The present invention relates to a method and apparatus for multi-point forming and, in particular, to a method and apparatus for multi-point forming of metal parts and/or plastics parts.

There is an increasing demand from building and marine architects, fagade designers and fabricators to produce buildings and marine hulls formed from curved panels in a variety of materials. These structures are characterised by the use of asymmetrical, non-repeating curved surfaces. Some of the surfaces may even include compound curves.

The fabrication of shaped metal panels for such projects using the current methods falls into two categories. Firstly the formation of unique shapes in small quantities employing the traditional techniques of wheeling, rolling and incremental sheet forming. These techniques rely on the skill and judgement of the operator to interpret the required shape. These techniques are inherently dimensionally inexact with a poor surface finish and are time consuming. Secondly, mass production quantities of identical shaped panels can be created employing the technology of stamping. This relies on the skill of the dye and punch tool maker. Due to the high cost of tooling this method is only suitable for one-off projects which can be resolved with identically repetitive tessellations. Otherwise, the utility of this technique is confined to production of a large number of identical products.

Furthermore, the fabrication of panels using the first category of standard techniques relies on the skill and judgement of the mould maker to interpret the shape required. The preparation of the panel is at least partially manual and may suffer from inaccuracies as the skilled mould maker interprets the data.

The fabrication of plastic panels for such projects using standard single use thermoforming moulds is very time consuming and very wasteful of materials as each mould can only be used for one panel and must then be destroyed. This is not only wasteful of resources, but also makes some projects prohibitively expensive.

In order to reduce the wastage of time and resources inherent in each of the methods described above, multi-point forming techniques have been used to prepare a series of different moulds sequentially using the same pins, reformatted for each new mould. Whilst this allows the mould to be effectively reused , there is still a disconnect between the shape data and the element groups used for the multi-point forming.

The present invention has been created in order to overcome some or all of the drawbacks identified with regard to the known state of the art.

According to the present invention there is provided a method of forming a curved sheet, the method comprising the steps of: configuring a first pin array to have a profile aligned with the curved sheet to be formed; configuring a second pin array to transport a flat sheet into contact with the first pin array; forming a curved sheet having the profile of the first pin array from the flat sheet; reconfiguring the second pin array to have a profile aligned with the curved sheet, and using the second pin array to move the curved sheet out of contact with the first pin array.

If the method is used for forming a curved sheet from a plastics or composite material, the second pin array, when it is reconfigured to have the profile of the curved sheet, protects newly formed curved sheet that may be delicate when newly formed. Moving them using a pin array that is closely configured to the shape of the sheet allows the sheet to be moved more quickly after forming, thereby speeding up the forming process.

The first pin array acts like a reconfigurable mould which can be reused. This reduces the wastage of resources inherent in the use of standard moulding techniques, where an individual mould has to be prepared for each sheet that has a different shape and must then be discarded after use.

The configuration of the first and second pin arrays may be controlled automatically based on digital data representing the curved shape to be formed. The digital data originates from the CAD data prepared by the architect showing the shape of the object to be fabricated. This data is digitally manipulated to provide instructions to a series of actuators provided on each of the pins within the first and second pin arrays. The actuators move the pins from their datum position so that the profile of each of the pin arrays is aligned with profile of the curved sheet to be created. In this way, the array is formed directly from the CAD data of the shape to be formed without this data being taken out of the digital realm and interpreted by a skilled operative. The method may further comprise the step of pre-treating the flat sheet before transporting the flat sheet into contact with the first pin array. Depending on the material from which the sheet is formed, different pre-treatment activities may be required. For example, steel sheet may have to be cleaned and/or de-greased before it is transported into contact with the first pin array. If aluminium sheet is used, it is typically provided with a low tack protective film that may need to be removed.

The step of forming the curved sheet may include the step of pressing the flat sheet between a first part of the first pin array and a second part of the first pin array.

If the sheet is a plastics or composite material, the step of forming the curved sheet may include the steps of covering the flat sheet with a diaphragm that is configured to form a seal around the first pin array and evacuating the first pin array.

When the first pin array is evacuated the seal formed by the diaphragm forces the flat sheet to deform so that the profile of the sheet matches the profile of the first array of pins, thereby forming a curved sheet.

The method applied to plastics or composite materials may further comprise the step of heating the flat sheet before transporting the flat sheet into contact with the first pin array. The flat sheet will be more malleable when it has been heated and therefore it can be more easily formed into a curved sheet.

The method may further comprise the step of cooling the curved sheet before it is moved out of contact with the first array of pins. The cooling of the curved sheet ensures that the sheet is sufficiently resilient that it will not deform when it is removed from the first array of pins.

The method may further comprise the steps of: configuring a third pin array to have a profile aligned with the curved sheet; using the second pin array to transport the curved sheet into contact with the third pin array and trimming the curved sheet.

The provision of a third pin array that has a profile that is aligned with the curved sheet enables the curved sheet to be supported and held securely whilst the sheet is cut to size. This enables the curved sheet to have a different shape from the flat sheet.

