Accelerated production method for electroformed mold inserts

Abstract

The present invention discloses a method, comprising the following steps: placing a mandrel having an optionally textured surface in an electrolytic cell to form a cushion layer, wherein the cushion layer comprises a negative image of the optionally textured surface formed by metal electrolytic deposition; fixing the cushion layer with a working side down on a reference plane with a fixture; optically scanning the cushion layer to reverse engineer the geometry of a non-working surface, wherein reverse engineering the geometry of the non-working surface includes developing a profile of the non-working surface and a thickness of the cushion layer; and adding material to the non-working surface of the cushion layer by additive manufacturing to form a mold insert.

Description

[0001] Cross-references to related patent applications

[0002] This application claims the benefit of U.S. Patent Application No. 62 / 860,940 filed on June 13, 2019, which is incorporated herein by reference in its entirety and becomes a part of the present invention. Background Art

[0003] The present disclosure relates to a method for accelerating the production of electroformed mold inserts.

[0004] Mold inserts often feature surfaces with complex textures and shapes with complex topography. Electroforming is often an effective method for manufacturing molds and mold inserts with complex exterior shapes and interior geometries. However, molds and mold inserts made with this process often have uneven thicknesses due to variations in deposition rates during electroforming. Therefore, a quick method to correct these problems is needed. Summary of the invention

[0005] The present invention discloses a method, comprising the following steps: placing a mandrel having an optionally textured surface in an electrolytic cell to form a cushion layer, wherein the cushion layer comprises a negative image of the optionally textured surface formed by metal electrolytic deposition; fixing the cushion layer with a working side down on a reference plane with a fixture; optically scanning the cushion layer to reverse engineer the geometry of a non-working surface, wherein reverse engineering the geometry of the non-working surface includes developing a profile of the non-working surface and a thickness of the cushion layer; and adding material to the non-working surface of the cushion layer by additive manufacturing to form a mold insert. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The accompanying figure is a schematic diagram of an exemplary process for producing a cushion layer for mass production of surface replicas. DETAILED DESCRIPTION

[0007] The process described below provides a means to significantly reduce the time and cost of producing electroformed molds for high-fidelity injection molding, resin transfer molding, and / or embossing applications. The process can be used to make molds for both thermoplastic and thermoset polymer production operations. The process includes the steps of forming a thin electroform, affixing it working side down to a reference plane, optionally laser scanning the electroformed surface to reverse engineer the subsequent geometry of the non-working surface, machining the surface to address additive manufacturing if necessary, and then 3D printing metal on the back of the electroform to increase its overall thickness for process tooling applications. Other additive manufacturing processes such as cold spray additive manufacturing, plating, or flame spraying (or manufacturing processes that do not include additive manufacturing) can be performed to increase the overall thickness.

[0008] Adding 3D metal printing to the process allows conformal, capillary or traditional cooling channels to be printed directly into the body of the insert to improve mold performance. Fasteners can also be 3D printed on the back of the insert for attachment to other substrates.

[0009] Compared to processes that do not use additive manufacturing, the use of 3D additive printing, in addition to the electrolytic manufacturing of the metal underlayer, can reduce the production time of electroformed nickel inserts by up to 3 days. Modern 3D printing technology can deposit nickel alloys at a rate of up to 0.5 kilograms per hour (kg / h). This means that an insert measuring 6 inches by 6 inches can be printed to a thickness of 0.5 inches in about 5 hours.

[0010] This method is described in detail in the present invention with reference to the accompanying drawings, wherein a mandrel 100 having an optionally textured surface 102 is placed in an electrolytic cell 104 to produce a metal pad 106 (also referred to herein as an electroform) on the surface 102. Additive manufacturing can then be used to enhance the metal electroform 106 to form an enhanced metal electroform 108. The enhanced metal electroform 108 can then be used to cast other parts in a mass production process.

[0011] Mandrel 100 is a template that may have one or more textured surfaces 102. Textured surface 102 is optional. The textured surface may include regular or irregular features that need to be replicated on a large number of other surfaces in a batch production process. Mandrel 100 may include any conductive material that can be used in an electrolysis process without any dimensional changes in the electrolytic solution. The mandrel may include a metal, a conductive ceramic, or a conductive polymer. Suitable metals include copper, steel, brass, bronze, silver, aluminum, etc. or combinations thereof. Suitable conductive ceramics include indium tin oxide, antimony oxide, fluorine doped tin oxide (FTO), fluorine doped zinc oxide, RuO2, IrO2, SrRuO3, La 0.5 Sr 0.5 CoO3 or a combination thereof. The mandrel may also be made of intrinsically conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, etc. or a combination thereof. The mandrel may also be made of insulating polymers and insulating ceramics that become conductive by adding conductive fillers (such as carbon nanotubes, carbon black, metal particles, metal nanorods, etc. or a combination thereof).

