GB2583163A

GB2583163A - Additive manufacturing method and article produced therefrom

Info

Publication number: GB2583163A
Application number: GB2001006.2A
Authority: GB
Inventors: Stewart Gregg; Buchan Jamie; Jensen Sean; N Walker Stacey
Original assignee: Balmoral Comtec Ltd
Current assignee: Balmoral Comtec Ltd
Priority date: 2019-01-24
Filing date: 2020-01-23
Publication date: 2020-10-21
Also published as: WO2020152470A3; WO2020152470A2; GB201900978D0; GB202001006D0

Abstract

A method of additive manufacturing for forming a three-dimensional subsea structure protection article 20, the method comprising the steps:- providing a plurality of reactive polymer materials, supplying the reactive polymer materials to a dispensing apparatus for relative weight percentage calibration and for transport of the calibrated reactive polymer materials to a mixing head, mixing the reactive polymer materials to produce a mixed thermoset polymer printing media and dispensing the printing media through a nozzle 1 towards a table surface 4. In this connection, the table surface 4 and nozzle 1 undergo a sequence of relative movements to build up a three-dimensional article 20. Also, one or more of the reactive polymer materials are degassed prior to mixing. Also disclosed is a subsea article formed using the method.

Description

ADDITIVE MANUFACTURING METHOD AND ARTICLE PRODUCED THEREFROM

The present invention relates to an additive manufacturing method for producing three dimensional articles, and particularly, though not exclusively to such a method for producing articles that can operate in a subsea environment.

Additive manufacturing generally uses data computer-aided-design (CAD) software or 3D object scanners to direct items of hardware to deposit material, layer upon layer, in precise geometric shapes. As its name implies, additive manufacturing adds material to create an object. This is in contrast with more traditional manufacturing methods which remove material through, for example, milling or machining.

With additive manufacturing, three-dimensional objects are formed one layer at a time with each successive overlying layer bonding to the preceding layer of material.

In this connection, it is known to use different substances for layering material, including metal powder, thermoplastics, ceramics, composites, and glass.

Whilst there are a variety of different additive manufacturing processes, the present invention is primarily concerned with material dispensing where materials are dispensed through a nozzle. Relative movement of the nozzle with respect to a table or bed allows the object to be built up layer after layer.

In this regard, additive manufacturing processes have proved themselves to be invaluable in quickly and efficiently producing complicated and complex three dimensional objects for use as prototypes or applications that do not require significant strength characteristics.

An object of the present invention is to provide an additive manufacturing method for producing near-finished shape or final geometry objects which can operate in the harsh subsea environment.

According to the present invention there is provided a method of additive manufacturing for forming a subsea structure protection article, the method comprising the steps:-providing a plurality of reactive polymer materials; supplying the reactive polymer materials to a dispensing apparatus for relative weight percentage calibration and for transport of said calibrated reactive polymer materials to a mixing head; mixing the reactive polymer materials to produce a mixed thermoset polymer printing media; and dispensing the printing media through a nozzle towards a table surface, the table surface and nozzle undergoing a sequence of relative movements to build up a three-dimensional article; wherein one or more of the reactive polymer materials are degassed prior to mixing. In this way, an article with subsea functionality can be readily and effectively formed.

Preferably, the plurality of reactive polymer materials comprise first and second printing materials which are components of a liquid thermoset system, wherein the first printing material comprises one or more of a liquid thermosetting resin, polyol or a prepolymer, and wherein the second printing material comprises a liquid thermosetting curing agent which reacts with the first material to produce a thermosetting polymer.

Conveniently, prior to dispensing of the printing media, a thixotrope is added to one or more of the reactive polymer materials to form an augmented polymer material In preferred embodiments, the first printing material comprises a blend of liquid polyol resins or a blend of polyamine resins or a blend of polyol and polyamine resins.

Furthermore, the second printing material preferably comprises isocyanate reactive groups. In preferred embodiments, the isocyanate may be partially reacted with polyol to form a prepolymer isocyanate.

Preferably, the thixotrope is selected from an aromatic amine or silica. The aromatic amine may preferably be diethyltoluenediamine. The silica may be solid functionalised fumed silica.

The step of adding the thixotrope is preferably performed in anticipation of a printing operation, namely up to 60 minutes before the printing operation.

