the elementary parts, interposing between two layers, at least one or more sensors, in particular temperature and / or pressure sensors, the sensors being advantageously arranged on a flexible support such as a polymer support.

[0023] In another respect, the present application concerns a method for manufacturing a mold comprising steps consisting of: plan a set of elementary parts each forming a layer, at least one layer being equipped on one face with one or more temperature and / or pressure sensors, then assemble the elementary parts.

[0024] Advantageously, the temperature and / or pressure sensor(s) made directly on the stratum can be formed on the surface, by a technique such as printing or screen printing, which allows in particular easy and precise positioning of the sensor(s), implementation of a low-profile detection zone, and does not alter the stratum on which these sensors are made. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be better understood upon reading the description of the given exemplary embodiments, provided for illustrative purposes only and in no way limiting the application, with reference to the accompanying drawings in which: THE figures 1A-1C serve to illustrate an example of an instrumented strato-designed mold in the form of assembled layers and capable of integrating at least one measurement sensor, in particular for temperature and / or pressure or any other sensor capable of measuring a physical quantity, at an inter-layer location; the figure 2 provides an exploded view of the entire set of layers forming the instrumented mold; the figure 3 serves to illustrate a fluidic network integrated into the mold and equipped with channels formed in layers and in passages between layers of the assembly; the figure 4serves to illustrate an example of a flexible support incorporating one or more measurement sensors and which is suitable for insertion between elementary parts of a mold formed from an assembly of elementary parts; the figure 5 serves to illustrate an example of a flexible support detection zone equipped with sensors and reproducing the shape of a mold reception area; the figure 6 serves to illustrate an example of the arrangement of a connection zone for the flexible support, allowing signals from sensors to be transmitted outside the mold; the figure 7 serves to illustrate a particular arrangement of the active zone of the flexible support; the figures 8A-8B serve to illustrate a connection of the sensor support to an electronic circuit external to the mold and which can be housed beneath it; the figure 9 gives an exploded view of a variant of an instrumented mold formed from an assembly of layers and equipped with sensors made directly on a layer;

[0026] In addition, in the description below, terms that depend on the orientation of the device such as "horizontal", "vertical", "lateral", "under", "on" apply assuming that the structure is oriented as illustrated in the figures.

[0027] Identical, similar or equivalent parts of the different figures carry the same numerical references in order to facilitate the transition from one figure to another.

[0028] The different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more legible. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0029] We now refer to figures 1A-1Cshowing a mechanical part suitable for use as a mold 1 and represented respectively in a top view, a side view, and a perspective view. The mold 1 has, opposite its base 2, at least one cavity onto which a material is intended to be deposited, typically in a paste, liquid, or powder form. This material is then made to take the shape of the cavity as it solidifies, hardens, or agglomerates. The mold 1 here has at least one hollow cavity 3a, 3b with planes inclined relative to its base.

[0030] According to a specific embodiment, mold 1 can be used in the plastics industry and can be used to manufacture components from polymer material. Mold 1 can be designed to shape a sheet of plastic that is heated to a temperature, for example, around 70°C before being pressed onto the mold. Mold 1 can be made of metal, for example, aluminum.

[0031] Mold 1 here has the particularity, as on the figure 2, to be formed from an assembly of several elementary parts 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, called "strata", which are superimposed and integrate into this assembly one or more measurement sensors (not shown in these figures). The strata 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 may be in the form of elements of complementary shapes stacked together, some of these elements having the appearance of a layer or a structured plate. Layers 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 are assembled by means of a fixing method, for example, glue or welding, and / or by means of integral retaining elements such as, for example, inserts passing through the layers of the assembly and ensuring a link between the layers, or reinforcements ensuring lateral support of the assembly.

[0032] The thickness of the layers depends on the nature of the material from which they are formed and the required mechanical properties. Typically, when the layers are made of metal such as aluminum, a layer thickness of approximately 0.1 mm or greater can be expected.

[0033] Mold 1 may in particular have been formed by a process of type “stratoconception ®<” as described for example in document FR2673302, WO00 / 31599 or in documents WO2004 / 034165A1, WO2006 / 128983.

[0034] In this type of process, we start from a digital model of the mold in the form of an exchange file obtained from a computer-aided design file, for example in an STL format (for "STereo-Lithography") typically used in Additive Manufacturing software.

[0035] Using appropriate software, such as Stratoconcept®, a decomposition of the mold model into a series of elementary part models is generated. This decomposition can be performed computationally, with the user selecting input parameters such as: the decomposition plane(s), defined by slicing axes; the decomposition step(s); and the assembly technique for the elementary parts.

