Manufacturing process for producing a thermoplastic component

Abstract

Manufacturing process for producing a thermoplastic component (1) comprising the following steps: • Heating at least one first section of a thermoplastic semi-finished product (2) to a first temperature T1, such that the first section of the thermoplastic semi-finished product (2) is thermoplastically deformable; • Forming the first section of the thermoplastic semi-finished product (2), heated to temperature T1, from its initial shape to a near-net-shape shape, with subsequent retention of a form constraint of the thermoplastic semi-finished product (2) in the near-net-shape shape; • Heating at least one second section (3) of the thermoplastic semi-finished product (2) to a second temperature T2 until the at least one second section (3) is in a molten state, wherein the temperature T2 is greater than the temperature T1 (T2>T1); • Further forming of the thermoplastic semi-finished product (2) into the shape of the thermoplastic component (1); and • Cooling at least the first and at least one second section (3) of the thermoplastic semi-finished product (2) to a third temperature T3, wherein the temperature T3 is lower than the temperature T1 (T3

Description

[0001] The invention relates to a manufacturing process for producing a thermoplastic component, in particular for producing a thermoplastic rigid foam core.

[0002] For complex sandwich components, rigid foam cores are often used in industry. These cores must form a thin edge where the face sheets, usually made of carbon fibers or other fiber materials, are joined together with the rigid foam core to form the sandwich component. Such a manufacturing process for a sandwich component is described, for example, in WO 2016 / 020252 A1.

[0003] Furthermore, various methods for manufacturing sandwich components are known from the publication “Manufacturing of thermoplastic composite sandwich structures: A review of literature”, published in the “Journal of Thermoplastic Composite Materials” (2017, Vol. 30, No. 4).

[0004] Further relevant state of the art is given by DE 10 2015 007 886 A1 and DE 10 2013 214 536 A1.

[0005] Such rigid foam cores or thermoplastic components are currently manufactured by machining or foaming, which is slow, complex and therefore expensive.

[0006] Conventional thermoforming processes are unsuitable for manufacturing such cores because, during the manufacturing process for the sandwich components, the edge regions of the core, previously shaped by thermoforming, are re-deformed by pressure and temperature. These edge regions, which must be tapered to a point to join the face sheets, lose their cohesion during the manufacturing process and therefore do not allow for a durable shape in the sandwich components. Furthermore, the edge regions cannot be compacted to the desired thickness required for a smooth, visually appealing transition using a conventional thermoforming process.

[0007] The invention is therefore based on the objective of overcoming the aforementioned disadvantages and providing a method to quickly and inexpensively transform a thermoplastic semi-finished product into a thermoplastic component, whereby predetermined areas are to be irreversibly transformed in order to make the thermoplastic component dimensionally stable, at least in sections.

[0008] This problem is solved by the combination of features according to claim 1.

[0009] According to the invention, a manufacturing process for producing a thermoplastic component is proposed, comprising at least the following steps: • Heating at least one first section of a thermoplastic semi-finished product to a first temperature T1, so that the first section of the thermoplastic semi-finished product is thermoplastically deformable; • Forming the first section of the thermoplastic semi-finished product, heated to temperature T1, from its initial shape to a near-net-shape shape, with subsequent retention of a form constraint of the thermoplastic semi-finished product in the near-net-shape shape; • Heating at least one second section of the thermoplastic semi-finished product to a second temperature T2 until the at least one second section is in a molten state, wherein the temperature T2 is greater than the temperature T1 or T2>T1; • Further forming of the thermoplastic semi-finished product into the shape of the thermoplastic component; and • Cooling at least the first and at least one second section of the thermoplastic semi-finished product to a third temperature T3, wherein the temperature T3 is lower than the temperature T1 or T3. <T1.

[0010] A thermoplastic component, core, rigid foam component, or rigid foam core is understood to be a component made of a thermoplastically deformable material. Similarly, a thermoplastic semi-finished product is understood to be a starting product made of a thermoplastically deformable material.

[0011] Cooling can be achieved passively via cooling surfaces or actively via cooling channels. For active cooling, several cooling channels are advantageously provided, which dissipate the temperature via a heat-storing and heat-transferring medium, such as oil. Multiple oil circuits are advantageous for active cooling.

