Method of manufacturing a copy mould for an optical element

Abstract

A method is provided for manufacturing of moulds for manufacturing of an optical element. A master of the optical element is manufactured using a precising material deposition technology, like three-dimensional printing, for example on a substrate. Next, a master mould part is manufactured by casting a mould material on the deposited master. The master mould part is used for manufacturing of a master copy, by casting a master copy substance in the cavity of the master mould. The master copy substance may be different from the master substance. Next, a copy mould part is manufactured by casting a mould material on the master copy. The copy mould part is preferably part of a larger mould, with two or more parts and is used for manufacturing of the optical element by combining mould parts to provide a cavity for the casting of the optical element.

Description

[0001] Title: Method of manufacturing a copy mould for an optical element

[0002] TECHNICAL FIELD

[0003] The various aspects and implementations thereof relate to manufacturing of optical elements and moulds for casting such optical elements.

[0004] BACKGROUND

[0005] Various methods of manufacturing optical elements and moulds are known. It is important that any master object that may serve to manufacture the actual product is of good and robust quality, such that it may be stored for a longer time, without any major risk of deterioration.

[0006] SUMMARY

[0007] Certain materials providing master data for casting of optical elements such as lenses, like moulds or positive master shapes that may be provided by means of three-dimensional printing, may deteriorate under the influence of ambient atmosphere. Such deterioration may be drying out thus becoming brittle, deformation, or other, under the influence of temperature and / or a particular humidity level. Alternatively or additionally, such deterioration may be scratching. It is preferred to provide a method of manufacturing of moulds for production of optical elements that addresses these issue. Whereas this method is particularly well suited for the manufacturing of optical elements, it may also be used for other objects.

[0008] A first aspect provides a method of manufacturing a copy mould for an optical element. The method comprises receiving, in a three-dimensional printing system, a dataset providing a three-dimensional representation of the optical element, depositing on a substrate, by the three-dimensional printing system, an amount of master substance to provide a master piece in accordance with at least part of the dataset and providing, on the substrate, a master formwork around the master piece. In the master formwork, a first amount of mould substance is provided to settle, thus forming a master mould comprising a master cavity that is at least partially defined by the master piece. The master piece is separated from the master mould and a master copy material is cast in the master cavity of the master mould to provide a master copy that is allowed to settle. The master copy is removed from the master mould and a copy formwork is provided around the master copy. A second amount of mould substance is provided in the copy form work that is allowed to settle, thus forming a copy mould comprising a copy cavity, the copy cavity being at least partially defined by the master copy.

[0009] Firstly, this allows the master substance to be optimised for precision deposition, for example by means of three-dimensional digital printing. This requirement may not always be compatible with long shelf life of a master object. And this method allows for optimisation of the substance used for the master copy for shelflife - and precision casting.

[0010] Second, this method allows for quick reuse of the substrate. The substrate may be a precision instrument, with very well-defined dimensions and, optionally, well defined alignment markers at very well-defined positions, with tolerances in the orders of micrometres or less. Such substrate is difficult to manufacture, with expensive equipment. Hence, such substrates are expensive. Reuse of the substrates for printing further master pieces is thus preferred, with a short turnaround time.

[0011] Third, moulds may wear while being used. Casting a mould from master material may result in wear of the master substance, as this may not be optimised for casting of the mould. The substance for the master copy may be chosen differently and harder materials are available for casting, rather than for three-dimensional printing. From a proper master copy, many moulds may be manufactured, providing a virtually endless supply of copy moulds with copy cavities. It is noted that some deformation may occur during the method, depending on process parameters. With sufficient knowledge of such deformations, the deformations may be parametrised or otherwise calculated. These determined calculations may be used for transformation of the data in the dataset used to manufacture the master piece, such that the element used by casting material in the copy mould is a correct representation of the element represented by the dataset.

[0012] An implementation of the first aspect further comprises, prior to providing a first amount of mould substance, applying an alignment module to the substrate.

