Patent Application
20180169947
The present invention relates to additive manufacturing.
Additive manufacturing has gained solid acceptance as a tool for prototyping and production of unique/custom-fit products (hearing aids, jewelry, dental implants, etc.). For these and other applications, a well-known principle is to sequentially expose a photo-sensitive liquid to a suitable number of solidifying radiations with the purpose of building one or more products. This method is frequently referred to as stereolithography.
A well-known stereolithographic principle of operation is to position a light-source above a build vat that contains a photo-sensitive liquid. Said light-source projects an image with a desired geometry onto a build platform (that is placed immediately below the surface of said photo-sensitive liquid) to solidify the photo-sensitive liquid that lies between the light-source and the platform in a shape corresponding with the geometry of the projected image. Building of additional layers of the product to be manufactured may be done by lowering the build platform a distance corresponding with a desired layer thickness and projecting a second image with a desired geometry onto the newly formed layer.
To ensure that the surface of the photo-sensitive liquid is even, and thereby that building of a second layer can be initiated as soon as possible after the building of the first layer, recoating has emerged as a useful principle associated with stereolithography (and other methods of additive manufacturing, such as Selective Laser Sintering (SLS) and Selective Laser Melting (SLM)).
An exemplary embodiment of a recoat system is disclosed in patent specification EP045762A1, and comprises a doctor blade that is configured to move over a build platform that is disposed in a build vat containing a photo-sensitive liquid with the purpose of forming a substantially uniform surface. A dispenser unit is configured to dip into the build vat to collect an amount of photo-sensitive liquid and to distribute at least part of said amount over the free surface of the build vat before advancing the doctor blade to ensure that a sufficient amount of material is available for spreading over the surface of the build vat by the doctor blade. Patent specification JP0524120 discloses a similar principle where the dipping of a dispenser unit into the build vat is replaced with the scooping of photo-sensitive liquid from the build vat into a feeder unit that may then distribute the photo-sensitive liquid across the free surface of the build vat. Yet a similar principle is disclosed by patent specification U.S. Pat. No. 5,432,045, which drags a recoat unit across a free surface of a build vat to distribute unsolidified photo-sensitive liquid by means of a clearance between the recoat unit and the free surface that is small enough to cause suction of the unsolidified photo-sensitive liquid into the clearance due to surface tension.
Patent specification U.S. Pat. No. 5,902,537 discloses an alternative principle where a recoat unit comprising a counter-rotating roller is employed to distribute photo-sensitive liquid across a free surface of the build vat. Additionally or alternatively, a material dispenser and/or a material transporter are used to further improve distribution of material. In some embodiments of U.S. Pat. No. 5,902,537, material is drawn from the bottom of the build vat and pumped into the material dispenser.
Patent specification U.S. Pat. No. 5,922,364 discloses yet an alternative principle where a recoat unit is connected to a reservoir of photo-sensitive liquid that is external to the build vat and where photo-sensitive liquid may be transferred from said reservoir to said recoat unit by means of elevation of the reservoir to exploit a gravity feed mechanism or alternatively by means of a pump or a similar impelling means that produces a small positive pressure. Said positive pressure aids in ensuring a proper distribution of photo-sensitive liquid across the free surface of the build vat.
In summary, the disclosures referenced above provide methods for ensuring that a single material is homogeneously distributed across a free surface in preparation of solidification of a layer in an additive manufacturing process. However, there is an increasing interest in the application of additive manufacturing as a technology for higher-volume production of components that may be made of more than one material. For these applications, systems that are able to operate continuously, with a high degree of automation, and with the option of changing between multiple materials are desirable since they support increased flexibility and reductions in the time it takes to manufacture a product by additive manufacturing.
The present invention provides additively manufacturing products using multiple materials. It mitigates several of the factors that add to the manufacturing time in additive manufacturing apparatuses. It also mitigates other factors that may constrain the usefulness of additive manufacturing apparatuses, especially for higher volume production.
In a first aspect, the invention provides an additive manufacturing apparatus comprising:
In some embodiments, the recoat unit comprises a leveling unit configured to level at least a part of the added radiation-curable liquid.