[0036] From the elementary models, the elementary parts are then manufactured individually, for example by a 3D material cutting technique such as laser cutting, micro-milling machining, any other cutting technique or by molding.

[0037] The manufactured components are then assembled to reconstitute the mold. The components can be held securely together using a technique chosen from the following (non-exhaustive list): gluing, screwing, brazing, diffusion welding, hot isostatic pressing (HIP), or molding. The joining of the components can also be aided or achieved by using through-bolts such as inserts or external supports such as reinforcements or retaining brackets arranged on the lateral edges of the stacked layers.

[0038] Assembling the mold 1 in elementary layers facilitates the creation of one or more fluid circulation channels or vents, with various orientations. The channels can form a system creating at least one fluidic network extending throughout the assembly. An example of such a network 51 is illustrated on the figure 3 , and includes channels 5a, 5c, 5b located at different levels of the strata set, some horizontal channels 5a, 5c being understood in the illustrated example substantially parallel to the base 2, while one or more vertical channels 5b may be provided to link two by two horizontal channels 5a, 5c located in different planes.

[0039] The channel(s) may be formed, at least partially, by holes or trenches passing through one or more layers and / or by recesses or nozzles provided on the upper or lower face of a layer, or even on the lateral face of one or more layers. Assembling the mold in elementary layers also allows for the creation of 5D channels with specific shapes, particularly those with one or more curves. The channel network 51 may include a first circuit or set of channels used for mold thermal regulation, as well as a second circuit or set of channels for creating a vacuum at one or more points. Such a vacuum is implemented, for example, when the material to be formed is a sheet of polymer material that must be pressed firmly against the mold 1 to conform to the shape of the receiving surface.

[0040] To enable the control of a molding process, and in particular thermoforming, implemented using mold 1, this mold 1 is instrumented with one or more sensors to measure a physical quantity. Mold 1 can be equipped, in particular, with at least one temperature sensor and / or at least one pressure sensor integrated into the multi-layer assembly, and specifically located between two layers of this assembly. Constructing mold 1 in elementary layers advantageously allows for the integration of sensors without drilling. It is therefore possible to incorporate multiple sensors without weakening mold 1. When mold 1 is designed with a fluidic network, such sensor integration is also achieved without risk of damaging this network.

[0041] In the assembly example shown on the figure 2The measurement structure consists of a support (schematically represented by a plane Pi) equipped with sensors and extending between two stacked layers 1.3 and 1.4. A first layer 1.4 thus has a lower face 33 (not visible on the figure 2The measuring structure extends against a surface 31, opposite the lower face 33, and has a region 32 forming a molding or thermoforming surface 31, also called the "molding surface." The measuring structure is thus arranged on a second layer 1.3 located just below the first layer 1.4, which is intended to be in contact with the molding material. The temperature and / or pressure sensor(s) are therefore placed as close as possible to the material receiving surface, typically at a distance from the receiving surface on the order of the thickness of one layer, this thickness being less than 5 mm. Detection is performed as close as possible to the material / receiving surface interface, which allows for more precise control of the thermoforming process.To improve measurement accuracy, several pressure and temperature sensors can be provided under the surface of the mold, in particular according to a mesh or matrix arrangement of sensors.

[0042] The sensors are advantageously integrated into a flexible support 102, in other words a flexible support capable of allowing it to conform to a non-planar shape, in particular so as to be able to conform to a radius of curvature of less than 2.5mm.

[0043] The flexible support 102 is made of an elastic material typically based on polymer(s) such as, for example, polyethylene naphthalate (PEN). The support 102 has a thickness e which can be, for example, between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.3 mm, for example, on the order of 250 µm. Such a support 102 conforms to various non-planar topographies and can thus adapt to a mold having a complex-shaped material-holding surface.

[0044] In the example of implementation illustrated on the Figures 4 and 5 , the flexible support 102 equipped with sensors has a detection zone 104 of particular shape, here annular, which corresponds substantially to the shape of a material reception zone 3b of the mold 1.

