FR3040782A1 - DEVICE AND METHOD FOR CONTROLLING A THERMOFORMED PART - Google Patents

Abstract

The present invention relates to a device for controlling at least one thermoformed part (3) comprising at least one main face and at least one lateral face (3c, 3d, 3e, 3f) transverse to the main face, comprising: a first system for measuring the at least one main face of the thermoformed part (3) arranged to perform a first series of measurements; - a second measuring system (31a, 31b, 31c, 31d) of the at least one side face (3c, 3d, 3e, 3f) of the thermoformed part (3) arranged to perform a second series of measurements; at least one electronic control unit arranged to: ○ determine at least one value of a geometric quantity of the at least one thermoformed part (3) as a function of the first and second series of measurements; and to ○ compare said at least one value of a geometric magnitude of the at least one thermoformed part (3) with at least one reference value of said geometric magnitude corresponding to a reference part model. The present invention also relates to a method implementing the control device.

Description

The present invention relates to a device for controlling at least one thermoformed part, and to a method for controlling the thermoformed part.

It is known from the state of the art to produce thermoformed parts from specifications that can be in the form of diagrams or prototypes, by which the manufacturer sets the parameters of the production equipment.

When the geometry of the parts to be produced is complex, the quality control tests of the parts available in the state of the art generally do not allow measurements in any point directly.

The manufacturers then generally carry out a visual inspection or a control by taking samples intended to undergo often destructive tests. In addition, the control of parts is generally performed outside the production line which is not compatible with the production rates desired.

The control performed on these parts therefore presents a substantial uncertainty that may lead to the delivery of parts that do not comply with the specifications.

The present invention aims to solve all or part of the disadvantages mentioned above. For this purpose, the present invention relates to a control device for performing a control of at least one thermoformed room, comprising: a control location at which the thermoformed room is disposed; a plurality of measurement systems, each arranged to perform a series of measurements on the thermoformed part, the plurality of measurement systems thus generating a plurality of series of measurements; at least one electronic control unit arranged to: o determine at least one control value of a characteristic geometric quantity of the at least one thermoformed part as a function of at least a first series of measurements and a second series of measurements among the plurality of measurement series; and to compare said at least one control value of a characteristic geometric quantity of the at least one thermoformed part with at least one reference value of said characteristic geometrical quantity corresponding to a reference part model.

Thanks to the provisions of the invention, it is possible to use a simple kinematic device and therefore a simple and robust robotic assembly. The computation times are optimized by the use of the two measuring systems which, by their combination, make it possible to obtain a satisfactory measurement accuracy without requiring a large calculation capacity.

According to optional features of the control device according to the invention: said thermoformed piece comprises at least one main face, at least two of the plurality of measuring systems being arranged to each perform a series of measurements on the at least one a main face; said thermoformed part comprises at least one main face and at least one lateral face transverse to the main face, at least one measuring system among the plurality of measuring systems being arranged to perform a series of measurements on the at least one main face and at least one other one of the plurality of measurement systems being arranged to perform a series of measurements on the at least one side face; the control device comprises a translucent surface disposed at the control location, arranged to receive the thermoformed piece; the translucent surface is movable in translation in a first direction of extension; the first extension direction is substantially horizontal; at least one of the plurality of measurement systems is arranged to perform optical measurements; at least one of the plurality of measuring systems is arranged to perform a series of two-dimensional measurements; at least one measuring system among the plurality of measuring systems is arranged to perform a series of measurements by detection of a basic contour delimiting the thermoformed piece; at least one of the plurality of measurement systems comprises a light source and an optical detector disposed on either side of the control location; the light source and the optical detector are arranged on either side of the control location in a second direction of extension, transverse to the first direction of extension; the second extension direction is substantially vertical; at least one of the plurality of measuring systems is arranged to perform a series of measurements of the three-dimensional thermoformed part; at least one measuring system among the plurality of measuring systems is arranged to perform a series of measurements on a specific area of the thermoformed part with lighting conditions adapted to the desired resolution, at least one of the plurality of measurement systems. measurement system comprises a receiver, the at least one measurement system being arranged to perform a distance measurement between the thermoformed part and the receiver.