Some embodiments further comprise a suction element configured to retain or suck away excess radiation-curable liquid collected by the leveling unit during the recoat procedure. A particular set of embodiments comprise a suction element configured to partially or entirely drain said build vat from radiation-curable liquid, e.g. in preparation of a change of material and/or a cleaning process. In some embodiments, said suction element is integrated in the recoat unit whereas other embodiments comprise one or more suction elements that are external to the recoat unit. In some embodiments, the suction element is additionally and/or alternatively configured to suck away rinsing and/or dissolving agents that may be used during a rinsing and/or dissolving process. Some embodiments comprise a feeder unit that contains a single feeder unit element, while other embodiments comprise a feeder unit comprising multiple feeder unit elements. Some feeder units are based on the integration of all feeder unit elements into a single feeder unit, whereas other feeder units are based on some feeder unit elements that are integrated and some that are external to the feeder unit.
Some embodiments comprise a feeder unit element that is configured to receive and hold at least one container containing a (additional) radiation-curable liquid.
Some embodiments comprise a feeder unit element that is configured to store at least a first and a second radiation-curable liquid (where one may be a radiation curable liquid already contained in the build vat) with different chemical and/or thermal and/or electrical and/or mechanical characteristics and/or other differences. Some embodiments comprise a feeder unit element that is configured to feed at least said first and said second radiation-curable liquid to the recoat unit, whereas other embodiments comprise a feeder unit element that are external to the recoat unit. A particular set of embodiments comprise a feeder unit element adapted to feed at least said first radiation-curable liquid to the recoat unit and subsequently to feed at least said second radiation-curable liquid to the recoat unit.
Some embodiments comprise means for feeding initially a first radiation-curable liquid to the recoat unit with the purpose of building a first part of the product and subsequently changing to at least a second radiation-curable liquid (being different from the first radiation-curable liquid) with the purpose of building a second part of the products. For some of these applications, a rinsing process as disclosed below may be used to prepare the recoat unit and/or the build vat for receival of the second radiation-curable liquid. Other particular embodiments comprise a feeder unit element adapted to repeatedly change between said at least first and said at least second radiation-curable liquid, while yet other embodiments comprise a feeder unit element adapted to mix said at least first and second radiation-curable liquid in suitable proportions. Some embodiments are configured to provide combinations of the above.
Some embodiments comprise at least a first feeder unit element configured to monitor, using at least one monitor element, a state of cleanliness of a build vat and/or container and/or a build platform. In some embodiments, said at least one monitor element is integrated into the feeder unit, whereas other embodiments comprise at least one monitor element that is external to the feeder unit. Some embodiments comprise monitoring elements that are both integrated in the feeder unit and external to the feeder unit. Some embodiments comprise at least one monitor element that is integrated in the recoat unit. Some embodiments comprise monitoring means that are integrated in the radiation source. In some embodiments, monitoring means include a vision camera. In a particular subset of these embodiments, said vision camera monitors the state of cleanliness of the floor of said build vat and/or the state of cleanliness of the build platform.
Some embodiments comprise a feeder unit element that is configured to receive and hold at least one container containing a rinsing and/or dissolving agent.
Some embodiments comprise a feeder unit element that is configured to store one or more rinsing and/or dissolving agents. Some embodiments comprise a feeder unit element that is configured to feed said one or more rinsing and/or dissolving agents to the recoat unit to allow said recoat unit to supply said one or more rinsing and/or dissolving agents to the build vat and/or the build platform, whereas other embodiments comprise feeder unit elements for feeding rinsing and/or dissolving agents that are external to the recoat unit. Some embodiments comprise a feeder unit adapted to feed the dissolving agent to the recoat unit with the purpose of adjusting a viscosity of said at least first radiation-curable liquid before, during, or after feeding of said at least first radiation-curable liquid to the recoat unit. A particular set of embodiments comprise a feeder unit that is configured to receive and store at least one rinsing and/or dissolving agent in at least one container, after said at least one rinsing agent has been fed through the recoat unit to clean said unit, and subsequently aspirated back through the recoat unit, e.g. by means of the suction element. Yet a more particular set of embodiments comprise a feeder unit that is configured to feed at least a first rinsing and/or dissolving agent to said build vat holding said at least one radiation-curable liquid and/or said build platform. Alternative embodiments comprise means for feeding said at least first rinsing and/or dissolving agent to said build vat and/or said build platform after the radiation-curable liquid has been drained away by the suction element. Some embodiments comprise one or more elements for supplying pressurized and/or heated rinsing and/or dissolving agent. Some embodiments are configured to provide combinations of the above.
