A method of moulding an article and a mould

Abstract

A method of moulding a product where the mould has one or more indentations in the form of individual peaks or ridges, where the moulding material covers the peaks but not the valleys thereof. In this manner, demoulding of the moulded article requires less force.

Description

[0001] A METHOD OF MOULDING AN ARTICLE AND A MOULD

[0002] Background and scope of invention

[0003] Surface texture or surface property modification on industrial goods, is a well-known industrial discipline, used in many aspects of industrial manufacturing.

[0004] In particular thermal processing of plastic materials such as PE, PP or other thermoplastic materials are well-known topics for altering or adapting surface properties that fulfil certain requirements or desires.

[0005] Examples of such are blasting with sand, glass or carbon dioxide or laser engraving after finished processing of the goods.

[0006] In most cases, surface properties are sought applied during processing of the plastics in a tool or mold forming the plastic, so that a finished surface is provided simultaneously with the forming of the plastic article or the goods. But in some cases, applying the surface as a step during processing of the final product is preferred or the only possible option. An example of this is embossing logos or instructions, which may alter depending on different parameters, whereas the plastic article itself is the same.

[0007] Injection molding is one very widely used processing method of plastics, to form advanced geometries in one injection of plastics, and at the same time obtain surface finish - almost without limitations.

[0008] In the most advanced form, injection molds comprise areas providing visual effects on the finished article, which may also be applied with a semi-injection process. Thus, a very complicated visual effect as a hologram may be embossed in a piece of plastic (Plastic Decoration: TRUSTSEAL® (plastic-decoration.com), 2024).

[0009] In literature (Cent South Univ 29(10): 3368-3375. https: / / doi.org / 10.1007 / S11771-022-5157-8.) there are numerous examples of stainless steel, used as a base for laser texturing of surface to produce repellent or hydrophilic properties.

[0010] Used in combination with injection molding of plastic, a surface texturing of the cavity is fully or partly represented on the finished plastic article after demolding the article from the cavity.

[0011] The present invention relates to texturing of injection molding molds and texturing of tools used in processing plastic articles. The present invention aims at enhancing injection molding processing as well as enhancing properties of finished plastic goods.

[0012] The present invention further aims at enhancing the properties of a thermal process to texture the surface of a plastic article in process, or the properties of the finished plastic goods.

[0013] DESCRIPTION

[0014] A first aspect of the invention relates to a method of moulding an article, the method comprising the steps of: providing a mould with an inner surface portion having one or more indentations each having a bottom portion and where a top portion exists between neighbouring indentations, forming a body by providing a moulding substance on to the surface portion, removing the body from the surface portion, wherein the forming step comprises providing the moulding substance on to the surface portion so as to contact the top portions but not the bottom portions.

[0015] It has been found that when the substance does not cover the complete surface of the mould, demoulding of the moulded article is easier.

[0016] In one embodiment, the providing step comprises providing a mold where each indentation has a height between its bottom portion and a pertaining top portion, and wherein the providing step comprises providing the moulding substance into at least one indentation to a depth of no less than 10% of the height from the bottom portion of the pertaining indentation.

[0017] In that or another embodiment, the providing step comprises providing the mould with a plurality of indentations each having a depth of 200 um or less, such as 50 um or less, such as 10 um or less. The depth of an indentation, such as an indentation having a valley between two adjacent peaks could be a distance from a line between the peaks and the valley.

[0018] In one embodiment, the providing step may comprise providing the mould with a plurality of indentations, where a mean width of one or more of the indentations is 10-80 um.

[0019] An indentation may be point-shaped or elongated (straight or meandering / curved). Another aspect of the invention relates to a method of injection moulding an article, the method comprising:

[0020] - providing at least one mould part, with: at least one first mold surface, a boundary proximal imaginary surface offset the first surface, and which proximal imaginary surface is defined by limit of extreme ridges and peaks of material extending away from the first surface into the cavity of the first mould part, a boundary distal imaginary surface offset the first surface and which distal imaginary surface is defined by the lower limit of grooves or holes of the first surface away from cavity of the first mould part, wherein the, at least one first surface is being partly or fully defined by removing material laser modification and

[0021] - providing molding plastic on the first mold surface during the injection molding so that the molding plastic fills out from 20% to less than 100% of the grooves or holes of the first surface.