Conveniently, the first printing material further comprises one or more of catalysts, chain extenders, pigments or fillers.

The first printing material preferably has a specific gravity in the range of 1.00 to 1.50.

In preferred embodiments, the thixotrope is added to the first printing material to form an augmented first printing material.

Preferably, the first printing material is provided with diethyltoluenediamine in the range of 1 to 10% of total augmented weight. More preferably, the first printing material is provided with diethyltoluenediamine in the range of 3 to 7% of total augmented weight. Yet more preferably, the first printing material is loaded with substantially 5% diethyltoluenediamine of total augmented weight.

Alternatively, the first printing material is provided with silica filler up to 15% of total augmented weight.

Preferably, the thixotrope is added to the second printing material to form an augmented second printing material. In this connection, the second printing material is conveniently provided with silica filler up to 25% of total augmented weight.

Conveniently, the dispensing apparatus ensures the printing materials are measured and transported to a dispensing head for mixing in the correct ratio by weight.

Preferably, the dispensing head comprises a mixing unit for mixing the printing materials to produce a printing media. The mixing unit may comprise a dynamic mixer or a static mixer.

For a static mixer, the mixer preferably is a helical static mixer with a mixer of a length between 150 and 500 mm and has a diameter of 10 to 20 mm and has 8 to 48 elements.

Conveniently, the mixing unit comprises a dynamic mixer with a rotational speed of up to 10,000 revolutions per minute.

Preferably, the nozzle has a diameter of 1 to 20 mm, more preferably 2 to 5 mm and yet more preferably, substantially 2.5 mm.

The printing media is preferably dispensed at an output rate of between 0.6 to 1000 g/s. Further, the relative table surface/nozzle speed is preferably between 500 and 1000 mm/min and yet more preferably in the range 750 and 1000 mm/min.

Conveniently, the output rate is substantially 0.68 g/s with a relative nozzle to table speed of substantially 800 mm/min.

Whilst the relative movement between table and dispensing head can be all down to movement of the table or dispensing head alone, conveniently, relative horizontal movement is afforded by moving the table and relative vertical movement is afforded through moving the dispensing head.

Preferably, in a first pass of the dispensing head, the nozzle is set to be in the range 3 mm to 20 mm above the printing table.

Conveniently, in a first pass of the dispensing head, the nozzle is set to be in the range 4.5 to 5.5 mm above the printing table.

Preferably, after each pass, the nozzle height is raised by between 3 to 20 mm and conveniently by substantially 4mm.

In preferred embodiments, the printed article is cured at ambient temperature, within the range 10-30 °C.

In certain applications, the printed article is cured at a temperature in the range 30180 °C. Conveniently, the printed article is cured using an external heat source, which may comprise one or more localised heaters and/or may comprise a heated chamber.

The method may comprise the step of curing the printed article initially at ambient room temperature to allow it to set sufficiently to be moved to a heated chamber for full curing.

Alternatively, curing may be effected by one or more localised heaters without having to move the printed article into a chamber.

Conveniently, for certain applications the faces of the printed article are smoothed by way of a smoothing tool that follows the nozzle printing path.

The finished printed article may alternatively or additionally be further machined if necessary where precision surfaces are required.

According to a further aspect of the present invention there is provided a three dimensional printing method of forming a subsea structure protection article, the method comprising the steps:-providing first and second printing materials which when mixed form a mixed thermoset polymer printing media; and mixing said printing materials and extruding the printing media through a nozzle onto a surface; wherein the nozzle to surface relative speed is in the range 500 to 1000 mm/min, the printing media dispensing rate is in the range 0.6 to 1000 g/s and the nozzle aperture area is in the range 3 mm2 to 31,500 mm2.

Preferably, the nozzle to surface relative speed is in the range 750 to 850 mm/min, and the printing media dispensing rate is in the range 0.6 to 0.7 g/s the nozzle diameter is in the range 2 to 4 mm.

Conveniently, one or more of said first and second printing materials have a thixotrope added thereto.

Preferably, one or more of the first and second printing materials are degassed prior to mixing.

In preferred embodiments, the method is employed to form articles having one or more of a subsea buoyancy, subsea mechanical protection or subsea insulation application.