[0013] The alignment modules may be used as a marker providing an indication of the master piece relative to the substrate. This may be used at a later stage, for example for aligning multiple mould pieces. In such scenario, the alignment data provided by the alignment module may be transferred to the copy moulds, via the master copy.

[0014] Another implementation further comprises providing, by means of at least part of the alignment module, at least one master alignment marker to the master copy. This allows for transfer of alignment data to the copy moulds for aligning copy moulds for manufacturing of the optical element.

[0015] A further implementation further comprises, by means of the master alignment marker, providing a copy mould marker to the copy mould. By preserving and copying alignment data throughout the process, accuracy may be warranted.

[0016] In again another implementation, the substrate has a rectangular shape and the substrate comprises a hole near each of the four corners, and applying the alignment module comprises providing a rod in each of the four holes in the corners. This provides a convenient and efficient implementation.

[0017] In yet a further implementation, removing the separating the master piece from the master mould comprises removing the rods from the holes in the substrate, the rods being connected to the master mould after removal of the rods from the substrate. The rods may be either kept or removed, depending on compatibility with a particular implementation of the process.

[0018] In again a further implementation the master formwork comprises a set of walls having in orientation substantially perpendicular to the substrate; and a lid having an orientation substantially parallel to the substrate. The lid may be used to ensure a substantially planar side of the mould, opposite to the cavity.

[0019] In yet another implementation, after settling of the first amount of mould substance and removal of the master form work, the lid is connected to the master mould. An advantage of this implementation is that the lid may provide rigidity. If this is not required, for example because an insert like a skeleton is provided in the mould, or for another reason, the lid may be removed.

[0020] In a further implementation, the master formwork has a master formwork footprint outline that is larger than a substrate footprint outline of the substrate and the method further comprises providing a casting ground provided under the substrate while providing the first amount of mould substance. An advantage of this implementation is that the master cavity comprises a part that is defined by the substrate. This, in turn, may be advantageous for alignment purposes.

[0021] In again another implementation, the copy formwork has a copy formwork footprint outline that smaller than a substrate footprint outline of the substrate; and the amount of master substance deposited has an object footprint outline that is smaller than the copy formwork footprint outline. In this implementation, the substrate is not copied to the copy moulds. Second, the master pieces are printed such that they are in full copiable and may thus be copied to the copy moulds. In another implementation, the copy formwork footprint is larger than an area of the master copy defined by defined by alignment markers in the master copy, which holes are defined by the rods in the master mould. This implementation allows for the holes - or other alignment markers - to be copied to the master copy and later also to the copy moulds.

[0022] Yet a further implementation further comprises subjecting the master copy to a surface treatment. The surface treatment may be used to improve characteristics of the surface of the master copy, like smoothness, hardness or enhance other physical and / or chemical physical properties, like tendency to adhere to other materials (like the mould material or materials of alignment elements).

[0023] In again a further implementation, the surface treatment is applied after the master copy has been removed from the master mould. On the other hand, a substance for enhancing the master copy may also be provided in the master cavity, prior to casting of the master copy.

[0024] In yet another implementation, the surface treatment comprises at least one of milling and applying a coating to the master copy. Apart from providing a coating, also material may be removed. Such may be done by means of milling or etching. Such milling and etching may be all of the surface or selectively, at particular locations.

[0025] A further implementation further comprises, prior to providing the first amount of mould substance, providing a master mould skeleton as an example of an insert around the deposited amount of master substance. A preferred material for the mould is an elastomer, like silicon rubber. Such materials and elastomers in general - but also other materials - may not provide sufficient rigidity to make the mould suitable for casting with a desired tolerance. This implementation address that issue.

[0026] In a further implementation, the master mould skeleton comprises at least one of an organic polymer and a metal. Such materials allow for relative cheap and simple manufacturing of the insert. In again another implementation, the first mould amount and the second mould amount comprise an elastomer, for example sihcon rubber. Such materials allow for relatively easy casting and accommodate properly to shapes in other materials. Second, any castings may be conveniently removed.

