WO2024194433A1

WO2024194433A1 - Scanner unit, apparatus and method for scanning large units

Info

Publication number: WO2024194433A1
Application number: PCT/EP2024/057668
Authority: WO
Inventors: Benjamin Becsei CHRISTIANSEN; Anders Vestergaard; Alexander Becsei CHRISTIANSEN; Kasper VESTERAA
Original assignee: Becster Aps
Priority date: 2023-03-22
Filing date: 2024-03-21
Publication date: 2024-09-26

Abstract

The present invention relates to a scanner for large units where the scanning may take place while the units are still positioned in a mould or another place of constructions, and the scanning may take place before the unit has hardened, during hardening or after the large unit is completed, and even after the large unit has been positioned at its operational position. In particular, the inventions relates to a scanner unit for scanning a volume of a large unit (1), the scanner unit comprises a plurality of probes (5) each probe (5) either transmitting and/or receiving electromagnetic radiation, and which probes (5) during operation are directed to a volume of the unit (1), the scanner unit comprises at least two transmitting probes (5) or comprises at least one transmitting probe (5) and one receiving probe (5), and the scanner unit is either configured to move along the surface of the unit (1) during operation and/or the scanner unit is configured to scan the unit (1) while the unit (1) move pass the scanner unit during operation, optionally either the scanner unit or the unit (1) is stationary during operation. Each part of the volume of the unit (1) being scanned is during operation enlightened by transmitted radiation from at least two different positions, either from one probe (5) being sequentially at two or more different positions, or from two or more probes (5) being simultaneously at two different position, receiving probes (5) of the scanner unit are configured to receive reflected or transmitted electromagnetic radiation data from the volume of the unit (1) during operation, and to transmit the data to a data processing unit (19) configured to transfer received data into images or other visual data.

Description

Scanner unit, apparatus and method for scanning large units.

The present invention relates to a scanner for large units where the scanning may take place while the units are still positioned in a mould or another place of constructions, and the scanning may take place before the unit has hardened, during hardening or after the large unit is completed, and even after the large unit has been positioned at its operational position.

In particular, the present invention relates to an apparatus and a method for scanning large units shortly after or during completion where the temperature of the large unit may be high, and the unit may not be completely hardened.

Background of the invention

Non-destructive testing with electromagnetic waves has received increasing attention in recent years owing to its advantages of non-contact inspection, no need of medium creating contact, relatively easy measurement setup and no ionising radiation hazards.

Traditionally, non-destructive testing of large units such as wind turbine blades, boats, material for blades, materials for boats, fiber beams for construction, or the like is done by ultrasound testing. However, when testing with ultrasound it is necessary for the ultrasoundunit to be in physical contact with the tested unit and it is also necessary to have a liquid flowing between the ultrasound-unit and the tested unit.

In the article "A review of microwave testing of fibre-reinforced polymer composites" by Zhen Li et al., published in Nondestructive Testing and Evaluation, April 2019, relates to scanning of glass fibre reinforced polymers (GFRP) which composites are used in aerospace, naval, automotive construction and wind industries. It is recognized that air voids, unintentional fiber direction (wrinkles) or placement may occur during the manufacturing process of GFRPs and in service GFRP composites are subjected to degradation which leads to damages in form of fibre/matrix debonding, matrix cracking, delamination (ply separation and fibre breakage. These degradation damages occur internally and may not be visible on the surface. The article describes that non-destructive testing may be done with microwaves which are electromagnetic (EM) radiation with frequencies between 300 MHz (wavelength of 1 m) and 300 GHz (wavelength of 1 mm). In paragraph 2.1, page 4, it is disclosed that for a glass fibre-epoxy mixture, the effective permittivity changes as a function of parameters like frequency, fibre volume fraction, cure state, porosity and fibre orientation. Thus, it is possible to extract useful information about these parameters from the permittivity.

Empirical mixing formulae can be adopted for the prediction of the effective dielectric constant, such as Wiener limits, Maxwell Garnett formula and Looyenga formula. In these closed-form solutions, the effective dielectric constant is a function of the dielectric properties of the fibre and resin. The methods for testing illustrated in this article are based on small test pieces e.g. the transmission line method or the open-ended probe method or the free-space measurement method (see paragraphs 3.1, 3.1, 3.2, 3.3 and 3.4, pages 7- 10). However, the article does not disclose any methods being suitable for scanning large units such as boats or wind turbine blades or parts thereof or raw material, and the article does not suggest detecting of voids in an uncured unit or in a not completely hardened unit.

WO 2008/051953 Al discloses a method for detecting an anomaly in a composite material comprising directing two transmitted electromagnetic wave signals orthogonally polarized with respect to each other from a probe to the composite material. The probe and composite material are positioned for near-field evaluation of the probe, receiving two reflected signals corresponding to said two transmitted orthogonally polarized signals, applying the two detector output voltages to a compensator circuit to compensate for changes in standoff distance between the probe and the composite material. The compensator circuit generates a compensated voltage signal as a function of a detector output parallel voltage, a detector output perpendicular voltage, and a transformation voltage, and issues information about the composite material based on the compensated voltage signal. Fig. 3 of this document shows a practical application comprising a sample or specimen, a reflectometer, and a scanner. The scanner mechanically moves the reflectometer with an open-ended waveguide probe in defined x and y, and possible in z, directions in such a way that the reflectometer is moved across the specimen taking data until the entire surface has been examined. The specimen comprises CFRP laminated to concrete ([0036]). The apparatus and method disclosed in WO 2008/051953 Al is directed to detecting disbonds and delamination between CFRP laminates and concrete, not for detecting internal voids in moulded units.

US 5.486.319 A discloses a tire cure control system wherein a computer-based data acquisition and process control unit that uses non-invasive, direct cure measurements to adjust the length of cure so that all cured articles such as tires will be cured to the same extent in the minimum amount of time. The system includes at least one microwave probe placed in the mold and a processor to process probe data and to initiate a control action principally initiating a mold opening sequence at the optimal time. Initiation of the mold opening sequence at least in part is based upon a measurement of the time rate of change of the attenuation of microwave energy caused by the curing rubber compound in the mold. This system is specifically directed towards process optimization and only measures the cure-state of the tested unit, the system does not identify flaws in the moulded unit. Also, the system does not comprise a scanning unit as such because neither the tested unit nor the probes move.