The trimming of the curved sheet comprises a trimming tool following a path that defines the nominal profile of the curved sheet. The trimming of the curved sheet uses a trimming tool that follows a path in order to maximise the flexibility of the method as a whole in that the path of the trimming tool is not constrained and therefore the sheet can be cut to any shape. This is a contrast to a cutting tool that acts like a stamp and cuts the shape as a whole in one action or a guillotine which cuts only straight sections.

The choice of trimming tool will be dictated by the choice of the material from which the sheet is fabricated and the thickness of that sheet. The trimming tool may be a laser or, alternatively a water jet, mechanical milling machine, an oxyacetylene torch or an electron beam.

The method may further comprise checking for conflicts between a path of the trimming tool and the position of the pins in the third pin array and, if a conflict is detected, retracting the pin or pins that are subject of the conflict. The conflict checking and resolution ensures that the trimming tool has complete freedom of movement to cut the curved sheet to any shape that is required.

Furthermore, according to the present invention there is provided a manufacturing cell for fabricating curved sheets, the cell comprising: a first array of pins that can be configured to have a profile aligned with the curved sheet to be formed; a second array of connectors that can be configured firstly to interface with a flat sheet and secondly to have a profile aligned with the curved sheet.

The second array may comprise pins or one or more clamps that are configured to interface with the edge of the sheet. Throughout the forming process, the sheet remains resilient and therefore it does not necessarily require the support of a second array of pins. However, the use of a second array of pins can ease the handling of a sheet that is considerably smaller, in at least one dimension than the first array of pins.

The second array of pins may have a lower density that the first array of pins. The first array of pins is used to form the curved sheet and therefore they must be sufficiently closely packed that they form a substantially continuous surface. There must not be sufficient space between the pins for the sheet to deform between the pins and leave a witness mark identifying the edge of the pins.

In contrast, the second array of pins needs only to be of a sufficient density to hold the sheet and to move it through the manufacturing cell. The density of the second array of pins may therefore be 1/10 ^th of the density of the first array. For example, if the material to be pressed is 2mm thick, then 25 pins/m ² may be provided. Alternatively, if the material is in the region of 50mm thick then only 9 - 16 pins/m ² may be required. If the material is considerably thinner, for example 0.75mm to 1.5mm then a higher density of pins, up to 36 pins /m ² would be required.

The pins of the second array may be provided with suction pads for holding the sheet securely without marking the sheet.

The cell may be further provided with a blanket that is configured to lie on the first array of pins. The blanket enables any surface texture provided on the sheet prior to forming can be preserved.

The first pin array comprises a first part and a second part, which may comprise complementary first and second punches. The cell may further comprise a press configured to press together the first and second parts of the first pin array. Alternatively, the first pin array may comprise a single array of pins.

The first pin array may be divided into a plurality of modules. By providing a first pin array that is divided into a plurality of modules, one module can be removed and replaced if it is malfunctioning. This considerably reduces the time when the cell is non-operative as a repair to one module does not incapacitate the cell as a whole.

The second and/or third arrays are also divided into a plurality of modules. If all of the arrays are modular, then the cell as a whole can be reconfigured to process sheets of different shapes. For example, if 50 modules that measure 0.5m x 0.5m are provided they may either be configured to press 2.5m x 5.0m flat sheets or 1 m x 12.5m flat sheets. Alternatively, if a job requires a slightly different press area, then additional modules can be added. For example, although in some industries, the standard sheet size is 2.5m x 5.0m, thus requiring 50 0.5m x 0.5m modules, some sheet may be provided as 2.5m x 6.0m. However, rather than requiring an entirely new first array, 10 further modules can be added to the 50 used in the 2.5m x 5.0m configuration. The modular nature of the cell makes it much more adaptable.

If the cell is to be used for forming metal, a press may be provided for each module. The provision of a separate press for each module, means that each press can be of a lower specification than a single press that acts over the entire first array. For example, if the first array is 2.5m x 5.0m, a 2500mt press is required. If, in contrast, the first array is provided by 50 modules that measure 0.5m x 0.5m and each module is served by a dedicated press, the presses only need to be 50mt presses. As a result, considerably more cost effective presses with lower complexity can be used to achieve the same effect.

Each module is provided with an actuator configured to move each of the pins. The provision of a separate actuator for each of the modules speeds up the process of reconfiguring the first array.

When the cell is used with plastics or composite material the cell may further comprise a diaphragm and a vacuum assembly. The diaphragm preferably takes the form of a resilient frame and a flexible portion within the frame. The frame is preferably sized so that it can cover the first pin array in its entirety. In use, the frame forms a seal around the first pin array so that the vacuum assembly can form a partial vacuum around the first pin array and thereby cause the flat sheet to deform to match the profile of the first pin array thereby forming a curved sheet. When the frame is providing a seal, the flexible portion holds the flat sheet in close contact with the first pin array. The flexible portion may be elastic and may be formed of rubber.