Some embodiments comprise a feeder unit element configured to provide a shielding or covering of said build vat and/or said build platform during the feeding of said rinsing and/or dissolving agent into said build vat. For some embodiments, said shielding or covering is configured to provide an air-tight seal or lid to the build vat with the purpose of avoiding an escape of rinsing and/or dissolving agent from the container. This is of particular relevance where pressurized and/or heated rinsing and/or dissolving agent is used.
Some embodiments comprise a feeder unit element that is configured to receive and hold at least a first container containing a coating agent.
Some embodiments comprise a feeder unit element that is configured to store one or more coating agents. Some embodiments comprise a feeding unit element that is configured to feed said one or more coating agents to the recoat unit with the purpose of distributing said one or more coating agents across at least a part of the build vat floor and/or the build platform, whereas other embodiments comprise feeding unit elements for feeding coating agents that are external to the recoat unit. In a particular set of embodiments, said coating serves the purpose of modifying the adhesive properties and/or other properties of said build vat floor and/or said build platform. Such modifications may include reducing or increasing adhesiveness of the build vat floor and/or said build platform. In another set of embodiments, such modifications may include changing properties of the products to be manufactured, such as color, mechanical characteristics, electrical characteristics, chemical characteristics, thermal characteristics
Some embodiments comprise a feeder unit element that is configured to supply a stream of air and/or gas, e.g. atmospheric air, carbon dioxide, etc. In some embodiments, said feeder unit element is configured to supply said stream of air and/or gas through the recoat unit and into the container and/or across the build platform, whereas other embodiments comprise air supply elements that are external to the recoat unit. Some embodiments comprise supplies of air and/or that may be heated or cooled. Some embodiments comprise supplies of air and/or gas that may be dried or humid. Some embodiments comprise supplies of air and/or gas that may be filtered and/or sterile. Some embodiments comprise supplies of air and/or gas that may be pressurized. Some embodiments are configured to provide combinations of the above.
Some embodiments comprise a feeder unit element configured to provide a shielding or covering of said build vat and/or said build platform (the same as mentioned above or alternatively a different) during the supply of said stream of air and/or gas into said build vat. For some embodiments, said shielding or covering is configured to provide an air-tight seal or lid to the build vat with the purpose of avoiding an escape of air and/or gas from the build vat. This is of particular relevance where pressurized air and/or gas is used.
Some embodiments comprise a feeder unit element that is configured to stir, agitate, rotate, and/or otherwise homogenize one or more radiation-curable liquids and/or one or more rinsing and/or dissolving agents before and/or after having been used, and/or one or more coating agents during storage and/or feeding. In some embodiments, said stirring is done to prevent sedimentation and/or other dwell-related artifacts that may change the characteristics of said stored materials.
Some embodiments comprise a feeder unit element that is configured to recognize at least a first radiation-curable liquid and/or rinsing and/or dissolving agent and/or coating agent and/or one or more of the additives mentioned above and elsewhere to ensure its appropriate identity and/or composition and/or the identity of the supplier, and/or the date of manufacture as well as other parameters that are of importance such as process parameters, amount, etc. Some embodiments comprise barcode readers that can read bar code information provided on the containers that are loaded into the system, while other embodiments comprise RFID readers that read RFID tags provided on the containers that are loaded into the system. Other means of recognition will be known to those skilled in the art, and are encompassed in this invention. Particular embodiments provide means for communicating to a quality management system the information gathered about the identity, composition, supplier identity, date of manufacture and other parameters that may be of relevance.
Some embodiments provide feeder unit elements with poka-yoke means for avoiding the erroneous placement of one or more containers containing either radiation-curable liquid, rinsing and/or dissolving agent either before or after usage and/or coating agent. Such poka-yoke means may include differentiating the size (height, width, depth) of container-receiving elements and/or of containers and differentiating the interfaces connecting the containers with the feeder unit.
