A method for manufacturing by injection molding a part comprising at least one raised feature that has at least one sharp edge, and a part obtained by said method.

Abstract

The invention relates to a method for manufacturing a part comprising a thermoforming step of a coating (48), a positioning step of the coating (48) in a cavity (52) of a mold (54) against a molding face (F54) corresponding to a visible face of the part to be obtained, and a step of injecting a material into the cavity (52), the molding face (F54) of the mold (54) comprising a sharp edge (56.1) for each sharp edge present on the visible face of the part to be obtained. At the end of the thermoforming step, the coating (48) includes, for each sharp edge of the visible face of the part, a rounded edge (60) which has a radius of curvature greater than or equal to a first threshold so as not to generate marks at the level of the first layer of the coating.This solution avoids double marking at each sharp edge after the injection step. Figure 6.

Description

Title of the invention: Injection molding method for manufacturing a part comprising at least one raised feature having at least one sharp edge, and part obtained by said method

[0001] The present application relates to a method for manufacturing by injection of a part comprising at least one relief shape which has at least one sharp edge and to a part obtained from said method.

[0002] According to an embodiment visible in figures 3 and 4, a part 10 comprises a visible surface F10 as well as at least one prismatic hollow shape 12 which has several facets 12.1 to 12.6 connected by sharp edges 14.

[0003] For the purposes of this application, a sharp edge is defined as an edge which has a radius of curvature of a few tenths of a millimeter, less than 0.5 mm.

[0004] The part 10 comprises a body 16 made of plastic material which has a face F16 oriented towards the visible face F10 and a coating 18 which has a first face 18.1 pressed against the face F16 of the body 16 and intimately bonded to the latter and a second face 18.2 corresponding to the visible face F10 of the part 10.

[0005] As illustrated in detail in [Fig. 1], the coating 18 comprises at least first and second layers 20.1, 20.2 superimposed one on top of the other, the first layer 20.1 being an ink layer. Generally, the second layer 20.2 is a transparent layer. The first layer 20.1 may be positioned on either the first or second face 18.1, 18.2 of the coating 18.

[0006] According to one method, an injection manufacturing process for part 10 includes a step of positioning a coating 18 in a cavity 22 of a mold 24, against a molding face F24 of the mold 24, a step of injecting a material into the cavity 22 to obtain the body 16, a cooling step and then a demolding step to remove part 10 from the mold 24.

[0007] This manufacturing technique is known as IML (for Insert Molding Labelling) or IMF (Insert Molding Forming).

[0008] The molding face F24 of the mold 24 has the same geometry as the visible surface F10 of the part 10. For each hollow shape 12, the molding face F24 includes a protruding shape 26, complementary to the hollow shape 12, which has several facets connected by sharp edges.

[0009] Prior to placing the coating 18 in the mold 24, the process includes a thermoforming step of the coating 18 during which the second face 18.2 of the coating 18 is pressed against a thermoforming face which comprises, for each hollow shape at the level of the second face 18.2 of the Coating 18, a protruding shape, complementary to the recessed shape 12, comprising several facets connected by sharp edges. This thermoforming face is identical to the molding face F24 of the mold 24.

[0010] This thermoforming step of the coating 18 is mandatory because if the latter is flat and not deformed when positioned in the mold 24, the injection characteristics (temperature and pressure among others) during the injection step are not sufficient for the coating 18 to be correctly pressed against the molding face F24 of the mold 24 and to conform to its shapes, in particular its sharp edges.

[0011] As illustrated in [Fig. 1], after the thermoforming step, the coating 18 comprises, on its first and second faces 18.1 and 18.2, respectively protruding and recessed shapes, each with several facets connected by sharp edges. During this thermoforming step, the coating 18 is heated and pressed against the thermoforming face. Following the thermoforming step, the second face 18.2 of the coating 18 does not have a geometry perfectly identical to the visible surface F10 of the part 10 to be obtained, due to shrinkage phenomena that are difficult to control and dimensional variations inherent in the manufacturing of the thermoforming face against which the coating 18 is deformed.