A vacuum pump may be provided for each module. The provision of a separate pump for each module, means that each pump can be of a lower specification than a single pump that acts over the entire first array. As a result, considerably more cost effective parts with reduced internal complexity may be used to achieve the same effect.

Furthermore, when the cell is used with plastics or composite material, the cell may further comprise a heater for heating the flat sheet. When the flat sheet has been heated it becomes more malleable so it is easier to cause the deformation required to form the curved sheet. The cell may further comprise at least one further heater. Depending on the material that is chosen, it may take a considerable length of time to heat the flat sheet. If the time taken to heat the flat sheet exceeds the time taken to form the curved sheet, the pin arrays will be idle unless more than one heater is provided. A number of different flat sheets can be heated simultaneously and introduced to the first array of pins sequentially.

The cell may further comprise a chiller unit that is configured to cool the curved sheet in situ on the first array of pins. Because the deformation of the flat sheet to create the curved sheet takes place when the sheet has been rendered more malleable by the application of heat, the sheet has to be cooled before it is removed from the first array of pins to ensure that it retains its shape. Whilst the sheet could be allowed to cool under ambient conditions, this may occupy the first array of pins for an unacceptable length of time.

The cell may further comprise a third array of pins and a trimming tool. The third array of pins has a reduced density relative to the density of the first array of pins. Each of the pins within the third array may also be configured to be reduced to the datum height to allow the trimming tool to trim the curved sheet without impediment.

The trimming tool may be a laser. Alternatively, the trimming tool may be a water jet, an oxyacetylene torch, an electron beam or a mechanical milling machine. The selection of appropriate trimming tool will be dictated by the choice of material of the sheet and the thickness of the material.

The third array of pins may be provided with suction pads in order to secure the curved sheet whilst the trimming tool is active.

Each of the pins in the first, second and third arrays may comprise a stem and a head and wherein the head can tilt relative to the stem. The head may be mounted on the stem using a ball and socket joint. The ball and socket joint allows the pin head to tilt passively as it comes into contact with either the blanket or the sheet. This tilting brings the overall surface of the first array of pins closer to a continuous surface and reduces the risk of witness marks form the edges of the pin heads.

Moreover, according to the present invention there is provided a method of controlling a manufacturing cell for fabricating curved sheets, the method comprising the steps of: importing data defining the envelope of the object to be formed from the curved sheets; processing the data using rules relating to the properties of the materials from which the curved sheets are to be fabricated in order to identify an acceptable tile pattern of curved sheets on the object; re-orientating each tile in space to give the minimum excursion from the horizontal; instructing the manufacturing cell to configure a first pin array to have a profile aligned with the curved sheet to be formed; and configure a second connector array to transport a flat sheet into contact with the first pin array. The method may be carried out in a facility remote from the manufacturing cell.

The processing of the data may further comprise correction of the position of the first array of pins to compensate for the material properties. In particular, the data will be corrected to take into account the way in which the shape of the curved sheet will develop after pressing. This behaviour is sometimes referred to as spring-back.

In contrast, the second array of connectors will not be configured to take these properties into account as the second array will move the curved sheet once it has undergone spring-back.

The processing of data may further comprise analysis of the data against a set of rules relating to the acceptable appearance of sheet edges. For example, having sheets that are arranged such that the joints between the sheets are displayed close to, but not exactly vertically or horizontally might be considered to be aesthetically displeasing and therefore the analysis would favour sheets that are substantially vertical or horizontal or cut at a considerable angle from the horizontal or vertical direction.

The method may further comprise the step of checking the actual position of the pins in the first array with the position that they were instructed to take up. The checking step may include a clash detection check identifying any pins that have been incorrectly deployed, or may be faulty that are considerably out of line with the curved surface. In addition, the checking step may include a detailed remote optical inspection of the position of each pin relative to the position that it was instructed to take up. The checking of the position of each pin may be carried out simultaneously or sequentially using optical systems such as video cameras or laser distance checking technology. A further checking step may be carried out after the curved sheet has been formed. This may be carried out when the curved sheet has been positioned for trimming.

Furthermore, according to the present invention there is provided a control system for a manufacturing cell for fabricating curved sheets, the system comprising; a data connection for importing data defining the envelope of the object to be formed from the curved sheets; a memory for storing rules relating to the properties of the materials from which the curved sheets are to be fabricated; a device for processing the data using rules stored in the memory in order to identify an acceptable tile pattern of curved sheets on the object; a device for re-orientating the data relating to each tile in space to give the minimum excursion from the horizontal; a controller configured to control the pins in a first pin array to have a profile aligned with the curved sheet to be formed; and to control the connectors in a second array to assume a position suitable for transporting a flat sheet into contact with the first pin array; and to control the connectors in the second array to be reconfigured to assume a position suitable for transporting the curved sheet out of contact with the first pin array.