According to one aspect of the invention, a reference part model is a physical part.

In this case, measurements of characteristic geometric quantities are made on the reference part model to obtain reference values.

According to one aspect of the invention, the reference part model is a computer-aided design (CAD) file.

According to one aspect of the invention, the control device is arranged in a production line of thermoformed parts. Thus, the control of the thermoformed parts is achieved within the production line, and the production rates are improved.

According to one aspect of the invention, the control device comprises: a location for loading the thermoformed part; the control location arranged to receive the thermoformed piece; an ejection location of the thermoformed part.

According to one aspect of the invention, the loading location, the inspection location and the ejection location are aligned in the second extension direction.

According to one aspect of the invention, the alignment formed by the loading location, the inspection location and the ejection location is substantially collinear with an axis of a portion of the production line in which the device control is integrated. Thus, little robotics is needed to move the thermoformed parts into the control device, which reduces the complexity and cost of producing the thermoformed parts.

According to one aspect of the invention, the alignment formed by the loading location, the control location and the ejection location is transverse, and preferably perpendicular to, the axis of the portion of the chain of production in which the control device is integrated.

According to one aspect of the invention, a stacking station of the thermoformed parts waiting to be controlled is disposed on the portion of the production line, near and upstream of the control device. This arrangement optimizes the workflow.

According to one aspect of the invention, the translucent surface is arranged to move between the loading location and the ejection location.

According to one aspect of the invention, the first measurement system is arranged to perform a series of measurements by detecting an image and a drop shadow of the thermoformed part.

According to one aspect of the invention, the first measurement system is arranged to perform a series of measurements by detecting an image of the at least one main face of the thermoformed part with lighting conditions adapted to the desired resolution. .

According to one aspect of the invention, the second measurement system comprises at least one triangulation laser movable in translation in a longitudinal direction of the at least one lateral face.

According to one aspect of the invention, the control device is mobile.

According to one aspect of the invention, the control device comprises a user interface allowing the operator to define the test areas on the reference part model.

According to one aspect of the invention, the series of measurements are performed by mechanical probing.

According to one aspect of the invention, the series of measurements are carried out by profilometry.

According to one aspect of the invention, the reference values of the characteristic geometrical quantities are determined by optical measurements of a reference part model.

According to one aspect of the invention, the reference values of the characteristic geometrical quantities are determined on the basis of a three-dimensional model of a reference part model.

In particular, the three-dimensional model is obtained by adaptation of a computer-aided design (CAD) file. The invention makes it possible to make the CAD information assimilable by the measurement software.

According to one aspect of the invention, the control device comprises an electronic control unit arranged to determine at least one control value of a geometrical quantity characteristic of the at least one thermoformed piece as a function of the first and second series of measurements. .

According to one aspect of the invention, the control device comprises an electronic control unit arranged to compare said at least one control value of a characteristic geometric quantity of the at least one thermoformed part with at least one reference value of said characteristic geometric magnitude corresponding to a reference part model

According to one aspect of the invention, the electronic control unit comprises a processor and a random access memory.

According to one aspect of the invention, the electronic control unit comprises a read-only memory.

According to one aspect of the invention, the processor is arranged to communicate with the measurement systems via communication interfaces.

According to one aspect of the invention, the thermoformed part comprises a skirt. A characteristic geometrical size of the thermoformed piece may for example be the width of the skirt.

According to one aspect of the invention, the thermoformed part comprises holes. A characteristic geometric quantity may be the distance from the hole to one of the lateral faces of the thermoformed part or a dimension of the hole, for example the radius of the hole if it is circular.

According to one aspect of the invention, a characteristic geometrical quantity may for example be an angle between two adjacent lateral faces.