[0045] The detection zone 104 in this example is equipped with both pressure sensors 112 and temperature sensors 111 distributed at a given interval on the annular region. The sensor(s), as well as the conductive tracks 123, 125 for connecting the sensors, can be formed at least partially by a conductive ink deposited, for example, by screen printing or inkjet printing, onto the flexible substrate, typically made of a polymer material. Sensors made using such a technique have a reduced footprint. For example, the sensors 111, 112 are made of a conductive ink of the epoxy paste type loaded with silver particles. The temperature sensor 111 can, for example, be made as described in the document "Temperature sensor realized by inkjet printing process on flexible substrate," MD Dankoco, GY Tesfay, E. Benevent, M.Bendahan, Materials, Science & Engineering B, 205 (2016) 1-5], while the pressure sensor 112 can for example be formed in the manner described in the document “Low-Cost Thin and Flexible Screen-Printed Pressure Sensor”, Daniel Gräbner, Marcel Tintelott, Gerrit Dumstorff and Walter Lang, Proc Eurosensors, 6, (2017),616.

[0046] The positioning of the detection zone 104 and the sensors 111, 112 in relation to the fluidic network 51 and the relief of the assembly is typically planned during the numerical modeling of the mold, for example by using a specific module of a software tool as mentioned previously.

[0047] In the example of implementation illustrated on the figures 6 And 7giving a partial perspective view of the instrumented mold 1, the annular detection zone 104 is positioned according to the arrangement of cooling channels 5e, 5f, 5g, and is provided in this particular example around a circular fluidic channel 5h.

[0048] To enable the recovery of signals from the sensors in the detection zone 104 to an electronic processing circuit, it can be provided that at least one connection zone of the flexible support integrating one or more conductive tracks is curved and makes a non-zero angle α, in the illustrated example of the order of 90° with said detection zone 104.

[0049] In the illustrated case where the detection zone 104 of the flexible support 102 is located below and against a layer called the first layer (the lower face of which is represented by a line 133) and a layer called the second layer (the upper face of which is represented by a line 134), the connection zone 106 extends into the assembly against a lateral face of this second layer. This curved shape of the connection zone 106 facilitates the transmission of signals from the sensors out of the mold and, for example, towards a processing circuit that may be located below the base 2 of the mold 1.

[0050] In the example illustrated on the figures 8A-8Bproviding respectively a perspective view of mold 1 mounted on a support S and a bottom view of mold 1, a cavity 23 is provided in the base 2 of mold 1 to accommodate an electronic circuit C1. The electronic circuit C1 housed in cavity 23 typically includes a signal processing stage for the sensor(s), with functions such as signal shaping, amplification, filtering, and analog-to-digital conversion. Advantageously, the electronic circuit C1 also includes a control stage Ei for actuators, in particular electric actuators for one or more fluid control valves in the previously mentioned fluid network. The electronic circuit C1 is typically in the form of a circuit board. The fluid network may include, for example, a cooling network through which water circulates, and a suction network.The suction network can open onto the surface and help to press the shaped material onto the mold.

[0051] Instrumenting mold 1 allows for better control of the forming process. The instrumented mold, connected to the electronic circuit C1, can thus form an active and autonomous system capable of influencing the molding conditions. Certain parameters, particularly those of the mold 1 cooling fluid network, can be adjusted based on sensor measurements, for example, using control software embedded in the electronic circuit C1. The parameters of the suction network can also be adjusted, modifying the suction to influence the material being molded.

[0052] Through this software, it is also possible to establish communication between mold 1 and an external device, in particular a production machine.

[0053] In addition to dynamically controlling the molding process parameters (for example, by controlling temperature, controlling heat transfer fluid or air valves, or controlling vacuum valves) based on measurements taken by the integrated sensor(s), instrumentation of mold 1 can also be provided to monitor its characteristics. Measurements from mold 1 can thus be sent to or transmitted by a remote mold maintenance device to allow for monitoring, potentially remotely, of changes in the mold 1's physical parameters, including deformation, by inserting strain gauges or sensors. The strain gauges can be manufactured using the same technology as the pressure sensors; only the reading of the measured value differs.

[0054] Monitoring the mold's workload, occupancy rate, location, and lifespan by collecting measurements from the sensor(s) can be performed. Sensor data can be used for mold maintenance and to monitor for any potential deviations.

[0055] The electronic processing circuit C1, which in this example is housed under the instrumented mold 1, can be connected to an external numerical control device D for production machines or even to an external network, for example via wireless links, allowing remote control of the mold. Such a system can improve the management of available tooling within a factory.

[0056] As an alternative to the example embodiment, the detection zone (104) is arranged on a stratum (1.3) among said strata.

[0057] An assembly variant is illustrated on the figure 9This time, the plan is to integrate a detection zone directly onto a layer of the mold in layers 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, and 1.8. In this variant, mold 1 incorporates sensors for measuring physical parameter(s), particularly pressure and / or temperature, on one face of layer 1.3. In this case, the sensor(s) can be produced, for example, by printing or screen printing on this layer, or using a technique similar to that described previously for the flexible substrate. A detection zone is thus formed directly on the surface of a layer, without necessarily having to machine the layer to house a sensor within its thickness.