The control system may be configured to control a manufacturing cell as described above.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 a shows a cross section through a first array that forms part of a manufacturing cell according to the present invention;

Figure 1 b shows a cross section through an alternative first array that forms part of a manufacturing cell according to the present invention

Figure 2 shows a plan view of part of a first array of pins shown in Figures 1a and/or 1 b;

Figures 3A and 3 show a perspective view of a second array that forms part of the manufacturing cell; Figure 4 shows a cross section th rough a third array that forms part of a manufacturing cell according to the present invention;

Figure 5 shows a perspective view of an example of a manufacturing cell according to the present invention;

Figure 6 is a flow diagram showing steps in the method of operating the manufacturing cell shown in Figure 4.

Figure 1a shows a section through a first array 100 that has two height adjustable punch matrices 101 , 103 enabling a sheet to be pressed from above and below to form a curved sheet. In order to create a curved form with a constant cross section, the two punch matrices 101 , 103 are configured to have complementary profiles. Figure 1 b shows a section through an alternative first array 100 that has a single height adjustable matrix 101 over which a sheet may be drawn by hydraulically operated clamps (not shown) in order to form a curved sheet.

Each punch matrix 101 , 103 has an array of pins 102. Each pin 102 has a head 104 and a stem 106. The stem 106 extends substantially orthogonally from a pin bed 108 that defines a datum. Although only a small number of pins 102 is shown in Figures 1 a and 1 b, it will be understood that the array 100 comprises considerably more pins than can be illustrated. The array 100 extends in two dimensions and may comprise in the region of 2000 pins. As the number of pins 102 is increased for a given size of punch matrix, the size of the heads 104 can be reduced. A reduced head size results in the punch matrix 101 , 103 having a smoother surface.

The heads 104 of the pins 102 are domed and circular. Alternatively, the heads 104 may be of any two dimensional geometry including, but not limited to, a square, a triangle, a hexagon or other regular or irregular polygon. The heads 104 of the pins 102 preferably tessellate in order to provide an almost continuous curved geometry. The domed shape of the pin heads 104 enables the sheet to move slightly relative to the first array 100. Furthermore, the domed shape allows for good contact to be provided between the pin and the sheet to be pressed, even when adjacent pins are not at the same height.

In the example shown in Figure 1 b, the heads 104 of the pins 102 are also articulated as the pin head 104 is mounted on the stem 106 using a ball and socket joint. In the example shown in Figure 1 b, a ball 1 10 is provided at the end of the stem 106 adjacent the head 104. The head 104 is provided with a socket 112. The socket 1 12 is at least hemispherical so that the ball 1 10 cannot become detached from the socket 1 12. The range of movement of the head 104 is limited by the extent of the socket 1 12. As the socket 1 12 tends towards a sphere, the range of movement of the head becomes more limited. In other examples, not illustrated, the ball could be attached to the head and the socket could be attached to the stem.

The range of movement of a pin head from its neutral position orthogonal to the stem 106 dictates the maximum tangency that the matrix 101 can attain. The tangency is the angle between two shapes that form part of the curved sheet to be formed. As the angle through which the pin can rotate is dictated by the extent of the socket 1 12 surrounding the ball 110, the maximum tangency attainable by the matrix 101 is attained when the ball of a first pin 102 has rotated as far as the socket 1 12 will permit in one direction and the ball of the adjacent pin 102 has rotated as far as possible in the socket in the opposite direction. In practice, the maximum operational tangency may be less than the maximum tangency of the matrix itself as a result of the constraints of the material being formed as some materials become brittle if they are exposed to an excessive tangency. The maximum tangency may be within the range of 5° to 60°, more particularly 35° to 45°, for example 40°.

The stem 106 of the pin 102 enables the head 104 to be extended or retracted to reconfigure the first array of pins so that the matrix 101 , 103 as a whole provides a curved geometry that matches the required curved shape of the sheet to be pressed. Each stem 106 is provided with an actuator which may be a screw thread or a piston which may be electrically or hydraulically operable. Alternatively, the actuator may be a step motor. The actuator is configured to extend or retract the stem 106. Once the stem 106 has been extended, the actuator must lock the pin 102 in the extended position. A separate locking mechanism is provided so that the actuator does not have to support the weight of the press. Instead, the locking mechanism disengages the actuators and locks the pins.

If a single matrix 101 is used, then the shape that can be created will also be limited by the minimum radius that can be achieved by the matrix. In this context, the minimum radius is the radius through which a sheet can be drawn using only the hydraulic stretch forming of the metal around the perimeter of the press. The minimum radius will therefore be dictated, at least in part by the size of the press as, in a large press, the maximum distance from the perimeter to a shape to be formed is greater than in a smaller press. For example using a 2m x 4m matrix, the minimum radius of curvature is in the region of 8.8m, whereas using a 1 m x 1 m matrix the minimum radius is in the region of 0.8m (800mm).

The circular heads 104 of the pins 102 is shown in Figure 2. Therefore, each head does not tessellate with the adjacent heads 104. The extent of the gaps between the heads is not sufficient for the material of the sheet to deform between the heads 104. In order to ensure that the gaps between the heads are minimised, each row of heads is offset relative to the adjacent rows in order to provide a triangulated or honeycomb formation as illustrated in Figure 2. In an alternative example, not illustrated, the heads may be arranged in a grid. The use of a circular head is advantageous in that it ensures that the head 104 can rotate relative to the stem without coming into contact with one or more of the adjacent heads.