US 2021/0379843 Al discloses a system comprising a deposition head configured to deposit multiple tows in a stacked configuration one layer at a time. Each tow of the multiple tows is a currently-applied tow when the tow is a most-recently deposited tow of the multiple tows, and a tow of the multiple tows is a covered tow when the tow is directly covered by the currently-applied tow. The system also comprises a probe head, configured to move along and be spatially offset from the currently-applied tow after deposition of the currently- applied tow. The probe head is configured to transmit an incident microwave beam into the currently-applied tow as the probe head moves along the currently-applied tow. The incident microwave beam has a frequency low enough to pass entirely through the currently-applied tow and high enough to pass entirely through no more than the currently-applied tow and the covered tow. This system specifically tests the top layer of uncured material, and the test is limited to a cross-section of the top material.

Hence, an industrially applicable method for non-destructive testing of large, moulded units with electromagnetic radiation is not available, particularly not a method which may be applied while a mouldable unit is still positioned in a mould or is in the production phase in general.

When applying a scanning unit or an apparatus according to the invention, it is possible to obtain detailed images of defects such as voids or cracks inside the mouldable unit or cracks or roughness on the surface of the mouldable unit, wrinkles i.e. fibre misalignment of fibre layers, state of curing, resin flow during moulding, etc. Also, the scanning unit or apparatus according to the present invention may be used to scan porous materials i.e. foam materials or similar materials having a certain content of gas such as air, which materials are often used as filling material or layer for e.g. wind turbine blades to keep the blade both strong and of low weight.

Summary of the invention

Thus, an object of the present invention is to provide an improved apparatus and method for doing non-destructive testing of large units by scanning of the large units either during or after being moulded or cast in a mould.

Thus, a first aspect of the invention relates to a scanner unit comprising a plurality of probes (5) each probe (5) either transmitting and/or receiving electromagnetic radiation, and which probes (5) during operation are directed to a volume of the unit (1), the scanner unit comprises at least two transmitting probes (5) and/or comprises at least one transmitting probe (5) and one receiving probe (5), the scanner unit is either configured to move along the surface of the unit (1) during operation and/or the scanner unit is configured to scan the unit (1) while the unit (1) moves pass the scanner unit during operation, optionally either the scanner unit or the unit (1) is stationary during operation, wherein each part of the volume of the unit (1) being scanned is during operation enlightened by transmitted radiation from at least two different positions, either from one probe (5) being sequentially at two or more different positions, or from two or more probes (5) being simultaneously at two different position, and receiving probes (5) of the scanner unit are configured to receive reflected or transmitted electromagnetic radiation data from the volume of the unit (1) during operation, and to transmit the data to a data processing unit (19) configured to transfer received data into images or other visual data.

When the scanner unit is configured to receive reflected electromagnetic radiation then the receiving probes (5) are position close to the transmitting probe(s) (5) i.e. normally at same side of the unit (1) as the transmitting probe(s) (5). When the scanner unit is configured to receive transmitted electromagnetic radiation then the receiving probe(s) (5) are position on an opposite side of the unit (1) as the transmitted electromagnetic radiation passes through the unit (1).

When the scanner is configured to receive transmitted electromagnetic radiation, then the receiving probe(s) (5) positioned on an opposite side relative to the transmitting probe(s) (5) is/are coordinated to move together with the transmitting probe(s) (5) or in a controlled manner relative to the transmitting probe(s) (5). When the scanner unit is configured to receive reflected electromagnetic radiation, then the receiving probe(s) and the transmitting probe(s) may be positioned on the same moving unit.

When the scanner unit is configured to scan the unit (1) while the unit (1) moves pass the scanner both the receiving probe(s) and transmitting probe(s) (5) may be positioned stationary, e.g. in a wall or a scaffold fitted around the passing unit (1).

According to any embodiment of the first aspect, the scanner unit may be configured to scan a unit (1) comprising or being constituted of a mouldable material, and during operation i.e. during scanning, the unit (1) may be in a state hardened to final use, or the unit (1) may be in a state of hardening, or the unit (1) may be in a liquid state where mouldable material is flowing into a mould.

According to any embodiment of the first aspect, the scanner unit may be configured to scan a unit (1) comprising or being constituted of a mouldable material combined with a non- mouldable material e.g. structural units of steel or of carbon fiber or of another structural material.

According to any embodiment of the first aspect, the scanner unit may comprise at least three, or at least four, or at least five, or at least six, or at least ten transmitting probes (5).

According to any embodiment of the first aspect, the transmitting probes (5) may be positioned linearly e.g. as a straight or curved line, or as an array e.g. comprising more than one line of probes (5).

According to any embodiment of the first aspect, the frequency region for probes (5) transmitting electromagnetic radiation may be in the microwave regions from about 1 gigahertz (GHz), up to about 300 gigahertz (GHz), and preferably in the regions 5 - 60 GHz, or in the region 10 - 30 GHz, or in the region 10 - 20 GHz.

According to any embodiment of the first aspect, the scanner unit may comprise two or more groups of probes each group comprising at least one or two or three transmitting probe(s) (5), where each group of probes (5) transmit electromagnetic radiation in different regions e.g. a first group of probes (5) transmit electromagnetic radiation in the region 10-20 GHz and a second group of probes (5) transmit electromagnetic radiation in the region 20 - 30 GHz. According to any embodiment of the first aspect, the unit (1) to be scanned may be a large unit where a large unit is a unit being larger than 1 m in at least one dimension, or being > 2 meters, or > 3 meters, or > 4 meters, or > 5 meters, or > 6 meters, or > 7 meters, or > 8 meters, or > 9 meters, or > 10 meters, or > 15 meters, in at least one dimension, and the scanner unit is configured to move along an inner or an outer surface of such a large unit (1) during operation normally in the complete length.

According to any embodiment of the first aspect, the scanner unit may comprise an accelerometer configured to measure the velocity of the scanner unit relative to the unit (1) or relative to a stationary point, and/or the scanner unit may comprise a distance measuring device which is configured to measure a distance either to the unit (1) or to a stationary point.

According to a second aspect of the invention, the invention relates to an apparatus comprising a scanner unit according to the first aspect, and a data processing unit (19).

According to any embodiment of the second aspect, the apparatus may comprise moving means configured to either move the scanner unit relative to a unit (1) to be scanned or to move the unit (1) to be scanned relative to the scanner. The moving means may comprise or be constituted by a drone i.e. an unmanned vehicle such as an unmanned aerial vehicle (UAV) or an unmanned ground vehicle (UGV) on which drone the plurality of probes are mounted.