[0022] In one embodiment, the first surface is being partly defined by removing material from the surface using a laser. Then, said removing of material may define 1% to 100 % of the first surface, preferred in the range 40% to 100%.

[0023] In another aspect of the invention, a laser is used for modifying a surface on an injection mould part, used for manufacturing of injection molded plastic parts, preferred being thermoplastic parts.

[0024] In another aspect of the invention a laser is used for imprinting a surface texture on a tool part for thermo-processing of existing plastic articles or goods in a semi-final state.

[0025] In yet another aspect of the invention, the laser texturing is applied on cavity parts surfaces, first, second or a third surface, which may be used to mount or attach inside the mould being part of the molding part cavity for injection of plastic.

[0026] In yet another aspect of the invention, the laser texturing is applied on elements that may be attached a thermo-processing tool.

[0027] In one aspect of the invention, the surface modified by laser may possess a microscopic landscape of material from the mould or cavity part. The landscape may have ridges and peaks extending from the solid material into the cavity in a proximal direction (nearest the plastic part being processed). In similar ways, the landscape may form valleys and holes in the distal direction (into the solid material of the cavity form).

[0028] Given a local form or shape of the cavity, it is possible to form an imaginary distal and proximate surface / plane enclosing the peaks / ridges and valleys / holes, representing two imaginary planes or surfaces with a distance Z.

[0029] For a normal grinded and even polished surface of e.g. steel, such distance Z would be quite low, whereas a sand-blasted surface would have a much higher Z value. In the literature, characterization of surface roughness is normally defined in a more complex manner, but for the present invention disclosure, the said defining of Z has been found helpful.

[0030] In one aspect of the invention another imaginary surface or plane - midway in-between the proximate plane and the distal plane - may be defined. The distance towards either the proximate or the distal plane / surface is then Z / 2.

[0031] The invention discloses a surface structure or texturing in which the material of the mold or cavity is distributed such that by partly or fully use of the laser the distance Z is 0-200 pm or less, such as 0-50 pm or 0-10 pm, depending on the application and other factors.

[0032] In one aspect of the invention, the laser may modify in the range of 1% to 100% of the area of a first surface, that is used for imprinting plastic processed.

[0033] In another aspect of the invention, the laser may modify in the range of 1% to 20% of the area of a first surface, that is used for imprinting plastic processed.

[0034] In another aspect of the invention, the laser may modify in the range of 1% to 5% of the area of a first surface, that is used for imprinting plastic processed.

[0035] It must be understood that the said intervals reflects the expected need for modification of surfaces. In some cases only sporadic laser modification of an area representing a first surface is needed, to obtain changes in properties during processing or resulting in altered properties of the finished goods.

[0036] With respect to said laser modification is meant that any area influenced by the laser will have reduced material as the laser either evaporates material or that by local sudden heating causes sudden fragmentation of nearby material resulting in loss of material locally of the surface.

[0037] Laser modification may also imply change in material properties, e.g. heating - dehardening material. Thus, in one aspect the change in material properties results in loss of strength which may be used to removes material during a following first use of the tool. The material simply breaks off and follow is carried away by the plastic during one or more first moldings.

[0038] The modification of a first surface may provide texturing as certain patterns may either be repeated or follow certain rules or predetermined outcome.

[0039] Thus, in some cases, the modification by laser may be more extensive with respect to certain areas and textures, whereas other sites or areas of the first surface are less, or not modified by laser.

[0040] In another aspect of the invention, the mould - or cavity - surfaces may be more than one first surface, but many different, in which the modification by laser is used to modify each and bring different properties to different parts of the mould or cavity surfaces.

[0041] Thus, a mould may have cavity surfaces containing a first, second or third surface. Though the number three is mentioned, the cavity may of course comprise even more surfaces - modified by laser.

[0042] In another aspect of the invention, the mould may have a first and second surface adjacent to each other. The surface texturing of the first and the second surface may be different, so technical or cosmetic properties of the two surfaces are different as well. The transition zone between the first and the second surface may be non existing, extensive (0-10 mm) or varying along their border.

[0043] The transition zone may further comprise an individual texturing or pattern, that may provide a mixture of the first and second surface properties or a graduating shift from the first surface pattern to the second surface pattern.

[0044] In yet another aspect of the invention, the surface modification may lead to a characteristic of the surface pattern or texture. In one embodiment the modification by laser is used to create a first surface in which certain rules are used to determine how and where modification of the surface is needed or relevant.

