The present invention relates to Additive Layer Manufacturing.
Additive Layer Manufacture (ALM) is used for repeated layering of desired material(s) in order to create structural components. The term “additive” is used to contrast conventional manufacturing processes such as milling or turning in which material from a solid layer or object is taken away or removed.
The material in an ALM process might be added to an existing structure in the form of cladding, or for the repair or addition of fixings. Alternatively, it may be the free form deposition of a material to form an independent structure. In blown powder ALM systems, powder is delivered from a powder stock by a delivery system. The powder feed is directed into the path of a laser beam, which heats the powder and melts it. Upon cooling a fully dense solid is produced. This process is repeated so as to provide the layered structure as desired.
ALM is a relatively mature process and there are a number of machines commercially available. However, all these machines use relatively simple powder delivery systems that have not changed for many years: the lasers are either continuous or pulsed and it is possible to alter the power or turn it on and off as required. During processing the powder forms a continuous stream and this introduces many difficulties and limitations to the process.
Embodiments of the present invention can address at least some of the problems discussed above. Embodiments can provide an additive layer manufacturing system with improved control over the supply of the powder feed.
According to one aspect of the present invention, there is provided an additive layer manufacturing system comprising a powder delivery system providing at least one powder feed from a powder stock to a powder exit adjacent to a deposition point; wherein the powder delivery system further comprises at least one valve system proximal to the powder exit for controlling the flow of the at least one powder feeds at the deposition point.
The system may further comprise a laser beam directed at the deposition point.
As the valve system is located close to the exit point of the powder, the effect of the valve system is instantaneous and sharp.
The powder delivery system may further comprise a nozzle, the nozzle comprising the at least one valve system. The valve system may be present adjacent to the tip of the nozzle. The laser beam can be directed at the deposition point through a passage in the nozzle. The nozzle may be at the tip of a deposition head. The laser and nozzle may be provided integrated into a deposition head.
A plurality of powder delivery systems may be provided. Each powder delivery system can comprise a valve system proximal to a powder exit for controlling the flow of powder feed at the deposition point. Each powder exit may be provided in the nozzle. Each powder feed can comprise a different material. The or each powder feed can comprise metals, ceramics, powders, fibres or mixtures thereof.
The valve system may selectively divert the powder feed away from the deposition point. The valve system may divert the powder feed back to the powder stock. Alternatively, the valve system may divert the powder feed into a separate container for recycling.
The valve system can comprise an inlet line, an outlet line and a bypass line, and a valve arranged to selectively connect the inlet line to the outlet line or bypass line.
According to a further aspect of the invention there is provided a method of preparing a layered structure, the method including:
The method may include:
The powder delivery system can comprise a plurality of valve systems. The method can further comprise selectively activating the at least one valve system to alternate or mix different materials.
The method may further comprise selectively activating the at least one valve system such that no powder exits at the deposition point while activating the laser to apply a heat treatment or laser process to material at the deposition point.
Alternatively or additionally, the method may comprise providing a fluid delivery system and, further comprising selectively activating the valve system such that no powder exits at the deposition point, while deactivating the laser and activating the fluid delivery system to provide thermal management (including forced cooling) of material at the deposition point.
According to a further aspect of the invention provides an additive layer manufacturing deposition head comprising at least one valve system substantially as herein described or for use in a method substantially as herein described. The Additive Layer Manufacturing deposition head may include an arrangement for receiving at least one powder feed from a powder stock and at least one valve system arranged, in use, proximal to a powder exit adjacent to a deposition point for controlling the flow of the at least one powder feed at the deposition point.
Whilst the invention has been described above, it extends to any inventive combination of features set out above or in the following description. Although illustrative embodiments of the invention are described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments. As such, many modifications and variations will be apparent to the practitioners skilled in the art. Furthermore, it is contemplated that a particular feature described either individually or as part of an embodiment can be combined with other individually described features, or parts or other embodiments, even if the other features and embodiments make no mention of the particular feature. Thus, the invention extends to such specific combinations not already discussed.
The invention may be performed in various ways, and, by way of example only, an embodiment thereof will now be described, reference being made to the accompanying drawings in which:
As seen in
The powder delivery system 104 provides two powder feeds 114A, 114B from two powder stocks (illustrated schematically at 115A, 115B in
The nozzle 108 is provided with a first valve system 116A and a second valve system 116B proximal to the powder exit 112 at the tip of the nozzle. An example distance/range from the valves to the tip of the nozzle is about 15 cm, although in other embodiments the distance can be less than around 10 cm. Each valve system comprises an inlet line 118A, 118B connected to their respective feed 114A, 114B, a respective outlet line 120A, 120B connected to the powder exit 112 and a respective bypass line 122A, 122B. As explained below, the valve systems 116A, 116B may be selectively activated to direct powder from their associated feeds 114A, 114B to the powder exit or to divert their powder feed away from the exit via the respective bypass lines 122A, 122B. The valves in the systems 116A, 116B may be bidirectional valves. The skilled person will appreciate that embodiments of the invention allow the powder feed(s) at the powder exit to be quickly turned on/off as desired by providing a valve system close to the powder exit. Embodiments of the invention may respond quickly to desired changes by diverting a substantially continuous powder feed away from the powder exit rather than attempting to stop and start the flow.
In use, the additive layer manufacturing system 100 is aligned with the required deposition point 110 on a substrate. The first and second valve systems 116A, 116B are opened and closed as desired in order to control the flow of the first and second powder feeds 114A, 114B from the first and second powder feed stocks to the powder exit 112 of the nozzle 108.
In
In
In
As explained below with reference to
A fluid (gas or liquid) stream can be used to provide thermal management, for example forced cooling, of the dynamically treated area. The fluid or gas may be provided via a separate outlet (not shown) on the nozzle. Alternatively, as shown in
The skilled person will appreciated from the above description that in embodiments of the invention the powder feed may only be dispensed from the system when the laser is on. This advantageously increases the powder utilisation. Furthermore, any powder wastage which occurs when moving the nozzle from one location to another may be significantly reduced due to the valve systems.
The ALM system described here may significantly reduce any stray powder. Due to the effects of stray powder, known ALM systems have to be used inside a close cell. The ALM system of embodiments of the invention can however be operated without a cell.
The skilled person in the art will appreciate that by utilising each powder exit in the nozzle to deliver a different powder feed, a dynamic and complex mix of materials/alloys may be deposited at the deposition point. For example, a first powder feed may provide a metal feed and a second powder feed may provide a feed of short fibres (for example, carbon fibres). By alternating the two feed sources (by switching the valve systems on the first and second nozzles on and off alternatively as required), a complex metal-fibre matrix can be produced. The laser power can be adjusted according to which powder feed has been deposited, therefore by using materials with different melt temperatures, different types of matrix can be fabricated.
The skilled person will also appreciate that further modifications may be made to the above embodiments without departing from the scope of the invention. For example, the additive layer manufacturing system may be provided with a further nozzle for depositing an adhesive layer to provide a bonding layer between dissimilar materials.
Number | Date | Country | Kind |
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11275048.4 | Mar 2011 | EP | regional |
1105034.1 | Mar 2011 | GB | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/GB2012/050606 | 3/20/2012 | WO | 00 | 9/24/2013 |