GB2570160A - Method of processing glass - Google Patents

Abstract

A method of processing glass, the method comprising selecting a precursor comprising a glass such as glass powder, glass particles or glass fibre, wherein said glass powder, glass particles or glass fibre has a plurality of glass properties; selecting a source of electromagnetic (“EM”) radiation; wherein at least one of said glass properties is optimised for use with said EM source; and transforming said precursor into a glass product using said EM source. The properties and irradiation conditions are selected such that thermal stresses in the glass are controlled and cracking is limited. The process may be used in additive layer manufacturing to form glass components. The glass components may be of bioactive glass and may be biomedical implants.

Description

Method of Processing Glass [0001] The present invention relates to a method of processing glass using sources of electromagnetic radiation to manufacture complex 3D structures. The invention relates particularly, but not exclusively, to additive manufacturing techniques for glass and/or vitreous materials.

BACKGROUND [0002] Lasers are conventionally used to create 3D structures in glass in a variety of wellknown subtractive processes. For example, lasers can etch or engrave at the surface or within a glass body and CO2 lasers are routinely used to cut glass substrates. US 7,399,721 B2 describes a glass that can be laser processed by ablation or evaporation caused by the beam energy absorbed in the glass.

[0003] US 2003-0045420 describes a ‘glass adapted for laser processing’. A mother glass is adapted to allow the resultant glass to absorb laser energy through the mono-photon absorbing process or the multi-photon absorbing process. These types of absorption are desired to cause abrasion or evaporation of the adapted glass to remove a specific portion of the glass.

[0004] US 6,262,389 describes a laser processable glass substrate and laser processing method for sheet glass production. The patent describes a silicate sheet of glass that contains relevant dopants such that when the glass is immersed in a molten salt comprising of 50% (mol) silver nitrate and 50% (mol) sodium nitrate, sodium ions on the surface of the glass sheet are eluted and silver ions present in the molten salt diffuse onto the surface of the glass. Following this ion exchange process, a UV laser beam is applied to the glass to evaporate or ablate the silver ions from the surface of the glass to obtain a smooth finish without causing cracking or breakage.

[0005] Conventional techniques for creating 3D glass structures are relatively quick and inexpensive but limited to simple geometries. Complex 3D glass structures can be conventionally formed by using moulds, or by the use of a two component sintering system, whereby a polymer is added and then ‘burnt out’, leaving the desired glass structure. Creating complex 3D structures is slow, expensive and subtractive processes generate a high volume of waste material.

[0006] In the field, there has been recent interest in the possibility of applying additive manufacturing techniques to glass. The additive manufacture of glass objects can be divided into two categories: direct and indirect sintering and melting. Indirect sintering and melting uses a binding material with a low melting point to adhere particles together. In Marcelli et al (2011), “The guide to glass 3D printing: developments, methods, diagnostics and results” (Rapid Prototyping Journal), a binder jetting technique was explored using water/alcohol mix to bond together virgin and recycled soda-lime-silicate glass powders containing sugar. The “green” structure was then post-sintered. This study highlights that 3D printing with glass requires careful modification of parameters such as particle size and distribution, binder and binder activator, layer thickness and printing saturation.

[0007] WO2013/103600 describes an extrusion based additive manufacturing system for 3D structural electronic, electromagnetic and electromechanical components or devices. The system comprises a method comprising the steps of: creating one or more layers of a three-dimensional substrate by depositing a substrate material in a layer-by-layer fashion, wherein the substrate includes a plurality of interconnection cavities and component cavities; filling the interconnection cavities with a conductive material; and placing one or more components in the component cavities. Whilst it is stated that the substrate may optionally comprise a glass, it is not disclosed how this may be achieved.

[0008] Grzybowski, R. et al. (2009) “Extraordinary laser-induced swelling of oxide glasses” Optics express 17:7, 5058 - 5068 describes the use of lasers to add additional features to already fabricated sheets of glass, particularly borosilicate glasses, which have been doped to improve laser absorption. Lasers in the near-infrared range are used to create modified surface textures, namely bumps, on the surface of the sheet of glass, reaching heights of 10-13% of the initial surface thickness. Doping elements used include Fe, Ti, Co, Ce and other transition metals. The irradiated portion of the glass swells, leading to the bump formations. The effect was observed in a wide range of glass compositions and the effect was observed as reversible in borosilicate glasses. The paper reports that iteratively applying higher or lower laser exposure energies enables the adjustment of bump height with sub-micron precision. Mechanisms that underpin this phenomenon are not definitively understood by the author, however he hypothesises that laser heating of the glass, directional flow and glass melting each play a role.

[0009] A publication by HP Laboratories, HPL-2012-198 published 6 Sept 2012 ‘3D Printing of Transparent Glass’ identifies that maintaining transparency is a major challenge for 3D printed glass. The publication comments with respect to 3D printing warm glass and 3D printing cold glass, wherein cold glass refers to materials in which glass is used as a strengthening component in another cured matrix. When 3D printing warm glass, glass powder or frit is shaped in a mould and fired at moderate temperatures, fusing the powder into a solid glass object. Success of this method is highly dependent on temperature; if temperature is insufficient, the powder may simply stick together without melting to form a smooth body. Research has demonstrated that finer particle sizes give better detail in 3D printed warm glasses, but also causes more bubbles to be trapped in the glass, compromising mechanical and optical integrity.

[0010] Direct sintering involves melting or sintering a powdered material directly with the laser. Selective laser sintering (SLS), often referred to as Select Laser Melting (SLM), is an established art in the manufacturing industry and is commonly used for product development, rapid prototyping and additive manufacturing processes. Laser sintering uses high power lasers to fuse plastic, metal or ceramic. The laser is applied in the X and Y directions on the surface of the powder, building up cross-sectional layers iteratively from a 3D CAD digital solid model of the desired end product. Whilst SLS is a wellestablished technique for the printing of plastics, metals and ceramics, the use of SLS for 3D printing glasses has is not well understood, and attempts at 3D printing glasses have been unsuccessful.

[0011] For example, Krishna, C et al (2004), Fabrication of 13-93 bioactive glass scaffolds for bone tissue engineering using indirect selective laser sintering demonstrates a technique whereby a binder has to be combined with the glass in order to achieve ‘green’ 3D structures which have to be subsequently sintered to create a fully-glass structure. The study highlighted that in order to minimize thermal effects during sintering the processing temperature was kept at 60°C, which was just below the melting temperature of the stearic acid binder, highlighting that standard SLS techniques used on metals (which do not need binders) cannot be directly applied to glass materials.

[0012] It is widely acknowledged that silica glasses (and, for the same reason, most other types of glasses) are notoriously difficult to shape due to the high temperature melting required. Kotz, F et al (2017), “Three-dimensional printing of transparent fused silica glass” (Nature) acknowledges this challenge, claiming that until now only two methods for shaping glass in 3D printing have been demonstrated, “a fused deposition molding approach in which soda lime glass is heated to around 1,000°C and a manual wire feeding approach in which a glass filament is melted using a laser beam”. Kotz goes on to describe a route for creating 3D structures from silica glass using a photocurable silica nano-composite, whereby laser irradiation is used to cure the polymer to create a ‘green’ structure that has to be subsequently sintered at higher temperatures.

[0013] Krzyzanowski, M et al (2016), “3D analysis of thermal and stress evolution during laser cladding of bioactive glass coatings” (Journal of the Mechanical Behavior of Biomedical Materials, 59) highlighted the challenges in controlling thermal and strainstress transient fields during laser cladding of bioactive glass coatings through a series of modelling experiments which investigated the sintering of multiple layers of bioactive glass material onto a titanium surface. In this work the model and technique employed maximised interaction between the laser and the precursor material. As is typical in additive manufacturing processes, parameters were optimised to minimise the heat affected zone around the laser spot during the additive process.

[0014] Mortiz, N. et al (2004) “Characterisation of bioactive glass coatings on titanium substrates produced using CO₂ laser” describes a technique for using a CO2 laser to sinter bioactive and inert glass powders onto titanium substrates. A CO2 continuous wave laser (emitting 10pm EM radiation) is used as bioactive glass is opaque in this region. Thin coatings (30-40pm thick) were achieved, however some cracking was observed which is likely to be exaggerated in thicker coatings.

