An article with 3D printed features

Abstract

Stereographic printing 3 on a porous substrate 4 penetrates 7 through it and onto an underlying bonding substrate 6. Preferably the substrates 4, 6 are flexible, the bonding substrate 6 is more wettable than the porous substrate 4, and the porous substrate 4 has higher degree of capillarity than the bonding substrate 6. The substrates 6, 4 are preferably placed on a last 2 and the three-dimensional printed features 8 are overprinted with another 3D print layer. The wearable article produced is a glove.

Description

The present invention relates to an article with 3D printed features. When 3D printing features on to an article, such as an item of clothing, an important requirement is that the 3D printed features bond securely with the substrate of the article. Our earlier WO2022 / 223945 discloses a method of 3D printing protective features directly onto the glove. In order to ensure a good bond between the features and the glove fabric, the material used for the 3D printing must be able to bond successfully with the glove fabric. In practice, this significantly limits the materials which can be used, and therefore the type of articles that can be used in this process. For example, an extruded material such as a 3D printed resin does not bond well with many knitted fabrics which are commonly used for gloves. The present invention relates to an article according to claim 1. This article comprises a porous substrate and a bonding substrate. The two different layers fulfil different functions. The 3D printed features bond to the bonding substrate. This can indirectly bond materials (porous substrate and 3D printable material) together that typically have poor bond strength. As a result of this, the porous substrate, which usually forms the outer face of the article, can be selected for other reasons, such as durability, flexibility, breathability, etc., without being constrained by a need to bond to the 3D printed features. This also allows greater freedom in selecting the printable material. The porous and bonding substrates may be rigid. However, preferably, at least one of the substrates and more preferably both are flexible. The bonding substrate preferably has higher wetting properties in respect of the fluid printable material than the porous substrate. Good wetting properties ensure that the fluid printable material readily spreads across and into the bonding substrate thereby increasing the surface area and hence the bonding strength between the 3D printed material and the bonding substrate. The bonding substrate is selected for its ability to form a bond with the 3D printed material. Preferably it has a high surface area. It may be, for example, an open cell foam or a rotary spun fabric. However, preferably, it is a non-woven fabric such as a felt. The porous substrate preferably has a higher degree of capillarity in respect of the fluid printable material than the bonding substrate. The high degree of capillarity ensures that the fluid printable material is readily wicked through the porous substrate towards the bonding substrate. The porous substrate is generally the layer which forms the outer surface of the article and may be a conventional material which is used to make such articles. This may, for example, be knitted or woven fabric or a perforated leather. If the desired material is not naturally porous, the part of the article that receives the 3D printed material may be perforated prior to the printing step. The printable material may extend fully through the bonding substrate. This would enhance the bonding, but the presence of the 3D printed features on this side of the bonding substate would make the article uncomfortable to wear if the bonding substrate forms the inner layer of the article. In this case, an additional liner may be provided beneath the bonding substrate in order to address this issue. However, preferably, the printable material does not extend to the face of the bonding substrate furthest from the porous substrate. This allows the bonding substrate to form the inner layer of the article without requiring an additional liner. The article is preferably a wearable article. This may be a larger article such as a jacket or trousers or may be a smaller article such as an elbow or knee protector, and is most preferably a glove. The present invention also extends to a method of claim 9. The pores of the porous substrate are preferably narrower in a direction perpendicular to the printing direction than the width of the bead of 3D printed material as it impinges on the porous substrate. Making the bead larger than the pore width ensures that at least some of the 3D printed material impinges on the porous substrate whilst the remainder passes through in order to bond with the bonding substrate, thereby helping to anchor the porous substrate with respect to the bonding substrate. The method could be carried out on an article to which the bonding substrate has been attached to the porous substrate in a separate step prior to the 3D printing process. However, when the porous substrate is part of a wearable article the method preferably further comprises placing the bonding substrate on a support, placing the wearable article on the support on top of the bonding substrate and printing the 3D printed material on to the article. This allows a conventional article, such as a glove, to be manufactured in a conventional manner. The method can then be carried out as a separate step placing the article on the bonding substrate in a 3D printer. In the case of a glove, the support is preferably a last. The article may be printed with the 3D printer nozzle spaced from the printed article. However, preferably, the nozzle of the 3D printer is pressed into the article during the printing process. This enhances the penetration of the 3D printed material into the article. There may be a single layer of 3D printed material. However, preferably additional layers of 3D printed material are printed onto the 3D printed features. This allows more complex features to be built up. Examples of an article and method in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a schematic cross-section of a first article and method; Fig. 2 is a similar schematic view of a second article and method; Fig. 3 is a similar schematic view of a third article and method; Fig. 4 is a schematic plan view of a portion of a first porous substrate; Fig. 5 is a similar view of a second porous substrate; Fig. 6 is a schematic cross-section of part of an article; and Figs. 7 to 9 are plan views of part of an article showing difference configurations of 3D printed features. The method involves the 3D printing of features on to an article. The 3D printing process is described in greater detail in WO2022 / 223945. WO2023 / 209348 describes printing of a foamed protective article which could also be used with the present invention. The 3D printed features may be formed, for example, of TPU and may be built up in several layers to form a protective article. Other types of features may be formed. These may provide, for example, thermal insulation, electrical conductivity for sensing, abrasion resistance or cut resistance. The features may also effectively act to join layers together thereby acting as a stitching replacement. Combinations of these features may be used. The 3D printing potentially allows a number of operations to be replaced in that it can combine multiple parts / substrates and therefore replace one or more of the conventional stitching, adhesive, or heat bonding processes. Fig. 1 shows an article 1 on a bed 2 of a 3D printer. 3D printed material is extruded from a 3D printer nozzle 3. The article 1 comprises a porous substrate 4, in this case made up a single layer designated by top and bottom surfaces 5 which may, for example, be knitted or woven. The bonding substrate 6 is immediately below the porous substrate 4. This is, for example, a layer of felt. As shown in Fig. 1, the printer nozzle 3 is pushed into the surface of the article 1 thereby deflecting the porous substrate 4 and bonding substrate 6. This aids the penetration of the 3D printed material 7 into the substrate. As shown in Fig. 1, the 3D printed material 7 has passed through the porous substrate 4 and into the bonding substrate 6 in which it spreads out before solidifying in order to firmly anchor the 3D printed material 7 in the article 1. In the finished article, a part 8 of the 3D printed material 7 provides a protruding feature, for example, to provide impact protection. The 3D printed material 7 stops short of the lower surface of the bonding substrate 6. As a result, the lower surface of the bonding substrate 6 can be comfortably worn without requiring a separate liner. A strong bond (chemical, mechanical and / or thermal) between the printed material 7 and bonding substrate 6 allows for the printed material 7 to only need to mechanically lock the porous substrate 4 in position, as the printed material forms a matrix about the porous substrate 4. It may be beneficial for the porous substrate 4 to have relatively weak bonds with the printed material 7, to allow the printed material to penetrate the porous substrate 4 with the least amount of resistance. Fig. 2 shows a similar view in which at least the bonding substrate 6 is formed of a rigid material. In this case the nozzle 3 is not pressed into the article but is rather spaced a short distance from the top of the porous substrate 4. Fig. 3 is similar to Fig. 1, except that porous substrate 4 comprises two layers. These may have different properties, materials, densities etc.. An example of a woven porous substrate is shown in Fig. 4. Woven threads 9 create a number of square / rectangular pores 10 which provide gaps for the 3D printed material 7 to penetrate through the porous substrate 4 and into the bonding substrate 6. The width of the bead of material produced from the 3D printed nozzle 3 is wider than the width of the pore 10 in a direction perpendicular to the direction of travel of the nozzle 3. This ensures that at least some of the 3D printed material 7 always impinges on the porous substrate 4 while the remainder will pass through the pores 10, in order to anchor the porous substrate 4 with respect to the bonding substrate 6. This could be the only mechanism for joining the two substrates 4, 6. Alternatively, two substrates may be joined in an additional manner, for example, by being bonded or sewn together. Optimal combinations of extruded material 7 bead size and porous substrate 4 pore size are determined by considering: extruded material viscosity, extruded material wetting characteristics, substrate wetting properties (e.g., surface tension), and number and thicknesses of porous substrate layers. For any given combination of extruded material and porous substrate, the pore size of the substrate should be selected as a function of extruded material swell / bead size. Beads that are relatively narrow in diameter compared to substrate pore size may be able to penetrate deeper into the bonding substrate. Fig. 5 is a view similar to Fig. 4 showing a knitted porous substrate. Again, the size of the pores 10 is such that the bead of 3D printed material will inevitably contact at least some part of the surrounding threads 9 to anchor the thread in place. Fig. 6 shows a cross-section of a finished article produced according to the method of Fig. 3. In this case, first layer 11 has a protruding portion 8 extending above the substrate 4. Subsequent layers 12 are printed in a conventional manner on top of the first layer 11 in subsequent passes of the nozzle 3. This allows larger features to be built up on the surface 5 of the article. The layers 12 may all have the same material and may be the same material as the layer 11. Alternatively, different layers may be printed in order to vary the properties of the printed features. As shown in Fig. 7, the 3D printed article 7 may be in the form of a lattice with upstanding 10 walls. This may, for example, be a Penrose lattice as disclosed in WO2022 / 018411. Additionally, 3D printed feature 7 may provide a perimeter to a relatively large area as shown in Fig. 8. As a further alternative, a relatively large area is shown in Fig. 9. 15