According to any embodiment of the second aspect, the moving means may comprise a robotic arm controlling the movements of the scanner unit, or the moving means may comprise one or more wheels e.g. a cart or tracks controlled to move the scanner unit along the surface of a large unit (1) in a constant or at least previously determined varying distance.

According to any embodiment of the second aspect, the moving means may be configured to move all transmitting probes (5) simultaneously and in same direction, or the moving means may be configured to move a first group of probes (5) at a first velocity and/or in a first direction or pattern and a second group of transmitting probes (5) at a second velocity and/or in a second direction or pattern.

According to any embodiment of the second aspect, the unit (1) to be scanned may be a large unit and a large unit is defined by being larger than 1 m in at least one dimension, or being > 2 meters, or > 3 meters, or > 4 meters, or > 5 meters, or > 6 meters, or > 7 meters, or > 8 meters, or > 9 meters, or > 10 meters, or > 15 meters, in at least one dimension, and the moving means of the apparatus are configured to move the scanner unit along an inner or an outer surface of such a large unit (1) during operation normally in the complete length.

According to any embodiment of the second aspect, the data processing unit (19) may comprise means configured to visualize defects or anomalies in the scanned volume of the unit (1), the visualisation may be in form of an image (20), coordinates, text message or other visual presentation.

According to any embodiment of the second aspect, the apparatus may further comprise means configured to determine a defect or anomaly in an image prepared by the data processing unit (19).

According to a third aspect of the invention, the invention relates to a method for nondestructive examination of a volume of a large unit (1) comprising the following steps:

- providing an apparatus according to the second aspect,

- determining operational parameters for the scanner unit to be applied during operation which operational parameters comprises at least working distance and moving pattern of the scanner unit, velocity of the scanner unit, applied frequency of the transmitting probes (5),

- turning on i.e. activating the scanner unit,

- moving the active scanner unit, i.e. scanning, according to the operational parameters while each probe (5) transmits and/or receives electromagnetic radiation at a sequence of positions relative to the volume of the unit (1),

- transmitting received signals to a data processing unit (19) where the received signals are treated to create an image identifying defects in the unit (1) which defects comprises voids or porosities, delamination, misalignment of fibres, defects of glued joints such as misplacement or low adherence, or surface irregularities.

According to any embodiment of the third aspect, the received signals transmitted to the data processing unit (19) and used to identify defects in the unit (1), in case of an identified defect may be used to amend moulding parameters such as flow direction and/or size of flow, and/or temperature of inlet flow and inside mould, and/or size of vacuum during moulding.

According to any embodiment of the third aspect, the identification of a defect may set a visual or audible alarm.

According to any embodiment of the third aspect, the unit (1) may comprise a mouldable material and scanning of the unit (1) is done while

- the unit (1) is in a state hardened to final use and optionally in an operational position i.e. in a position where it may be put to use i.e. be operated, or

- the unit (1) is in a mould and in a state of hardening, or

- the unit (1) is in a liquid state and in a mould or entering into or filling up a mould. Brief description of the figures

Figure 1 shows a first embodiment of an apparatus according to the invention scanning a cylindrical unit of a mouldable material.

Figure 2 shows an end view of the same embodiment as fig. 1.

Figure 3 shows a second embodiment of an apparatus according to the invention scanning a cylindrical unit of a mouldable material.

Figure 4 shows a third embodiment of an apparatus according to the invention where the probes are fixed to an inner moulding par

Figure 5 shows a fourth embodiment of an apparatus according to the invention where the probes are fixed to an outer moulding part.

Figures 6 - 12 show cut-through views illustrating how probes of an apparatus according to the invention may be positioned relative to a moulding part and a unit to be or being scanned during operation.

Figure 13 shows a block diagram for a closed control loop for a real time scanning.

Figure 14 illustrates the composition of a construction such as a wind turbine blade.

Figures 15A and 15B show two embodiments of cut-through views of constructions shown in fig. 14.

Figure 16 illustrates two different scanning units scanning a large unit such as a wind turbine blade from the inside.

Figure 17 illustrates an apparatus according to the invention.

Detailed description of the invention

Definitions

Prior to discussing the present invention in further details, the following terms and conventions will first be defined :

Mouldable material - A mouldable material is a material which is fluid or liquid before production and which during production hardens or stiffens to a solid product which may also be referred to as a moulded product. For mouldable materials the process of hardening may be irreversible. A mouldable material may comprise one or more polymers, concrete or other inorganic materials such as mortar, clay etc., or a composite material comprising a mouldable material in combination with a non-mouldable material such as steel, iron, stones, polymer, in a form of particles, powder, sticks, lattice or supporting structures.

Composite material - A composite material or composite is a material which is produced from two or more constituent materials where one constituent material in the context of the present invention is a mouldable material. The constituent materials normally have dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual constituent materials. Within the finished structure, the individual constituent materials remain separate and distinct, distinguishing composites from mixtures and solid solutions. Microwaves - Microwaves have frequencies ranging from about 1 gigahertz (GHz), up to about 300 gigahertz (GHz) and wavelengths of about 30 to 0,1 centimetres according to the Encyclopaedia Britannica.

Electromagnetic radiation - EM radiation is transmitted in waves or particles at different wavelengths and frequencies. The broad range of wavelengths is known as the electromagnetic spectrum EM spectrum. The EM spectrum is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency. The common designations are radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma-rays. Microwaves fall in the range of the EM spectrum between radio and infrared light.

Ultrasound - Sound waves with frequencies higher than the upper audible limit of human hearing are called ultrasound. Ultrasound has a frequency above 20,000 Hertz (20 kHz).

In general - When this expression is used in the specification it must be understood that the feature described by the expression may be used with all embodiments of the invention. Even if the feature is mentioned in the detailed part of the specification.

A drone - unmanned or unpiloted flying device also referred to as an unmanned aerial vehicle (UAV) or an unmanned grounded vehicle. It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

Also, a specific reference number have the same name and meaning for all embodiments.