Some embodiments comprise a feeder unit element that is configured to keep track of the age of at least a first radiation-curable liquid (e.g. located in the build vat and/or in a container) and/or rinsing and/or dissolving agent and/or coating agent after it has been received in the feeder unit. Particular embodiments also keep track of other parameters that may influence the performance characteristics of said at least a first radiation-curable liquid (e.g. located in the build vat and/or in a container), such as exposure to light, heat, cold, humidity, etc. Particular embodiments provide means for communicating to a user and/or a resource planning system that a pre-defined age has been reached. Other embodiments provide means for documenting to a quality management system the age as well as exposure to light, heat, cold, humidity of a given radiation-curable liquid and/or rinsing and/or dissolving agent and/or coating agent, as well as the time said radiation-curable liquid and/or rinsing and/or dissolving agent and/or coating agent has been stored in the feeder unit.
Some embodiments comprise a feeder unit element that is configured to keep track of the amount of radiation-curable liquid, rinsing and/or dissolving agent either before or after usage and/or coating agent found in each container and/or in the build vat. Particular embodiments provide means for communicating to a user and/or a resource planning system that a pre-defined lower threshold has been reached.
It is to be understood that combinations of feeder unit elements as disclosed above and elsewhere equally are anticipated.
Some embodiments further comprise:
A second aspect of the invention provides a method for manufacturing a product in an additive manufacturing apparatus, the apparatus comprising:
The method comprises:
In some embodiments of the second aspect, the adding of additional radiation-curable liquid is performed by a feeder unit configured to sweep across at least a part of the surface of the radiation-curable liquid and resupplying the additional radiation-curable liquid during the sweep.
Similarly to the first aspect, the method may comprise heating of radiation-curable liquid. This reduces the viscosity of the liquid.
In some embodiments of the method, the feeder unit further comprises a leveling unit configured to level at least a part of the added radiation-curable liquid.
The one or more radiation-curable liquids may e.g. be selected from the group consisting of resin, additives (ceramics, metals, chalk, plastics, colours, cellulose, wax, glass, etc.), UV blockers, UV-enhancers, etc.
Radiation-curable liquid may also be a material that is firm at room temperature, such as certain waxes.
To form a new layer of the product, the manufactured part 250 must be moved down by lowering the build platform 105. The new position is shown in
The recoat unit in accordance with embodiments of the present invention readies the radiation-curable liquid surface 103 for manufacturing of the next product layer, increasing the manufacturing speed.
The recoat unit illustrated in
An additional feeder unit 313 and an additional suction element 312 allow the recoating process to proceed from the second standby position. After formation of the next layer, the recoat unit travels back across the surface, adding liquid and leveling the surface.
The recoat unit in accordance with this embodiment readies the radiation-curable liquid surface 603 for manufacturing of the next product layer.
After solidification of the next layer, the recoat process can be repeated.
Similarly to the recoat unit in
1. Rinsing fluid is drawn from the container labelled “Clean”, and injected into the vat through the supply unit 610.
2. The rinsing fluid dissolves unused liquid in front of the blade 715 (assuming for this example a leftward direction of travel in
3. As the recoat unit reaches the other end of the vat, it sucks most of the remaining rinsing fluid into the waste container. Small amounts of rinsing fluid that are not removed from the vat may either be dried away—e.g. by circulating air and/or gas through the suction nozzles or by placing the vat in a heat chamber—or the solvent may remain in the build vat if it is compatible with the radiation-curable liquid. In some embodiments, radiation-curable liquid may be circulated through the recoat unit in a final rinsing step, which primes the entire system for repeat operation
4. Once the recoat unit has reached the other end, the direction of travel may be reversed and optionally repeated one or more times if needed. If the direction of travel is reversed (assuming a rightward direction of travel in
In some embodiments (not shown), gas and/or air is circulated into the build vat to speed up a drying of the build vat following rinsing.
| Number | Date | Country | Kind |
|---|---|---|---|
| PA201570295 | May 2015 | DK | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/061354 | 5/19/2016 | WO | 00 |