[0045] Thus, in some embodiments, the pattern may be very simple but repeated across the entire first surface.

[0046] In other embodiments, the pattern may consist of a characteristic surface in a small region of the first surface, and which region is then repeated numerous times across the entire surface.

[0047] Example of a column pattern used for texturing of the first surface: In one embodiment of the invention, the first surface may be modified by a laser to represent a surface with microscopic pillars or columns of almost equal height, cross sectional area and distance. Example of such modification is illustrated in the surface of figure 3. The height of the columns may be as much as Z but may also be less. It should be understood that ideally the laser may modify the first surface to have such pillars and their spacing very consistent. Though, it must considered that the surface may have started with another texturing made by e.g. sand blasting, meaning that the perfection of the texture may be less perfect, than what the illustration indicates and there may be both areas where the pillars cannot reach full height (Z), nor be perfect cuts into the already existing blasted surface texture.

[0048] In some cases, the modification may only be made to cover 10-50% of the first surface, whereas the remining surface cannot lead to perfect columns. In other cases it is chosen to distribute the modifications to certain regions of the first surface considered most suitable for such modification. In this way high efficiency of processing the modification is reached as laser modification of the surface is both time and energy consuming.

[0049] The columns in the example (illustrated in figure 3) disclose a pattern that is repeated endlessly within the area of a first surface. Each pillar is positioned with a distance of D to the adjacent pillar. The pillar may be cylindrical or any other cross-sectional form. In case it is cylindrical or almost cylindrical, the diameter may be D2, leaving the center-to-center distance of two pillars to be DI (D-D2).

[0050] The range in dimensions of the columns may be so that D is in the range of 0,01-200 pm and Z in the same range. D2 may be in the range of 0,01-150 pm.

[0051] In some embodiments the edge, near the end of the column, is influencing final properties of the surface. Thus, for some versions, the end of the column is not sharp edged, but rounded - or smooth - without having a specific radius. To help characterize the surface, a rounding 'R' may be introduced. This is illustrated in figure 4, in which the geometry of the column edge must be held within the area defined by the dotted line with a radius of R.

[0052] It is found that large radius may reduce the columns tendency of getting 'locked' during sliding of plastics across the first surface e.g. during removal of plastics after processing. Having a larger radius allows the column to 'bend' without introducing a 'sharp' edge of the column to get tangled with the plastic material.

[0053] Of course, if the radius is very large (D2 / 2), the top of the column is more a sphere like end of the pillars, this also allows for the melted or softened plastic to enter deeply into the groove or spacing between the columns. In such case the 'sticking' may increase as the plastic geometry needs to be lifted somewhat more from the surface, in order to slide across the surface. In one embodiment of the invention, parameters in the injection molding process are adjusted so that the molded plastic does not enter the pattern or texture fully, but lesser. Thus, in some embodiments, the plastic fills out less than 100% of the pattern of the first surface, but still more than 20%.

[0054] In one example, such property enables the 'pillars' bend and allow the plastic to slide off the surface, which would have been difficult if the plastic was fully formed into the grooves. Figure 5 illustrates such properties of the surface in combination with the molding process parameters. used for texturing of the first surface:

[0055] In another example the texturing is used for embossing certain dimple protrusions of the first surface, so that during molding dimples or dimple like structures are imprinted to the plastic article being formed.

[0056] In figure 6 such surface structure is illustrated. Z may be in the range of 0-200 pm and the distance D between the dimples may be in the range of 0-1000 pm, but not limited to this.

[0057] It is understood that such texturing of the surface may require that the 100% of the area in the first surface is modified by laser, to ensure that the protrusions, that produce the dimples, are free of the surrounding material.

[0058] The dimples may cover as little as 1-20% of the total area of the first surface.

[0059] Thus, of course, it is understood that such texturing requires more use of the laser, as significant amount of material needs to be removed in a rather large depth (up to 200 pm), leaving back the negative imprint of the dimples on the first surface. used for texturina of the first surface:

[0060] In some embodiments, the texturing is less repeatable and more randomly, still applying to certain rules of how and where or the depth.

[0061] In figure 7, an example of such surface is illustrated, the surface comprising numerous indentations made by a laser . The grooves or indentations are formed by either melting the surface or evaporating material. I the first case, the material may be heated to the melting point, during which sputtering of material in the center creates a local crater or indentation. The laser may be any type of laser producing a very high power / heating locally in a very short period of time. Example could be a laser referred to as FemtoLaser. Another type of laser e.g. an IR. laser with less power may also be used.