[0027] In yet a further implementation, the master copy material comprises a polyurethane. Polyurethane may settle - cures, hardens, solidifies - quickly after casting, depending on the detailed ingredients used. Second, a wide variety is available, including transparent varieties. Transparent varieties may be useful for optical inspection of the master copy.

[0028] A second aspect provides a method for manufacturing an optical element. The method comprises manufacturing a first production mould part according to a method according to any one of the preceding claims, wherein the amount of master substance deposited is in accordance with a first sub-set of the dataset and manufacturing a second production mould part according to a method according to any one of the preceding claims, wherein the amount of master substance deposited is in accordance with a second sub-set of the dataset, the second sub-set being complementary to the first sub-set. The method further comprises combining the first production mould with the second production mould, such that cavities of the first production mould and the second production mould face one another, thus forming a product cavity, providing a product substance in the product cavity, the product cavity having a shape equivalent to that of the optical element. The product substance is allowed to settle thus forming the optical element; and the first production mould part and the second production mould part are removed from the optical element. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The various aspects and implementations thereof will now be discussed in further detail in conjunction with drawings. In the drawings, Figure 1: shows a flowchart;

[0030] Figure 2: shows two master pieces on a substrate;

[0031] Figure 3: shows a substrate with a form work;

[0032] Figure 4: shows a master mould;

[0033] Figure 5: shows a master copy as a copy of a master;

[0034] Figure 6: shows the master copy with a form work;

[0035] Figure 7: shows copy moulds based on the master copy;

[0036] Figure 8: shows the copy moulds combined; and

[0037] Figure 9: shows an optical element.

[0038] DETAILED DESCRIPTION

[0039] The various aspects and implementations thereof will be discussed in conjunction with a flowchart 100 shown by Figure 1 and with drawings showing products of the various parts of the flowchart 100, shown by Figure 2 through Figure 9. In the list below, brief summaries of the various parts of the flowchart 100 are provided.

[0040] 102 start procedure

[0041] 104 print master

[0042] 106 apply skeleton

[0043] 108 apply rods

[0044] 110 apply form work

[0045] 112 provide mould substance

[0046] 114 apply lid

[0047] 116 settle

[0048] 118 remove formwork

[0049] 120 remove substrate with print 122 cast master copy

[0050] 124 settle

[0051] 126 remove master copy

[0052] 128 apply skeleton

[0053] 130 apply rods

[0054] 132 apply form work

[0055] 134 provide mould substance

[0056] 136 apply lid

[0057] 138 settle

[0058] 140 remove master copy from mould

[0059] 142 all working moulds done?

[0060] 144 apply rods in moulds

[0061] 146 combine moulds

[0062] 148 supply product substance

[0063] 150 settle

[0064] 152 remove product from moulds

[0065] 154 end

[0066] The procedure starts in a terminator 102 and proceeds to receiving data by a three-dimensional printer that is arranged to deposit a fluid material on a substrate 202. Figure 2 shows an isometric view and a cross-section of the substrate 202. On the substrate 202, 200, a first amount of master substance forming a first master piece 204 and a second amount of master substance forming a second master piece 206 are deposited, in step 104.

[0067] The first master piece 204 and the second master piece 206 may provide representations of a front and back side of a prescription lens. In another example, the first master piece 204 and the second master piece 206 provide either back sides or front sides of left and right prescription lenses. Whereas Figure 2 shows two amounts of master substance deposited on the substrate 202, it is noted that the various aspects and examples thereof may also be used with only one amount of master substance deposited on the substrate 202.

[0068] The master substance is deposited using a three-dimensional printing process. Preferably, UV curable substance is used as a master substance. In the configuration shown by Figure 2, two master pieces are printed on the substrate 202. In another example, one or more than two master pieces are provided on the substrate 202.