According to a further aspect of the present invention there is provided a subsea structure protection article formed by way of the manufacturing method defined above.

Preferably, the subsea article has a maximum operational depth of 7000 meters.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying figures, of which:-Figure 1 shows a schematic view of apparatus for use in the present invention; Figure 2 shows a perspective view of the apparatus of Figure 1, and Figure 3 shows a flow diagram of a manufacturing process according to the present invention.

As shown in Figures 1 and 2, apparatus of the present invention generally comprises various components of an additive printing device, such as a 3-dimensional printer.

In this respect, a printing nozzle 1 is mounted on a support structure 2, the nozzle receiving mixed printing media 3 that has undergone certain preparatory processes, as described in more detail below.

A printing table 4 is provided below the nozzle, the table and nozzle being arranged to allow relative three dimensional movement there-between, namely in x, y and z directions. In this regard, one or both of the nozzle and the table are moveable to achieve the relative movement.

With the present invention, the printing media 3 is formed by mixing certain printing material ingredients. Firstly, a first material takes the form of Material A, provided in tank 9. Material A comprises one or more of a liquid thermosetting resin, polyol and/or a pre-polymer. Material A can further contain a plurality of chemical materials including, but not limited to, catalysts, chain extenders, pigments and fillers. Material A has a combined specific gravity (SG) of in the range 1.00 to 1.50, and preferably substantially 1.04. Material A may be degassed.

A second printing material, Material B, comprises a liquid thermosetting curing agent, typically containing isocyanate reactive groups, which reacts with the first material to produce a polymer, and is provided in tank 11. As with Material A, Material B may be degassed.

A third material, Material C, comprises a thixotrope and may be, but is not limited to, an aromatic amine, for example liquid (diethyltoluenediamine) or solid (fumed silica). Again Material C may be degassed.

As shown in Figure 1, the third material, Material C is combined into Material A. In a preferred embodiment, Material A may as such be loaded with 5% of total augmented weight diethyltoluenediame to form augmented Material Al. The diethyltoluenediame is in this regard preferably provided in a maximum/minimum range 1-10% of total augmented weight, or more preferably provided in a maximum/minimum range 3-7% of total augmented weight. Material Al is not thixotropic using this set of ingredients at this stage.

Alternatively, Material A may be loaded with up to 15% of total augmented weight silica filler as a third material, to form Material Al. In this alternative, Material Al would be thixotropic at this stage. Material Al may be degassed.

Whilst in the above embodiment, the thixotrope is added to the resin, polyol and/or a pre-polymer of Material A, in alternative embodiments the thixotrope could be added to the curing agent of Material B. In this connection, for such an embodiment the thixotrope of Material C may be up to 25 % silica filler of total augmented weight.

Furthermore, the thixotrope may be added with Material A and Material B, either once they have been combined or at the same time they are combined.

In the present embodiment, dispensing equipment 12 then collects Material Al and Material B and transports them to the nozzle dispensing head 14 where they are mixed. Additionally, the dispensing equipment 12 is calibrated to ensure the correct ratio of liquid parts Al and B is dispensed.

In this connection, the materials are dispensed separately through to the head 14 with each being collected separately into a weighing receptacle. Each part is separately weighed to determine the weight ratio of the parts. The dispensing equipment is set to dispense more or less of either part and checks progress until the weight ratio for the material in question is correct. The dispensing equipment 12 is thereby calibrated to ensure the correct ratio of parts Al and B is dispensed.

The dispensing head 14 includes an integrated mixing apparatus and this may include one or more of a dynamic mixer and/or a static mixer.

In this connection, a suitable static mixer preferably has a maximum/minimum range of 150-500 mm length, 10-20 mm diameter with 8-48 elements, and more preferably a length of 250 mm, a diameter 11.90 mm, with 32 elements.

A preferred dynamic mixer may have one or more of the following features:-a grooved body, i.e. a shaft rotating with grooves to create turbulent mixing; a shaft having series of 20-50 pins extending perpendicular to the shaft; a speed of rotation of between 500 and 4000rpm; the shaft being 100-300mm long; the shaft having a diameter of 25-150mm; a nozzle having a diameter of between 12.5 and 75mm; an output range of between 2 and 200 kg/min and an electrically driven motor drive. The dynamic mixer may furthermore have a rotational speed of up to 10,000 revolutions per minute.