The present invention furthermore relates to a method for controlling a thermoformed part comprising at least one main face and at least one lateral face transverse to the main face, comprising the steps of: A. producing a plurality of series of measurements, B determining at least one control value of a characteristic geometrical size of the thermoformed part as a function of at least a first series of measurements and a second series of measurements, C. comparing said at least one control value with a magnitude geometric characteristic of the at least one piece thermoformed to at least one reference value of said characteristic geometric magnitude corresponding to a reference part model.

According to optional features of the control method according to the invention: at least one series of measurements among the plurality of series of measurements is performed on the at least one main face; at least one series of measurements among the plurality of series of measurements is performed on the at least one lateral face; step C comprises the sub-steps consisting of: C.I. determining a difference in value between the at least one control value of a characteristic geometric quantity of the at least one thermoformed part and the at least one reference value of said characteristic geometrical quantity corresponding to a reference part model , C.2. comparing the value difference with a predetermined threshold value; determining a control value of a first intermediate geometrical quantity from the first series of measurements and a control value of a second intermediate geometrical quantity from the second series of measurements, the control value of the geometrical quantity. characteristic of the thermoformed part being determined as a function of the control values of the first intermediate geometrical quantity and the second intermediate geometrical quantity; for example, the first intermediate geometrical quantity and the second intermediate geometrical quantity may correspond to position data, the characteristic geometric magnitude possibly corresponding to a distance measurement;

For example, the thermoformed part comprises a skirt. In this case, a first intermediate geometrical quantity would be the position of the contour of the skirt, a second intermediate geometrical size would be the position of its intersection with the rest of the thermoformed part and the characteristic geometrical size would be the width of the skirt. The control value of the width of the skirt is then obtained by subtraction between the values of the first and second characteristic geometrical quantities, at least a first intermediate value of the characteristic geometrical quantity is determined from the first series of measurements and at least a second intermediate value of the characteristic geometric quantity from the second series of measurements, the control value of the characteristic geometrical quantity of the thermoformed part being determined as a function of said first and second intermediate values; for example, a statistical relation can be applied to obtain the geometrical magnitude; the conformity of the thermoformed part is determined according to the difference in value; if the difference in value is less than the threshold value, it is considered that the thermoformed part is compliant; if the difference in value is greater than the threshold value, it is considered that the thermoformed part is not in conformity; the control of the thermoformed part is carried out within a production cycle; if the thermoformed part is in conformity, it is reintroduced into the production cycle.

According to one aspect of the invention, prior to step A, the workpiece is manually loaded into the control device.

According to one aspect of the invention, prior to step A, the thermoformed part is automatically loaded into the control device.

According to one aspect of the invention, the loading of the part in the control device is provided by a robotic device. Other features and advantages of the present invention will emerge in the light of the following description and the examination of the appended figures, in which: FIG. 1 represents a view of the outside of the control device; FIG. 2 represents a view from above of a housing of the control device; Figure 3 shows the housing of the control device; Figure 4 shows a central zone of the inner housing of the control device, accommodating a thermoformed room; Figure 5 shows a top view of the inner housing of the control device; Figure 6 shows a scraper system of the control device; FIG. 7 represents an electronic control unit of the control device; Figure 8 shows the steps of controlling a thermoformed part; Figures 9a and 9b show the contour control of the thermoformed part; Figures 10a, 10b and 10c show the control of the linearity of the thermoformed part; Figures 11a, 11b and 11c show the control of the width of the skirt and the centering of the cut.

In all of these figures, identical or similar references denote identical or similar members or sets of members.

FIG. 1 shows a device 1 for controlling a thermoformed part 3. The control device 1 comprises an opening 5 allowing access to an inner housing 7 of the control device 1. The control device 1 further comprises an interface user having a screen 9a and a keyboard 9b.

As shown in Figure 2, the control device 1 comprises a translucent surface 11, movable in translation in a first direction of extension Dl, substantially horizontal. The translucent surface 11 is intended to receive the thermoformed part 3. The translucent surface 11 is arranged to slide on rails 13a, 13b in a central zone 21 of the inner housing 7 comprising a loading location 15, accessible to the user, a control location 17 where measurements on the thermoformed room are made, and an ejection location 19, for ejection of the thermoformed room 3 of the control device 1. The loading location 15, the control location 17 and the ejection location 19 are aligned in the first extension direction D1.