[0012] Forming at or near temperature T1 creates internal stresses in the thermoplastic semi-finished product, particularly in areas with a high degree of deformation. These internal stresses can cause the affected areas to lose their cohesion during subsequent manufacturing steps to produce a sandwich component. To minimize these internal stresses and ensure high dimensional stability in the thermoplastic component, the areas or sections that are at risk of losing their shape in subsequent manufacturing steps are heated to temperature T2. The thermoplastic material in these areas or sections fuses, at least partially, causing any existing foam structure to collapse or dissolve.The heating time for the second sections to temperature T2 is preferably less than 120 seconds, and more preferably between 10 and 30 seconds. The cooling time to temperature T3 is preferably between 1 and 2 minutes.

[0013] The first section extends at least over part of the length of the thermoplastic semi-finished product; preferably, the entire thermoplastic semi-finished product is heated to temperature T1.

[0014] It is further advantageous if the first temperature T1 lies within a temperature range of the thermoplastic semi-finished product in which the thermoplastic semi-finished product is thermoplastically deformable, the second temperature T2 is equal to or above the melting temperature of the thermoplastic semi-finished product, and / or the third temperature T3 lies below the temperature range of the thermoplastic semi-finished product in which the thermoplastic semi-finished product is thermoplastically deformable. Preferably, the temperature T1 lies between 210 °C and 230 °C, the temperature T2 between 260 °C and 265 °C, and the temperature T3 between 80 °C and 100 °C.

[0015] Furthermore, it is advantageous for the process that the thermoplastic semi-finished product is made of a thermoplastically deformable plastic, in particular PET, and that the thermoplastically deformable plastic is in a foam structure or is formed as a thermoplastic rigid foam.

[0016] An advantage of this further development is that the first section of the thermoplastic semi-finished product, heated to temperature T1, is formed from its initial shape to a near-net-shape shape by a press tool comprising a first and a second press tool side, which exert a predetermined force on the semi-finished product. The press tool cools the thermoplastic semi-finished product to a temperature below T1, preferably at temperature T3.

[0017] The first section of the thermoplastic semi-finished product, together with at least one second section of the thermoplastic semi-finished product which is heated to the second temperature T2, is advantageously further formed by the press tool into the shape of the thermoplastic component, whereby the predetermined force is maintained or increased. The further forming is carried out after or in parallel with the heating of the second section to temperature T2.

[0018] The at least one second section of the thermoplastic semi-finished product is advantageously an outer edge region of the thermoplastic component extending along a longitudinal direction X of the thermoplastic component.

[0019] It is further advantageous that the at least one second section of the thermoplastic semi-finished product, through reshaping and further forming in a lateral direction Y, which runs orthogonally to the longitudinal direction X, continuously decreases from a first height H1 to a second height H2, wherein the second height is preferably between 5% and 10% of the height H1. The height H2 can advantageously be reduced to such an extent that the outer section detaches from the thermoplastic component and a tapered end is formed.

[0020] The second height along the longitudinal direction X is advantageously varied at intervals, so that sections with differing second heights H2 are created in the longitudinal direction X. These sections hold the outermost sections of the thermoplastic semi-finished product to the thermoplastic component by means of webs and form the outer edge region of the thermoplastic component, separating them from the outermost sections of the thermoplastic semi-finished product. The webs hold the outermost sections of the thermoplastic semi-finished product to the thermoplastic component, allowing them to be removed from the mold without additional measures. The outermost sections can then be easily separated or broken off from the thermoplastic component in subsequent manufacturing steps.

[0021] Another advantage is that the manufacturing process • a cuboid rigid foam semi-finished product is heated to temperature T1 and formed by a pressing tool, so that the height of the cuboid rigid foam semi-finished product in its outer edge areas is continuously reduced in its width direction and • the cuboid-shaped rigid foam semi-finished product is heated to temperature T2 at least in an area of ​​the continuously reduced height and is formed by the pressing tool into the shape of the thermoplastic component, so that the area of ​​the continuously reduced height is at least partially fused and an outer edge area of ​​the thermoplastic component is formed at least section by section in a longitudinal direction of the rigid foam semi-finished product on the outer side of the area with continuously reduced height.