[0012] As illustrated in [Fig.1], the first layer 20.1 of ink has along each sharp edge a cut 28 which forms a straight mark generally white of contrasting color with the rest of the first layer 20.1 of ink.

[0013] During the step of placing the coating 18 in the mold 24, the shapes of the second face 18.2 of the coating 18 are supposed to perfectly coincide with those of the molding face F24 of the mold 24.

[0014] Despite all the care taken in this setup, the sharp edges of the second face 18.2 of the coating 18 and those of the mold face F24 of the mold 24 are not perfectly superimposed. Consequently, as illustrated in [Fig. 4], during the injection step, each sharp edge 30.1 of the second face 18.2 of the coating 18 that is not perfectly superimposed with a given sharp edge of the mold face F24 of the mold 24 is flattened, and a new sharp edge 30.2 is formed in the coating 18 at the given sharp edge of the mold face F24 of the mold 24. Along the new sharp edge 30.2, the first layer 20.1 of ink has a cut that forms a straight line mark, generally white, of a contrasting color with the rest of the first layer 20.1 of ink.

[0015] Thus, as illustrated in [Fig. 4], instead of obtaining a single straight mark, some sharp edges have two marks, a first mark associated with the sharp edge 30.1 produced during the thermoforming step and flattened thus than a second mark associated with the new sharp edge 30.2 obtained during the injection stage.

[0016] The presence of two marks instead of one is not satisfactory.

[0017] The present invention aims to remedy all or part of the drawbacks of the prior art.

[0018] To this end, the invention relates to a method for manufacturing a part by injection, said part comprising at least one visible face, at least one coating at the level of the visible face and at least one relief shape provided with at least one sharp edge at the level of the visible face, said coating comprising at least one layer capable of being marked when the coating is deformed along a sharp edge.This process includes a thermoforming step of the coating, a positioning step of the coating in a cavity of a mold, against a molding face of the mold, a step of injecting a material into the cavity, a cooling step and then a demolding step of the part; the molding face of the mold comprising, for each relief shape of the part, a relief shape of complementary shape which has a sharp edge for each sharp edge of the part, the coating having at the end of the thermoforming step an edge for each sharp edge present on the visible face.

[0019] According to the invention, each edge of the coating corresponding to a sharp edge of the visible face of the part is rounded and has a radius of curvature greater than or equal to a first threshold so as not to generate a mark at the level of the first layer of the coating.

[0020] Providing rounded edges instead of sharp edges on the thermoformed coating avoids double marking at each sharp edge after the injection step.

[0021] The invention also relates to a part obtained from the process.

[0022] Other features and advantages will become apparent from the following description of the invention, given by way of example only, with reference to the accompanying drawings, among which:

[0023] [Fig. 1] is a schematic cross-section of a coating illustrating an embodiment of the prior art,

[0024] [Fig.2] is a schematic cross-section of a mold in which the coating of [Fig.1] is positioned, illustrating an embodiment of the prior art,

[0025] [Fig.3] is a schematic cross-section of a part obtained from the mold visible in [Fig.3] illustrating an embodiment of the prior art,

[0026] [Fig.4] is a top view of a portion of the part obtained, visible in [Fig.3].

[0027] [Fig.5] is a schematic cross-section of a coating illustrating one embodiment of the invention,

[0028] [Fig.6] is a schematic cross-section of a mold in which the coating of [Fig.5] is positioned, illustrating one embodiment of the invention.

[0029] [Fig.7] is a schematic cross-section of a part obtained from the mold visible in [Fig.6] illustrating one embodiment of the invention,

[0030] [Fig.8] is a top view of a part of the obtained part visible in [Fig.7].

[0031] According to an embodiment shown in Figures 7 and 8, a part 40 comprises a visible surface F40 as well as at least one prismatic hollow shape 42 which has several facets 42.1 to 42.6 connected by sharp edges 44.

[0032] Of course, the invention is not limited to hollow shapes for part 40. Whatever the embodiment, the part 40 to be obtained includes at least one relief shape (hollow or raised) which has at least one sharp edge 44.