[0015] Comesana et al (2011) Three-dimensional bioactive glass implants fabricated by rapid prototyping based on CO2 laser cladding discloses a method of making a 3D bioactive glass implant comprising feeding glass powder and melting it with a laser to build up a 3D object layer by layer. Very high laser powers were required, leading to excessive heating which led to undesirable crystallization within the bulk ofthe glass which affected bioactive properties. A detailed analysis of the integrity and cracking within the resulting structure is not provided.

[0016] EP-A-2840071 discloses a SLS method of making a glass coating on a glass substrate (fig. 1 and claim 1) comprising depositing glass powder with an ultra-low coefficient of thermal expansion, applying laser to melt the glass and repeating the operation to obtain a multi-layer coating. The corresponding apparatus comprises a laser and a powder bed as receiving means for the precursor (§ [0022]).

[0017] Klein, J of MIT, USA (2015) explored laser sintering in his thesis ybmission%20.(.l)...pdf) and concludes that preventing the melted glass from clustering into droplets was rather challenging. The droplet formation prevented layer bonding in the X and Y axes resulting in unsuccessful end products. Additionally, the settings that were needed to melt the glass were not sustainable for long duration runs. As such he focused on a Fused Deposition Modelling (FDM) approach, which started from molten glass. This work is reported by Klein, J et al (2015) in the paper “Additive Manufacturing of Optically

Transparent Glass”, (3D Printing and Additive Manufacturing), which states that ‘sintered glass objects printed using [Selective Laser Melting] are commercially available but they are extremely fragile and appear opaque due to the light scattering from glass powders caused by incomplete densification’.

[0018] Luo et al (2014), “Additive Manufacturing of Glass” (Journal of Manufacturing Science and Engineering Vol. 136) attempted to use a SLS powder bed technique with a CO2 laser to build solid walls from a soda-lime-silicate glass powder and compared them against a wire fed process. This work concluded that it was not possible to print multiple layers of glass using SLS without significant cracking due to thermal stresses created in the part during the deposition process.

[0019] Fateri et al (2015), “Selective Laser Melting of Soda-Lime Glass Powder” (Int J. of Appl. Ceram. Technol. 53-61) did successfully use a CO2 laser to print a series of 3D objects out of soda-lime-silicate glass powders, how the surface finish was poor and the resolution was not quantified but appeared to be relatively coarse; post-processing was required to finish off the shape and the review did not undertake a comprehensive analysis of the mechanical integrity of the fabricated parts and so it is not possible to determine how mechanically stable the parts were.

[0020] US 2003-104920 A1 describes a technique whereby a CO2 laser is used to sinter pure SiO2 powders into large parts, where fine resolution or structure is not required. It is acknowledged that the laser power needs to be varied, this is achieved through varying laser power, displacement rate, focus. Although it is inferred that other laser wavelengths could be used, there is no exploration as to how other wavelengths could be used successfully with the described technique.

[0021] EP2784045A1 highlights the technical challenge in SLS when the wavelength of the laser significantly differs from the absorption of the powder (which could be a bioactive glass) emphasizing the only known solution is to increase laser energy/reduce laser scanning speed (which leads to poor quality of the final item) and proposing a solution whereby a separate substance (liquid, solid, gas, but preferably powder), referred to as a ‘vector’, that absorbs at the wavelength of the laser is added to the powder.

[0022] US20070238056A1 highlights the same issue, adding that only expensive CO2 lasers are suitable for processing such materials, which creates process constraints. This patent addresses the problem when the absorption properties of the material do not align with the emitted EM wavelength through selective application an absorbing material onto the powder prior to EM irradiation, such that lower cost EM sources can be used.

[0023] Other additive manufacturing techniques for the production of metal or polymeric materials are well established. Fused deposition additive manufacturing involves the production of a part by extruding small beads of melted material to form layers. A plastic filament or metal wire is unwound from a coil and supplies the melted material to a heated extrusion nozzle which can turn the flow of melted material on and off. A worm-drive typically pushes the filament into the nozzle at a controlled rate and the material hardens immediately after extrusion from the nozzle. The material most typically consists of selfhardening waxes, thermoplastic resins, molten metals, two-part epoxies or foaming plastics, which adhere to the previous layer with an adequate bond upon solidification. Further details are described in US 5,340,433 and US 5,121,329.

[0024] Stereolithography, also referred to as SLA, uses light, typically in the UV range, to convert photosensitive liquid plastic resins and composites into solid layers. A laser beam traces a cross sectional pattern for each layer on the surface of the liquid resin. The exposure to the ultraviolet light solidifies the new layer and binds the new layer to the previous layer. Stereolithography requires the use of support structures which attach the part to an elevator platform on which the part is being printed. The support structure prevents deflection due to gravity and secures the cross sections in place. Whilst stereolithography can produce a multitude of shapes, it is often expensive and parts produced by this method can experience warping, shrinkage and curl due to phase change. SLA is limited to photo-polymeric materials and therefore not suited for glass production.

[0025] 3D printing uses ink-jet technology to apply a binder to powder deposited in layers prior to curing the binder with heat or ultraviolet light. US 5,387,380 describes a process for making a component by depositing a first layer of a powder material in a confined region and then depositing a binder material to selected regions of the layer of powder material to produce a layer of bonded powder material at the selected regions. Such steps are repeated a selected number of times to produce successive layers of selected regions of bonded powder material so as to form the desired component. The unbonded powder material is then removed. In some cases the component may be further processed as, for example, by heating it to further strengthen the bonding thereof. US 5,387,380 mentions that the powder material could be powdered ceramic, powdered metal or a powdered glass. However, use of powdered glass is not sufficiently described to enable a workable technique. Glass powder does not readily bond to typical binder materials used. In the instance where a glass powder does bond to a binder material, further part geometries are limited to simple shapes and further processing is required, such as the addition of a support powder and further heat treatments.

[0026] EP-A-1942084 discloses (claims 28 and 29; example 2) a method of joining a first glass substrate to a second glass substrate via a sealing material. The sealing materials comprises a glass frit and ceramic powder (§ [0113]) and the glass frit contains a dopant absorbing the laser radiation purely for the purposes of absorbing laser radiation as efficiently as possible (§ [0025], [0104]). The obtained product comprises two glass pieces joined by a sealant glass product.

[0027] Despite numerous additive manufacturing techniques being available for metal, ceramics and polymers, none of the known prior art describes an effectively workable technique that can be used to convert glass or vitreous materials into robust 3D structures with fine resolution without the need for extensive post-processing steps.

BRIEF SUMMARY OF THE DISCLOSURE [0028] The invention is defined in the appended claims. In accordance with a first aspect of the present invention there is provided a method of processing glass to control thermal stress and/or to maximise the geometrical precision of features therein. The method comprises the steps of:

providing a glass precursor having a plurality of glass properties;

providing a source of electromagnetic “EM” radiation, having a plurality of EM source properties and capable of emitting EM radiation to a moveable EM spot area to produce an actively EM-affected area and an actively EM-affected volume in a target material;

applying the EM source to the glass precursor to produce said actively EM-affected surface area and said actively EM-affected volume in the glass precursor;

controlling said actively EM-affected area of the glass precursor such that the actively EM affected area is larger than the EM spot area;

controlling said actively EM-affected volume to control a thermal difference and/or a thermal gradient within said glass precursor; and transforming the glass precursor into a glass component using said EM source.

[0029] The method may also include the step of controlling the actively EM affected volume to avoid or control crystallisation characteristics within the glass precursor.

[0030] Controlling the EM affected area and/or EM affected volume comprises optimising one or more of:

one or more of said glass properties;

one or more of said EM source properties;

one or more characteristics of said EM spot area; and the degree of scattering of EM radiation within the glass precursor [0031] Selecting a precursor where at least one of the glass properties is optimised for use with the EM source enables the transitioning between an unstructured precursor and a structured glass product. An example of a structured glass product is a 3D glass structure.

[0032] The method may comprise: matching one or more precursor properties to one or more electromagnetic source properties to control the actively EM-affected area and volume; and applying an electromagnetic source having those electromagnetic source properties to a precursor having those precursor properties in order to transition the precursor into a glass product.

[0033] Building a glass product may involve laying down one or more successive layers of precursor on an existing glass layer which has already been fused together. The absorption profile of the precursor may be optimised to control the absorption of the EM radiation by the precursor to optimise the actively EM-affected volume. By controlling the actively EM-affected area and volume, the energy may remain localised within the precursor layer and top surface layers, rather than penetrating deeply into the bulk of the glass structure. This reduces excess heating and minimises thermal stresses which could lead to mechanical or structural issues within the glass product, particularly in glass products with complex structures.