[0022] By ensuring that the pressing tool rests against the thermoplastic semi-finished product, the forming constraint is maintained and the thermoplastic semi-finished product is further formed during or after partial heating to temperature T2.

[0023] Furthermore, it is advantageous if at least one second section of the thermoplastic semi-finished product is a central area extending along a longitudinal direction X of the thermoplastic component, in which the height of the thermoplastic component is reduced. This allows ribs and stiffeners to be formed in the central area of ​​the thermoplastic component, which stabilize the thermoplastic component, make it more resilient, and enable the bonding of further layers in subsequent process steps without compromising the shape of the thermoplastic component.

[0024] The features disclosed above can be combined in any way as far as is technically possible and they do not contradict each other.

[0025] Other advantageous embodiments of the invention are characterized in the dependent claims or are described in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. The figures show: Fig. 1 a thermoplastic semi-finished product and an opened press tool, Fig. 2 a thermoplastic semi-finished product in a closed pressing tool, Fig. 3 a thermoplastic component and an open press tool, Fig. 4 a thermoplastic component with detached external areas of a component and an open press tool, Fig. 5 a thermoplastic semi-finished product, Fig. 6 a thermoplastic component, Fig. 7 another thermoplastic semi-finished product and a press tool.

[0026] The figures are schematic examples. Identical reference symbols in the figures indicate identical functional and / or structural features.

[0027] Fig. Figure 1 shows a front view of a thermoplastic semi-finished product 2 in a press tool with a first press tool side 11 and a second press tool side 12. The thermoplastic semi-finished product 2 is positioned between the two press tool sides 11, 12, and no force is yet exerted on the thermoplastic semi-finished product 2 by the press tool. Cooling of the thermoplastic semi-finished product 2 does not yet occur via the cooling channels 6. The cooling channels 6 are distributed at regular intervals along the surface of the two press tool sides 11 to enable uniform cooling of predetermined areas of the thermoplastic semi-finished product 2.

[0028] Fig. Figure 2 shows the press tool enclosed around the thermoplastic component 1. Heating elements 7 in the first and second sides 11, 12 of the press tool heat the thermoplastic semi-finished product 2, enabling the two sides 11, 12 to form the thermoplastic component 1. During this process, outer sections 5 are squeezed outwards by the two sides of the press tool, forming the second section 3.

[0029] In Fig. Figure 3 shows the thermoplastic component 1 after cooling by oil circulating in the cooling channels 6, separated from the first side 11 and the second side 12 of the press tool. The outer sections 5 of the thermoplastic component 1 are still attached to the two outer edge regions by means of webs. These webs adjoin the second sections 3 outwards.

[0030] The Fig. 4 shows an arrangement like Fig. 3, wherein the webs on the two outer surfaces of the thermoplastic component 2 are cut, thereby separating the outer sections 5 of the thermoplastic semi-finished product 2 from the thermoplastic component 1.

[0031] A thermoplastic semi-finished product 2 with longitudinal direction X and width direction Y is in Fig. Figure 5 shows the extent of the thermoplastic semi-finished product 2 in the longitudinal direction X, which is not shown to scale.

[0032] Fig. Figure 6 shows the thermoplastic component 1 with its longitudinal direction X and its width direction Y, wherein the thermoplastic component 1 becomes continuously thinner in the second sections 3 or the respective edge regions from a first height H1 to a second height H2 and forms the tapered outer edge region 4.

[0033] Fig. Figure 7 shows a thermoplastic component 1 as in Fig., however, the thermoplastic component 1 has central areas 13 reduced in height, with the surface profile of the top and bottom surfaces being asymmetrical to each other.

[0034] The invention is not limited in its implementation to the preferred embodiments specified above. Rather, a number of variants are conceivable that utilize the presented solution even in fundamentally different designs. For example, the thermoplastic component could have a completely different basic shape.