[0033] The part 40 comprises a body 46 made of plastic material which has a face F46 oriented towards the visible face F40 and at least a coating 48 which has a first face 48.1 pressed against the face F46 of the body 46 and intimately bonded to the latter and a second face 48.2 corresponding to the visible face F40 of the part 40.

[0034] As illustrated in detail in [Fig. 1], the coating 48 comprises at least The first and second layers 50.1, 50.2 are superimposed one on top of the other, the first layer 50.1 being an ink layer. Generally, the second layer 50.2 is a transparent layer. The first layer 50.1 may be positioned at the level of the first or second face 48.1, 48.2 of the coating 48 or be offset from them. Regardless of the embodiment, the coating 48 includes at least one layer 50.1 capable of being marked when the coating 48 is deformed along a sharp edge.

[0035] The body 46 can be made of polycarbonate or poly-methyl methacrylate acrylic. Of course, the invention is not limited to these materials.

[0036] The first layer 50.1 of ink is made of indium. Of course, the invention is not limited to this material.

[0037] The second layer 50.2, which serves as a support layer for the ink, is made of one of the following materials: polycarbonate or polymethyl methacrylate. Of course, the invention is not limited to these materials. Alternatively, the second layer 50.2 may comprise several co-extruded films of polycarbonate and / or polymethyl methacrylate.

[0038] To give an order of magnitude and in a non-limiting manner, the first layer 50.1 of ink has a thickness of less than 1 pm.

[0039] To give an order of magnitude and in a non-limiting manner, the second layer 50.2 has a thickness between a few microns and a few tenths of a millimeter.

[0040] According to one method, an injection manufacturing process for part 40 includes a step of positioning a coating 48 in a cavity 52 of a mold 54, against a molding face F54 of the mold 54, a step of injecting the material of the body 46 into the cavity 52, a cooling step and then a demolding step in order to remove part 40 from the mold 54.

[0041] This manufacturing technique is known as IML (for Insert Molding Labelling) or IMF (Insert Molding Forming).

[0042] These different steps are not described further because they may be identical to those of the prior art.

[0043] The mold face F54 of the mold 54 has the same geometry as the visible surface F40 of the part 40 to be obtained. For each recessed shape 42, the mold face F54 of the mold 54 includes a protruding shape 56, complementary to the recessed shape 42, which has several facets connected by sharp edges 56.1.

[0044] The shapes of the mold face F54 of the mold 54 are not further detailed because they vary depending on the part 40 to be obtained. Regardless of the embodiment, the mold face F54 of the mold 54 has, for each relief shape 42 of the part 40 to be obtained, a relief shape 56 complementary to that of the relief shape 42 of the part 40 to be obtained, this relief shape 56 having a sharp edge 56.1 for each sharp edge 44 of the part 40 to be obtained.

[0045] Prior to the placement of the coating 48 in the mold 54, the process includes a thermoforming step of the coating 48 during which the second face 48.2 of the coating 48 is pressed against a thermoforming face which includes a thermoforming relief shape for each relief shape at the level of the second face 48.2 of the coating 48.

[0046] According to one configuration, the thermoforming face includes, for each hollow shape at the level of the second face 48.2 of the coating 48, a protruding shape.

[0047] During this thermoforming step, the coating 48 is heated and pressed against the thermoforming face.

[0048] As illustrated in [Fig.5], after the thermoforming step, the coating 48 comprises at its first and second faces 48.1, 48.2 respectively protruding and recessed shapes which each have facets connected by edges.

[0049] Whatever the configuration of the part 40 to be obtained, the coating 48 comprises, for each relief shape 42 of the part 40 to be obtained, a relief shape 58 at the level of each of its first and second faces 48.1, 48.2, each relief shape 58 of the coating having an edge 60 for each sharp edge 44 of the relief shape 42 of the part to be obtained.

[0050] When the part 40 to be obtained comprises a recessed relief shape, the second face 48.2 of the coating 48 has a recessed relief shape and the first face 48.1 of the coating 48 has a raised relief shape. Conversely, when the part 40 to be obtained comprises a raised relief shape, the second face 48.2 of the coating 48 has a raised shape and the first face 48.1 of the coating 48 has a recessed relief shape.