As represented in FIG. 3, the central zone 21 is disposed between an upper zone 23 and a lower zone 25. The upper zone 23, the central zone 21 and the lower zone 25 are aligned in a second extension direction D2, which is substantially vertical. .

An example of a thermoformed part 3 intended to be controlled by the control device 1, is shown in FIG. 4. The thermoformed part 3 comprises two opposite main faces. One of the main faces is in contact with the translucent surface 11 and is said lower face 3a. The opposite main face is said upper face 3b. The upper face 3b is disposed facing the upper portion 23 of the inner housing 7 of the control device 1. The upper face 3b comprises reliefs.

The thermoformed piece 3 further comprises four lateral faces 3c, 3d, 3e, 3f, substantially transverse to the main faces 3a, 3b. The side faces 3c, 3d, 3e, 3f may comprise reliefs, for example here a skirt.

The control device 1 comprises a plurality of measuring systems intended to perform series of measurements on the main faces 3a, 3b, and lateral 3c, 3d, 3e, 3f.

A first measurement system comprises an optical measuring instrument 27, arranged to perform measurements in two dimensions. The first measuring system is intended to produce measurement series on the main faces 3a, 3b of the thermoformed part 3. The measuring instrument 27 comprises a bright light projector 27a, arranged in particular for emitting flashes of light. The bright light projector 27a is disposed in the upper zone 23 of the inner housing 7. The measuring instrument 27 further comprises a detector 27b disposed in the lower zone 25 of the inner housing 7.

A second measurement system comprises an optical measuring instrument 29 arranged to produce series of measurements in three dimensions. The second measuring system is intended to produce measurement series on the main faces 3a, 3b of the thermoformed part 3. The measuring instrument 29 is disposed in an upper part 23 of the inner housing 7. The measuring instrument 29 includes a laser and a detector. The laser is arranged to project light with lighting conditions adapted to the desired resolution on the upper face 3b of the thermoformed piece 3.

A third measuring system 30 shown in FIG. 5 is intended to produce series of measurements on the lateral faces 3c, 3d, 3e, 3f of the thermoformed part 3. The third measurement system 30 comprises four measuring instruments 31a, 31b , 31c, 31d substantially identical disposed in the central zone 21 of the inner housing 7. The four measuring instruments 31a, 31b, 31c, 31d are each arranged facing a side face 3c, 3d, 3e, 3f respectively, when the Translucent surface 11 is in the control location 17. The four measuring instruments 31a, 31b, 31c, 31d each comprise a transmitter / receiver, here triangulation lasers 33a, 33b, 33c, 33d respectively. The triangulation lasers 33a, 33b, 33c, 33d are movable in translation each on a rail 35a, 35b, 35c, 35d respectively. The triangulation lasers 33a, 33b, 33c, 33d allow the control of the linearity of the profile of the thermoformed part 3.

As shown in FIG. 6, the control device 1 further comprises a scraping system 37 for ejecting the thermoformed part 3 from the inner housing 7 of the control device 1, when the translucent surface 11 is in the location of ejection 19. The scraping system 37 comprises a push portion 37a movable in translation on a rail 37b between a rest position and an ejection position. At the beginning of the race, the pusher portion 37a is in the rest position. The pusher portion 37a then comes against the thermoformed part 3 and pushes the thermoformed part 3 to its ejection position. When the pusher portion 37a is in the ejection position, the thermoformed piece 3 is out of the housing 7 and falls into a recovery tank.

As shown in FIG. 7, the control device 1 comprises an electronic control unit 40. The electronic control unit 40 comprises a random access memory 41, a read-only memory 51 and a processor 43. The random access memory 41, the read-only memory 51 and the processor 43 communicate through communication interfaces 44, 53. The measuring instrument 27 communicates with the processor 43 through a communication interface 45. The measuring instrument 29 communicates with the processor 43 through an interface of FIG. communication 47.