[0034] In contrast, EP-A-2840071 mentioned above reinforces the difficulty in managing thermal stresses in order to apply and sinter successive layers of glass powder to a substrate, claiming that SLS is only feasible when using glass precursor materials with a very low coefficient of thermal expansion are used.

[0035] In Krzyzanowski, M etal (2016), “3D analysis of thermal and stress evolution during laser cladding of bioactive glass coatings” (Journal of the Mechanical Behavior of Biomedical Materials, 59) mentioned above, no attempt was undertaken to optimise either EM source or precursor properties to control the EM affected volume.

[0036] In EP-A-1942084 mentioned above, no mention is made as to whether this technique relates to applying subsequent layers to the original joint. No mention is made as to any attempt to tune the absorption properties of the glass to optimise the absorption properties of the precursor in order to control the EM affected volume within the substrate and surrounding material, nor the use of this technique to control adverse effects such as thermally induced cracking, thermal stresses, or crystallization.

[0037] The wavelength profile of the EM source may be optimised to control absorption of the EM radiation by the precursor, the penetration depth of the EM radiation into the glass product and the actively EM-affected volume.

[0038] By controlling the absorption of the EM radiation by the precursor, lower EM source power may be used to transform the precursor into the glass product.

[0039] The use of lower EM source power is advantageous because glass is a poor thermal conductor and high laser power can result in damage to the glass product or a glass product which does not have a desired structure. When building up a glass product by laying down one or more successive layers of precursor, the heating caused by high laser powers may cause a layer to bead on the surface of a previous layer rather than forming a desired structure.

[0040] The use of lower EM source power is also advantageous because high EM source power can adversely affect chemistry of the glass material, for example, by reacting with gas in the atmosphere, or through loss of volatile components within the glass matrix.

[0041] Optimising may comprise overlapping at least a portion of the EM source wavelength profile with an absorption profile (such as an absorption band) of the precursor.

[0042] The EM source properties may comprise any one or more of: wavelength, a wavelength profile polarisation, focus, numerical aperture, average power, peak power and pulse characteristics. The EM source may be a continuous wave source.

[0043] The precursor may be optimised to at least one or more of: wavelength, average power, pulse length, repetition rate, pulse peak power, speed of travel, focus/depth of field, spot size/shape, beam energy profile and numerical aperture of the EM source.

[0044] The EM source average power may be between 0.1 W and 400 W. EM source average powers in this range have been found to be particularly suitable for transforming the precursor into the glass product.

[0045] The EM source average power may be in the range of 0.25 W and 20 W. EM source average powers in this range have been found to provide the optimal conditions for transforming the precursor into the glass product.

[0046] The EM source average power may be between 2 W and 40 W.

[0047] The EM source average power may be optimised to improve material flow while avoiding extreme thermal stresses in the glass product.

[0048] The EM source average power may be optimised to reduce beading.

[0049] The EM source average power may be less than 20 W to reduce beading and/or cracking.

[0050] The EM source average power may be in the range 20 W and 40 W. EM source average powers in this range have been found to particularly suitable for transforming the precursor into the glass product at a relatively high speed of travel, especially where resolution is not critical (for example, when forming a glass product having relatively large feature sizes, or when using the method to join two or more glass components), or for precursors having lower levels of dopant.

[0051] The EM source average power may be in the range of 20 W and 400 W. EM source average powers in this range may be suitable for joining two or more glass components.

[0052] The speed of travel may be based on the resolution required to define a feature of the glass product. For example, a slower speed of travel may be used to define small features, whereas a higher speed of travel may be used to define coarse features. Optimising the speed of travel allows a balance to be struck between speed and resolution.

[0053] The speed of travel, EM source average power and/or EM spot area may be controlled to manage thermally induced stress in the glass product. This allows a glass product to be formed with desired stress properties without requiring further processing stages in the manufacturing of the glass product. The EM spot area may be increased to anneal the glass product and relieve thermally induced stress.

[0054] The speed of travel may be controlled to anneal the glass product, for example, by reducing the speed of travel of the EM source. This avoids the need for the glass product to be annealed separately, removing a stage from the process of manufacturing the glass product.

[0055] The speed of travel may be in the range of 20 mm/sec and 40 mm/sec. This range has proven suitable, in particular, for sintering the precursor to form the glass product while being easy to control and providing sufficient resolution.

[0056] The EM spot area characteristics may comprise any one or more of: distribution of irradiance within the EM spot area, position of the EM spot area, orientation of the EM spot area, direction of movement of the EM spot area and speed of movement of the EM spot area.

[0057] In an embodiment said source of EM radiation comprises two or more sources of EM radiation, each source having a plurality of EM source properties and each source having a plurality of EM spot area characteristics, wherein said controlling comprises one or both of:

optimising said EM source properties of each of the two or more sources of EM radiation differently, relative to each other; and optimising said EM spot area characteristics of each of the two or more sources of EM radiation differently, relative to each other.

[0058] Optimising the EM source properties “differently” may mean optimising a different property of each source or may mean optimising the same property but in a different way or to a different extent.

[0059] Said one or more glass properties may comprise any one or more of: emissivity, heat capacity, thermal conductivity, an EM absorption profile, a coefficient of thermal expansion, an EM absorption coefficient at a wavelength of the EM source, an EM absorption coefficient at a wavelength of thermal radiation generated during said transforming.

[0060] Other glass properties which may be optimised include composition and/or doping elements, viscosity, refractive index, heat transfer, heat capacity, thermal conductivity, the size, shape, aspect ratio, chemical and/or physical surface condition or surface texture of particles, fibres or powder.

[0061] A material property of the precursor may be selected based on a desired property of the glass product.

[0062] A melting point and/or flowability of the precursor may be optimised, which can improve bonding of the precursor into the glass product.

[0063] A desired thermal property of the precursor may be optimised. For example, a thermal expansion coefficient of the precursor may be optimised to reduce undesirable stress within the glass product, which may remove the need for subsequent processing and/or annealing of the glass product.

[0064] The precursor may be optimised to modify the absorption profile of the precursor. The absorption profile of the precursor may be matched with the EM source wavelength profile by using a precursor comprising a dopant. The precursor may be doped so that the absorption profile of the precursor overlaps at least a portion of the EM source wavelength profile. By doping the precursor, the absorption profile of the precursor may be modified, meaning that the glass product may be made from any type of glass, meaning that glass products having any desired property, such as a desired optical property, can be formed.

[0065] By using a doped precursor, the absorption profile of the precursor may be modified so that a cheap, readily available, or compact EM source (such as a laser) may be used in the method. For example, an EM source (such as a laser) emitting light between 300 nm and 1600 nm may be used. Preferably, an EM source (such as a laser) emitting light between one of the following wavelength ranges may be used: 300 nm and 400 nm; 300 nm and 500 nm, 500 nm and 600 nm; 800 nm and 1000 nm; 1000 nm and 1100 nm; and 1100 nm and 1600 nm.

[0066] One or more of particle size, particle shape and particle aspect ratio may be optimised. These properties have been found to control the ability to match the structure of the glass product with the desired structure.

[0067] The precursor may comprise spherical particles. The spherical particles may have an average sphericity greater than 0.8, preferably greater than 0.9, and more preferably greater than 0.95. Spherical particles have been found to perform better and are easier to spread meaning that, for example, spherical particles result in smoother layers.

[0068] Said applying the EM source may comprise moving a position of the EM spot area relative to the glass precursor or vice versa. The position of the EM spot area could be mechanically moved, or moved via use of reflection.

[0069] Preferably, the source of EM radiation comprises a laser. Alternatively, the EM source may be a microwave source or focussed sunlight.

[0070] In an embodiment, the glass precursor comprises one or more dopants arranged to control an EM absorption coefficient of the precursor. The dopant may be an element, such as iron. The dopant may be an element in a selected oxidation state, such as Fe²⁺ or Fe³⁺. The oxidation state may be chosen to control absorption of the EM radiation by the precursor, or a desired property of the glass product (such as transparency).

[0071] In an embodiment, the glass precursor comprises any one or more of: a glass powder, glass particles or glass fibres.