[0062] Thus, in this example numerous such indentations are spread across the first surface to create a certain pattern. In a surface texturing analyser, such surface may be analysed to reveal the position and depth of indentations.

[0063] Figure 8 discloses a first surface by which the said laser modification has been applied, and which surface is part of a molding cavity. During measuring of the demolding force, it is found that the shown texture reveals a significant lowered demolding force, when compared to traditional surface treatments.

[0064] The surface in illustration 8 has been colored depending on depth of laser modification (dots). A The more bluish or dark, the deeper the indentations made by laser.

[0065] It should be considered that even though the examples present certain changes in properties, many applications may be addressed using the presented laser modification of a first surface.

[0066] Thus, in some cases, friction control between the cavity surface and the plastic molded - may be lowered, decreasing cycle time, lowering wear of mold, decreasing need of release agent use or allowing for less draft angling on parts being molded.

[0067] But apart from improving the processing of the material, other properties of the final product may be obtained simultaneously or as the main purpose of modifying the surface.

[0068] Sealing properties plastic against plastic or other materials, may be increased for the final plastic article. Other properties of the produced plastic article may be obtained, such as reduction in wear or reduction in friction for surfaces acting against other surfaces during use, may also be obtained.

[0069] Finally, both hydrophobic or hydrophilic surface properties may be obtained in final plastic articles.

[0070] EMBODIMENTS

[0071] 1: A method to provide enhanced performance of an injection molding process, comprising:

[0072] - at least one mould part, with at least one first mold surface being in contact with the molding plastic during the injection molding, - a boundary proximal imaginary surface offset the first surface, and which proximal imaginary surface is defined by limit of extreme ridges and peaks of material extending away from the first surface into the cavity of the first mould part,

[0073] - a boundary distal imaginary surface offset the first surface and which distal imaginary surface is defined by the lower limit of grooves or holes of the first surface away from cavity of the first mould part, wherein the, at least one first surface is being partly or fully defined by removing material laser modification.

[0074] 2: A method to provide an enhanced performance of an injection molding process as in embodiment 1, wherein the distance between the imaginary proximate and distal surface is 200 um or less.

[0075] 3: A method to provide an enhanced performance of an injection molding process as in embodiment 1, wherein the distance between the imaginary proximate and distal surface is 50 um or less.

[0076] 4: A method to provide an enhanced performance of an injection molding process as in embodiment 1, wherein the distance between the imaginary proximate and distal surface is 10 um or less.

[0077] 5: A method to provide an enhanced performance of an injection molding process as in embodiment 1, wherein the 20% to 50% of the first mould imaginary surface material is situated in the proximal direction from a split plane / surface mid between the imaginary proximate mold surface and the imaginary distal mould surface, and 50% to 80% in the distal direction.

[0078] 6: A method to provide an enhanced performance of an injection molding process as in embodiment 1, wherein a laser modifies the texture in the range of 1% 100% of the first mould surface area.

[0079] 7: A method to provide an enhanced performance of an injection molding process as in embodiment 6, wherein the laser modifies the texture in the range of 1% to 20% of the first mould surface area.

[0080] 8: A method to provide an enhanced performance of an injection molding process as in embodiment 6, wherein the laser modifies the texture in the range of 1% to 5% of the first mould surface area. 9: A method to provide enhanced performance of an injection molding process as in previous embodiments, wherein the mould contains a second mold surface modified by a laser.

[0081] 10: A method to provide enhanced performance of an injection molding process as in previous embodiments, wherein the laser modification takes place one, two, three times on the same area of the first surface.

[0082] 11: A method to provide enhanced performance of an injection molding process as in previous embodiments, wherein the laser modification takes place on a steel or aluminum part that has an altered first surface, e.g. by additive surface treatment such as DLC or ChromeCarbide.

[0083] 12: A method to provide an enhanced performance of an injection molding process as in previous embodiments, wherein the first and the second surface have reduced mould release force.

[0084] 13: A mould part containing a first surface according to any of the previous embodiments.

[0085] 14: An article made of thermo-plastic, being moulded or formed in contact with the first mold surface according to any previous embodiments, obtaining a first article surface texture that is fully or partly defined by the first mold surface texture.