[0069] In the context of this application, a three-dimensional printing process is a process of deposition of a fluid in small controlled amounts by means of a dispensing head. Movement of the dispensing head may be controlled, based on the data received by the printing process. This allows the three-dimensional printer to accurately deposit small amounts of fluid at specific locations on the substrate and on already deposited fluid. After deposition, the master substance is allowed to settle, for example by means of curing under influence of one or more of UV-radiation and thermal energy. In another example, the master fluid is solidified while losing thermal energy.

[0070] After deposition of the master substance, a mould skeleton 214 is provided around the first master piece 204 and the second master piece 206, as shown in the right part of Figure 3. The mould skeleton 214 comprises an open structure that may be provided as a cage around the first master piece 204 and the second master piece 206. The mould skeleton 214 is open to a fluid that may be used for forming a mould, as will be discussed below. The mould skeleton 214 may enhance stiffness of a mould to be formed. To that purpose, the mould skeleton 214 may comprise an organic polymer, like PETG - Polyethylene terephthalate glycol -, PE - polyethylene -, other, or a combination of two or more thereof. In another implementation, the mould skeleton 214 may comprise one or more metals, like iron, chromium, vanadium, magnesium, copper, other, or a combination of two or more thereof. In another implementation, the mould skeleton 214 comprises one or more metals and one or more organic polymer substances.

[0071] The mould skeleton 214 is in this example an inner skeleton, provided as an example of an insert for the mould, which mould is discussed below. In another implementation, the skeleton 214 may be provided as an exoskeleton, that may at least partially be provided outside a mould, which mould is discussed below.

[0072] In the substrate 202, substrate holes 208 (Figure 2) are provided. In this example, holes are provided at each corner of the rectangular substrate 202. Furthermore, additional holes are provided near the centre of the long sides of the rectangular substrate; one at each side of the centre of each long side. In step 108, rods 212 or pins are provided in the substrate holes 208. The rods 212 comprise steel, a single metal composition like aluminium or iron or another composition of metals. In another implementation, the rods 212 comprise an organic polymer. In step 110, the master formwork 210 or casting box is provided around the mould skeleton 214. In this implementation, the footprint of the master formwork 210 is larger than the footprint of the substrate 202. This means that the master formwork 210 surrounds the substrate 202. Under the substrate, a casting floor 218 is provided. The casting floor 218 serves as a bottom of the casting box provided by the master formwork 210 and the casting floor 218.

[0073] Subsequently, in step 112, a mould substance is provided in the casting box thus provided. When the mould substance has been cast in the casting box, a lid 216 may be provided on top of the casting box. As such, the like 216 may be considered as a part of the formwork. The lid 216 may be supported by the rods 212. In another implementation, the mould substance is supplied in the casting box while the lid 216 has already been placed on top of the casting box. After casting of the mould substance, the mould substance is allowed to settle. As mould substance, preferably an elastomer like silicon rubber is used. However, another elastomer or another substance may be used as well - as long as it is a substance to which the master substance is resistant, once the master substance has settled.

[0074] Figure 4 shows a master mould 220 that is provided after the master formwork 210 has been removed in step 118 and the substrate 202 with the first master piece 204 and the second master piece 206 have been removed from a first master cavity 222 and a second cavity 224, respectively. In the example shown by Figure 4, the rods 212 and the lid 216 are connected to the master mould 220, for example by virtue of adhesive properties of the material of the master mould 220. This means that upon separation of the substrate 202 and the mould 220, the rods 212 are removed from the substrate. In another implementation, at least one of the lid 216 the rods 212 are not connected to the master mould 220 and may be removed from the master mould 220. Optionally, other alignment elements may be provided at a later stage.

[0075] In step 122, a master copy substance is cast in the first master cavity 222 and the second cavity 224 and the rest of the cavity formed in the master mould 220 that has been left by removing the substrate 202. As a master copy substance, a transparent polyurethane may be used. This allows for convenient casting and relatively quick curing of the substance to a solid structure, which is the master copy 230 as shown by Figure 5.