[0072] Said transforming may comprise fusing or melting said glass powder, glass particles, or glass fibres together. Said transforming may comprise selective laser sintering or direct laser sintering.

[0073] Transforming the precursor into the glass product may be part of an additive manufacturing process.

[0074] Transforming may comprise one of: fusing the glass powder or glass particles to form the glass product. The glass powder or glass particles may be fused using a laser.

[0075] Transforming may comprise melting the glass fibre to form the glass product. The glass fibre may be melted using a laser.

[0076] Transforming may be employed to progressively form a 3D glass structure, such as an optical element, or a biomedical implant.

[0077] The transforming may comprise forming a glass product having a specific surface texture.

[0078] The transforming may comprise forming a feature on an existing glass substrate, such as a sheet of glass, glass bottle or glass container. This allows the surface texture or shape of the glass substrate to be modified. The feature may be a pattern of bumps or lines on the base of a glass bottle, which may improve the strength of the glass bottle. The feature may be a logo or decoration on the outside of a glass bottle or glass container, which provides a convenient way to put a logo or decoration onto a plain glass bottle or glass container.

[0079] The glass product may be applied to a metal or metal alloy.

[0080] The glass product may be applied to a ceramic or a glass-ceramic.

[0081] The glass product may be applied to a glass.

[0082] The glass precursor may be processed alternately and/or in combination with a metal or metal alloy to form a glass-metal composite.

[0083] The glass precursor may be processed alternately and/or in combination with a ceramic or glass-ceramic.

[0084] The glass precursor may be processed alternately and/or in combination with a different glass precursor.

[0085] The glass product may be suitable for use as an optical element. For example, the glass product may be suitable for use in an optical sensor, preferably a solar diffuser cell. The method allows any glass precursor material to be transformed into a glass product by optimising the EM source properties and/or the glass properties. This is an advantage because it means that a custom-shaped optical element may be formed from any material, including materials (such as fused silica) which is challenging to machine.

[0086] The glass-metal composite may be suitable for use in an optical sensor, preferably, a solar diffuser cell.

[0087] The glass product may be suitable for use as an implant. The method provides a convenient way of producing implants with any desired shape or properties. The biomedical implant may be, for example, a femoral stem, an acetabular cup or any component of a knee or shoulder joint prosthesis.

[0088] The glass product may comprise a bioactive material, which improves integration and acceptance of an implant into a body into which the implant is implanted. The bioactive material may be, for example, Bioglass® 45S5, 6P57, 58S, 70S30C, S53P4, or any other suitable glass having a bioactive effect in the human or animal body.

[0089] A dopant may be selected which is compatible with the bioactive material. Some dopants (such as dopants containing iron) may inhibit or reduce the bioactivity of the bioactive material.

[0090] The glass product may comprise a porous structure. The porous structure may be formed by forming the glass product in layers with different structures. The porous structure may improve the ability of the glass product to be used as an implant, for example, by allowing blood vessels to knit into the structure which improves integration and acceptance of an implant into a body into which the implant is implanted.

[0091] The pore size may be between one of: 300 micrometres and 2000 micrometres; 300 micrometres and 1000 micrometres; and 1000 and 2000 micrometres.

[0092] The glass product may be adhered to a metal or metal alloy, preferably to form a biomedical implant. The metal or metal alloy may provide strength and resilience to the implant, while the glass product improves integration of the implant with a body into which the implant is implanted.

[0093] In an embodiment, the glass component comprises a bioactive material.

[0094] The glass precursor may be processed alternately and/or in combination with a metal or a metal alloy to form a glass-metal composite component.

[0095] In an embodiment, the glass component is applied to a substrate comprising any one of or combination of one or more of: a metal, a metal alloy, a ceramic, a glass and a glass ceramic. The glass component may comprise a porous structure. Optionally the pore size may be a range selected from: 300 - 2000 micrometres, 300 - 1000 micrometres, 1000 - 2000 micrometres.

[0096] Optionally, said glass component comprises a biomedical implant. The method provides a convenient way of producing implants with any desired shape or properties.

[0097] According to another aspect of the invention there is provided an additive manufacturing process comprising the method of any of the preceding paragraphs.

[0098] According to another aspect of the invention there is provided a non-transitory computer readable medium having computer readable instructions stored thereon which, when executed by a computer, are arranged to perform a method or process according to any of the preceding paragraphs.

[0099] According to another aspect of the invention there is provided a biomedical implant manufactured using the method or process of any of the preceding paragraphs.

[00100] According to another aspect of the invention there is provided an apparatus for processing glass according to the method or process of any of the preceding paragraphs, the apparatus comprising:

means for receiving a glass precursor having a plurality of glass properties;

a source of electromagnetic “EM” radiation, having a plurality of EM source properties and capable of emitting EM radiation across an EM spot area to produce an EM affected surface area and an EM affected volume in a target material;

means for applying the EM source to the glass precursor to produce said EM-affected surface area and EM affected volume in the glass precursor; and means for controlling an EM affected area of the glass precursor such that the EM affected area is larger than the EM spot area and for controlling said EM-affected volume to control a thermal difference and/or a thermal gradient within said glass precursor;

wherein the apparatus is arranged to transform said glass precursor to a glass component using said EM source.

[00101] In an embodiment, the apparatus further comprises means for controlling the actively EM affected volume to control the crystallisation characteristics within the glass precursor.

[00102] In an embodiment, said means for controlling the EM affected area and/or EM affected volume is arranged to optimise one or more of:

one or more of said glass properties;

one or more of said EM source properties;

one or more characteristics of said EM spot area and the degree of scattering of EM radiation within the glass precursor.

[00103] In an embodiment, said means for controlling comprises a system for controlling any one or more of: distribution of irradiance within the EM spot area, position of the EM spot area, orientation of the EM spot area, direction of movement of the EM spot area and speed of movement of the EM spot area.

[00104] In an embodiment, the apparatus comprises a computer numerical control “CNC” router wherein a rotary cutter of the CNC router is replaced by one or more laser optics arrangements.

[00105] Optionally, the apparatus is arranged to form a three dimensional glass component by fusing consecutive layers of said glass precursor using the EM source or by melting the glass precursor onto a substrate using the EM source.

[00106] The apparatus may further comprise a means for receiving a three dimensional glass item, wherein the apparatus is arranged to apply said glass component to the three dimensional glass item.

[00107] Said applying the EM source may comprise repeated application of the EM source to the precursor and said means for controlling may be arranged to, between successive applications of the EM source, re-optimise one or more of any of:

said glass properties;

said EM source properties;

said characteristics of said EM spot area; and the degree of scattering of EM radiation within the precursor.

[00108] Optionally, the precursor may be a first precursor and the method may further comprise selecting at least one additional precursor, wherein said applying the EM source comprises repeated applications of the EM source to the precursor and, between one or more successive applications, applying said at least one additional precursor either individually, or in combination with the first precursor.

[00109] This may allow EM source or precursor properties to be optimised to produce the desired geometry or properties of the present portion of a 3D glass structure being formed.

[00110] In an embodiment, said means for receiving the glass precursor comprises a powder bed having a controllable temperature.

[00111] The apparatus may further comprise a void above the powder bed in which pressure applied to the powder bed can be controlled. The void may contain a vacuum, a partial vacuum, a liquid or a gas. The packing density of a glass powder composition in the powder bed may be controlled.

[00112] The EM source may be a continuous wave source. By optimising the EM source properties and/or the glass properties, in particular, by matching the absorption profile of the precursor with the EM source wavelength profile (for example, by doping the precursor), the use of a pulsed source (such as a pulsed laser) is not needed to transform the precursor into a glass product. The EM source may be selected to have a wavelength at which a glass component has a high transmission, wherein the glass component is placed between the EM source and the precursor. This may allow for transforming the precursor into the glass product through a window or substrate, for example, to allow the glass product to be formed inside another structure such as a sealed container.

[00113] The method may comprise joining a glass component to a further glass component using the glass product. Joining the glass component and the further glass component in this way can result in less residual stress and less potential for fracture than joining the glass component and the further glass component by thermally sintering an intermediary frit or sealing glass which requires heating the glass component and the further glass component together. Using this method reduced the reliance on matching thermal expansion coefficients and/or tailored geometries of the glass component and further glass component, meaning that a much wider range of glass components (including those with different thermal expansions coefficients) can be joined.