Fig. 1 shows a first embodiment of an apparatus according to the invention comprising a scanner unit for scanning a unit 1 comprising a mouldable material. For short, a unit comprising a mouldable material is named a "mouldable unit" and the shown mouldable unit 1 comprises an inner opening 2. However, the mouldable unit may also be in form of a flat piece or e.g. part of a larger unit which part after moulding is to be glued or otherwise assembled with other parts of the larger unit to constitute a complete large unit.

"A large unit" is in the context of the present invention a unit being larger than 1 m in at least one dimension which dimension is referred to as the "length" of the large unit. A large unit subjected to scanning by a scanner according to the claims may be significantly larger than 1 m, e.g. a large unit may be > 2 meters, or > 3 meters, or > 4 meters, or > 5 meters, or > 6 meters, or > 7 meters, or > 8 meters, or > 9 meters, or > 10 meters, or > 15 meters, in at least one dimension. In some cases, a large unit may be up to 50 meters, or up to 100 meters, or up to 200 meters in the length dimension.

The thickness of the material of the large unit, may be > 0,5 cm, or > 1,0 cm, > 2,0 cm, and < 30 cm, or < 25 cm, normally the thickness of the material of the large unit is between 1 and 20 cm.

As the scanner unit of the present invention is directed to scanning large units, a scanner unit according to the invention is generally adapted to move along the surface of such a large unit, normally in the complete length of the large unit, or alternatively, the large unit is adapted to move pass the scanner unit, normally in the complete length, while the scanner unit may be kept stationary. Alternatively, both the scanner unit is adapted to move over a part of the length of the large unit, while the unit to be scanned is also adapted to move pass the scanner unit. To adapt the scanner unit to pass along the large unit at a suitable distance and in a suitable pattern, the scanner unit may be made mobile. E.g., the scanner unit may slide along a trail positioned beside or above the large unit, e.g. beside or above a mould where the large unit is formed and hardened, or the scanner unit may be mounted on a transport unit with wheels or similar which may be driven along the large unit.

The scanner unit comprises a plurality of probes 5 and according to the first embodiment the plurality of probes 5 is fixed to a scanner bar 4. The probes 5 according to this embodiment transmit electromagnetic radiation and during operation the probes are directed towards the mouldable unit 1. There is a distance d between the probes 5 and the surface of the unit 1 facing each probe 5.

Each probe 5 may comprise both a transmitter transmitting electromagnetic radiation and a receiver receiving reflected electromagnetic radiation. Alternatively, two or more of the probes 5 may comprise a transmitter whereas one or more of the probes may comprise a receiver.

The receiving/transmitting probes 5 may be positioned on the same side of the unit 1, i.e. may face the same surface of the unit, 1 or the receiving/transmitting probes 5 may be positioned on opposite sides of the unit 1 i.e. the receiving/transmitting probes 5 may face opposite surfaces of the unit 1. The relative position of the receiving/transmitting probes 5 depend on whether the electromagnetic radiation passes through the scanned unit or is reflected from the surface or volume of the scanned unit.

In general, each probe 5 may each have a broad or a narrow field of view or directionality. A broad field of view or directionality i.e. where each probe transmits and receives from a larger area require more computation of the received signals to determine the location of a defect. However, it enables the transceivers to receive and transmit from different locations simultaneously, resulting in more information for the complete system. A narrow field of view or directionality results in less interference and simpler computation. As the moulded unit 1 and the scanner unit is moved relative to each other during operation, electromagnetic radiation normally in form of microwaves emitted from the probes enlighten the material many times at slightly different locations. A single probe 5 may transmit microwaves in overlapping areas as the probe 5 is moved forward during scanning, and neighbouring probes 5 may transmit microwaves in overlapping areas simultaneously. The microwaves received from the multiple locations are combined to form a 3D image of the area scanned by the scanner unit. The following algorithms may be used to combine the received signals into a 3D image:

■ omega-k algorithm (SAR)

■ Range Migration Algorithm(SAR)

■ Matched Filter (SAR)

■ Back projection (SAR)

■ Time Reversal

■ Neural Networks

■ Convolution Neural Networks

The obtained 3D image may then be subjected to further processing to identify defects in the material. The first embodiment comprises four probes 5, however, in general a scanner unit may comprise many more probes e.g. 10 - 100 probes. The optimal number of probes 5 depends on the size and shape of the mouldable unit 1 including surface area, shape and thickness of the material constituting the mouldable unit 1.

In general, electromagnetic probes of the present invention may operate in the microwave region 300 MHz and 300 GHz, preferably in the region of 5 - 60 GHz, or in the region of 10- 30 GHz. Choosing exactly which frequency to operate at is a trade-off between using a low frequency resulting in a low resolution but high penetration depth, whereas radiation with high frequencies has a higher resolution but lower penetration depth. The optimal frequency will therefore depend on the mouldable unit 1 being produced, if it is necessary to have a high penetration depth, it is necessary to lower the frequency. However, as the present invention comprises a plurality of probes 5, the probes 5 may be positioned at different positions relative to the mouldable unit 1 e.g. pointing towards both an inner and an outer surface of the mouldable unit 1.

In general, the probes or antennas shown in the figures are illustrated as being rather large, however, the probes 5 are commercially available and may be very small, e.g. a few centimetres or less in cross-section. Also, the bar may be much smaller than indicated by the illustrations.

The mouldable unit 1 shown in fig. 1 is approximately cylindrical and illustrates a large unit such as a piece or part of a wind turbine blade. A wind turbine blade may be scanned as a complete unit or as two half units if the blade is moulded by the "butterfly" technique. However, an apparatus comprising a scanner unit according to the invention may be adapted to scan mouldable units 1 of any shape, e.g. the mouldable unit 1 may comprise a concave or convex shape constituting a vessel or a boat, or an airfoiled shape constituting a wind turbine blade or a wing, or the mouldable unit 1 may comprise compact solid parts such as spars or beams etc. During manufacturing or in an operational state the mouldable unit 1 may comprise an inner opening 2 extending in a longitudinal direction of the mouldable unit 1 i.e. from one end to an opposite end of the mouldable unit 1.

The mouldable unit 1 of fig. 1 is held in a stationary position by supports 3. The scanning unit is positioned above the mouldable unit 1, i.e. opposite the supports 3, and scanning is carried out by moving the scanning bar 4 in a direction parallel to the surface of the mouldable unit 1 while the probes 5 transmit and receive electromagnetic radiation. The probes 5 can have broad or narrow directionality and whether they have one or the other is a trade-off. When the mouldable unit 1 is kept stationary during scanning, the bar 4 to which bar 4 the probes 5 are fixed, is moved by not shown moving means during scanning.