In a different example, not illustrated, the heads could be hexagonal, triangular or any other suitable polygonal shape. If the shape tessellates a small gap will be provided around the entire perimeter of each of the heads to ensure that adjacent heads do not come into contact with one another.

In a further example, not illustrated, the heads of one or more of the pins in the first array may be replaced by a conventional fixed die and punch die configured to represent detailed shape that is to be embossed onto the curved sheet. For example the shape may be a logo or trade mark that is positioned in the same position on each of the sheets. Alternatively, the die may enable the provision of a fixing that can be used to attach the sheets either to one another or to a substrate after they have been formed. The stems of the pins can be used to extend or retract the die relative to the pin bed so that the die conformed to the profile of the curved sheet to be formed.

In the example illustrated in Figures 1 a and 1 b the upper surface of the pin heads 104 is flat. This helps to minimise faceting on the curved sheet. However, if a regular pattern needs to be embossed onto the surface, then each pin head 104 can be domed or pointed or provided with any other suitable profile to provide an embossed shape on the curved sheet. The provision of the profile on the pin heads 104 ensure that the embossing occurs orthogonal to the surface of the sheet at every point. It also allows the pattern to be embossed at the same time as the curved sheet is formed so that the embossing does not have to be done as a separate manufacturing step which could compromise the integrity of the material and would certainly make the manufacture process take longer.

The pin heads in the examples shown are 50mm in diameter, although in other examples they may be between 40mm and 70mm or even upwards of 150mm. The size of the pin heads is dictated by the thickness of the material and the quality of finish required in the curved sheet. For example, if the cell is being used with material with thickness upwards of 75mm thick to fabricate parts that will be used in the interior of an oil tanker, then the thickness of the material means that faceting will not occur until the pin heads are quite large. Furthermore, because the curved sheets will not be open to close scrutiny then a small amount of faceting might be acceptable. Alternatively, if the cell is being used to 5mm thick material for the exterior of a luxury yacht then small pin heads must be used because faceting is not acceptable and the threshold head size at which faceting will occur is smaller than the threshold when dealing with thicker material.

Figures 3A and 3B show an array of clamps 300 which act as connectors to connect with the sheet for the purposes of moving it into and out of contact with the first array of pins. Each clamp has a pair of jaws 302, 304 that project substantially horizontally so that they can clamp the edge of the sheet 200. Each of the clamps 300 is provided on a stem 306 which enables the clamp 300 to be extended or retracted relative to a datum line. In Figure 3A the array of clamps 300 is configured to transport a flat sheet 200. In Figure 3B the array has been reconfigured to transport a curved sheet 202. This reconfiguration has occurred by virtue of a change in the length of one or more of the stems 306.

The stems 306 of the clamps are attached to the jaws 302, 304 by a neck portion 308 which extends substantially horizontally so that the distance between the stems 306 holding one side of the sheet and the stems holding the opposite side of the sheet is greater than the width of the first array of pins. As a result the clamp 300 can introduce a flat sheet between the two parts of the first array of pins with ease.

In an alternative example, shown as part of Figure 5, the second array 142 is an inverted version of the array shown in Figure 4. Figure 4 shows a cross section through a third array 400 of pins. Each pin 402 has a head 404 and a stem 406. The stem 406 extends substantially orthogonally from a pin bed 408 that defines a datum. Each stem 406 is provided with an actuator (not shown). The actuator may be a screw thread or a piston which may be electrically or hydraulically operable. Alternatively, the actuator may be a step motor. The actuator is configured to extend the stem 406 above the pin bed 408. The actuators can be deployed in order to reconfigure the geometry of the array from a substantially flat geometry so that it corresponds with the nominal shape of a curved sheet.

The pin head 404 is mounted on the stem 406 using a ball and socket joint. In the example shown in Figure 4, a ball 410 is provided at the end of the stem 406 adjacent the head 404. The head 404 is provided with a socket 412. The socket 412 is at least hemispherical so that the ball 410 cannot become detached from the socket 412. The range of movement of the head 404 is limited by the extent of the socket 412. As the socket 412 tends towards a sphere, the range of movement of the head becomes more limited. In other examples, not illustrated, the ball could be attached to the head and the socket could be attached to the stem.

Figures 5a and 5b show the first array of pins illustrated in detail in Figures 1 and 2, in the context of a manufacturing cell 120. Each manufacturing cell 120 has a pre- treating region 130; a pressing region 140 and a trimming station 150. The manufacturing cell 120 illustrated in Figure 5a is optimised for preparing curved sheets of materials including aluminium, steel, corten or stainless steel. The thickness of the sheet may range from 0.25mm to in excess of 75mm although many applications will require sheet in the range of 3mm to 25mm thick.

In the example illustrated in Figure 5a, the pre-treating region 130 includes a de- greasing zone 132 in which the surface of the flat sheets can be treated to ensure that it is grease free before being introduced into the pressing region 140.