[00114] The glass component and the further glass component may be joined to create a sealed glass envelope, for example, to contain a pressurised gas or maintain a vacuum.

[00115] An optical element (such as a window) may be joined to a glass component. The EM source may be optimised such that the optical element (such as the window) has a high transmission for the EM source. In this way, the EM source is not absorbed by the optical element (and therefore the optical element is not damaged by the EM source and the EM source does not cause thermal expansion of the optical element) but the EM source is absorbed by the precursor thereby processing the precursor into a glass product to join the optical element to the glass component.

[00116] The precursor may comprise a mixture of a glass powder, glass particles and/or glass fibre. The precursor may be a frit.

[00117] An optical sensor may be provided comprising a glass product formed using the method or process described above.

[00118] By at least one of the EM source properties being optimised for the glass properties and/or at least one of the glass properties being optimised for the EM source properties, the method allows any precursor material to be transformed into a glass product for use as an optical element in an optical sensor. This is an advantage because it means that a custom-shaped optical element may be formed from any material, including materials (such as fused silica) which is challenging to machine.

[00119] The optical sensor may comprise a glass-metal composite formed using the method or process described above. The optical sensor may be a solar diffuser cell.

[00120] The glass product may comprise a bioactive material, which improves integration and acceptance of an implant into a body into which the implant is implanted.

[00121] The glass product may comprise a porous structure. The porous structure may be formed by forming the glass product in layers with different structures. The porous structure may improve the ability of the glass product to be used as an implant, for example, by allowing blood vessels to knit into the structure which improves integration and acceptance of an implant into a body into which the implant is implanted [00122] The glass product may be adhered to a metal or metal alloy, preferably to form a biomedical implant. The metal or metal alloy may provide strength and resilience to the implant, while the glass product improves integration of the implant with a body into which the implant is implanted.

[00123] The pore size may be between 300 micrometres and 2000 micrometres, preferably 300 and 1000 micrometres, or 1000 micrometres and 2000 micrometres.

[00124] According another aspect, there is provided a glass item comprising two or more glass components, wherein the glass components are fused together using a glass product using a method according to the first aspect.

[00125] According to another aspect, there is provided a glass item comprising a surface feature created by applying glass product to the glass item using the method according to the first aspect.

[00126] The glass item may be a sheet of glass, a glass bottle or a glass container.

[00127] The surface feature may be a feature which improves strength of the glass item, for example, a pattern of bumps or lines on the base of a glass bottle which improves the strength of the glass bottle.

[00128] The surface feature may be a logo or decoration on the outside of the glass item.

[00129] The apparatus may be configured to receive data defining a 3D glass structure, and the apparatus may be configured to form the 3D glass structure based on the data.

[00130] Applying the EM source may comprise repeated application of the EM source to the precursor and the apparatus is arranged to, between successive applications of the EM source, re-optimise at least one of the glass properties for use with the EM source and/or re-optimise at least one of the EM source properties for use with the glass composition feed.

[00131] Re-optimisation may be based on the geometry of the present portion of the 3D glass article being formed.

[00132] Further features of the invention are defined in the appended claims.

[00133] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS [00134] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1A is a block diagram illustrating a method of processing glass in accordance with an embodiment of the invention;

Figure 1B is a schematic top view showing the EM-spot area and actively EMaffected area;

Figure 1C is a schematic cross-sectional view showing the actively EM-affected volume;

Figure 2 is a schematic diagram of an apparatus capable of implementing the method;

Figure 3 is a Z - stage for use in a method of processing glass according to an embodiment of the invention;

Figure 4 is a schematic diagram of apparatus for processing glass according to an embodiment of the invention;

Figure 5 is a graph illustrative ofthe relative absorption of light at different wavelengths emitted by an ytterbium fibre laser by an unmodified glass and that same glass modified with 1 mole % Fe³⁺;

Figures 6A and 6B are schematic diagrams illustrative ofthe difference in energy transfer in an unmodified glass as compared with that same glass modified with 1 mole% Fe³⁺;

Figure 7 is a schematic diagram of a system suitable for producing raised features on an existing glass substrate;

Figure 8A is a schematic diagram of apparatus for producing raised features on an existing glass substrate;

Figure 8B is a schematic diagram of a print head apparatus for use with the apparatus of Figure 8A;

Figure 9A is schematic diagram of apparatus for printing features onto a substrate according to an embodiment of the invention;

Figure 9B is a schematic diagram illustrating an alternative configuration of apparatus for printing features onto a substrate, according to an embodiment of the invention;

Figure 9C is a schematic diagram illustrating a further alternative configuration of apparatus for printing features onto a substrate, according to an embodiment of the invention;

Figure 10A is a schematic diagram illustrative of a configuration of apparatus for fusing two glass components together, in accordance with an embodiment of the invention;

Figure 10B is a graphical representation of the transmission properties of various components of a UV envelope at a wavelength of 355nm; and

Figure 10C is a schematic diagram demonstrating an example of how laser path angle can be altered such that the laser is directed away from the central axis of the laser.

DETAILED DESCRIPTION [00135] Additive manufacturing using a glass powder, particle or fibre composition is achieved by using a source of electromagnetic (“EM”) radiation, for example a laser, to modify a property, structure or state of the glass to create the desired shape.

[00136] As summarised above, the additive manufacturing method of processing glass described herein involves controlling an actively EM-affected surface area and an actively EM-affected volume by optimising one or more glass properties, one or more EM source properties and/or one or more characteristics of the surface area directly impinged upon by radiation from the EM source (the “EM spot area”).

[00137] Typical EM source properties which could be optimised for a specific glass powder, particle or fibre composition include: wavelength, average power, pulse length, repetition rate, pulse peak power, speed of travel, focus/depth of field, spot size/shape, beam energy profile and/or numerical aperture.

[00138] Typical glass properties which could be optimised for a specific EM source include: composition and/or doping elements, viscosity, absorption properties, refractive index, heat transfer, heat capacity, thermal conductivity, particle size, particle shape, particle aspect ratio, particle chemical and/or physical surface condition and/or the particle surface texture.

[00139] Throughout the description and claims of this specification, the following terms may be understood in view of the below explanations:

[00140] The term “EM spot area” means a surface area directly impinged upon by EM radiation from an EM source.

[00141] The term “actively EM-affected surface area” means a surface area affected by the EM radiation from the EM source (for example by photon absorption and/or by heating and/or by scattering) as the EM spot is moved across a surface. The actively EM-affected surface area remains actively affected until both the EM spot has been removed and the surface has fully cooled.

[00142] The term “actively EM-affected volume” means a volume affected by the EM radiation from the EM source (for example by photon absorption and/or by heating and/or by scattering) as the EM spot is moved across a surface . The actively EM-affected volume remains actively affected until both the EM spot has been removed and the volume has fully cooled.

[00143] The term “heat affected volume” is the volume within the actively EM-affected volume that is heated by the EM radiation from the EM source.

[00144] The term “thermal difference” refers to the difference in temperature measured at two points.

[00145] The term “thermal gradient” means the distance between the two points at which the thermal difference is measured.

[00146] The term “thermal stress” means a mechanical stress introduced in a component or material as a result of a thermal difference therein wherein some or all of the component or material is not free to expand or contract in response to the thermal difference.

[00147] The term “controlling crystallisation characteristics” includes the possibility of controlling crystallisation characteristics in order to avoid crystallisation occurring altogether.

[00148] The term “a bioactive material” means a material having an interaction with or effect on any cell or tissue of the human body.

[00149] The term “absorption properties” includes, inter alia, absorption coefficient as a function of laser wavelength and intensity; as well as the dispersion; refractive index properties of the glass and how these properties change as a function of time, temperature and material thickness and the manner in which the laser radiation is absorbed and scattered within the material/powder bed.

[00150] The term “glass” means a metastable material, that lacks long range order at the atomic scale insofar as no preferred diffraction occurs in X-ray diffraction; such material may be metallic, inorganic or organic. In the context of this specification, the term “metastable material” means a material that is kinetically stable but thermodynamically unstable.

[00151] Processing using the method and/or the apparatus described herein may start with a glass and finish with a glass; may start with a non-glass and finish with a glass; or start with a glass and finish with a non-glass. This may include a mixture of glass and nonglass for example a glass ceramic (partially crystalline glass).

[00152] A method 100 of processing glass in accordance with one embodiment of the invention is illustrated in Figure 1A. The embodiment is described in relation to glass powder, but glass fibres or glass particles could equally be used.