Fig. 2 shows the same embodiment as fig. 1 from an end view. Fig. 2 illustrates how radiation from each of the four probes 5 are directed to different points or areas inside the volume of the mouldable unit 1 in such a way that a volume of the mouldable unit 1 is enlightened simultaneously by transmitted radiation from at least two different positions from two neighbouring probes 5.

Fig. 3 shows a second embodiment of an apparatus according to the invention comprising the same elements as the first embodiment of figs. 1 and 2. The mouldable unit 1 of fig. 1 is also according to this embodiment held in a stationary position by supports 3, but the scanning unit is positioned at the right side of the mouldable unit 1, i.e. at an angle of 90 degrees relative to the supports 3. Also, according to the second embodiment scanning is carried out by moving the scanning bar 4 in a direction parallel to the surface of the mouldable unit 1 while the probes 5 transmit and receive electromagnetic radiation. The probes 5 can have broad or narrow directionality and whether they have one or the other is a trade-off. When the mouldable unit 1 is kept stationary during scanning, the bar 4 is moved by not shown moving means during scanning.

The embodiments of fig. 1, 2 and 3 may also illustrate a single embodiment where the scanning unit may be moved between two or more positions by mechanical means and where a scanning may then be done from different positions while moving the scanning unit along the surface of the mouldable unit 1 several times at different positions such as along the top of the mouldable unit 1 and along a side of the mouldable unit 1.

Fig. 4 shows a third embodiment where a scanning unit is attached to or embedded in a moulding part 6 being part of or constituting a mould during moulding i.e. during manufacturing of the mouldable unit 1 by shaping and hardening. When positioning the scanning unit in a moulding part 6 it is possible to follow the manufacturing process in real time e.g. by observing the flow of liquid material, and to observe errors when they occur and repair the errors while the mouldable material is still soft. The inner moulding part 6 may be a polymer membrane or a film to which the probes are fixed or attached.

In general, when monitoring a process such as a hardening process which may take several hours for a large unit 1, the scanning may be repeated one, two or more times, or be repeated every period of time such as every 10^th or 30^th minute, and either for the complete unit or for a part of the unit 1. Scanning of a unit 1 may also be repeated after hardening or curing is completed.

According to the third embodiment, the scanning unit comprises probes 5 attached to or embedded in an inner moulding part 6, a mandrel, which during moulding supports and shapes an inner surface of the mouldable unit 1. The probes 5 constituting the scanner unit may be distributed along the complete surface of the inner moulding part 6 and may then scan during the complete or part of the manufacturing process, to detect liquid flow, curing state, unattended movement of fiber material or other core material. Alternatively, the probes 5 may be distributed e.g. at a position or an area around the inner moulding part 6 and the probes 5 may then scan during removal of the inner moulding part 6 from the moulding position.

Fig. 5 shows a fourth embodiment where a scanning unit is attached to or embedded in a moulding part 6 being part of a mould during moulding i.e. during manufacturing of the mouldable unit 1 by shaping and hardening. According to the fourth embodiment, the scanning unit comprises probes 5 attached to or embedded in an outer moulding part 6 which during moulding supports and shapes an outer surface of the mouldable unit 1. The probes 5 may be distributed along the complete surface of the outer moulding part 6 and may then scan during the complete or part of the manufacturing process, alternatively, the probes 5 may be distributed e.g. at a position or an area around the outer moulding part 6.

Fig. 6 illustrates the positioning of probes 5 of a scanning unit relative to a mouldable unit 1. The probes 5 of the scanning unit are positioned close to an outer surface of a moulding part 6. There may be a narrow air gap between the probes 5 and the outer surface of the moulding part 6 during operation, alternatively, the probes 5 may be in contact with i.e. touch, the outer surface of the moulding part 6. At the beginning of a manufacturing process the mouldable material which after the manufacturing process constitute the mouldable unit 1 may be in close contact with the inner surface of the moulding part 6, but at the end of the manufacturing process an air gap 7 may have formed between the inner surface of the moulding part 6 and the mouldable unit 1. Fig. 6 illustrates how a defect 8 such as a void may be present in the mouldable unit 1, such a defect may be detected by the scanning unit according to the invention. The surface of the mouldable unit 1 not being in contact with the moulding part 6 during the manufacturing process may be covered by a membrane 9.

Fig. 7 also illustrates the positioning of probes 5 of a scanning unit relative to a mouldable unit 1. Fig. 7 comprises and illustrates the same elements as shown in fig. 6, however, the probes 5 of the scanning unit are completely embedded in the moulding part 6. The probes 5 faces the surface of the mouldable unit 1 and during manufacturing an air gap may form between the surface of the probes 5 and the surface of the mouldable unit 1.

Fig. 8 also illustrates the positioning of probes 5 of a scanning unit relative to a mouldable unit 1. Fig. 8 comprises and illustrates the same elements as shown in fig. 6 and 7, however, the probes 5 of the scanning unit of fig. 8 are partly embedded in the moulding part 6 leaving no air gap between the probes 5 and the moulding part 6 during operation.

Fig. 9 illustrates the positioning of probes 5 of a scanning unit relative to a mouldable unit 1. The probes 5 of the scanning unit are positioned at distance d to an outer surface of mouldable part 6. The distance d may be between 5 cm to 7 m. The scanning unit is position facing an "inner" surface of the mouldable unit 1, i.e. a surface facing away from the moulding part 6. At the beginning of a manufacturing process the mouldable material which after the manufacturing process constitute the mouldable unit 1 may be in close contact with an inner surface of the moulding part 6, but at the end of the manufacturing process an air gap 7 may have formed between the inner surface of the moulding part 6 and the mouldable unit 1. Fig. 9 illustrates how a defect 8 such as a void may be present in the mouldable unit 1, and such a defect may be detected by the scanning unit according to the invention. The surface of the mouldable unit 1 which is not in contact with the moulding part 6 during the manufacturing process may be covered by a membrane 9.

Fig. 10 also illustrates the positioning of probes 5 of a scanning unit relative to a mouldable unit 1 at a distance d to the unit 1. According to this apparatus, the moulding part 6 is constituted by a cylindrical form used to form a cylindrical mouldable unit 1 and the mouldable unit 1 therefore comprise an internal air gap 10. The probes 5 of the scanning unit may scan the complete cylindrical mouldable unit 1 although positioned at only one side i.e. the scanning unit may scan several layers, in the shown embodiment a double-layer.