[0051] Unlike the prior art, at the end of the thermoforming step, the coating 48 does not have, for each of the sharp edges 44 of the part 40 to be obtained, a sharp edge but a rounded edge 60 which has a radius of curvature greater than or equal to 1 mm and preferably between 1 and 2 mm.

[0052] As illustrated in [Fig. 5], at each rounded edge 60, the first layer 50.1 of ink does not show any breaks along each rounded edge 60. Thus, the coating 48 does not show any white mark of contrasting color with the rest of the first layer 50.1 of ink.

[0053] According to the invention, after the thermoforming operation, the coating 48 has rounded edges 60, each of which has a radius of curvature greater than or equal to a first threshold so as not to generate marks at the level of the first layer 50.1. This radius of curvature must be less than or equal to a second threshold to allow the coating 48 to be pressed against the molding face F54 of the mold 54 and to conform to each sharp edge 56.1 of the mold 54 during the injection step.

[0054] This first threshold is notably dependent on the ink. This first threshold is on the order of 1 mm.

[0055] The second threshold depends on the parameters, including injection pressure and temperature, used during the injection step. This second threshold is on the order of 2 mm.

[0056] According to one embodiment, the thermoforming face against which the second face 48.2 of the coating 48 is pressed during the thermoforming step has overall the same geometry as the molding face F54 of the mold 54 against which the thermoformed coating is pressed during the injection step, each sharp edge 44 being replaced by a rounded edge 60.

[0057] After being placed in the mold 54, the second face 48.2 of the coating 48 is positioned against the mold face F54 of the mold 54. As illustrated in [Fig. 6], in the areas of the rounded edges 60, the coating 48 is not in contact with the mold face F54. During the injection step, the injected material is at sufficient temperature and pressure to deform the coating 48 and press it against the mold face F54 so that it conforms to the sharp edges 56.1 of the mold face F54 of the mold 54. Along each sharp edge formed during the injection step, the first layer 50.1 of ink has a cut that forms a straight line mark, usually white, in contrasting color to the rest of the first layer of ink (50.1).

[0058] Thus, unlike the prior art, only one mark is present on the right of each sharp edge 44 of the piece 40 obtained.

Claims

Demands

1. A method for manufacturing a part by injection, said part (40) having at least one visible face (F40), at least one coating (48) on the visible face (F40) and at least one raised shape (42) having at least one sharp edge (44) on the visible face (F40), said coating (48) having at least one layer (50.1) capable of being marked when the coating (48) is deformed along a sharp edge; the method comprising a thermoforming step of the coating (48), a positioning step of the coating (48) in a cavity (52) of a mold (54), against a molding face (F54) of the mold (54), an injection step of a material into the cavity (52), a cooling step and then a demolding step of the part (40); the molding face (F54) of the mold (54) comprising, for each relief shape (42) of the part (40), a relief shape (56) of complementary shape which has a sharp edge (56.1) for each sharp edge (44) of the part (40), the coating (48) having at the end of the thermoforming step an edge (60) for each sharp edge (44) present on the visible face (F40); characterized in that each edge (60) of the coating (48) corresponding to a sharp edge (44) of the visible face (F40) of the part (40) is rounded and has a radius of curvature greater than or equal to a first threshold so as not to generate marks at the level of the first layer (50.1) of the coating.

2. A method for manufacturing a part by injection according to the preceding claim, characterized in that the first threshold is on the order of 1 mm.

3. A method for manufacturing a part by injection according to any one of the preceding claims, characterized in that the radius of curvature of each rounded edge (60) is less than or equal to a second threshold to allow the coating (48) to be pressed against the molding face (F54) of the mold (54) and to conform to each sharp edge (56.1) of the mold (54) during the injection step.

4. A method for manufacturing a part by injection according to the preceding claim, characterized in that the second threshold is on the order of 2 mm.

5. Part obtained from a manufacturing process according to one of the preceding claims.

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