Claims

1. An article comprising:a porous substrate at an outer face of the articlea bonding substrate beneath the porous substrate, and3D printable material which extends through the porous substrate forming features on the outer face of the article and which penetrates into the bonding substrate to bond to the bonding substrate.

2. An article according to claim 1, wherein at least one of the substrates is flexible.

3. An article according to claim 1 or claim 2, wherein the bonding substrate has higherwetting properties in respect of the fluid printable material than the porous substrate.

4. An article according to any preceding claim, wherein the bonding substrate is a felt.

5. An article according to any preceding claim, wherein the porous substrate has ahigher degree of capillarity in respect of the fluid printable material than the bonding substrate.

6. An article according to any preceding claim, wherein the printable material does not extend to the face of the bonding substrate furthest from the porous substrate.

7. An article according to any preceding claim, wherein the article is a wearable article.

8. An article according to any preceding claim, wherein the article is a glove.

9. A method of forming an article comprising:a porous substrate at an outer face of the article and a bonding substrate beneath the porous substrate:the method comprising extruding 3D printing material from a 3D printing nozzle such that some of the 3D printing material passes through the porous substrate and bonds to the flexible bonding substrate to form 3D printed features which protrude from the outer face of the article.

10. A method according to claim 9, wherein the pores of the porous substrate are narrower in a direction perpendicular to the printing direction than the width of the bead of 3D printed material as it impinges on the porous substrate.5 11. A method according to claim 9 or claim 10, wherein the porous substrate is part of awearable article and the method comprises placing the bonding substrate on a support, placing the wearable article on the support on top of the bonding substrate and printing the 3D printing material onto the article.10 12. A method according to claim 11, wherein the support is a last.

13. A method according to any of claims 9 to 12, wherein the nozzle of the 3D printer ispressed into the article during the printing process.15 14. A method according to any of claims 9 to 12, wherein additional layers of 3D printedmaterial are printed onto the 3D printed features.

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