Having gone through the mixing process, the thixotropic printing media is dispensed through nozzle 1. The nozzle diameter is preferably 2.5mm, but may be within the range of 1-20 mm depending upon requirements.

In certain preferred embodiments for small scale articles, the printing media is dispensed at a pre-set output rate of 0.68 g/s for a table speed of 800 mm/min. In this connection, the output rate is preferably within the range of 0.6 to 0.7 g/s.

However, the output rate is preferably within the range of 0.6g/s to 1000 g/s in order to encompass larger scale articles. For the larger end of the scale, the printing media is dispensed at a pre-set output rate substantially of 1000 g/s for a table speed of 800 mm/min.

As discussed, relative movement is arranged between the table and the dispensing head nozzle. In the preferred embodiment, the table, or at least a surface thereof, is arranged to move in the x and y directions, namely in the horizontal plane. The range of table speed is in this respect preferably between 500 and 1000 mm/min and more preferably in the range 750 to 850 mm/min. Relative movement in the horizontal plane may alternatively be provided by only moving the dispensing head, or by a combination of moving the dispensing head and the table.

In the preferred embodiment, printing media is dispensed onto the moving table with a height adjusting head 14, so that relative movement in the z direction, namely the vertical plane is provided through movement of the dispensing head rather than the table. Each of the movements is carefully controllable in accordance with instructions from a predetermined manufacturing template and controlled through suitable software.

In this respect, data input capabilities allow pre-programmed tool paths to be followed in order to build up the article being manufactured.

In one example, for first pass, the nozzle 1 is set at a start height of 4.5 mm to 5.5 mm above the printing table 4. In this connection, the nozzle start height ranges between 3 to 20 mm depending upon requirements.

For subsequent layers, head height may be raised by 4 mm after each complete layer. In this respect, a height step change could potentially be from 3 to 20 mm depending upon circumstances.

In certain embodiments, a heated chamber may be provided to aid in curing material. In this connection, whilst the printed article may be cured purely at ambient temperature within the range 10-30°C during 3D printing process, in certain applications, the printed article may be cured in a heated chamber at a temperature in the range 30-180 °C. Alternatively, curing can be effected by one or more localised heaters, thereby avoiding the need to move the article to such a chamber.

The invention may as such comprise the step of curing the printed article initially at ambient room temperature to allow it to set sufficiently to be moved to a heated chamber for full curing. In certain embodiments, the printed geometry can thus undergo a final cure regime.

Furthermore, a 'smoother' may be provided to follow behind dispensing nozzle to smooth ribbed exterior. This may comprise a flat spatula or trowel follower that smooths laid material after deposition.

Where required, a finial finishing process may be employed to gain net or final shape and/or for removal of a ribbed exterior profile that may be formed as a result of the printing process.