The four measuring instruments 31a, 31b, 31c, 31d communicate with the processor 43 through a communication interface 49.

The processor 43 also communicates with the user interface 9a, 9b through a communication interface 55. The user interface 9a, 9b is arranged to send instructions to the processor.

The processor 43 controls an actuator of the translucent plate 11 through a communication interface 57. The processor 43 communicates with an actuator of the scraping system 37 through a communication interface 59. The processor is arranged to send commands to said actuators.

As represented in FIG. 8, in a first step E1, the user, before the launch of the production cycle, enters so-called reference values VR of characteristic geometrical quantities GGC of a reference part model via the intermediary of FIG. user interface 9a, 9b.

In a step E2, the user enters, for each characteristic geometric quantity GGC, a threshold value VS of a difference in value EV between a determined value VD of a characteristic geometric quantity GGC of the thermoformed part 3 and a reference value VR corresponding to a reference part model.

The processor 43 collects the reference values VR of the characteristic geometrical quantities GGC and the corresponding threshold values VS and stores them in the random access memory 41 and / or in the read-only memory 51.

In a step E3, the user disposes the thermoformed piece 3 on the translucent surface 11 which is in the loading location 15, placing the lower face 3a against the translucent surface 11. The translucent surface 11 moves along the rails 13a, 13b to the control location 17.

In a step E4, the measuring instrument 27 carries out a first series of SMI measurements. The bright light projector 27a emits a flash and the detector 27b retrieves an image of the underside 3a of the thermoformed piece 3 in drop shadow. This series of SMI measurements allows the detection of a contour of the thermoformed part 3.

In a step E4 ', the data corresponding to the first measurement series SMI are communicated to the processor 43 which copies them into the random access memory 41 and / or the read-only memory 51.

In a step E5, the measuring instrument 29 carries out a second series of measurements SM2. The laser projects light with lighting conditions adapted to the desired resolution on the upper face 3b of the thermoformed part 3. The detector collects an image that makes it possible to highlight the relief of the upper face 3b of the thermoformed part 3. In other words, the detection of an image of the thermoformed part 3 on which light with lighting conditions adapted to the desired resolution makes it possible to obtain three-dimensional measurements on the upper face 3b of the part thermoformed 3.

In a step E5 ', the data corresponding to the second series of measurements SM2 are communicated to the processor 43 which copies them into the random access memory 41 and / or the read-only memory 51.

In a step E6, the four measuring instruments 31a, 31b, 31c, 31d perform a third series of measurements SM3 on the side faces 3c, 3d, 3e, 3f. This series of measurements SM3 makes it possible to determine the linearity of the profile of the thermoformed part.

In a step E6 ', the data corresponding to the third series of measurements SM3 are communicated to the processor 43 which copies them into the random access memory 41 and / or the read-only memory 51.

In a step E7, the processor combines the first, second and third series of measurements in order to determine VC control values of characteristic geometric quantities of the thermoformed part 3.

In order to obtain these VC control values, the processor performs intermediate calculations.

For example, the first series of measurements SMI makes it possible to determine the position of the contour of the thermoformed part 3. The third series of measurements SM3 makes it possible to determine the reliefs of the lateral faces 3c, 3d, 3e, 3f of the thermoformed part 3. The The position of the contour of the thermoformed part 3 constitutes a first intermediate geometrical quantity and the relief of the lateral faces 3c, 3d, 3e, 3f constitutes a second intermediate geometrical size. The combination of the control values of the first and second intermediate geometrical quantities makes it possible to obtain the control value VC of the width of the skirt of the thermoformed part 3, the width of the skirt constituting here a characteristic geometric size GGC sought.

According to one embodiment, intermediate values of the same characteristic geometric magnitude could be used and combined to obtain the control value of this same characteristic geometric magnitude.