Claims

CLAIMS1. A method of moulding an article, the method comprising the steps of: providing a mould with an inner surface portion having one or more indentations each having a bottom portion and where a top portion exists between neighbouring indentations, forming a body by providing a moulding substance on to the surface portion, removing the body from the surface portion, wherein the forming step comprises providing the moulding substance on to the surface portion so as to contact the top portions but not the bottom portions.

2. The method of claim 1, wherein the providing step comprises providing a mold where each indentation has a height between its bottom portion and a pertaining top portion, and wherein the providing step comprises providing the moulding substance into at least one indentation to a depth of no less than 10% of the height from the bottom portion of the pertaining indentation.

3. The method according to claim 1 or 2, wherein the providing step comprises providing the mould with a plurality of indentations each having a depth of 200 um or less, such as 50 um or less, such as 10 um or less.

4. The method according to any of the preceding claims, wherein the providing step comprises providing the mould with a plurality of indentations, where a mean width of one or more of the indentations is 10-80 um.

5. A method of injection moulding an article, the method comprising:- providing at least one mould part, with: at least one first mold surface, a boundary proximal imaginary surface offset the first surface, and which proximal imaginary surface is defined by limit of extreme ridges and peaks of material extending away from the first surface into the cavity of the first mould part, a boundary distal imaginary surface offset the first surface and which distal imaginary surface is defined by the lower limit of grooves or holes of the first surface away fromcavity of the first mould part, wherein the, at least one first surface is being partly or fully defined by removing material laser modification and- providing molding plastic on the first mold surface during the injection molding so that the molding plastic fills out from 20% to less than 100% of the grooves or holes of the first surface.

6. A method according to claim 5, wherein the first surface is being partly defined by removing material from the surface using a laser.

7. A method according to claim 6, wherein the said removing of material is defining 1% to 100 % of the first surface, preferred in the range 40% to 100%.8: A method to provide enhanced performance of an injection molding process, comprising:- at least one mould part, with at least one first mold surface being in contact with the molding plastic during the injection molding,- a boundary proximal imaginary surface offset the first surface, and which proximal imaginary surface is defined by limit of extreme ridges and peaks of material extending away from the first surface into the cavity of the first mould part,- a boundary distal imaginary surface offset the first surface and which distal imaginary surface is defined by the lower limit of grooves or holes of the first surface away from cavity of the first mould part, wherein the, at least one first surface is being partly or fully defined by removing material laser modification.9: A method to provide an enhanced performance of an injection molding process as in claim 8, wherein the distance between the imaginary proximate and distal surface is 200 um or less, such as 50 um or less, such as 10 um or less.10: A method to provide an enhanced performance of an injection molding process as in claim 8, wherein the 20% to 50% of the first mould imaginary surface material is situated in the proximal direction from a split plane / surface mid between the imaginary proximate mold surface and the imaginary distal mould surface, and 50% to 80% in the distal direction.11: A method to provide an enhanced performance of an injection molding process as in claim 8, wherein a laser modifies the texture in the range of 1% 100% of the first mould surface area, suchas in the range of 1% to 20% of the first mould surface area, such as in the range of 1% to 5% of the first mould surface area.12: A method to provide enhanced performance of an injection molding process as in previous claims 8-11, wherein: the mould contains a second mold surface modified by a laser, the laser modification takes place one, two, three times on the same area of the first surface, the laser modification takes place on a steel or aluminum part that has an altered first surface, e.g. by additive surface treatment such as DLC or ChromeCarbide and / or the first and the second surface have reduced mould release force.13: A mould part containing a first surface according to any of the previous claims 8-12.14: An article made of thermo-plastic, being moulded or formed in contact with the first mold surface according to any previous claim 8-12, obtaining a first article surface texture that is fully or partly defined by the first mold surface texture.15: A method of injection moulding an article, the method comprising:- providing at least one mould part, with: at least one first mold surface, a boundary proximal imaginary surface offset the first surface, and which proximal imaginary surface is defined by limit of extreme ridges and peaks of material extending away from the first surface into the cavity of the first mould part, a boundary distal imaginary surface offset the first surface and which distal imaginary surface is defined by the lower limit of grooves or holes of the first surface away from cavity of the first mould part, wherein the, at least one first surface is being partly or fully defined by removing material laser modification and- providing molding plastic on the first mold surface during the injection molding so that the molding plastic fills out from 20% to less than 100% of the grooves or holes of the first surface.

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