Claims

Claims:- 1. A method of additive manufacturing for forming a subsea structure protection article, the method comprising the steps:-providing a plurality of reactive polymer materials; supplying the reactive polymer materials to a dispensing apparatus for relative weight percentage calibration and for transport of said calibrated reactive polymer materials to a mixing head; mixing the reactive polymer materials to produce a mixed thermoset polymer printing media; and dispensing the printing media through a nozzle towards a table surface, the table surface and nozzle undergoing a sequence of relative movements to build up a three-dimensional article; wherein one or more of the reactive polymer materials are degassed prior to mixing.
2. The method of claim 1, wherein the plurality of reactive polymer materials comprise first and second printing materials which are components of a liquid thermoset system, wherein the first printing material comprises one or more of a liquid thermosetting resin, polyol or a prepolymer, and wherein the second printing material comprises a liquid thermosetting curing agent which reacts with the first material to produce a thermosetting polymer.
3. The method of claim 2, wherein prior to dispensing of the printing media, a thixotrope is added to one or more of the reactive polymer materials to form an augmented polymer material.
4. The method of claim 2 or 3, wherein the first printing material comprises a blend of liquid polyol resins or a blend of polyamine resins or a blend of polyol and polyamine resins.
5. The method of any one of claims 2 to 4, wherein the second printing material comprises isocyanate reactive groups.
6. The method of claim 3, wherein the thixotrope is selected from one of aromatic amine or silica.
7. The method of claim 3, wherein the thixotrope is diethyltoluenediamine.
The method of claim 6, wherein the silica is solid functionalised fumed silica.
9. The method of any one of claims 2 to 8, wherein the first printing material further comprises one or more of catalysts, chain extenders, pigments or fillers.
10. The method of any one of claims 2 to 9, wherein the first printing material has a specific gravity in the range of 1.00 to 1.50.
11. The method of claim 3, wherein the thixotrope is added to the first printing material to form an augmented first printing material.
12. The method of claim 11, and one or more of: a) wherein the first printing material is provided with diethyltoluenediamine in the range of 1 to 10% of total augmented weight; or b) wherein the first printing material is provided with diethyltoluenediamine in the range of 3 to 7% of total augmented weight; or c) wherein the first printing material is provided with diethyltoluenediamine in the range of 5% of total augmented weight.
13. The method of claim 11, wherein the first printing material is provided with silica filler up to 15% of total augmented weight.
14. The method of claim 3, wherein the thixotrope is added to the second printing material to form an augmented second printing material.
15. The method of claim 14, wherein the second printing material is provided with silica filler up to 25% of total augmented weight.
16. The method of any preceding claim, wherein the dispensing apparatus acts to ensure the printing materials are measured and transported to a dispensing head for mixing in the correct ratio by weight.
17. The method of claim 16, wherein the dispensing head comprises a mixing unit for mixing the printing materials to produce a printing media.
18. The method of claim 17, wherein the mixing unit comprises a static mixer.
19. The method of claim 18, wherein the mixer unit comprises a helical static mixer with a mixer of a length between 150 and 500 mm, a diameter of 10 to 20 mm and 8 to 48 elements.
20. The method of claim 17, wherein the mixing unit comprises a dynamic mixer with a rotational speed of up to 10,000 revolutions per minute.
21. The method of any preceding claim, wherein the nozzle has a diameter of 1 to 20 mm.
22. The method of any preceding claim, wherein the printing media is dispensed at an output rate of between 0.6 to 1000 g/s and the relative table surface/nozzle speed is between 500 and 1000 mm/min.
23. The method of any preceding claim, wherein the output rate is substantially 0.68 g/s with a relative nozzle to table speed of substantially 800 mm/min.
24. The method of any preceding claim, wherein the output rate is substantially 1000 g/s with a relative nozzle to table speed of substantially 800 mm/min.
25. The method of any preceding claim, wherein in a first pass of the nozzle, the nozzle is set to be in the range 3 to 20 mm above the printing table.
26. The method of claim 25, wherein after each pass, the nozzle height is raised by substantially 4mm.
27. The method of any preceding claim, comprising the step of curing the printed article at ambient temperature, within the range 10-30° C.
28. The method of any preceding claim, further comprising the step of curing the article with one or more localised heaters.
29. The method of any preceding claim, comprising the step of initially curing the printed article on the table to allow it to set sufficiently and then moving it to a heated chamber for full curing.
30. The method of any preceding claim, wherein faces of the printed article are smoothed by way of a smoothing tool that follows the nozzle printing path. 10
31. A three dimensional printing method of forming a subsea structure protection article, the method comprising the steps:-providing first and second printing materials which when mixed form a mixed thermoset polymer printing media; and mixing said printing materials and extruding the printing media through a nozzle onto a surface; wherein the nozzle to surface relative speed is in the range 500 to 1000 mm/min, the printing media dispensing rate is in the range 0.6 to 1000 g/s and the nozzle aperture area is in the ran ge 3 mm2 to 31,500 mm 2
32. The method of claim 31, wherein the nozzle to surface relative speed is in the range 750 to 850 mm/min, and the printing media dispensing rate is in the range 0.6 to 0.7 g/s the nozzle diameter is in the range 2 to 4 mm.
33. The method of claim 31 or claim 32, wherein one or more of said first and second printing materials have a thixotrope added thereto.
34. The method of any one of claims 31 to 33, wherein one or more of the first and second printing materials are degassed prior to mixing.
35. A subsea structure protection article formed from the method of any preceding claim, the subsea article having a maximum operating depth of 7000 meters.