In a step E8, the processor determines a difference in value EV between the VC control values of the characteristic geometrical quantities GGC of the thermoformed part 3 and the reference values VR of the characteristic geometrical quantities GGC of the corresponding reference part model. Deviations of value EV are stored in the RAM 41 and / or in the read-only memory 51.

In a step E9, the processor compares the value deviations EV with the threshold value VS indicated by the user.

If the difference is less than the threshold value, the thermoformed part 3 is considered as compliant and is reintroduced into the production circuit in a step E10. The part is reintroduced manually or automatically, depending on the equipment used, the rates and the thickness of the thermoformed part.

If the difference is greater than the threshold value, the thermoformed part 3 is considered as non-compliant. In a step Eli, the processor issues a command and the translucent surface 11 moves in the ejection location 19. The processor 43 then controls the scraper system which ejects the thermoformed part 3 of the inner housing 7 to a collection bin .

For example, as shown in FIG. 9a, the control device 1 makes it possible to control the presence, the position and the size of the holes, as well as the presence of defects in the thermoformed part 3. For example, a geometrical quantity can here be the diameter of the circular holes. The control device 1 indicates for each hole the value of the difference between the value of the reference diameter and the value of the measured diameter. In this example, the thermoformed part has a defect, here a hole. The control device identifies it by the expression "DEFAULT" and indicates its dimensions.

Figure 9b shows an example of a thermoformed piece 3 in which a hole is missing. The control device 1 indicates it to the user by the expression "MISSING".

Figures 10a, 10b and 10c show linearity measurement results of the profile. Figure 10c corresponds to the measurement of a piece having a significant buckling.

In Figures 11a, 11b and 11c, the width of the skirt and the centering of the cut are controlled. This control is achieved by the synthesis of the measurements of the different measurement systems. In FIG. 11a and 11b, the synthesis of the measurements made by the measuring instrument 27 and by the measuring system 30 makes it possible to determine the width I of the skirt. Indeed, the measuring instrument 27 makes it possible to obtain the widest contours of the thermoformed part 3 and the measurement system 30 makes it possible to determine the reliefs of the lateral faces 3c, 3d, 3e, 3f.

As shown in FIG. 11c, the synthesis of the measurements makes it possible to determine the position of the edges of the thermoformed part, here represented by the arrows X and Y. Thus it is possible to measure a Theta angle between the X and Y edges in order to control the geometry of the thermoformed part 3. The determination of the position of the X and Y edges also makes it possible to control the position of the holes with respect to these X, Y edges.

Of course, the present invention is not limited to the embodiment described and shown, provided by way of illustrative and non-limiting example.

According to another embodiment, the geometric values of a reference part model are values measured on a physical reference part model by the first and second measurement systems.

Claims (17)