The manufacturing cell 120 illustrated in Figure 5b is optimised for preparing curved sheets of materials including thermoplastics and composites such as filled acrylics and filled polyesters that might be used in kitchen work surfaces, for example.

In the example illustrated in Figure 5b, the heating region 130 includes one heater 132 that is sized to accept the flat sheets that are being processed in the manufacturing cell 120. Depending on the properties of the material that is being used , it can take considerably longer to bring a flat sheet up to the correct temperature than it takes to press the sheet to form a curved sheet. In order to ensure that the efficiency of the manufacturing cell as a whole can be optimised, more than one heater can be provided so that a number of flat sheets can be heated simultaneously. Each heater 132 is configured to heat the flat sheet so that it becomes sufficiently malleable for use in the pressing region 140. The time taken to heat the flat sheet will depend on the thickness of the sheet and the thermal properties of the material from which the sheet is formed. Some materials are capable of responding to large temperature gradients whereas other materials can become brittle if heated or cooled too quickly.

The pressing region 140 of the example illustrated in Figure 5a includes a first array of pins 100 comprising either a complementary pair of first and second punch matrix 101 , 103 or a single matrix 101 , a second array of pins 142 and a press 146. The matrix 101 or the matrices 101 , 103 forming the first array of pins 100 can be configured to have a profile to match the nominal profile of a curved sheet to be formed using the cell. The pins 102 in the first array are closely packed as shown in Figures 1 and 2. As illustrated in Figure 5b, the pressing region 140 has a diaphragm 144 and a vacuum assembly 146b. The blanket 148 is not shown in Figure 5b for the sake of clarity.

The first array of pins 100 includes in the region of 2000 pins, each of which has a diameter of between 2mm and 500mm, preferably 40mm and 70mm, and more preferably 50mm. The first pin array is therefore 2.5m by 5.0m. Each of the pins is configured to be capable of extending up to, but not limited to, 1 m from the pin bed 108. The size of the pin heads and the number of pin heads can be scaled up or down depending on the application.

The pins of the second array of pins 142 are similar to the pins in the first array 100 in that they can be extended from a pin bed using individual actuators and each pin

102 has a head 104 and a stem 106. The second array of pins is a single sided array that approximately replicates the shape of the upper or single punch matrix 101 of the first array 100. Furthermore, the density of the pins 102 in the second array is considerably lower than the density of the pins in the first array 100. The second array of pins is used for transporting the sheet between the different parts of the cell

120. The second array of pins can therefore be configured so that all of the stems are of equal length in order to allow a flat sheet to be transported from heating region 130 to the pressing region 140. The second array of pins can then be reconfigured to have a profile that matches the desired profile of the curved sheet. The second array of pins is then used to remove the curved sheet from the first array of pins and transport it to the trimming station 150. The transporting of the sheet by the second array of pins is a mere translation of the sheet in the horizontal plane in the example shown in the Figures. However, in different configurations of the cell the transporting of the sheet may include translation to any position in the plane parallel to the pin bed, and optionally vertical translation and even rotation of the second array to bring the curved sheet into contact with a vertically configured third array.

In order to transport the sheet in its flat and curved configuration, the second array of pins can be configured so that all of the stems are of equal length in order to allow a flat sheet to be transported from the pre-treating region 130 into the pressing region 140. The second array of pins can then be reconfigured to have a profile that matches the nominal profile of the curved sheet. The second array of pins is then used to remove the curved sheet from the first array of pins and transport it to the trimming station 150.

The heads 104 of the pins 102 of the second array 142 are provided with suction pads 143. The suction pads 143 enable the pins of the second array to be attached to the sheet without damaging it.

In the example illustrated in Figure 5a, the press 146 is used to push together the first and second parts of the first array of pins in order to deform the sheet that is disposed between the sheets.

In order to reduce the appearance of faceting on the curved metal sheet, a blanket 148 is provided on the first array of pins. The blanket 148 helps to provide a continuous geometry against which the curved sheet may be formed. In addition, the provision of the blanket ensures that if the surface of the flat sheet is textured or embossed, the texture or embossing will be retained after the pressing of the sheet. The blanket 148 is formed from a highly elastic rubber that is capable of deforming to retain the surface contours of the sheet.

In the example illustrated in Figure 5b, for use with plastics or composite materials, The diaphragm 144 and vacuum assembly 146 act together with the first array of pins 100 to deform a flat sheet 200 to create a curved sheet 202. The diaphragm 144 has a frame 145 and a flexible portion 147 that is located within the frame 145. The diaphragm 144 is sized to cover the first array of pins 100 and to form a seal with the edge of the pin bed 108. The diaphragm 144 is provided so that the cell does not rely on the edges of the flat sheet 200 to form the seal. This enables the cell to be used with flat sheets that are smaller in at least one dimension than the first array of pins. Once a flat sheet 200 has been placed on the first array of pins 100, the diaphragm 144 covers the pins and the frame 145 forms a seal with the edge of the pin bed 108. The flexible portion 147 deforms to fit closely around the pins and the sheet. The vacuum assembly 146 then draws air through the pin array 100 and deforms the flat sheet 200 to form a curved sheet. If the modules of the first array are reconfigured to be a different size and/or shape, then a different diaphragm 144 needs to be provided.

