Method for shaping a film-like/sheet-like material

Abstract

Method for shaping a film/sheet, particularly for making three-dimensional shapes in it, in which case the outlines of the shape to be formed are warmed/heated and the film/sheet is stretched along the heated outline, in order to cause the part of the film/sheet inside it to deviate from the plane of the surface. The heated outlines are created by, for example, directing a moving beam of thermal radiation onto it. A countersurface is provided to limit the stretching and ensure that rupture does not occur. By repeating the procedure sequentially, a great variety of shapes may be created.

Claims

1. A method for shaping a material film or sheet for making three-dimensional shapes, wherein the film or sheet is heated and a pressure difference is applied by means of a pressure medium to one side of the film or sheet; the heating being performed along an outline of the three-dimensional shape to be formed to a temperature which will permit a change in the shape of the film or sheet in the area of the heated outline and will create stretching along the heated outline in order to cause the unheated part of the film or sheet inside the outline to deviate from its initial plane, the targeted three-dimensional shape being divided into two-dimensional slices, the outlines of which in the film or sheet are sequentially heated and subjected to a pressure difference to generate the desired shape, comprising the following steps: providing a countersurface to limit the stretching of the heated material during a stretching stage, allowing the material to cool and harden, moving the countersurface to a new position, heating a next outline, applying a pressure difference to stretch the material along said next heated outline until the material again meets the countersurface, and repeating the process until the desired shape is obtained.

2. The method according to claim 1, wherein the heated outlines are formed in the film or sheet by directing a moving beam of thermal radiation to it.

3. The method according to claim 1, wherein the film or sheet consists of an organic polymer, particularly of a thermoplastic material.

4. The method according to claim 1, wherein the film or sheet has a composite structure.

5. The method according to claim 1, wherein the film or sheet is metal or a metal alloy.

6. The method according to claim 1, wherein pulses of pressurized medium are used to shape the film or sheet in different directions in different stages.

7. The method according to claim 1, wherein the heating is performed by using a source of collimated or focused infrared or laser light.

8. The method according to claim 1, wherein in the shaping, a computer-based system is used, into which the three-dimensional model to be formed is loaded.

Description

[0013] Thus:

[0014] FIG. 1 shows the initial situation, the first outline being applied on an essentially flat sheet of material,

[0015] FIG. 2 shows the step of applying a pressure difference,

[0016] FIG. 3 shows how the stretching is limited, and

[0017] FIG. 4 shows the final product.

[0018] Thus, FIG. 1 shows an essentially sheet-like initial product 1, on which a shape to be made is indicated by dotted lines 2. Following the edge line of the shape 2, it is bordered by a line marked by broken lines 3, along which the area is heated to a temperature that permits a pressure-pulse stage, which takes place next. The source of the heating radiation 4 is marked with the reference number 5. The source can be, for example, a laser light source.

[0019] No more detailed reference is made here to laser technology, which is one possible heat source, because this area of technology will be conventional technology to one skilled in the art.

[0020] The intention is to heat the outlines of the image in the material to such a temperature that in the following stage, the outlines will be sufficiently elastic for a pressure difference to cause stretching in the material, so that the heated parts of the material sheet or film heated along the desired outlines will stretch and the unheated area remaining inside the heated lines will rise from the level of the material, in the direction of the lower pressure.

[0021] FIG. 2 shows the vacuum and/or excess pressure treatment described above. In this case, a lower pressure prevails above the sheet 1 than below it, so that a portion of the sheet heated along its outlines rises upwards from the level of the rest of the sheet/film.

[0022] FIG. 3 shows how a beam from a laser 6 is directed to a galvanometric scanning mirror device 7, corresponding to the generally depicted radiation source 5 of FIG. 1. A computer or a special purpose microprocessor (not shown) controls the scanning mirrors 7 so that the laser heating pattern draws a contour onto the sheet material 1 that is attached to a chamber 8, in which the pressure has been reduced relative to the outside of the chamber. Inside the chamber 8, there is a flat horizontal platform 9 that is attached to a vertically movable translation mechanism 10. This platform acts as a countersurface limiting the movement of the sheet portion that shifts due to the pressure difference between the upper and lower surface of the sheet.

[0023] Initially, the platform 9 is located at a height below the top surface of the chamber 8 corresponding to the desired and allowable stretching of the heated contour area. After the laser beam softens the first contour, the pressure differential above the sheet material 1 pushes the material within the contour area to abut the platform 9. When the laser is turned off, the material cools and hardens maintaining the step shape. The platform can now be moved down by another desired increment. The system is now ready for the laser to soften the next contour and the pressure above pushes the interior of the contour again to abut the platform 9. The process continues until the defined shape has been formed through consecutive heating and stretching steps.