A control device for controlling at least one thermoformed room (3), comprising: a control location at which the thermoformed room is disposed; a plurality of measurement systems (27, 29, 30), each arranged to perform a series of measurements on the thermoformed part (3), the plurality of measurement systems (27, 29, 30) thereby generating a plurality of series Measurement (SM) at least one electronic control unit (40) arranged to: o determine at least one control value (VC) of a characteristic geometric quantity (GGC) of the at least one thermoformed part (3) as a function of at least a first series of measurements (SMI) and a second series of measurements (SM2) among the plurality of measurement series (SM); and to compare said at least one control value (VC) of a characteristic geometric quantity (GGC) of the at least one thermoformed part (3) with at least one reference value (VR) of said characteristic geometric magnitude ( GGC) corresponding to a reference part model. 2. Control device according to claim 1, wherein said thermoformed piece (3) comprises at least one main face (3a, 3b), at least two measuring systems among the plurality of measuring systems (27, 29, 30). being arranged to each perform a series of measurements on the at least one main face (3a, 3b). 3. Control device according to one of claims 1 or 2, wherein said thermoformed piece comprises at least one main face (3a, 3b) and at least one side face (3c, 3d, 3e, 3f) transverse to the face (3a, 3b), at least one of the plurality of measuring systems (27, 29, 30) being arranged to perform a series of measurements on the at least one main face (3a, 3b) and the at least one of the plurality of measuring systems (27, 29, 30) being arranged to perform a series of measurements on the at least one side face (3c, 3d, 3e, 3f). 4. Control device according to one of the preceding claims, comprising a translucent surface (11) disposed at the control location (21), arranged to receive the thermoformed part (3). 5. Control device according to one of the preceding claims, wherein at least one of the plurality of measuring systems (27, 29, 30) is arranged to perform optical measurements. 6. Control device according to one of the preceding claims, wherein at least one of the plurality of measuring systems (27, 29, 30) is arranged to perform a series of measurements in two dimensions. 7. Control device according to one of the preceding claims, wherein at least one of the plurality of measurement systems (27, 29, 30) is arranged to perform a series of measurements by detection of a contour of base, delimiting the thermoformed piece (3). 8. Control device according to one of the preceding claims, wherein at least one of the plurality of measurement systems (27, 29, 30) comprises a light source (27a) and an optical detector (27b). , arranged on either side of the control location (21). 9. Control device according to one of the preceding claims, wherein at least one of the plurality of measurement systems (27, 29, 30) is arranged to perform a series of measurements of the thermoformed piece (3). in three dimensions. 10. Control device according to one of the preceding claims, wherein at least one measuring system among the plurality of measuring systems is arranged to perform a series of measurements on a specific area of the thermoformed part (3) with conditions. lighting adapted to the desired resolution. 11. Control device according to one of the preceding claims, wherein at least one of the plurality of measurement systems (27, 29, 30) comprises a receiver (33a, 33b, 33c, 33d), the at least one measuring system being arranged to perform a distance measurement between the thermoformed piece (3) and the receiver (33a, 33b, 33c, 33d). 12. A method for controlling a thermoformed part (3) comprising at least one main face (3a, 3b) and at least one lateral face (3c, 3d, 3e, 3f) transverse to the main face (3a, 3b), comprising the steps of: A. realizing a plurality of measurement series, B. determining at least one control value (VC) of a characteristic geometric quantity (GGC) of the thermoformed part (3) as a function of at least a first series of measurements (SMI) and a second series of measurements (SM2), C. comparing said at least one control value (VC) with a characteristic geometric quantity (GGC) of the at least one thermoformed piece (3 ) at least one reference value (VR) of said characteristic geometric magnitude (GGC) corresponding to a reference part model. 13. Control method according to claim 12, wherein at least one series of measurements among the plurality of measurement series (SM) is performed on the at least one main face (3a, 3b). 14. Control method according to one of claims 12 or 13, wherein at least one series of measurements among the plurality of measurement series (SM) is performed on the at least one side face (3c, 3d, 3e, 3f). 15. Control method according to one of claims 12 to 14, wherein step C comprises the substeps consisting of: C.I. determining a difference in value (EV) between the at least one control value of a characteristic geometric quantity (GGC) of the at least one thermoformed part (3) and the at least one reference value (VR) of said characteristic geometric magnitude (GGC) corresponding to a reference part model, C.2. compare the difference in value (EV) with a predetermined threshold value (VS). 16. Control method according to one of claims 12 to 15, wherein a control value (VC) of a first intermediate geometrical quantity is determined from the first series of measurements (SMI) and a control value ( VC) of a second intermediate geometrical quantity from the second series of measurements (SM2), the control value (VC) of the characteristic geometrical quantity (GGC) of the thermoformed part (3) being determined as a function of the values of controlling (VC) the first intermediate geometrical magnitude and the second intermediate geometrical magnitude. 17. Control method according to one of claims 12 to 16, wherein at least a first intermediate value of the characteristic geometric magnitude (GGC) is determined from the first series of measurements (SMI) and at least one second value. intermediate of the characteristic geometric magnitude (GGC) from the second series of measurements (SM2), the control value (VC) of the characteristic geometric quantity (GGC) of the thermoformed part (3) being determined according to said first and second intermediate values (Vil, VI2).