[0076] Figure 5 shows the master copy 230 after removal from the master mould in step 126. In the master copy 230, master copy holes 232 are provided, as defined by the rods 212 in the master mould 220. The master copy 230 comprises a first copy piece 234 and a second copy piece 236, as copies of the first master piece 204 and the second master piece 206, respectively.

[0077] The master copy 230 may subsequently be subjected to a surface treatment. Such surface treatment may comprise the application of a coating. Such coating may provide scratch protection to the master copy 230. Alternatively or additionally, such coating may enhance smoothness of a surface of the master copy 230. Additionally or alternatively, the coating may enhance other or more properties of the master copy 230. Additionally or alternatively, the master copy 230 may be subjected to a corona treatment, for example by means of a flame.

[0078] The master copy 230 serves as a master for providing a working mould. On the master copy 230, a mould skeleton structure may be provided equivalent to the skeleton shown by Figure 3, in step 128. Figure 6 shows the master copy 230 provided with copy rods 242 provided in the master copy holes 232, in step 130. In step 132, a copy formwork 244 is provided on the master copy 230. In this example, the copy formwork 244 comprises a barrier between the first copy piece 234 and the second copy piece 236.

[0079] The copy form work 244 has in this example a footprint that is smaller than the footprint of the master copy 230 and larger than the first copy piece 234 and larger than the second copy piece 236. More in particular, each of the two spaces provided by the copy formwork 244 has a footprint larger than an area defined by the four master copy holes 232 in each space of the copy formwork 244.

[0080] By providing the barrier, a first working mould 252 may be provided based on the first copy piece 234 and a second working mould 254 may be provided based on the second copy piece 236, as shown by Figure 7. The first working mould 252 and the second working mould 254 are provided in step 134 by casting moulding substance in the space provided by the copy form work 244 and the working copy 230. The first working mould 252 has a first working cavity 256 complementary to the first master piece 204. The second working mould 254 has a second working cavity 258 complementary to the second master piece 206.

[0081] Optionally, a lid may be applied on top of the copy form work 234, equivalent to as step 114, described in conjunction with Figure 3. Subsequently, the mould compound is allowed to settle, as discussed above. In step 140, the master copy is removed from the first working mould 252 and the second working mould 254.

[0082] If all production mould parts for manufacturing of a particular optical element have been manufactured, the process continues to step 144. If it is determined in step 142 that more mould parts are required for manufacturing of the optical element, the process branches back to step 104. In the examples discussed here, two complementary working moulds are manufactured in parallel. In another example, complementary mould are manufactured in series.

[0083] Optionally, the copy rods 242 are removed from the first working mould 252 and the second working mould 254 as well. If that is the case, mating mould rods 262 are provided in holes of the first working mould 252 and the second working mould 254 in step 146. The holes in the first working mould 252 and in the second working mould 254 are shaped by means of the copy rods 242. The mating rods 262 enable precise alignment of the first working mould 252 and the second working mould 254 while combining the mould parts in step 146, as shown by Figure 8. In step 148, a product substance is cast in a cavity 270 provided by the first working mould 252 and the second working mould 254 for manufacturing of the optical element 290, as shown by Figure 9. The product substance is preferably a transparent resin.

[0084] As such, the various examples relate to a method for manufacturing of moulds for manufacturing of an optical element. A master of the optical element is manufactured using a precising material deposition technology, like three-dimensional printing, for example on a substrate. Next, a master mould part is manufactured by casting a mould material on the deposited master. The master mould part is used for manufacturing of a master copy, by casting a master copy substance in the cavity of the master mould. The master copy substance may be different from the master substance. Next, a copy mould part is manufactured by casting a mould material on the master copy. The copy mould part is preferably part of a larger mould, with two or more parts and is used for manufacturing of the optical element by combining mould parts to provide a cavity for the casting of the optical element.