[00153] A source of electromagnetic (EM) radiation, such as a laser 10 is provided. In this example, the laser 10 is a diode-pumped, single-mode, continuous wave, ytterbium fibre laser with emission in the near infrared spectral range (1070nm ± 5nm). In instances where certain transmission properties are required by the end product, for example if the end material must have a uniform transparency across a certain portion of the electromagnetic (EM) spectrum, then a laser 10 is chosen which emits at a wavelength in which it is acceptable for the glass to have a low transmission. Focussing optics 26 with a specified focus of 100nm (not shown) are used to focus the laser 10 to have an EM spot area having a diameter of approximately 20pm. A glass powder feeder 12 is provided with a glass powder 14 having a composition which is tailored 15 to modify its degree of interaction with the laser 10 as desired. For example, the glass composition could be altered such that the glass has an increased absorption at the emitted wavelength of the laser 10.

[00154] Preferably, the glass powder feeder 12 feeds the glass powder 14 onto a Z stage 13 which can be selectively moved up and down in the Z direction. A guiding mirror system 16 is used to direct the focussed laser beam in a prescribed path at a controlled work-path speed relative to the powder surface 18 to selectively fuse the glass powder 14 in the X-Y plane. In this stage, a cross sectional layer of fused glass is built up and immediately thereafter, the Z stage 13 is moved in the Z direction and more glass powder 14 is fed onto the powder bed surface 18 before being fused by the focussed laser 10 again moving in a prescribed path at a controlled work-path speed relative to the powder surface 18. In this way, the glass powder 14 is built into a three-dimensional (3D) article, layer by layer in an iterative fusing process. The entire process is conducted under a controlled environment 20 and the laser speed and path is controlled to influence the integrity of the resultant structure. A computer 22 may control the movement of the Z stage 13, the movement of the mirror 16 to ensure a desired speed and path of the laser 10 and the rate at which the powder feeder 12 deposits glass powder 14 onto the Z stage 13. The computer 22 may also directly control the laser 10. Software 24 for controlling the computer 22 may be provided. A user has the option to manually control the computer 22, or alternatively, the software 24 may have the capability of calculating the appropriate instructions for the computer 22 when a user inputs details of the glass powder composition, the EM source and optionally their desired end product.

[00155] Figures 1B and 1C illustrate the EM spot area, actively EM-affected area and actively EM-affected volume. EM radiation from the laser 10 is incident on the surface of glass powder 14 at an EM spot area 5 which is typically circular.

[00156] An area larger than the EM spot area 5 is affected by the incident EM radiation, this being the actively EM-affected area 6. Because glass is a poor thermal conductor, the size and shape of the actively EM-affected area 6, is generally controlled by moving the EM spot 5 with respect to the surface of the glass powder 14 (as indicated by the arrows in Figure 1B). Equally, the glass powder may be moved with respect to the EM spot 5. The actively EM-affected area 6 may also be influenced by defocussing the EM beam such that the diameter of the EM spot 5 area is increased.

[00157] As the effect of the EM radiation penetrates beneath the surface of the glass powder 14, an actively EM-affected volume 7 arises. The actively EM-affected volume may be generally hemi-spherical, with a gradient temperature across the volume, optimised so as to minimise thermal stresses within the glass structure.

[00158] The actively EM-affected surface 6 and actively EM-affected volume 7 comprise a surface and volume, respectively, of the glass powder 14 which are influenced or affected by the EM spot, even though the EM spot may not be directly impinging thereon. The surface and volume remain actively affected after the EM spot has passed over or been switched off, until the material has fully cooled. The glass powder 14 is primarily actively EM affected by photon absorption. There is also a heat affected volume associated with the EM affected volume which was not directly impinged upon by the EM spot but into which heat has been conducted from the surrounding material. Scattering of the EM radiation will also influence the actively EM affected surface 6 and volume 7.

[00159] Figure 2 illustrates an apparatus 200 capable of implementing a method of processing glass in accordance with an embodiment of the invention. In this embodiment, the source of EM radiation is a laser 10. The guiding mirror system 16 allows 2-axis positioning of the laser beam and may further comprise two rotatable and displaceable mirrors 16a, 16b which enable the laser beam to be directed in a path as desired. Focussing optics 26 tailor particular properties of the laser 10, such as EM spot area. Glass powder 14 is fed from a powder feeder 12 to a Z stage 13 which allows fine incremental movement. A build piston 28 is further incorporated to advance or retreat the Z stage 13 to create void for a new layer or to dispense additional powder from feeder 12, respectively. A number of 3D shapes, protrusions or voids can be incorporated into the surface of the build piston 30 in order to create voids in the end product of a desired geometry.

[00160] Figure 3 illustrates an alternative configuration 300 of a Z stage 13 for feeding additional material onto the Z stage 13 for sintering. A first piston 30 advances through a corresponding first aperture 31 to create a void for a new layer of material. A second piston 32 advances through a corresponding second aperture 34 to dispense additional powder 14. A linear spreader 36 moves horizontally along a linear path, across the surface of stage 13, thereby transferring material from the surface of the second piston 32 to the surface of the first piston 30. To that end, it can be said that the first piston 30 acts as a build piston and the second piston 32 acts as a feed piston. As in the example illustrated by Figure 2, a number of 3D shapes, protrusions or voids can be incorporated into the surface of the build piston 30 in order to create voids in the end product of a desired geometry. In the examples illustrated in both Figure 2 and Figure 3, the build piston 30 incorporates a 6 point star shaped protrusion 39 onto the surface of the piston 30.

[00161] As illustrated in Figure 4, any of the configurations described above may further comprise a heating coil 40 eccentric to the space which may be occupied by the piston 28 (or, in the embodiment illustrated by Figure 3, eccentric to the space which may be occupied by one or both of the pistons 30, 32) and a means for non-contact temperature measurement 42, such as a pyrometer, placed near to the point at which the laser beam 17 meets the surface of the glass powder 14. This enables temperature to be monitored throughout the process. Other environmental conditions which must be controlled include gas composition, pressure, humidity and airflow rate.

[00162] Figure 5 is a graph 500 illustrative of the relative absorption of light at different wavelengths by modified 46a and unmodified 6P57 glass 48a having the composition 56.5 S1O211.0 Na2O 3.0 K2O 15.0 CaO 8.5 MgO 6.0 P2O5 (wt%). The X axis 50 represents wavelength of light in nm emitted from an ytterbium fibre laser. A first plot 48 represents relative absorption by an unmodified glass 48a of light having a wavelength ranging between 250nm and 2500nm. A second plot 46 represents relative absorption of light having a wavelength ranging between 250nm and 2500nm by a glass 46a doped with 1 mol% Fe³⁺, which, in this example, was added in the form of 0.1%(wt) iron oxide as a supplement, rather than by substitution. Overall, the graph 500 demonstrates that doping this particular glass with Fe³⁺ significantly improves the absorption of light emitted from the ytterbium laser at 1070nm 52, reducing the penetration depth of the EM-radiation into the material and thus reducing the EM affected volume.

[00163] The difference in energy transfer at a specific wavelength in an unmodified 6P57 glass 600 and a glass 610 doped with 1 mol% Fe³⁺ is illustrated in Figures 6A and 6B, respectively. As incident light 56a reaches the glass 600, a large amount of light is scattered 58a as the energy transfer in the unmodified glass is dominated by light scatter. As a result, the glass is substantially transparent at this wavelength and a larger area of the glass 60a is affected by incident light, illustrated by the circled actively EM affected area 60a. In contrast, as incident light 56b reaches the doped glass 610, a far smaller amount of light scattering 58b occurs and the energy transfer is largely dominated by light absorption, rendering the doped glass 610 more opaque at this wavelength. As a result, a smaller actively EM affected area of the glass 60b is affected by the incident light. This allows control of the actively EM affected volume to the top few layers of the build to enable sintering with increased precision.

[00164] In an embodiment, features can be created on existing glass substrates, such as sheet glass, glass bottles or container glass. As illustrated by Figure 7, a glass powder or fibre material 14 with controlled properties 15 to achieve desired absorption characteristics for a chosen laser 10 is provided. In this way, the actively EM-affected area and actively EM-affected volume can be controlled. The material is delivered to a printing apparatus 70 via a feeder 12. The printing apparatus 70 further comprises a print head, positioned close to a substrate workpiece on which raised features are to be printed, can be moveable or can be fixed into position, depending on a user’s preference.