Fig. 11 also illustrates the positioning of probes 5 of a scanning unit relative to a mouldable unit 1 at a distance d to the unit 1. According to this apparatus, a lower part of a moulding part 6 remains below the cylindrical mouldable unit 1 which comprises an air-filled gap 10. The probes 5 of the scanning unit may scan the complete cylindrical mouldable unit 1 although the scanning unit is positioned above the cylindrical unit 1 i.e. the scanning unit may scan several layers, in the shown embodiment a double-layer of mouldable material. Fig. 12 illustrates how probes 5 of a scanning unit according to the invention may be positioned at constant distance d around or along a curved surface of a mouldable unit 1.

In general, the probes 5 may be positioned in such a way that the radiation from the probe 5 hits the surface of the unit 1 in a perpendicular direction.

The invention also relates to a method for non-destructive examination of a unit 1 comprising a mouldable material such as a composite material. The method comprises:

- positioning a scanner unit according to the invention in working distance from the unit to be scanned either before or during or after manufacturing of the unit 1,

- turning on i.e. operating the scanner unit by providing the plurality of probes 5 to transmit electromagnetic radiation and receiving a response signal,

- when the scanner unit is operating each probe 5 transmits and/or receives electromagnetic radiation at each position for a period determined according to the material constituting the unit 1 being scanned,

- the received signals are then transmitted to a computation unit where the signals are treated to identify defects in the unit 1 such as voids or surface irregularities, or fiber misalignment/misplacement, delamination, cracks, curing state, or similar.

Any defects may be presented as an image or coordinates in order for a user to identify the defects, and either arrange for rectification of the defects or disposal of the defect unit.

The probes 5 may either form an array distributed over an area or volume of the unit 1 to be scanned in such a way that the array of probes is stationary during operation, or the probes 5 may form an array distributed over a bar 4 e.g. in a line, which bar 4 while the array is moved along the stationary area or volume of the unit 1 to be scanned during operation.

According to an embodiment, the signals received by receiving probes 5 which are transmitted to the computation unit and used to identify defects in the unit 1 may in case of identification of a defect be used to change moulding parameters such as direction and size of flow, temperature, and/or size of vacuum during moulding/casting.

During casting or moulding of a mouldable or composite unit, the apparatus scans a volume of the mouldable or composite material and computes the flow and location of the material during hardening receiving a large amount of data in real time. This received data can be used to generate a visual representation of the scanned material.

For composite material it is particularly advantageous that it is possible to obtain a picture of how the material flows through the composite layers. Such a representation can, for example, be used to control the flow of the hardening material. For example, by controlling the vacuum in a vacuum casting mould.

In general, a scanner unit comprising a plurality of probes 5 according to the invention may be mounted to a floor or a wall of the facility where the scanning is performed, or to a scaffold, or to a robot or robotic arm, or it may be mounted to the mould/mould tool. The scanner unit may be either movable relative to the surface of the mouldable unit 1 during scanning, or it may be stationary relative to the mouldable unit 1 during scanning. If the scanner unit is moved relative to the mouldable unit 1 during scanning, the scanner unit may be moved linearly e.g. back and forth between two or more positions, or it may be moved round or be moved irregularly e.g by a robotic arm or construction.

A block diagram for such a closed control loop is shown in fig 13, this block diagram comprises the following steps:

- a controller receives a set point or reference signal,

- the controller may increase or lower an actuator such as a valve controlling the in-flow of liquid material or temperature of the material,

- the casting or moulding process takes place in a cast/mould,

- an apparatus according to invention provided with a plurality of probes directing radiation in form of electromagnetic radiation toward the unit being moulded and register the returned response signals.

- the sensor data is returned from the scanning unit and send to a data processing unit,

- the data processing unit transfers the raw sensor data into images or similar understandable data which allows a reader to recognize defects in the unit which is being or has been moulded.

A large construction such as a wind turbine blade may comprise an internal opening 2 and may also comprise an internal enforcement such as one or more spar(s) Ila, 11b. A spar being a main structure element which carries the constructions main load. A spar may comprise an upper and a lower flange or cap and is normally connected by one or more shear webs 12.

During manufacturing of the construction, it is important that the spar 11 is correctly embedded and thereby attached to the surface material of the construction, the junction between the spar which may be a carbon beam, and the shell constituting the mouldable unit 1 is a critical point due to the difficulty in ensuring proper resin flow in such a contact section. However, it may be difficult to control whether the spar 11 has been duly attached or embedded in the mouldable material during production when the scanning unit is positioned outside the construction i.e. opposite the spar flange.

For a construction comprising an inner opening 2 or comprising parts or surfaces being difficult to reach with a floor, wall or scaffold mounted scanner unit e.g. because the parts or surfaces are positioned at a large height or positioned more or less hidden, it may be advantageous to use a scanner unit where the plurality of probes 5 during operation are mounted on a drone. A drone mounted scanner unit or a scanner unit comprising a drone may be able to reach and scan positions which are not within reach of a scanner unit which is mounted to the floor, a wall, a scaffold or similar. Especially, a scanner unit comprising a drone, or a drone mounted scanner unit may be able to fly through or along an inner opening 2 of a hollow construction such as a wind turbine blade.

Also, scanning by a scanning unit positioned inside an inner opening 2 of a mouldable unit 1 may be safer than a scanning by a scanning unit positioned outside the mouldable unit 1, as the inside opening is rarely used by staff during production and after mounting of the mouldable unit 1 at its operational position, the scanning unit may be protected from wind, rain and other conditions complicating a scanning. In general, it is possible to use the scanning unit according to the invention for measuring a flow of resin during moulding, for measuring the hardening of resin after moulding and for measuring conditions inside the mouldable unit 1 after mounting and even during operation.

When using a drone signals may be transmitted either by a wire or wirelessly.

A suitable drone acting as scanner unit may be equipped with four rotors and weigh less than 5 - 10 kg, and may preferably have a width or a maximal horizontal dimension of less than 0.4m and a height or vertical dimension of less than 0.2m, making the scanner unit suitable for flying inside a hollow construction such as a wind turbine blade between the webs (whether there's one or multiple) and the shell of the hollow construction. A compact size allows the scanner unit in form of a drone to reach almost all the way to the tip, e.g. enabling scanning of up to 98% of a wind turbine blade. During its flight within the hollow construction, the drone may e.g. change sides of a shear web (if the geometry allows it) during the return path either for obtaining a higher resolution scanning or to cover a larger area.