Claims

Claims1. A method of manufacturing a copy mould for an optical element, the method comprising: receiving, in a three-dimensional printing system, a dataset providing a three-dimensional representation of the optical element; depositing on a substrate, by the three-dimensional printing system, an amount of master substance to provide at least part of a master piece in accordance with at least part of the dataset; providing, on the substrate, a master formwork around the master piece; providing a first amount of mould substance in the master formwork; allowing the first amount of mould substance to settle, thus forming a master mould comprising a master cavity, the master cavity being at least partially defined by the master piece; separating the master piece from the master mould; casting a master copy substance in the master cavity of the master mould to provide a master copy; allowing the master copy substance to settle; removing the master copy from the master mould; providing a copy formwork around the master copy; providing a second amount of mould substance in the copy formwork; allowing the second amount of mould substance to settle, thus forming a copy mould comprising a copy cavity, the copy cavity being at least partially defined by the master copy.

2. The method according to claim 1, the method further comprising, prior to providing a first amount of mould substance, applying an alignment module to the substrate.

3. The method according to claim 2, further comprising providing, by means of at least part of the alignment module, at least one master alignment marker to the master copy.

4. The method of claim 3, further comprising, by means of the master alignment marker, providing a copy mould marker to the copy mould.

5. The method according to claim any one of the claims 2 to 4, wherein the substrate has a rectangular shape and the substrate comprises a hole near each of the four corners, and applying the alignment module comprises providing a rod in each of the four holes in the corners.

6. The method according to claim 5, wherein removing the master piece from the master mould comprises removing the rods from the holes in the substrate, the rods being connected to the master mould after removal of the rods from the substrate.

7. The method according to any one of the preceding claims, the master formwork comprising a set of walls having in orientation substantially perpendicular to the substrate; and a lid having an orientation substantially parallel to the substrate.

8. The method according to claim 7, wherein, after settling of the first amount of mould substance and removal of the master formwork, the lid is connected to the master mould.

9. The method according to any one of the preceding claims, wherein the master formwork has a master formwork footprint that islarger than a substrate footprint of the substrate and the method further comprises providing a casting ground provided under the substrate while providing the first amount of mould substance.

10. The method according to any one of the preceding claims, wherein the copy formwork has a copy formwork footprint outline that is smaller than a substrate footprint outline of the substrate; and the amount of master substance deposited has an object footprint outline that is smaller than the copy formwork footprint outline.

11. The method according to claim 10 to the extent dependent on claim 3, wherein the copy formwork footprint is larger than an area of the master copy defined by holes in the master copy, which holes are defined by the rods in the master mould.

12. The method according to any of the preceding claims, further comprising subjecting the master copy to a surface treatment.

13. The method according to claim 12, wherein the surface treatment is applied after the master copy has been removed from the master mould.

14. The method according to any one of claim 12 and claim 13, wherein the surface treatment comprises at least one of milling and applying a coating to the master copy.

15. The method according to anyone of the preceding claims, further comprising, prior to providing the first amount of mould substance, providing a master mould skeleton around the deposited amount of master substance.

16. The method according to claim 15, wherein the master mould skeleton comprises at least one of an organic polymer and a metal.

17. The method according to any one of the preceding claims, wherein the first amount of mould substance and the second amount of mould substance comprise an elastomer, for claim silicon rubber.

18. The method according to anyone of the preceding claim, wherein the master copy material comprises a polyurethane.

19. A method for manufacturing an optical element, the method comprising: manufacturing a first production mould part according to a method according to any one of the preceding claims, wherein the amount of master substance deposited is in accordance with a first sub-set of the dataset, the first production mould comprising a first cavity; providing a product substance in the first cavity; allowing the product substance to settle thus forming the optical element; and removing the first production mould part from the optical element.

20. The method according to claim 19, further comprising: manufacturing a second production mould part according to a method according to any one of the preceding claims, wherein the amount of master substance deposited is in accordance with a second subset of the dataset, the second sub-set being complementary to the first sub-set; combining the first production mould with the second production mould, such that cavities of the first production mould and the secondproduction mould face one another, thus forming a product cavity; and providing a product substance in the product cavity, the product cavity having a shape equivalent to that of the optical element.

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