[00165] As illustrated in Figure 8A, the glass substrate 66 is fixed to a stage 76 and may comprise any standard or non-standard piece of glassware, examples of which include, but are not limited to, a bottle, a drinking glass, a lens or a window. Upon delivery to the printing apparatus 70, the glass material 14 is melted by the laser 10 in a fine point, to produce the desired shape on the glass substrate 66. The stage 76 to which the substrate 66 is fixed allows for movement in 2 or more of the X, Y and Z axes, although the stage 76 may be fixed in place and the print head instead moved in 2 or more of the X, Y and Z axes to achieve produce a desired feature on the glass substrate. The laser 10, printing apparatus 70 and stage 76 are enclosed within a chamber 65 to enable the provision of a controlled environment 20 with respect to factors including temperature, pressure, airflow and humidity. Movement of the stage 76 and printing apparatus 70, control of the laser 10 and control of the flow of glass material 14 are controllable by means of a computer 22 or control system, which may be instructed by appropriate software 24.

[00166] A printing apparatus 70 is illustrated in Figure 8A. A hopper 71 may be supplied with glass material 14 of a specific particle size from a feeder 12 via a delivery tube 74. The powder is fed by compressed air to a nozzle situated next to the laser head which contains focussing optics 26 and the termination of the laser fibre which links to the laser source 10 and controller or computer 22. The printing apparatus 70 further comprises an orifice 72, which controls glass powder flow onto the substrate 66 by allowing powder to flow at a desired rate from the nozzle where it is melted by the laser to the substrate. Excess powder is removed by means of a powder removal tube 78 and an extraction system 68, such as an air knife or vacuum system. A connector tube 80 connects the extraction system 68 and the feeder 12 such that unused excess powder which has been removed can be reused and fed to the hopper 71 by the feeder 12 and delivery tube 74. This reduces the amount of waste product associated with this process.

[00167] Figure 8B illustrates an alternative configuration for the printing apparatus wherein the initial glass material 14 comprises a continuous fibre 81 on a spool 82. The glass fibre 81 is fed to the print head from the spool 82 by a series of rollers (not shown) to control the speed at which glass fibre 81 is fed into the print head. As in the configuration illustrated by Figure 8A, the glass fibre 81 is melted as it is deposited onto the glass article 66, on which features are to be created. Both printing apparatus configurations illustrated in Figures 8A and 8B can be mounted horizontally or vertically relative to the substrate 66.

[00168] In yet a further alternative embodiment, illustrated by Figure 9A, the method and apparatus described herein may be used to print protective features on a bottle or drinking glass at high speed on a production line. A glass article 66, on which a protective feature is to be printed, is mounted on a stage 76 which is rotatable through 360° by means of a stepper motor 86. An electromagnetic radiation source, which in this example is a laser 10, supplies radiation to one or more print heads 70a, 70b, 70c, which print heads are mounted next to or underneath the article 66 at a fived position. As the glass substrate 66 is rotated, the print head(s) print the desired features 88 onto the glass. As with previously described embodiments, glass feed rate, laser properties and movement, print head movement and additionally, the motor 86, are controlled by computer software 24 on a control system 22.

[00169] Figure 9B illustrates an alternative configuration to that presented in Figure 9A. As illustrated in Figure 9B, the article 66 to be processed is mounted horizontally. A clamp 92 holds the bottle by its neck 66a and connects the bottle to an arm 94 which arm is rotatable through 360° horizontally by means of a motor (not illustrated). The arm is attached to a base plate 96 by a rack and pinion drive 98. The rack and pinion 98 allows movement of the bottle substrate 66 in the Z direction, whilst the base plate 96 is moved in the X and Y directions by a belt and motor system 90 thereby moving the substrate 66. The printing apparatus 70 with laser and glass feed (not shown) is mounted above the substrate 66 and the entire assembly is controllable by software 24 on a control system or computer 22, enabling movement of the substrate 66 below the printing apparatus 70 to achieve the desired design to be laid down on the surface of the glass substrate 66.

[00170] Figure 9c illustrates a configuration of apparatus that could be used to build up a surface layer 89 or surface features 88 on a flat glass substrate 66. The panel substrate 66 is placed or clamped on a stage 76 below the printing apparatus 70 and electromagnetic radiation source. The stage 76 is controlled by two belts attached to stepper motors (not illustrated) which allow movement in the x and y axes. The printing apparatus 70 is mounted on a bracket attached to a rod (not illustrated) and is moved in the z axis 110 by a belt and stepper motor (not illustrated). The motor, printing apparatus 70 and powder feed are controlled by a computer 22 with appropriate software 24 installed. Careful matching of laser type and glass material enables the printing of features onto a glass that could otherwise be adversely affected by thermal bonding of material to its surface, for example, toughened glass panels.

[00171] In a further embodiment, the configuration presented in Figure 9C may also be adapted for the printing of complex features onto flat glass panels, for example to strengthen edges or holes.

[00172] Example 1 - fusing two glass components to create a single glass object [00173] Glass envelopes are used to enclose high end analytical components that contain a pressurised gas or maintain a vacuum. Such envelopes include a transmission component and a detection component. The material used for the enclosure must be able to transmit electromagnetic radiation in a desired range. Depending on the requirements of the envelope, it may not be possible or economically feasible to make the full enclosure using just one material, such as a material suitable for transmission. As such it is desirable to be able to construct sealed glass envelopes that incorporate a window with specific spectral properties. This must be joined to another material which forms the remainder of the envelope. Current practice is to thermally sinter a precursor in the form of an intermediary frit, or sealing glass, to join the window to the rest of the envelope. While this can achieve a strong air-tight bond, it requires for all of the joined components to be heated together. This can induce significant residual stresses within the glass when cooled from the sealing temperature. These stresses can weaken the joins and result in fracture. In practice, thermal expansion coefficients of the different glasses may be matched in an attempt to mitigate the aforementioned problems, however this cannot accommodate geometric considerations.

[00174] One embodiment of the present invention seeks to mitigate the aforementioned problems associated with joining multiple glass components. Taking the example of glass envelopes, heating of elements of the envelope other than the sealing area is minimised. This is achieved by modifying one or more laser parameters (wavelength, power, focus, beam shape, spot-size, speed of interaction etc.) in order to control the actively EMaffected area and/or actively EM-affected volume to sinter the sealing glass but minimise thermal expansion (and associated stresses) in the components to be joined.

[00175] In Figure 10A, a Wood’s Glass (barium-sodium-silicate glass incorporating approximately 9% nickel oxide) window 120, commonly used for UV emitting lamps 250 is sealed to a soda-lime-silica tubing, which is less expensive and more easily shaped. The window 120 is sealed to the soda-lime-silica tubing using a precursor in the form of an amber soda-lime silica glass frit as a sealing glass to form an envelope 250. A laser source 126 having programmable positioning (in this example, in the X 129 and Y 130 directions) and a wavelength of 355nm is provided.

[00176] Figure 10B illustrates transmission 165 of 355nm light 164 through various components of the UV envelope. A first plot 161 represents transmission 165 of materials between wavelengths 167 of 200nm and 900nm. A first line 160 represents the transmission spectra of the tubing material, which exhibits a high transmission (approximately 87%) at 355nm. A second line 162 represents the transmission spectra of the amber soda-lime silica sealing glass frit, which has a negligible transmission at 355nm. A second plot 163 represents transmittance 166 by the Wood’s glass UV window at wavelengths 167 between 200nm and 5pm. A first line 168 on the second plot 163 shows that at 355nm, the window has a transmittance of approximately 0.88. As a result, minimal interaction between the laser and the UV filter window and tubing materials will occur. However, in order to ensure that enough energy is imparted to cause localised sintering and binding of the sealing glass of the window and tubing materials, laser parameters are tailored. Specifically, a quasi-CW UV laser is used, having a wavelength of 355nm, a power of 4W, an EM spot size having a diameter of 0.5mm and a laser scan Speed 1500mm/min. The combination of parameters provides enough energy to fuse the join 124 whilst also having minimal interaction with the window 120 or the tubing 128. In this particular example, through controlling the actively EM-affected volume and the energy transferred into the parts, the thermal expansion of the assembly 250 was minimised and hence resulted in significantly less stress than is typical through conventional thermal sintering known in the art. This has particular benefit as Wood's glass has lower mechanical strength and higher thermal expansion than commonly used glasses, making it more vulnerable to thermal shocks and mechanical damage.