A drone or scanner unit according to the invention may be equipped with antennas 5 to emit electromagnetic waves and record feedback. These antennas 5 may be small standard antenna chips commonly used in communication equipment or cars for scanning of surroundings or especially produced antennas 5 adapted to the purpose. Their small size permits multiple antennas to be strategically placed on a drone thereby forming a highly efficient scanner unit. The antennas 5 can be positioned at various locations around the drone to facilitate scanning of the entire section in which the scanner unit is operating. The distance between the scanner unit and an inner surface of the hollow construction is not critical and can vary as the scanner unit navigates inside the hollow construction. The flight time i.e. the time it takes for the scanner unit to scan a complete hollow construction such as a wind turbine blade may normally be less than 10-15 min.

Fig. 14 illustrates an embodiment of mouldable unit 1 in form of a hollow construction such as a wind turbine blade which comprises two spars and two shear webs. Fig. 15A and 15B illustrate a cut-through view of two embodiments of such a large hollow construction.

The mouldable unit 1 which forms a hollow construction comprising one open end and one closed end comprises an inner opening 2 which extends in the longitudinal direction of the mouldable unit 1. Embedded in an upper wall or inner surface is a first spare Ila and opposite the first spar 11 is a second spare 11b embedded in a lower wall or inner surface. Two shear webs 12a, 12b connect the first and the second spars Ila, 11b.

Fig. 15A shows a first embodiment of a mouldable unit 1 comprising two spars, a first upper spar Ila and a second lower spar 11b and two shear webs 12a and 12b connect the first and the second spar Ila, 11b. The two shear webs 12a and 12b may define three inner openings 2 extending in the longitudinal direction of the mouldable unit 1.

Fig. 15B shows a second embodiment of a mouldable unit 1 comprising two spars, a first upper spar Ila and a second lower spar 11b and a single shear web 12a connects the first and the second spar Ila, 11b. The single shear web 12a may define two inner openings 2 extending in the longitudinal direction of the mouldable unit 1. Fig. 16 illustrates how drone i.e. an unmanned vehicle such as unmanned aerial vehicle (UAV) or an unmanned grounded vehicle (UGV) may be used to scan a unit 1. The large unit 1 being scanned may be a wind turbine blade normally having an airfoiled shaped crosssection.

The large unit 1 shown in fig. 16 comprises an outer layer 16 constituting an outer surface made of a strong material e.g. a composite material such as glass fibre, a central layer 17 made of a lightweight material e.g. porous material or a natural material such as balsa tree, or a polymer material such as foam e.g. PET foam, and an inner layer 18 constituting an inner surface also made of a strong material as the outer layer 16. In general, a unit 1 may comprise more than one light weight layers 17, and more than two strong layers 16, 18.

The unit 1 comprises two spars, a first upper spar Ila and a second lower spar 11b and a single shear web 12a connects the first and the second spar Ila, 11b. The single shear web 12a defines two inner openings 2 extending in the longitudinal direction of the mouldable unit 1.

In the first opening shown to the left, is shown an unmanned grounded vehicle 13 which is constituted of a base comprising wheels. A scanner bar 4 comprising a multiplicity of probes 5 is attached to the base of the vehicle 13 via an extendable mechanism 15. The extendable mechanism 15 makes it possible for the scanner 4 to scan at different heights. It is also illustrated that probes 5 may be attached directly to the base of the vehicle 13 in order to scan downwards.

In the second opening shown to the right, is shown an unmanned arial vehicle 14 where a scanner bar 4 comprising a multiplicity of probes 5 is attached to the body of the arial vehicle 14. The probes 5 of the scanner bar 4 is mounted at 360 degrees and allows scanning in all directions.

Fig. 17 illustrates an apparatus according to the invention comprising a scanner unit comprising three transmitting probes 5 (xi, x₂, x₃). During operation, the scanner unit may be moved to the right (indicated by an arrow) along an upward surface of the unit 1 to be scanned. The unit 1 to be scanned comprises a defect 8 in form of a void. Alternatively, the unit 1 to be scanned may be moved to the left (indicated by an arrow), or the scanner unit and the unit 1 to be scanned may both be moved simultaneously. According to the inventio, it is not significant which unit is moved as long as the scanner unit and the unit 1 are moved relative to each other.

The electromagnetic radiation transmitted from the probes 5 is illustrated as cone-shaped volumes, and during operation the radiation is transmitted from the probes 5 either continuously or intermittently as pulses.

The relative velocity (m/sec) by which the scanner unit passes along the surface of the unit 1 to be scanned may be adapted to or limited by the frequence of the radiation transmitted by the probes 5 or data acquisition speed, or transmission power or mechanical limitations for moving the bar forward, and the adaptation or limitation provides that the radiation penetrates to a desired depth of the unit 1 to be scanned. The relative velocity of the scanner unit is also adapted to provide a network of reflected radiation signals which results in a desired resolution of the final image of the scanned volume. The desired resolution depends on the unit 1 to be scanned, what the intended use of the unit 1 is and which defects must be found during a quality control, e.g. if voids having a maximum dimension of 2 mm must be found, then the resolution must be at least 0.5 - 1.0 mm.

As the scanner unit and the unit 1 to be scanned move relative to each other, the receiving probes 5 of the scanner unit receives reflected radiation from the scanned volume of the unit 1 being scanned. The received signals are transmitted or transferred to the data processing unit 19. As the relative velocity of the scanner unit is adapted, data from overlapping areas of the volume of the unit 1 being scanned is obtained and transferred to a data processing unit 19. The data processing unit 19 comprises or has access to an algorithm which can prepare a final image 20 of the volume scanned by the scanner unit. The algorithm is not part of the invention as such as many existing algorithms may be used for the purpose and depending on the unit 1 to be scanned and the circumstances during scanning the preferred algorithm may vary. However, the following algorithms are generally useful: omega-k algorithm (SAR), Range Migration Algorithm(SAR), Matched Filter (SAR), Back projection (SAR), Time Reversal, Neural Networks, Convolution Neural Networks.