[0012] The mandrel 100 with the optional textured surface 102 is then immersed in an electrolytic solution and electroplated to form a metal pad 106. The metal pad 106 is also called a metal shell. The electroplating solution 105 contains a metal electrode 103, which can be deposited on the textured surface 102 of the mandrel 100 to form a pad. The pad is usually called an electroformed body.

[0013] Suitable metals for forming the pad include nickel, copper, iron, aluminum, zinc, gold, platinum, titanium zirconium, cobalt, etc. or a combination thereof. In one embodiment, the pad formed by one or more of the above metals has a nominal thickness of 0.015 inches to 0.500 inches, preferably a nominal thickness of 0.02 inches to 0.330 inches. In a preferred embodiment, the pad contains nickel and has a thickness of 0.015 inches to 0.200 inches. The electroplating process may require 1 to 30 days, preferably 1 to 10 days.

[0014] The pad forms a flat "reclaim" area 107 around the actual cavity perimeter, which includes an optical "fiducial" target to provide a reference for the location of the cavity used in downstream processes. The reclaim area is basically the portion of material located at the outermost edge of the edge (such as the flat portion of the mandrel that will eventually form the mold parting line). It is used to locate, clamp, process and protect the useful surface on the shell.

[0015] The mat layer having a complementary surface to the mandrel surface is then separated from the mandrel. In other words, the surface of the mat layer 106 is a negative image of the optional textured surface 102. Due to the relatively small thickness of the formed mat layer, the mat layer is currently in a semi-rigid form. Because the mat layer lacks the strength to withstand downstream manufacturing processes, the textured surface cannot be replicated in this form.

[0016] In order to make the pad strong enough for use in multiple manufacturing processes, it needs to be reinforced with another material. To reinforce the pad, first secure it work side down (via a fixture such as a clamp) to a flat reference surface via vacuum, fasteners, adhesives, or mechanical clamps. This will eliminate any stress-related warping or bowing of the part prior to analysis and printing.

[0017] The non-working surfaces of the fixture and the mat are scanned with a non-contact 3D laser scanner or an optical scanning device to develop a digital model of the organic surface that has been formed on the non-working surface of the mat. In this case, the term "organic" is used to describe a surface with a unique geometry (such as a snowflake shape). Every organic surface is different and they rarely have reliable geometries that can be measured or easily defined by simple methods.

[0018] It is important to note that the non-working surface is placed inversely to the working surface (which may include texture). The working surface is the surface of the pad that contacts the mandrel. The scanned data is then used to reverse engineer the surface geometry of the pad. In this step, a reference target (visible using an optical measurement device) is measured based on the centerline of the fixture to understand the true position of the pad relative to the fixture. In other words, one or more points on the reference target can be used as reference points to determine the true position of the pad relative to the fixture.

[0019] In another embodiment, certain points on the mandrel are recorded and then the true position of the mat relative to the fixture can be determined by measuring certain points on the mat relative to points on the mandrel. In this method, the use of optical devices may not be required.

[0020] In one embodiment, the underlayer is laser scanned to reverse engineer the geometry of the non-working surface, wherein reverse engineering the geometry of the non-working surface includes developing a profile of the non-working surface and a thickness of the underlayer.

[0021] The geometry being reverse engineered is analyzed to identify areas where additive manufacturing technology may have problems. Using this data, a computer programmer will use 3D CAD / CAM (computer-aided design / computer-aided manufacturing) software to blend the existing pad geometry with the final geometry required for the insert and then output a CNC program or programs to generate the final geometry.

[0022] The datum target on the work side of the surface is used as a reference position to place the pad / fixture assembly in the additive / subtractive manufacturing machine and tilt it relative to the machine's coordinate system. Alternatively, the machine's coordinate system can be tilted to match the position of the part. If necessary, machining operations can be used to remove excess material from the pad. In short, this measurement helps minimize any defects in the pad during the electroplating process.