[0024] In the above figures, the stepped shape is shown roughly for reasons of clarity. In practice, the final shape may be achieved by slicing the final 3D shape into very thin 2D slices, from which the shaping of one slice at a time in the desired direction is performed as consecutive operations. Even a relatively simple final shape may involve a significant number of stages.

[0025] Negative shapes can also be made according to the invention. This refers to the fact that the desired shape is created with the aid of heating and excess or vacuum pressurization, which excess or vacuum pressurization is performed in the opposite direction to the general direction of the overall shape. In this case, it is also possible, if necessary, to exploit the memory property of the material, when re-heating of the outlines will return it to its former shape.

[0026] It is obvious that according to the invention, very many different types of material can be used. The most obvious material is an organic polymer. However, other materials that become plastic at a certain temperature are also suitable for use according to the invention. For example, nearly all metals soften to become malleable at a certain, specific temperature. One interesting area is also composite-structure films/sheets. Thus, whether the use of a specific material will succeed or not depends only on variables such as the dimensioning of the heating power source, the duration of its operation, and similar.

[0027] It is also obvious that reference to a sheet or film includes a large variation in material thicknesses.

[0028] The temperature is controlled in some suitable manner. The skilled person is aware of a large range of alternatives for this purpose in different fields of technology. However, it can be mentioned that temperature can be measured and its control performed, for example, with the aid of a heat camera based on infrared technology monitoring the laser beam. Temperature monitoring may be used in the general control of the process.

[0029] In this context, it should be noted that according to the aforementioned procedures, the heating can take place in such a way that a continuously heating radiation beam is moved along the outlines of the image to be formed, when the material will heat at the outlines.

[0030] Another way is one, in which the thermal radiation moves along a specific, usually backwards and forwards path, and heating occurs locally only at points located on the outlines of the image being formed. The movement of the thermal radiation can be achieved by moving a component creating thermal radiation, but more probably it will take place in such a way that the control of the thermal radiation takes place with the aid of mirrors, lenses, or corresponding optical elements, as exemplified above.

[0031] A third alternative is an embodiment where the heated area is created in such a way that a pattern shaped to correspond to the area to be heated by a thermal radiation beam is created in the heating head which is aimed at the material to be heated, and a heated area corresponding to the outlines of the shape, arises in a single operation. There are several ways of forming a thermal radiation beam of a desired shape, whereby optical methods are the most likely.

[0032] A procedure of this kind can be envisaged as very advantageous when a relatively simple product is being made in a large series.

[0033] A common feature in all of described embodiments is that the heating is performed only along the outline of the area to be raised from the initial plane.

[0034] According to the method according to the invention, the heating/pressurization cycles can be repeated for a desired number of new coordinates, which means that three-dimensional surfaces can be formed from a film/sheet in the same manner as in vacuum moulding, but in the present method the geometry of the piece is created directly by numerical control, without moulds.

[0035] It should also be noted, that shapes can also be formed, for example in such a way that, as already stated, shapes that are negative with respect to the previous stage are made onto three dimensional shapes created by one way or another in a stage. This refers, for example, to a situation, in which the product is shaped originally, by means of vacuum forming, for example, with the aid of a mould. For vacuum forming to be possible, the product must not have protrusions extending in opposite directions, as such a shape would prevent it from being detached from the mould.

[0036] By means of the method according to the invention, the shaping of a vacuum-moulded body can be carried out in a continuous operation, generating protrusions in any direction during the process. As such, the method is suitable for very many different purposes.

[0037] If desired, temperature and/or distance measurement can be used as variables controlling algorithms exclusively or in combination. Return and reshaping according to the prior art can also be used in this method.

[0038] Experiments have shown that liquid, as well as pressurized air or gas can be used for shaping, in which case the control of the shape becomes a mathematically calculable change in volume of each free-form change in shape.

[0039] In practice, an application can be based on a computer-based system, in which the desired three-dimensional model is loaded into the system, which slices the model into parts and which controls the heating and operating unit according to the model produced, the unit performing the shaping in stages of the film or sheet by heating specific outlines, performing the stretching of the material at the outlines with the aid of pressure, simultaneously controlling the movement of the countersurface limiting the stretching, and thus manufacturing the final product.

[0040] Any known system with the aid of which a targeted heating effect can be created can be used for heating. Such systems are particularly based on the use of laser or infrared-range light and on possible optical concentration, collimation or reflection of the light.

[0041] Because the return/returning of the film is not necessary in all cases, this extends the range of materials available for use.

[0042] The invention can be varied in many ways without nevertheless deviating from the scope of protection of the basic idea of the invention as defined in the accompanying claims.