[00177] This approach would not be possible using a wide variety of lasers typically used for materials processing. For example, a 10,600 nm CO2 laser system would not be usable for this technique, as the radiation would be absorbed by the Wood’s glass window material. For at least the same reason, a 1060 nm ytterbium Fibre Lasers or Nd:YAG (neodymium-doped yttrium aluminium garnet) laser system would not be useable either. In contrast, a 355 nm laser will be transmitted by both the Wood's Glass and the tubing material but will be absorbed by the precursor (soda-lime silica glass frit), such that the precursor will be melted with minimal laser energy input and minimal heating ofthe surrounding Wood's glass and tubing material.

[00178] Preferably, the laser may further be provided with multi-axis control, thereby enabling the control of the angle path. This would allow the laser to be directed away from the central axis of the tubing 128. For example, Figure 10C illustrates the laser source 126 as angled oblique to the central axis 140 of tubing 128. As such, the output 142 ofthe laser source 126 is directed away from the central axis ofthe tubing.

[00179] Example 2 - powder bed build process for production of a bioactive glass structure [00180] In one example, a bioactive glass powder (6P57, the composition of which is disclosed above) having a particle size of <45pm was doped with 1gFe⁺³ per mole. A stable 3D structure was achieved with a laser power varying in the range of between 8 watts and 16 watts, using a work-path speed varying between 300mm/min and 1500mm/min [00181] All ofthe features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[00182] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[00183] The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.

[00184] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[00185] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[00186] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims (33)

1. A method of processing glass to control thermal stress and/or to maximise the geometrical precision of features therein comprising:

providing a glass precursor having a plurality of glass properties;

providing a source of electromagnetic “EM” radiation, having a plurality of EM source properties and capable of emitting EM radiation to a moveable EM spot area to produce an actively EM-affected area and an actively EM-affected volume in a target material;

applying the EM source to the glass precursor to produce said actively EMaffected surface area and said actively EM-affected volume in the glass precursor;

controlling said actively EM-affected area of the glass precursor such that the actively EM-affected area is larger than the EM spot area;

controlling said actively EM-affected volume to control a thermal difference and/or a thermal gradient within said glass precursor; and transforming the glass precursor into a glass component using said EM source.

2. The method of claim 1 including the step of controlling said actively EM-affected volume to control the crystallisation characteristics within said glass precursor.

3. The method of claim 1 or claim 2, wherein said controlling the actively EM-affected area and/or actively EM-affected volume comprises optimising one or more of:

one or more of said glass properties;

one or more of said EM source properties;

one or more characteristics of said EM spot area; and the degree of scattering of EM radiation within said glass precursor.

4. The method of claim 3, wherein said EM source properties comprise any one or more of: wavelength, a wavelength profile polarisation, focus, numerical aperture, average power, peak power and pulse characteristics.

5. The method of claim 3 or claim 34 wherein said EM spot area characteristics comprise any one or more of: distribution of irradiance within the EM spot area, position of the EM spot area, orientation of the EM spot area, direction of movement of the EM spot area and speed of movement of the EM spot area.

6. The method of any preceding claim, wherein said source of EM radiation comprises two or more sources of EM radiation, each source having a plurality of EM source properties and each source having a plurality of EM spot area characteristics, wherein said controlling comprises one or both of:

optimising said EM source properties of each of the two or more sources of EM radiation differently, relative to each other; and optimising said EM spot area characteristics of each of the two or more sources of EM radiation differently, relative to each other.

7. The method of any preceding claim, wherein said one or more glass properties comprise any one or more of: emissivity; heat capacity; thermal conductivity; an EM absorption profile; a coefficient of thermal expansion; an EM absorption coefficient at a wavelength of the EM source; an EM absorption coefficient at a wavelength of thermal radiation generated during said transforming; refractive index; powder, particle or fibre size; powder, particle or fibre shape.

8. The method of any preceding claim, wherein said applying the EM source comprises moving a position of the EM spot area relative to the glass precursor.

9. The method of any preceding claim, wherein said applying the EM source comprises moving the glass precursor relative to the source of EM radiation.

10. The method of any preceding claim, wherein the source of EM radiation comprises a laser.

11. The method of any preceding claim, wherein the glass precursor comprises one or more dopants arranged to control an EM absorption coefficient of the precursor.

12. The method of any preceding claim, wherein the glass precursor comprises any one or more of: a glass powder, glass particles or glass fibres.

13. The method of any preceding claim, wherein said transforming comprises fusing said glass powder, glass particles, or glass fibres together.

14. The method of any preceding claim, wherein said transforming comprises selective laser sintering or direct laser sintering.

15. The method of any preceding claim, wherein the glass component comprises a bioactive material.

16. The method of any preceding claim, wherein the glass precursor is processed alternately and/or in combination with a metal or a metal alloy to form a glass-metal composite component.

17. The method of any preceding claim, wherein the glass component is applied to a substrate comprising any one of or combination of one or more of: a metal, a metal alloy, a ceramic, a glass and a glass ceramic.

18. The method of any preceding claim, wherein said glass component comprises a porous structure.

19. The method of any preceding, wherein said glass component comprises a biomedical implant.

20. An additive manufacturing process comprising the method of any of claims 1 to 19.

21. A non-transitory computer readable medium having computer readable instructions stored thereon which, when executed by a computer, are arranged to perform a method or process according to any of claims 1 to 20.

22. A biomedical implant manufactured using the method or process of any of claims 1 to 20.

23. An apparatus for processing glass according to the method or process of any of claims 1 to 20, the apparatus comprising:

means for receiving a glass precursor having a plurality of glass properties;

a source of electromagnetic “EM” radiation, having a plurality of EM source properties and capable of emitting EM radiation to a moveable EM spot area to produce an actively EM affected surface area and an actively EM affected volume in a target material;

means for applying the EM source to the glass precursor to produce said actively EM-affected surface area and actively EM affected volume in the glass precursor; and means for controlling an actively EM affected area of the glass precursor such that the EM affected area is larger than the EM spot area and for controlling said actively EM-affected volume to control a thermal difference and/or a thermal gradient within said glass precursor;

wherein the apparatus is arranged to transform said glass precursor to a glass component using said EM source.

24. The apparatus of claim 23 further comprising means for controlling said actively EM-affected volume to control the crystallisation characteristics within said glass precursor.

25. The apparatus of claim 23 or 24, wherein said means for controlling the actively EM affected area and/or actively EM affected volume is arranged to optimise one or more of:

one or more of said glass properties;

one or more of said EM source properties;

one or more characteristics of said EM spot area; and the degree of scattering of EM radiation within said glass precursor.

26. The apparatus of any of claims 23 to 25, wherein said means for controlling comprises a system for controlling any one or more of: distribution of irradiance within the EM spot area, position of the EM spot area, orientation of the EM spot area, direction of movement of the EM spot area and speed of movement of the EM spot area.

27. The apparatus of any of claims 23 to 26, wherein said apparatus comprises a computer numerical control “CNC” router wherein a rotary cutter of the CNC router is replaced by one or more laser optics arrangements.

28. The apparatus of any of claims 23 to 27, wherein the apparatus is arranged to form a three dimensional glass component by fusing consecutive layers of said glass precursor using the EM source.

29. The apparatus of any of claims 23 to 27, wherein the apparatus is arranged to form a three dimensional glass component by melting the glass precursor onto a substrate using the EM source.

30. The apparatus of claim 29, further comprising a means for receiving a three dimensional glass item, wherein the apparatus is arranged to apply said glass component to the three dimensional glass item.

31. The apparatus of claim 25 or any of claims 26 to 30 when dependent on claim 25, wherein said applying the EM source comprises repeated application of the EM source to the precursor and said means for controlling is arranged to, between successive applications of the EM source, re-optimise one or more of any of:

said glass properties;

said EM source properties;

said characteristics of said EM spot area; and the degree of scattering of EM radiation within the glass precursor.

32. The apparatus of any of claims 23 to 31, wherein said means for receiving the glass precursor comprises a powder bed having a controllable temperature.

33. The apparatus of claim 32, further comprising a void above the powder bed in which pressure applied to the powder bed can be controlled.