In order to reduce the appearance of faceting on the curved sheet, a blanket 148 is provided on the first array of pins. The blanket 148 prevents the sheet from oozing between the pins and helps to provide a continuous geometry against which the curved sheet may be formed. In addition, if a surface texture is to be imparted to the sheet, this can be achieved by providing the texture on the blanket 148. The blanket

148 is formed from a synthetic cellular material which is gas permeable so that the vacuum assembly can suck air through the blanket 148. In other examples the blanket may be omitted and surface texturing can be provided through the use of shaped pin heads 104.

Depending on the material of the sheet, the length of time that the curved sheet takes to become sufficiently resilient to be moved from the first array of pins may be excessive. In this case a chiller 149 is provided to cool the curved sheet.

The entire trimming station 150 may be located in a temperature controlled environment to ensure that the extent to which the curved sheet is cooled before and during the trimming process can be closely controlled.

In both of the illustrated examples, the trimming station 150 is provided to trim the curved sheet that is created in the pressing region 140. The trimming station 150 includes a third array 152 of pins and a trimming device 154. The third array of pins 152 has a low density of pins relative to the first array and the pins are provided with suction pads 153 in order to hold the sheet in position. The third array of pins 152 is a single array similar in shape to the lower punch matrix 103. The trimming device 154 is a laser which is mounted above the third array of pins 152 and is configured to travel along a path 156 around the perimeter of the sheet. In addition to cutting around the periphery of the sheet 202, the trimming device 154 can also engrave setting out marks, a barcode or other form of identification to show the correct orientation of the sheet and thereby to aid the operatives assembling the sheets into a finished product. Furthermore, the trimming device can provide holes, pockets, grooves at any point across the surface of the sheet or even a laser cut patterning applied across the entire sheet.

A fourth array of pins 158 is provided to remove the trimmed curved sheet from the trimming station 150. The pins of the fourth array of pins are substantially the same as the second array 142 which may be made up of pins or clamps as described above. However the provision of a further array means that the second and fourth arrays can act simultaneously ensuring that each region of the cell can operate at optimum capacity. Furthermore, the provision of a dedicated array of pins that interfaces with the sheet after the trimming process ensures that no debris from the trimming process can be introduced into the pressing region 140.

In the illustrated configuration the third array of pins 152 is configured to support the curved sheet from below and therefore the second array of pins 142 is configured to perform a simple translation in position of the curved sheet 202. In an alternative example, the datum plane of the third array of pins 152 may be configured vertically and therefore the second array of pins will be configured to move the curved sheet horizontally, vertically and also to rotate the curved sheet in order to bring it into contact with a vertically configured third pin array 152. This is a particularly advantageous configuration in situations wherein floor space is at a premium.

The first array 100 is divided into a number of modules, each of which comprises a first matrix 101 and a second matrix 103. Each module also includes a pair of actuators configured to extend and/or retract the pins within each of the two matrices.

In the illustrated example, the first array is 2.5m x 5.0m and is made up of 50 modules each measuring 0.5m x 0.5m. In order to provide 2500mt pressing force over the entire first array, each module requires a press capable of 50mt of force. As a result of the modular nature of the cell, the presses can be comparatively low-tech as the force that each one has to develop is comparatively low. I n addition , the number and configuration of the modules can be changed comparatively easily in order to enable the cell to be adapted for different assignments. For example, it is preferable to match the size of the first array to the size of the flat sheet and many industries use 2.5m x 5.0m as standard. However, if the cell needs to be reconfigured in order to form wind turbine blades which are considerably longer and narrower then 10 modules could be removed and the remaining modules arranged to provide a 1 m x 10m array.

The modular nature of the cell also minimises the down time in the case of a fault being detected. Instead of having to take the entire cell out of service until the fault can be rectified, the single module in which the fault has been identified can be removed and replaced and the cell can then continue to function whilst the faulty module is repaired. Whilst it is not practical to remove an entire cell for repair and therefore repairs will typically have to occur in situ, with a modular system repair work can be carried out remotely with the only work carried out on the site of the cell is the exchange of a faulty module for a fresh module.

Furthermore, each module is provided with a pair of actuators, one of which is configured to act on each matrix 101 , 103 within the module. This considerably speeds up the setting of the pins of the first array in comparison with a single actuator moving over the entire cell.

The cell 120 is capable of producing sheets rapidly. For example, the time taken for an individual sheet to pass through the cell may be about 1 hour. Of course, each part of the cell may contain a different sheet at any one time so whilst one or more sheets are being pre-treated, one may be pressed and one may be trimmed. The forming of the curved sheet from the flat sheet takes between 10 and 30 minutes, preferably 20 minutes.

Figure 6 shows a flow diagram of the steps in the method 600 of operating the manufacturing cell described above with reference to Figures 5a and 5b.