[0023] The above-mentioned machine tool is equipped with an additive manufacturing head 108, and then 3D prints additional material or any other suitable alloy (as shown by reference numeral 110) on the pad until a known, controlled geometry with a considerable thickness (up to 0.5 inches) is obtained. This additional material 110 added by the additive manufacturing process serves as a support. The support provides a uniform thickness to the pad. This increased thickness provides the pad with a certain strength and uniform size, so that the desired features can be consistently reproduced throughout the manufacturing process. During the additive manufacturing process, other support structures such as cooling lines, vacuum channels and other subsurface mold structures (not shown) can be printed in the support 110. The pad 106 with the support 110 can then be separated from the mandrel 100 to produce a mold insert 112 that can be used to mass produce replicas of the original textured surface 102. In one embodiment, the mandrel 100 can be supported by the mold insert 112 before scanning the pad with a non-contact 3D laser scanner or with an optical scanning device to develop a digital model of the organic surface.

[0024] Alternatively, posts of any desired length can be 3D printed to protrude from the back of the mat insert. These posts can then be machined using tap and socket or thread cutting techniques to form positive fasteners. This can be used to further reduce the required thickness of the electroformed mat. The mat is referred to herein as an electroform.

[0025] The back side of the insert is finished or ground to the final geometry and then inserted into the mold base (i.e., an injection molding machine, for example).

[0026] In summary, the method disclosed herein comprises the following steps: a mandrel with an optional textured surface is placed in an electrolytic cell to form a cushion. The cushion comprises a negative image of the optional textured surface (of the mandrel) formed by metal electrolytic deposition. The working side of the cushion is then fixed downward on a reference plane with a fixture, and the non-working surface is optically scanned to reverse engineer the geometry of the non-working surface. The optional scanning may include laser scanning. In one embodiment, a digital model of the cushion is developed by optical scanning using a non-contact three-dimensional laser scanner or an optical scanning device.

[0027] Scanning further includes measuring a reference target on the mat based on the centerline of the fixture to understand the true position of the mat relative to the fixture.

[0028] Reverse engineering the geometry of the non-working surface includes developing the profile of the non-working surface and the thickness of the pad. Additive manufacturing is then performed to add material to the non-working surface of the pad to facilitate pad defect correction. In one embodiment, the non-working surface of the electroformed body is metal 3D printed (additively manufactured) to increase its overall thickness for process mold applications. The pad to which material is added by the additive manufacturing process is called an insert. The material (added by additive manufacturing) can be metal nickel, copper, brass, iron, cobalt, aluminum or their alloys. Alloys such as steel, carbon steel, stainless steel, etc. can also be used. Other materials such as ceramics and polymers can also be used to increase the overall thickness or correct other defects in the pad.

[0029] The method also involves machining the non-working surface of the insert to solve any problems with additive manufacturing. Machining may include drilling, planing, milling, grinding, grinding, scraping, etc. or a combination thereof. The insert can then be used in other manufacturing equipment (such as an injection molding machine, compression molding machine, blow molding machine, etc.) to mass produce replicas of the original mandrel.

[0030] Although the present invention has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various modifications may be made to the invention without departing from the scope of the invention and that various elements of the invention may be substituted with equivalents. In addition, the content of the present invention may be extensively modified to accommodate specific circumstances or materials without departing from the basic scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed as the best mode contemplated for carrying out the present invention, but the present invention includes all embodiments within the scope of the appended claims.

Claims

1. A method for accelerating the production of electroforming mold inserts, comprising the following steps: placing a mandrel having an optionally textured surface in an electrolytic cell to form a cushion layer, wherein the cushion layer comprises a negative image of the optionally textured surface formed by electrolytic deposition of a metal; Fix the working side of the cushion downward on the reference plane with a clamp; optically scanning the underlayer to reverse engineer the geometry of the non-working surface, wherein reverse engineering the geometry of the non-working surface includes developing a profile of the non-working surface and a thickness of the underlayer; and Defect correction is performed by adding material to the non-working surface of the cushion layer through additive manufacturing to form a mold insert; wherein the defect correction includes increasing the thickness of the cushion layer.

2. The method of claim 1, further comprising machining the non-working surface.

3. The method according to claim 1, wherein: Stress-related warping or bending of the pad layer is reduced prior to optically scanning the pad layer.

4. The method according to claim 1, wherein: The optical scanning includes laser scanning.

5. The method according to claim 1, wherein: A digital model of the cushion is developed by optical scanning using a non-contact 3D laser scanner or an optical scanning device.

6. The method according to claim 1 further comprises measuring a reference target based on a center line of the fixture so as to understand the true position of the cushion layer relative to the fixture.

7. The method of claim 6, further comprising using a datum target on the work surface as a reference position and tilting the pad relative to a coordinate system of an additive manufacturing device.

8. The method of claim 6, further comprising using a reference target on the work surface as a reference position and tilting a coordinate system of the additive manufacturing device relative to the reference target on the base layer.

9. The method of claim 1, further comprising using the mold insert to make a replica of the mandrel.

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