[0058] A stack of layers, with at least one layer surface-functionalized with sensors produced by screen printing or printing, has a smaller footprint than other types of arrangements where a flexible sensor is inserted into an interlayer space and embedded, for example, in an adhesive used to bond two layers together. Sensors produced by screen printing or printed on the surface of a layer are also less intrusive because they are directly integrated into the mold structure. Typically, a sensor produced by printing or screen printing has a thickness that can be on the order of several micrometers, for example, less than 5 µm, while a discrete sensor inserted into an interlayer space can be on the order of a millimeter thick, including its coating or housing.

[0059] Mounting the sensors directly on a layer allows for the distribution of multiple sensors at close intervals and their precise positioning. With screen printing and printing techniques, a reduced detection zone is also achieved, thus minimizing the overall size and impact on the layer's design constraints.

[0060] Furthermore, this allows for precise sensor positioning, leading to improved accuracy of measurements taken by the detection zone. Sensor positioning can be advantageously chosen based, for example, on the results of a numerical simulation of the intended industrial process (injection molding, thermoforming, etc.) for the mold. With this variant, where a detection zone is integrated directly onto a layer, the connection to a signal processing circuit external to the mold can be achieved via conductive elements such as vias passing through the assembly and terminating on one or more external faces of the mold. A connector integrated onto or bonded to an external face of the layer(s) can also be used.

Claims

1. Mould (1) having at least one indentation (3a, 3b) on which a material is intended to be disposed to take the shape of this indentation and comprising a material-receiving surface, the mould being formed from an assembly of a plurality of layers (1.1,...,1.8), said mould incorporating, in the assembly of layers, one or more measuring sensors (111, 112), said one or more sensors being incorporated in a zone (104) called detection zone, the detection zone (104) being arranged between at least one first layer (1.4) among said layers and at least one second layer (1.3) among said layers, said first layer (1.4) being disposed on said second layer (1.3), wherein said detection zone (104) is arranged against a lower face (33) of said first layer (1.4), said lower face being opposite to an upper face (31) of said first layer, said upper face of said first layer forming at least one region of said material-receiving surface, said one or more sensors being disposed below the material-receiving surface, the detection zone (104) being arranged on a flexible support (102) disposed in an inter-layer space between the first and the second layer or being arranged on a layer among said layers, said sensors of said detection zone being sensors made by screen printing or printed on the surface of said second layer.

2. Mould according to claim 1, the sensors being arranged on the surface of said second layer (1.3) without passing through the thickness of said first layer.

3. Mould according to claim 1, wherein the detection zone (104) is arranged on a flexible support (102) and wherein the flexible support (102) comprises at least one so-called connection zone (106) incorporating one or more conductive tracks (123, 125) connected to said one or more sensors, said connection zone (106) making a non-zero angle α with said detection zone (104), said connection zone (106) extending against a lateral face of said second layer.

4. Mould according to claim 3, wherein the assembly comprises a base (2) opposite said receiving surface, said base being provided with a cavity (8) for receiving an electronic circuit (C1), said connection zone furthermore extending under said base (2) and being arranged so as to connect at least one of said conductive tracks (123, 125) to a conductive element of said electronic circuit.

5. Mould according to claim 4, wherein said electronic circuit is provided with at least one stage (Ei) for controlling one or more solenoid valves for controlling at least one fluidic network, the fluidic network being provided with one or more channels (51) extending in the assembly of layers6. Mould according to any one of claims 1 to 5, wherein the flexible support (102) is made of polymer material.

7. Mould according to one of claims 1 to 6, wherein said one or more sensors are formed at least partially of a conductive ink.

8. Mould according to one of claims 1 to 7, wherein among said sensors (111, 112) there are one or more temperature sensors (111) and / or one or more pressure sensors (112).

9. Method for making a mould according to one of claims 1 to 8, wherein the detection zone (104) is arranged on a flexible support (102), comprising: - providing a set of elementary parts each forming a layer, then - assembling the elementary parts, interposing between two layers at least one flexible support such as a polymeric support, the flexible support being provided with one or more temperature and / or pressure sensors.

10. Method for making a mould according to claim 1, wherein the detection zone (104) is arranged on a layer, the method comprising: - providing a set of elementary parts each forming a layer, at least one given layer being provided on one face with one or more temperature and / or pressure sensors, then - assembling the elementary parts.