Claims

[1] Manufacturing process for producing a thermoplastic component (1) comprising the following steps: • Heating at least one first section of a thermoplastic semi-finished product (2) to a first temperature T1, such that the first section of the thermoplastic semi-finished product (2) is thermoplastically deformable; • Forming the first section of the thermoplastic semi-finished product (2), heated to temperature T1, from its initial shape to a near-net-shape shape, with subsequent retention of a form constraint of the thermoplastic semi-finished product (2) in the near-net-shape shape; • Heating at least one second section (3) of the thermoplastic semi-finished product (2) to a second temperature T2 until the at least one second section (3) is in a molten state, wherein the temperature T2 is greater than the temperature T1 (T2>T1); • Further forming of the thermoplastic semi-finished product (2) into the shape of the thermoplastic component (1); and • Cooling at least the first and at least one second section (3) of the thermoplastic semi-finished product (2) to a third temperature T3, wherein the temperature T3 is lower than the temperature T1 (T3 <T1). [2] Manufacturing method according to claim 1, wherein the first temperature T1 is in a temperature range of the thermoplastic semi-finished product (2) in which the thermoplastic semi-finished product (2) is thermoplastically deformable, the second temperature T2 is equal to or above the melting temperature of the thermoplastic semi-finished product (2) and / or the third temperature T3 is below the temperature range of the thermoplastic semi-finished product (2) in which the thermoplastic semi-finished product (2) is thermoplastically deformable. [3] Manufacturing process according to one of the preceding claims, wherein the thermoplastic semi-finished product (2) is designed as a thermoplastic rigid foam. [4] Manufacturing process according to the preceding claim, wherein the rigid foam is formed from a polyethylene terephthalate (PET). [5] Manufacturing method according to one of the preceding claims, wherein at least the first section of the thermoplastic semi-finished product (2) heated to temperature T1 is formed from its initial shape by a press tool comprising a first and a second press tool side (11, 12) which act on the semi-finished product with a predetermined force to form it into a near-net shape. [6] Manufacturing method according to the preceding claim, wherein the first section of the thermoplastic semi-finished product (2) is further formed by the press tool into the shape of the thermoplastic component (1) with the at least one second section (3) of the thermoplastic semi-finished product (2) which is heated to the second temperature T2, while maintaining or increasing the predetermined force. [7] Manufacturing method according to one of the preceding claims, wherein the at least one second section (3) of the thermoplastic semi-finished product (2) is an outer edge region (4) extending along a longitudinal direction X of the thermoplastic component (1). [8] Manufacturing method according to the preceding claim, wherein the at least one second section (3) of the thermoplastic semi-finished product (2) decreases continuously in a width direction Y, which is orthogonal to the longitudinal direction X, from a first height H1 to a second height H2 and wherein the second height H2 is preferably between 5% and 10% of the height H1. [9] Manufacturing method according to the preceding claim, wherein the second height H2 is varied in intervals along the longitudinal direction X, so that sections with different second heights H2 are formed in the longitudinal direction X, which hold further outer sections (5) of the thermoplastic semi-finished product (2) by means of webs on the thermoplastic component (1) and which form the outer edge region (4) of the thermoplastic component (1) and are separated from the outer sections (5) of the thermoplastic semi-finished product (2). [10] Manufacturing process according to any one of the preceding claims, wherein • a cuboid rigid foam semi-finished product is heated to temperature T1 and formed by a pressing tool, so that the height of the cuboid rigid foam semi-finished product in its outer edge areas is continuously reduced in its width direction Y and • the cuboid rigid foam semi-finished product is heated to temperature T2 at least in an area of ​​the continuously reduced height and is formed by the pressing tool into the shape of the thermoplastic component (1), so that the area of ​​the continuously reduced height is at least partially fused and an outer edge area of ​​the thermoplastic component (1) is formed at least section by section in a longitudinal direction of the rigid foam semi-finished product on the outer side of the area with continuously reduced height. [11] Manufacturing method according to any one of the preceding claims 1 to 6, wherein the at least one second section (3) of the thermoplastic semi-finished product (2) is a central area (13) extending along a longitudinal direction X of the thermoplastic component (1) in which the height of the thermoplastic component is reduced.

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