Also, the apparatus may comprise means for identifying defects in the obtained final image. These means may comprise software which is part of data processing unit 19 or which may be accessed by the data processing unit 19 or which may be added as a further unit to the data processing unit 19.

Claims

1. A scanner unit for scanning a volume of a large unit (1), the scanner unit comprises a plurality of probes (5) each probe (5) either transmitting and/or receiving electromagnetic radiation, and which probes (5) during operation are directed to a volume of the unit (1),

- the scanner unit comprises at least two transmitting probes (5) or comprises at least one transmitting probe (5) and one receiving probe (5),

- the scanner unit is either configured to move along the surface of the unit (1) during operation and/or the scanner unit is configured to scan the unit (1) while the unit (1) move pass the scanner unit during operation, optionally either the scanner unit or the unit (1) is stationary during operation, characterized in that each part of the volume of the unit (1) being scanned is during operation enlightened by transmitted radiation from at least two different positions, either from one probe (5) being sequentially at two or more different positions, or from two or more probes (5) being simultaneously at two different position, receiving probes (5) of the scanner unit are configured to

- receive reflected or transmitted electromagnetic radiation data from the volume of the unit (1) during operation, and to

- transmit the data to a data processing unit (19) configured to transfer received data into images or other visual data.

2. A scanner unit according to claim 1, wherein the scanner unit is configured to scan a unit (1) comprising or being constituted of a mouldable material, and during operation i.e. during scanning, the unit (1) may be in a state hardened to final use, or the unit (1) may be in a state of hardening, or the unit (1) may be in a liquid state where mouldable material is flowing into a mould.

3. A scanner unit according to any previous claim, wherein the scanner unit is configured to scan a unit (1) comprising or being constituted of a mouldable material combined with a non-mouldable material e.g. structural units of steel or of carbon fiber or of another structural material.

4. A scanner unit according to any previous claim, wherein the scanner unit comprises at least three, or at least four, or at least five, or at least six, or at least ten transmitting probes (5).

5. A scanner unit according to any previous claim, wherein the transmitting probes (5) are positioned linearly e.g. as a straight or curved line, or as an array e.g. comprising more than one line of probes (5).

6. A scanner unit according to any previous claim, wherein the frequency region for probes (5) transmitting electromagnetic radiation is in the microwave regions from about 1 gigahertz (GHz), up to about 300 gigahertz (GHz), and preferably in the regions 5 - 60 GHz, or in the region 10 - 30 GHz, or in the region 10 - 20 GHz.

7. A scanner unit according to any previous claim, wherein the scanner unit comprises two or more groups of probes each group comprising at least one or two or three transmitting probe (5), where each group of probes (5) transmit electromagnetic radiation in different regions e.g. a first group of probes (5) transmit electromagnetic radiation in the region 10- 20 GHz and a second group of probes (5) transmit electromagnetic radiation in the region 20 - 30 GHz.

8. A scanner unit according to any of the claims 1-7, wherein the unit (1) to be scanned is a large unit being larger than 1 m in at least one dimension, or being > 2 meters, or > 3 meters, or > 4 meters, or > 5 meters, or > 6 meters, or > 7 meters, or > 8 meters, or > 9 meters, or > 10 meters, or > 15 meters, in at least one dimension, and the scanner unit is configured to move along an inner or an outer surface of such a large unit (1) during operation normally in the complete length.

9. A scanner unit according to any previous claim, wherein the scanner unit comprises an accelerometer configured to measure the velocity of the scanner unit relative to the unit (1) or relative to a stationary point, and/or the scanner unit comprises a distance measuring device which is configured to measure a distance either to the unit (1) or to a stationary point.

10. An apparatus comprising a scanner unit according to one of claims 1-9, and a data processing unit (19).

11. An apparatus according to claim 10, wherein the apparatus comprises moving means configured to either move the scanner unit relative to a unit (1) to be scanned or to move the unit (1) to be scanned relative to the scanner.

12. An apparatus according to claim 11, wherein the moving means comprises a drone i.e. an unmanned vehicle such as an unmanned aerial vehicle (UAV) or an unmanned grounded vehicle (UGV) on which drone the plurality of probes are mounted.

13. An apparatus according to claim 11, wherein the moving means comprises a robotic arm controlling the movements of the scanner unit, or the moving means comprises one or more wheels e.g. a cart or tracks controlled to move the scanner unit along the surface of a large unit (1) in a constant or at least previously determined varying distance.

14. An apparatus according claim 11 or 12 or 13, wherein the moving means move all transmitting probes (5) simultaneously and in same direction, or the moving means moves a first group of probes (5) at a first velocity and/or in a first direction or pattern and a second group of transmitting probes (5) at a second velocity and/or in a second direction or pattern.

15. An apparatus according to any of the claims 10-14, wherein the unit (1) to be scanned is a large unit being larger than 1 m in at least one dimension, or being > 2 meters, or > 3 meters, or > 4 meters, or > 5 meters, or > 6 meters, or > 7 meters, or > 8 meters, or > 9 meters, or > 10 meters, or > 15 meters, in at least one dimension, and the moving means of the apparatus are configured to move the scanner unit along an inner or an outer surface of such a large unit (1) during operation normally in the complete length.

16. An apparatus according to any of the claims 10-15, wherein the data processing unit (19) comprises means configured to visualize defects or anomalies in the scanned volume of the unit (1), the visualisation may be in form of an image (20), coordinates, text message or other visual presentation.

17. An apparatus according to any of the claims 10-16, which apparatus further comprises means configured to determine a defect or anomaly in an image prepared by the data processing unit (19).

18. Method for non-destructive examination of a volume of a large unit (1) comprising the following steps:

- providing an apparatus according to one of the claims 1-17,

- turning on i.e. activating the scanner unit,

19. A method according to claim 18, wherein the received signals transmitted to the data processing unit (19) and used to identify defects in the unit (1), in case of an identified defect are used to amend moulding parameters such as flow direction and/or size of flow, and/or temperature of inlet flow and inside mould, and/or size of vacuum during moulding.

20. A method according to claim 18 or 19, wherein identification of a defect sets a visual or audible alarm.

21. A method according to claim 18 or 19 or 20, wherein the unit (1) comprises a mouldable material and scanning of the unit (1) is done while

- the unit (1) is in a state hardened to final use and optionally in an operational position, or

- the unit (1) is in a mould and in a state of hardening, or

- the unit (1) in a liquid state and entering into a mould.