The method 600 operates in an operative free environment. This means that, when the cell is running well, there is no need for human intervention. This differs considerably from current techniques of skilled craftsmen making bespoke panels or curved sheets. It also differs considerably from the semi-automated lines used by the automotive industry where a large number of operatives each complete one or more manual tasks on each vehicle that is produced. The method described herein with reference to figure 6 deskills the making of the moulds and increases the repeatability and accuracy over and above what can be expected of operatives of a production line.

The method 600 includes a data analysis phase 610; an instructing phase 620; a forming phase 630 and a quality control phase 640. The entirety of the data analysis phase 610; and at least part of the instructing phase and the quality control phase 640 may be carried out at a location that is remote from the manufacturing cell 120.

The data analysis phase 610 involves taking data relating to the overall shape of the object to be formed directly from the electronic design tool that has been used by the architect, for example CAD packages such as Microstation, Maya, 3DStudio, Catia, SolidWorks, SolidEdge, Inventor, ProEngineer, Rhyno or similar package. This object to be formed may be a building, a wind turbine blade, a boat hull, a yacht or any other large and complex structure. Alternatively, the object may be much smaller, but more complex and requiring to be formed from thinner sheet. The object may be formed from in the region of 50 to 100 sheets, right up to many tens of thousands of sheets.

The data is subjected to a cut and slice analysis 612. In this step of the analysis, the data is analysed with reference to rules relating to the properties of the materials from which the object is to be made. This includes, for example, rules about the maximum extent of curvature that the first array can achieve and the material can tolerate. In addition, rules about acceptable tiling configurations are included. For example, angles close to but not exactly vertical or horizontal may be classed as aesthetically displeasing and therefore the analysis may favour tiling that is either aligned with the horizontal and vertical plane or is at a considerable angle to the horizontal. The result of the cut and slice analysis 612 is a series of virtual sheets superimposed on the object data in the position in which they will be positioned as part of the completed object.

The data is then subjected to a tiling analysis 614 in which each virtual sheet is extended to have an overlap with the adjacent sheets. This overlap effectively acts as a selvedge and can be trimmed. In this region the data is extrapolated to draw down the edges of the sheet back to the datum so that the curved sheet does not have edges that exceed the material properties and may be prone to splitting as a result of excessive stresses during cooling.

I n order to adapt the data output of the tiling analysis 614 so that it can be transmitted to the manufacturing cell, the data relating to each virtual sheet must be rotated and translated so that the virtual sheet oriented in a known position in space that can be defined as a datum. Each virtual sheet then lies as near to the horizontal as possible. This minimises the vertical excursion of the pins in the first array. Each virtual sheet is also rotated until it presents a domed, rather than dished form. Tiling control options include nurbs, parametric, procedural, algorithmic or manual control.

The data is then subjected to properties analysis 616. This calculates how the properties of the material will cause the shape of the curved sheet to deviate from the shape of the first pin array. In other words, the data is analysed to take spring back into account. The shape of the first pin array can then be altered to compensate for the spring back that is expected based on the material. In this way, once the material has sprung back as expected, the nominal shape will be achieved. In other words, the first pin array can be altered so that, once the material has deformed as expected, the desired shape will be achieved.

In the instructing phase 620, the position of the pins in the second, third and fourth pin arrays is taken from the output of the tiling analysis 614 as this is representative of the nominal shape of the curved sheet. The position of the pins in the first pin array is taken from the output of the properties analysis 616 as this is representative of the compensated shape of the curved sheet.

The quality assurance phase 640 proceeds throughout the pressing phase 630. The quality assurance phase 640 includes a first check 642 and a second check 644. The first check involves a simple clash detection check which identifies any pins that have malfunctioned and are positioned outside an acceptable envelope followed by a detailed comparison between the data output from the tiling analysis and the actual position of the pins of the first array 100. The actual position of each of the pins can be ascertained by an optical sensor such as a camera or a laser.

Providing the output of the first check 642 is satisfactory, the pressing phase 630 will proceed. The flat sheet 200 will be treated in the pre-treating region 130, moved by the second pin array into the pressing region 140, pressed to form a curved sheet 202. The second array of pins will be reconfigured to match the profile of the curved sheet and then deployed to move the curved sheet to the trimming station 150.

Once the curved sheet is at the trimming station 150 it rests on the third array of pins 152. Because the third array of pins 152 is configured to match the shape of the curved sheet, there should be only one correct position for the curved sheet. However, in order to ensure that the curved sheet 202 is correctly positioned prior to the deployment of the trimming device, the quality assurance phase includes a remote optical inspection 646 of the curved sheet. Providing that the remote optical inspection 646 confirms that the curved sheet is correctly positioned, the second array of pins is moved away and the trimming device is activated. Once the trimming process is complete, a further quality assurance operation 648 takes place to confirm that the profile of the curved sheet is correct, that the trimming has been correctly executed and also to check for the presence of any additional features added during the trimming process, for example grooves, pockets, holes or identification marks.